Superabsorbent polymers based on copolymers of charged and neutral monomers

Abstract

The present invention describes superabsorbent polymers made from copolymers of charged monomers and neutral monomers, wherein the neutral monomers are alkyl or aryl terminated neutral and hydrophilic monomers, the neutral and hydrophilic monomers are free of free hydroxyl groups and have a water solubility of at least 200 mg / mL. The copolymer-based superabsorbent polymers have significantly improved absorbency under load. The compositions and methods described herein can be used in a variety of absorbent products.

Description

Technical Field

[0001] The present disclosure relates to superabsorbent polymers made from copolymers of charged monomers and neutral monomers, wherein the neutral monomers are alkyl or aryl terminated neutral monomers and hydrophilic monomers, the monomers do not contain free hydroxyl groups and have a water solubility of at least 200 mg / mL. The superabsorbent polymers based on the copolymers have significantly improved absorbency under load. Compositions and methods according to the present disclosure can be used in a variety of absorbent products. Background Art

[0002] Superabsorbent polymer (SAP) is a three-dimensional network that can absorb and retain water (or other aqueous media) and physiological fluids such as urine and blood that exceed hundreds of times of its own dry weight, which usually depends on the ion concentration of the aqueous solution. SAP has applications in multiple fields, including medicine, personal care products, biomaterials, biosorbents and agriculture. The first commercial SAP was produced by the alkaline hydrolysis of starch-g-polyacrylonitrile in 1970. Although these polymers can absorb up to 500g / g of water, they are mechanically weak in their swollen state. SAP was developed for sanitary applications in Japan and the U.S. industry in the early 1980s. It has been found that SAP has the potential to replace fluff, making their use in sanitary products such as baby diapers and sanitary napkins cost-effective.

[0003] The desired characteristics of SAP include high absorption capacity, high and adjustable swelling rate, absorbency under high load, good swelling gel strength, high gel fraction after cross-linking, excellent durability and stability when swelling and during storage, non-toxicity and low cost. Although current hydrogel systems provide good performance in several aspects in these different aspects, there are several disadvantages in various preparations, including low absorbency under pressure, gel blocking (the initial layer of SAP forms a relatively impermeable barrier to subsequent water diffusion and deeper absorption into the material) and high sensitivity to electrolyte solutions. Various strategies have been adopted to address these challenges, including the formation of composite and nanocomposite hydrogels, interpenetrating polymer network (IPN) hydrogels and various surface treatments; However, there is still a need for improvement to enable the use of minimal materials in the widest possible range of applications.

[0004] The nature of the monomers and cross-linking agents, their concentrations and molar ratios are known to be the most important factors affecting the absorption capacity of SAPs. Acrylic acid, acrylamide and methacrylic acid are the most widely used monomers for commercial preparation of SAPs. However, the presence of some residual acrylamide in the gel poses a challenge to the practical use of such hydrogels for human health and personal care products. In contrast, the water absorption and swelling properties of ionic SAPs (e.g. based on acrylic acid or methacrylic acid) are significantly reduced in saline liquids, including physiological fluids such as urine and blood. The reason for this salt sensitivity is that counterions such as sodium ions (Na + ) can effectively shield the polymer backbone charge, leading to condensation of counterions with polymer-bound charged groups and thereby reducing the counterion entropy and direct chain-chain repulsion available to drive the swelling response.

[0005] A number of strategies have been developed for SAP to try to address some of these challenges.

[0006] As a representative example of the process in the field of zwitterionic copolymer SAP, Kabiri et al. reported the synthesis of hydrogels based on zwitterionic monomers [3-(methacrylamido)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide (MPDSAH) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) by solution polymerization (Kabiri et al., Polym AdvTechnol 2005; 16, 659–666). The free swelling in water increased from 2.3 g / g for the sample without AMPS to a maximum swelling of 212.3 g / g with 20 mol% AMPS, above which the swelling decreased again. In 0.9% saline solution, the lowest swelling of 12.6 g / g corresponded to the sample without AMPS, and after incorporation of 20 mol% AMPS, the swelling increased to 32.8 g / g. Due to the zwitterionic nature of the SAP, the swelling of the hydrogel was relatively independent of pH over a wide pH range; similar near-constant swelling was also observed in environments with various ionic strengths. However, the absorbency under load (AUL) was not measured, and the use of zwitterionic monomers as the primary monomer would result in significantly higher costs for producing SAP for commercial products.

[0007] As a representative example of an approach in the field of nanocomposite SAPs, Chen et al. synthesized superabsorbent hydrogels by solution copolymerization of partially neutralized acrylic acid and AMPS in the presence of a hydrophilic nanosized clay, Laponite XLG, to improve the gel's shape stability and mechanical properties (Chen et al., Appl Mech Mater 2013; 427-429: 364-367). Free swelling was observed to increase significantly with increasing AMPS, with the free swelling ratio increasing from 460 g / g xerogel for AA-only hydrogels to 750 g / g xerogel when the AMPS:AA molar ratio was 1. Further small improvements in water binding and significant improvements in gel shape stability were observed upon incorporation of clay up to 20 wt% of the total monomer content, consistent with a balance between adding highly charged and hygroscopic fillers (increased adsorption capacity) and introducing physical crosslinks into the system (reduced adsorption capacity). However, the interaction between nanoscale fillers and bulk gel is challenging for engineers, where the balance between higher gel-filler interaction (increased physical cross-linking and thus reduced swelling) and lower gel-filler interaction (filler aggregation) is critical to control to achieve the desired combination of higher strength and high swelling.

[0008] It is known that the absorbency of saline under load (AUL) can be improved by surface crosslinking reactions between the functional groups of SAP and suitable surface crosslinking agents. Surface crosslinking helps to improve the local mechanics of SAP particles at the particle surface, while also reducing the "gel blocking" typically observed with swollen particles, which poses a transport challenge for water to enter the SAP deeper within the SAP pad. Generally, higher crosslinking density on the surface of SAP particles imparts better AUL properties. Bifunctional compounds such as diglycidol and diols are mainly used for SAP surface treatment. Epoxysilane compounds, such as 3-glycidylpropoxytrimethoxysilane (GPS), are also used for surface modification of SAP. This compound can increase AUL through two mechanisms: reaction of carboxylic acid with epoxy groups of GPS and oligomerization of siloxane on the surface of SAP particles. However, surface crosslinking introduces additional processing steps and can increase the amount of leachable compounds of SAP unless the residual crosslinker is thoroughly removed from the hydrogel.

[0009] It is also known that multifunctional cross-linkers can be used not only to enhance mechanical strength, but also introduce other advantages to SAP due to their branched structure. For example, Ghasri et al. synthesized a glycerol-lactic acid-based star-shaped modifier (SM) for surface modification of sanitary SAP hydrogels to increase saline-AUL and swollen gel strength. Surface treatment resulted in an increase of up to 28% in AUL in the modified SAP (M. Ghasri et al., Polym Adv Technol., 2018; 1-10). Compared with the intact SAP (f = 0.84 for NaCl and f = 0.95–0.97 for CaCl2), the modified samples showed lower salt sensitivity factors (f) in NaCl (f = 0.7) and CaCl2 (f = 0.93–0.95), which is attributed to the chelating effect induced by such multifunctional modifiers. The deionized water-free swelling capacity of the intact SAP is approximately 366 g / g; however, the SAP and S 11 Surface cross-linking (SM contains one LA molecule in each arm) leads to Q DW The values ​​decreased (reduced to 249 and 219 g / g using 0.5 g and 1.5 g of crosslinker, respectively) 。 Thus, surface crosslinking using branched crosslinkers improves the AUL of the hydrogel rather than the free water binding capacity. Branched crosslinkers are also synthetically more complex and expensive to prepare, which is a key consideration for commercial applications in disposable products such as sanitary pads or diapers.

[0010] As an alternative to these strategies, this study discloses the rational engineering of the structure of SAP-containing polymers to optimize the number of residues in the SAP that are ionized and thus can induce Donnan equilibrium / direct chain repulsion.

[0011] Conventional superabsorbent materials (SAMs) are mainly made of two types of polymers: synthetic polymers and natural polymers. In general, synthetic superabsorbent polymers are charged polyelectrolytes, such as polyacrylic acid (PAA), polyvinyl sulfonic acid, polyvinyl phosphoric acid salts and partially hydrolyzed maleic anhydride copolymers. Natural polymers include both neutral polymers and charged polymers, such as carboxymethyl cellulose, sodium alginate, chitosan salts and modified starches. All of these known SAMs have substantial limitations. For example, the most widely used SAMs based on commercial PAA have limited absorbency under load (AUL) and are also very sensitive to salt.

[0012] Although copolymers of charged and neutral monomers are known for many applications, such as drug delivery and tissue engineering, they are generally considered undesirable for use as superabsorbent materials. Conventional wisdom is that the introduction of neutral monomers in place of charged monomers other than zwitterionic monomers in copolymer-based SAMs will reduce absorbency because charged species or moieties are believed to have more driving force than neutral species or moieties to provide osmotic pressure and electrical repulsion.

[0013] Furthermore, alkyl or aryl moieties are considered hydrophobic and not hydrophilic. To provide a more hydrophilic character, the alkyl moiety is often terminated with a hydroxyl group.

[0014] Surprisingly, in the present work it was found that the presence of hydroxyl groups is detrimental to the properties and performance of SAM particles.It was also surprisingly found that the introduction of neutral monomer units into SAMs reduces salt sensitivity compared to charged polyelectrolytes without neutral monomer units.

[0015] These findings are applicable to a variety of homopolyelectrolyte-based SAM systems. Homopolyelectrolyte-based SAMs are very sensitive to salt, which results in lower absorption of aqueous liquids containing high salt concentrations.

[0016] Described herein are SAMs made from copolymers of charged monomers and neutral monomers, wherein the neutral monomers are alkyl or aryl terminated neutral monomers and hydrophilic monomers, the monomers being free of free hydroxyl groups and having a water solubility of at least 200 mg / mL. The copolymer-based SAM particles have significantly improved absorbency under load.

[0017] Compositions and methods according to the present disclosure can be used in a variety of absorbent products.

[0018] Public Purpose

[0019] The present disclosure aims to address the low ionization level of AA-based SAPs by creating unstable charged superabsorbent structures that blend charged comonomers with nonionic monomers. The permanent charge on such materials, coupled with the potential to bind water through a variety of mechanisms, can enhance absorbency under a wide range of solution conditions. Summary of the invention

[0020] In one aspect, there is provided a superabsorbent polymer comprising

[0021] A copolymer comprising

[0022] The main part of the charged monomer;

[0023] a minor portion of alkyl or aryl terminated neutral and hydrophilic monomers; and

[0024] optional cross-linking agent;

[0025] The alkyl or aryl terminated neutral and hydrophilic monomer contains no free hydroxyl groups and has a water solubility of at least 200 mg / mL.

[0026] In another aspect, there is provided a method for preparing a superabsorbent polymer, the superabsorbent polymer comprising

[0027] A copolymer comprising

[0028] The main part of the charged monomer;

[0029] a minor portion of alkyl or aryl terminated neutral and hydrophilic monomers; and

[0030] optional cross-linking agent;

[0031] wherein the alkyl or aryl terminated neutral and hydrophilic monomer contains no free hydroxyl groups and has a water solubility of at least 200 mg / mL, the method comprising

[0032] forming a mixture comprising

[0033] Solvents

[0034] Charged monomer;

[0035] Alkyl or aryl terminated neutral and hydrophilic monomers; and

[0036] Optional cross-linking agent

[0037] Provoke a reaction; and

[0038] The mixture is reacted.

[0039] In yet another aspect, there is provided a method of using a superabsorbent polymer, the superabsorbent polymer comprising

[0040] A copolymer comprising

[0041] The main part of the charged monomer;

[0042] a minor portion of alkyl or aryl terminated neutral and hydrophilic monomers; and

[0043] optional cross-linking agent;

[0044] Wherein the alkyl or aryl terminated neutral and hydrophilic monomer contains no free hydroxyl groups and has a water solubility of at least 200 mg / mL, and the method comprises using the superabsorbent polymer in a consumer product. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1is an exemplary embodiment depicting AMPS-co-PEGMMA samples according to the present disclosure after swelling compared to commercial (surface cross-linked) samples and control (AA only, no surface cross-linking) samples.

[0046] Figure 2 is an exemplary embodiment depicting the shear storage modulus as a function of time during swelling for a commercial (surface cross-linked) sample (left), an AMPS-co-PEGMMA sample (center), and a control (AA only, no surface cross-linking) sample (right) according to the present disclosure. DETAILED DESCRIPTION

[0047] The superabsorbent polymer according to the present disclosure comprises a copolymer comprising a major portion of charged monomers, a minor portion of alkyl or aryl terminated neutral and hydrophilic monomers, and an optional crosslinking agent. The alkyl or aryl terminated neutral and hydrophilic monomers contain no free hydroxyl groups and have a water solubility of at least 200 mg / mL.

[0048] In some embodiments, the copolymer comprises two or more different types of monomers. In some embodiments, the copolymer comprises three or more different types of monomers. In some embodiments, the copolymer comprises four or more different types of monomers. In some embodiments, the copolymer comprises five or more different types of monomers. In some embodiments, the copolymer comprises six or more different types of monomers.

[0049] In some embodiments, the copolymer comprises one or more different kinds of charged monomers. In some embodiments, the copolymer comprises two or more different kinds of charged monomers. In some embodiments, the copolymer comprises three or more different kinds of charged monomers.

[0050] In some embodiments, the copolymer comprises one or more different kinds of alkyl or aryl terminated neutral and hydrophilic monomers. In some embodiments, the copolymer comprises two or more different kinds of alkyl or aryl terminated neutral and hydrophilic monomers. In some embodiments, the copolymer comprises three or more different kinds of alkyl or aryl terminated neutral and hydrophilic monomers.

[0051] In some embodiments, the copolymers are free of charged monomers and structured ordered arrangements of alkyl or aryl terminated neutral and hydrophilic monomers. In some embodiments, the copolymers are as random as possible. In some embodiments, the probability of finding a monomer residue of a given type at a particular point along the polymer backbone is approximately equal to the mole fraction of the monomer residue in the polymer backbone.

[0052] In some embodiments, the copolymer does not comprise a block copolymer of a charged monomer and an alkyl or aryl terminated neutral and hydrophilic monomer. In some embodiments, the copolymer does not comprise an alternating copolymer of a charged monomer and an alkyl or aryl terminated neutral and hydrophilic monomer. In some embodiments, the copolymer does not comprise a graft copolymer of a charged monomer, an alkyl or aryl terminated neutral and hydrophilic monomer.

[0053] In some embodiments, the major portion is greater than about 50 mol%, greater than about 51 mol%, greater than about 52 mol%, greater than about 53 mol%, greater than about 54 mol%, greater than about 55 mol%, greater than about 56 mol%, greater than about 57 mol%, greater than about 58 mol%, greater than about 59 mol%, greater than about 60 mol%, greater than about 61 mol%, greater than about 62 mol%, greater than about 63 mol%, greater than about 64 mol%, greater than about 65 mol%, greater than about 66 mol%, greater than about 67 mol%, greater than about 68 mol%, greater than about 69 mol%, greater than about 70 mol%, greater than about 71 mol%, greater than about 72 mol%, greater than about 73 mol%, greater than about 74 mol%, greater than about 75 mol%, greater than about 76 mol%, greater than about 77 mol%, greater than about 78 mol%, greater than about 79 mol%, greater than about 80 mol%, greater than about 81 mol%, greater than about 82 mol%, greater than about 83 mol%, greater than about 84 mol%, greater than about 85 mol%, greater than about 86 mol%, greater than about 87 mol%, greater than about 88 mol%, greater than about 89 mol%, greater than about 90 mol%, greater than about 91 mol%, greater than about 92 mol%, greater than about 93 mol%, greater than about 94 mol%, greater than about 95 mol%, greater than about 96 mol%, greater than about 97 mol%, greater than about 98 mol%, greater than about 99 mol%, greater than about 100 mol%, greater than about 101 mol%, greater than about 102 mol%, greater than about 103 mol%, greater than about 104 mol%, greater than about %, greater than about 73 mol %, greater than about 74 mol %, greater than about 75 mol %, greater than about 76 mol %, greater than about 77 mol %, greater than about 78 mol %, greater than about 79 mol %, greater than about 80 mol %, greater than about 81 mol %, greater than about 82 mol %, greater than about 83 mol %, greater than about 84 mol %, greater than about 85 mol %, greater than about 86 mol %, greater than about 87 mol %, greater than about 88 mol %, greater than about 89 mol %, greater than 90 mol %, greater than about 91 mol %, greater than about 92 mol %, greater than about 93 mol %, greater than about 94 mol % or greater than about 95 mol % of the copolymer is present.

[0054] In some embodiments, the major portion is present in an amount greater than about 65% by weight of the copolymer.

[0055] In some embodiments, the minor portion is greater than about 5 mol%, greater than about 6 mol%, greater than about 7 mol%, greater than about 8 mol%, greater than about 9 mol%, greater than about 10 mol%, greater than about 11 mol%, greater than about 12 mol%, greater than about 13 mol%, greater than about 14 mol%, greater than about 15 mol%, greater than about 16 mol%, greater than about 17 mol%, greater than about 18 mol%, greater than about 19 mol%, greater than about 20 mol%, greater than about 21 mol%, greater than about 22 mol%, greater than about 23 mol%, greater than about 24 mol%, greater than about 25 mol%, greater than about 26 mol%, greater than about 27 mol%, greater than about 28 mol%, greater than about 29 mol%, greater than about 30 mol%, greater than about 31 mol%, greater than about 32 mol%, greater than about 33 mol%, greater than about 34 mol%, greater than about 35 mol%, greater than about 36 mol%, greater than about 37 mol%, greater than about 38 mol%, greater than about 39 mol%, greater than about 40 mol%, greater than about 41 mol%, greater than about 42 mol%, greater than about 43 mol%, greater than about 44 mol%, greater than about 45 mol%, greater than about 46 mol%, greater than about 47 mol%, greater than about 48 mol%, greater than about 49 mol%, greater than about 50 mol%, greater than about 51 mol%, greater than about %, greater than about 47 mol %, greater than about 48 mol %, greater than about 49 mol %, greater than about 50 mol %, greater than about 51 mol %, greater than about 52 mol %, greater than about 53 mol %, greater than about 54 mol %, greater than about 55 mol %, greater than about 56 mol %, greater than about 57 mol %, greater than about 58 mol %, greater than about 59 mol %, greater than about 60 mol %, greater than about 61 mol %, greater than about 62 mol %, greater than about 63 mol %, greater than about 64 mol %, greater than about 65 mol %, greater than about 66 mol %, greater than about 67 mol %, greater than about 68 mol %, greater than about 69 mol %, greater than about 70 mol %, greater than about 71 mol %, greater than about 72 mol %, greater than about 73 mol %, greater than about 74 mol %, greater than about 75 mol %, greater than about 76 mol %, greater than about 77 mol %, greater than about 78 mol %, greater than about 79 mol %,

[0056] In some embodiments, the minor portion is less than about 5 mol%, less than about 6 mol%, less than about 7 mol%, less than about 8 mol%, less than about 9 mol%, less than about 10 mol%, less than about 11 mol%, less than about 12 mol%, less than about 13 mol%, less than about 14 mol%, less than about 15 mol%, less than about 16 mol%, less than about 17 mol%, less than about 18 mol%, less than about 19 mol%, less than about 20 mol%, less than about 21 mol%, less than about 22 mol%, less than about 23 mol%, less than about 24 mol%, less than about 25 mol%, less than about 26 mol%, less than about 27 mol%, less than about 28 mol%, less than about 29 mol%, less than about 30 mol%, less than about 31 mol%, less than about 32 mol%, less than about 33 mol%, less than about 34 mol%, less than about 35 mol%, less than about 36 mol%, less than about 37 mol%, less than about 38 mol%, less than about 39 mol%, less than about 40 mol%, less than about 41 mol%, less than about 42 mol%, less than about 43 mol%, less than about 44 mol%, less than about 45 mol%, less than about 46 mol%, less than about 47 mol%, less than about 48 mol%, less than about 49 mol%, less than about 50 mol%, less than about 51 mol%, less than about 52 mol%, less than about 53 mol%, less than about 54 mol%, less than about 55 mol%, less than about 56 mol%, less than about 57 mol%, less than about 58 mol%, less than about 59 mol%, less than about 60 mol%, less than about %, less than about 47 mol %, less than about 48 mol %, less than about 49 mol %, less than about 50 mol %, less than about 51 mol %, less than about 52 mol %, less than about 53 mol %, less than about 54 mol %, less than about 55 mol %, less than about 56 mol %, less than about 57 mol %, less than about 58 mol %, less than about 59 mol %, less than about 60 mol %, less than about 61 mol %, less than about 62 mol %, less than about 63 mol %, less than about 64 mol %, less than about 65 mol %, less than about 66 mol %, less than about 67 mol %, less than about 68 mol %, less than about 69 mol %, less than about 70 mol %, less than about 71 mol %, less than about 72 mol %, less than about 73 mol %, less than about 74 mol %, less than about

[0057] In some embodiments, the minor moiety is present in an amount less than about 35 mole percent of the copolymer.

[0058] In some embodiments, the main part is present in an amount greater than about 50 mol% of the copolymer, and the minor part is present in an amount less than about 50 mol% of the copolymer. In some embodiments, the main part is present in an amount greater than about 55 mol% of the copolymer, and the minor part is present in an amount less than about 45 mol% of the copolymer. In some embodiments, the main part is present in an amount greater than about 60 mol% of the copolymer, and the minor part is present in an amount less than about 40 mol% of the copolymer. In some embodiments, the main part is present in an amount greater than about 65 mol% of the copolymer, and the minor part is present in an amount less than about 35 mol% of the copolymer. In some embodiments, the main part is present in an amount greater than about 70 mol% of the copolymer, and the minor part is present in an amount less than about 30 mol% of the copolymer. In some embodiments, the main part is present in an amount greater than about 75 mol% of the copolymer, and the minor part is present in an amount less than about 25 mol% of the copolymer. In some embodiments, the major portion is present in an amount greater than about 80 mol% of the copolymer, and the minor portion is present in an amount less than about 20 mol% of the copolymer. In some embodiments, the major portion is present in an amount greater than about 85 mol% of the copolymer, and the minor portion is present in an amount less than about 15 mol% of the copolymer. In some embodiments, the major portion is present in an amount greater than about 90 mol% of the copolymer, and the minor portion is present in an amount less than about 10 mol% of the copolymer. In some embodiments, the major portion is present in an amount greater than about 95 mol% of the copolymer, and the minor portion is present in an amount less than about 5 mol% of the copolymer.

[0059] In some embodiments, the major portion is present in an amount greater than about 65 mole percent of the copolymer and the minor portion is present in an amount less than about 35 mole percent of the copolymer.

[0060] In some embodiments, the superabsorbent polymer is in a form selected from the group consisting of particles, gels, fibers, beads, liquids, solids, pastes, or combinations thereof. In some embodiments, the superabsorbent polymer is a gel. In some embodiments, the superabsorbent polymer is a particle.

[0061] In some embodiments, the superabsorbent polymer is in the form of a diameter ranging from about 100 μm to about 1000 μm, from about 100 μm to about 900 μm, from about 100 μm to about 800 μm, from about 100 μm to about 700 μm, from about 100 μm to about 600 μm, from about 100 μm to about 500 μm, from about 100 μm to about 400 μm, from about 100 μm to about 300 μm, or from about 100 μm to about 200 μm. In some embodiments, the superabsorbent polymer is in the form of a diameter ranging from about 200 μm to about 900 μm, from about 300 μm to about 800 μm, from about 400 μm to about 700 μm, or from about 500 μm to about 600 μm.

[0062] In some embodiments, the superabsorbent polymer is in the form of a particle having a diameter ranging from about 300 μm to about 600 μm.

[0063] In some embodiments, the superabsorbent polymer is a particle having a diameter in the range of about 100 μm to about 1000 μm. In some embodiments, the superabsorbent polymer is a particle having a diameter in the range of about 300 μm to about 600 μm.

[0064] In some embodiments, the superabsorbent polymer does not comprise a crosslinking agent. In some embodiments, the superabsorbent polymer comprises one or more crosslinking agents. In some embodiments, the superabsorbent polymer comprises two or more crosslinking agents.

[0065] In some embodiments, the superabsorbent polymer comprises a crosslinker selected from the group consisting of methylene (bis)acrylamide (MBAA), poly(ethylene glycol diacrylate) (PEGDA), ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA), poly(ethylene glycol dimethacrylate) (PEGDMA), and combinations thereof.

[0066] In some embodiments, the superabsorbent polymer is slightly crosslinked. In some embodiments, the superabsorbent polymer has a crosslinker density in the range of about 0.1 mol % to about 1 mol %. In some embodiments, the superabsorbent polymer has a crosslinker density in the range of about 0.2 mol % to about 1 mol %.

[0067] In some embodiments, the superabsorbent polymer is surface cross-linked.

[0068] In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility greater than about 200 mg / mL. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility greater than about 250 mg / mL. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility greater than about 300 mg / mL. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility greater than about 350 mg / mL. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility greater than about 400 mg / mL. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility greater than about 450 mg / mL. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility greater than about 500 mg / mL.

[0069] In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility in the range of about 200 mg / mL to about 500 mg / mL.

[0070] In some embodiments, the major portion of the charged monomers comprises charged monomers having a molecular weight of less than about 150 g / mol. In some embodiments, the major portion of the charged monomers comprises charged monomers having a molecular weight of less than about 125 g / mol. In some embodiments, the major portion of the charged monomers comprises charged monomers having a molecular weight of less than about 100 g / mol. In some embodiments, the major portion of the charged monomers comprises charged monomers having a molecular weight of less than about 75 g / mol. In some embodiments, the major portion of the charged monomers comprises charged monomers having a molecular weight of less than about 50 g / mol. In some embodiments, the major portion of the charged monomers comprises charged monomers having a molecular weight of less than about 25 g / mol.

[0071] In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 150 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 200 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 250 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 300 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 350 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 400 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 450 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 500 g / mol.

[0072] In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 1500 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 1000 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 900 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 800 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 700 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 600 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 500 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 400 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 300 g / mol. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 200 g / mol. In some embodiments, the minor portion of the alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 100 g / mol.

[0073] In some embodiments, the minor portion of the alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than about 1000 g / mol.

[0074] In some embodiments, the major portion of charged monomers comprises charged monomers having a molecular weight less than about 150 g / mol, and the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight greater than about 150 g / mol.

[0075] In some embodiments, the majority of the charged monomers comprise charged monomers having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. In some embodiments, the majority of the charged monomers comprise charged monomers having 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. In some embodiments, the majority of the charged monomers comprise charged monomers having 1, 2, 3, 4, 5, or 6 oxygen atoms. In some embodiments, the majority of the charged monomers comprise charged monomers having 2, 3, 4, 5, or 6 oxygen atoms.

[0076] In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, or 54 carbon atoms. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 carbon atoms. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 oxygen atoms. In some embodiments, the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 oxygen atoms.

[0077] In some embodiments, a major portion of the charged monomers comprises charged monomers having a net negative charge. In some embodiments, a major portion of the charged monomers comprises charged monomers having a net positive charge.

[0078] In some embodiments, the majority of charged monomers comprises charged monomers having one negative or positive charge. In some embodiments, the majority of charged monomers comprises charged monomers having two negative or positive charges. In some embodiments, the majority of charged monomers comprises charged monomers having three negative or positive charges. In some embodiments, the majority of charged monomers comprises charged monomers having more than three negative or positive charges.

[0079] In some embodiments, the minor portion of the alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having no net charge.

[0080] In some embodiments, the minor portion of the alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers selected from the group consisting of polyethylene glycol monomethyl ether monomethacrylate acrylic acid, methoxyethyl ester, a compound according to Formula I:

[0081]

[0082] Where n is a number in the range of 1-50 and R 1 and R 2 Each is independently selected from the group consisting of hydrogen and a linear or branched C1-C6 alkyl group.

[0083] In some embodiments, n is a number in the range of 1-20. In some embodiments, n is a number in the range of 1-10.

[0084] In some embodiments, R 1 is selected from the group consisting of hydrogen and methyl.

[0085] In some embodiments, R 2 Selected from the group consisting of linear or branched C1-C3 alkyl groups.

[0086] In some embodiments, the major portion of the charged monomers comprises a charged monomer selected from the group consisting of acrylic acid or methacrylic acid or a salt thereof, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl methacrylate, 3-sulfopropyl acrylate, an acrylate or methacrylate monomer having a tethered sulfate group or a salt thereof, a salt of an ethylene-linker-acid unit, a salt of an ethylene-linker-acid unit wherein the linker has a length of at least 3 angstroms, a vinyl sulfate monomer, acrylic acid, vinyl sulfonic acid, vinyl phosphoric acid, a salt of a partially hydrolyzed maleic anhydride monomer, and combinations thereof.

[0087] In some embodiments, the major portion of the charged monomers comprises a charged monomer selected from the group consisting of acrylic acid, vinyl sulfonic acid, vinyl phosphoric acid, salts of partially hydrolyzed maleic anhydride monomers, and combinations thereof.

[0088] In some embodiments, the copolymer does not include zwitterionic charged monomers. In some embodiments, the copolymer does not include nonionic monomers.

[0089] In some embodiments, the copolymer is synthesized according to a method selected from the group consisting of free radical polymerization, anionic polymerization, controlled radical polymerization methods, atom transfer radical polymerization (ATRP), nitroxide-mediated radical polymerization (NMP), reversible addition-fragmentation chain transfer polymerization (RAFT), and combinations thereof. In some embodiments, the copolymer is synthesized according to free radical polymerization.

[0090] In some embodiments, free radicals can be generated by photolysis, thermal decomposition, or ambient redox conditions.

[0091] In some embodiments, the copolymer is synthesized according to a method comprising forming a mixture comprising a solvent, charged, alkyl or aryl terminated neutral and hydrophilic monomers, and optionally a crosslinking agent; initiating a redox reaction; and reacting the mixture.

[0092] In some embodiments, the method step of initiating a redox reaction comprises adding a redox initiator, a accelerator, or a combination thereof to the mixture.

[0093] In some embodiments, the initiator is an organic compound. In some embodiments, the initiator is selected from the group consisting of azo compounds, organic peroxide compounds, organic persulfate compounds, and combinations thereof. In some embodiments, the initiator is an azo compound. In some embodiments, the initiator is an organic peroxide compound. In some embodiments, the initiator is an organic persulfate compound.

[0094] In some embodiments, the initiator is an inorganic compound. In some embodiments, the initiator is selected from the group consisting of inorganic peroxide compounds, metal reducing agents, iron, chromium, palladium, titanium, cobalt, copper, and combinations thereof. In some embodiments, the initiator is an inorganic peroxide compound. In some embodiments, the initiator is selected from the group consisting of potassium persulfate, ammonium persulfate, and combinations thereof. In some embodiments, the reduction of hydrogen peroxide or alkyl hydroperoxide can be by iron or other reducing agents such as Cr 2+ 、V 2+ 、Ti 3+ 、Co 2+ Cu + conduct.

[0095] In some embodiments, the initiator is an oxidizing agent. In some embodiments, the initiator is a persulfate. In some embodiments, the initiator is selected from the group consisting of potassium persulfate, ammonium persulfate, and combinations thereof.

[0096] In some embodiments, the promoter is an organic compound. In some embodiments, the promoter is an organic base. In some embodiments, the promoter is tetramethylethylenediamine (TEMED). In other embodiments, the promoter is sodium pyrosulfite (SPS). In some embodiments, no promoter is used. In some embodiments, the promoter is selected from the group consisting of an organic compound, an organic base, TEMED, SPS, no promoter, and combinations thereof.

[0097] In some embodiments, the method step of reacting the mixture comprises reacting the mixture in an inert atmosphere. In some embodiments, the method step of reacting the mixture comprises reacting the mixture in a static inert atmosphere. In some embodiments, the method step of reacting the mixture comprises reacting the mixture in a dynamic inert atmosphere. In some embodiments, the method step of reacting the mixture comprises reacting the mixture under an inert gas flow.

[0098] In some embodiments, the method step of reacting the mixture comprises reacting the mixture in an inert atmosphere selected from the group consisting of N2, CO2, noble gases, helium, neon, argon, krypton, xenon, and combinations thereof. In some embodiments, the method step of reacting the mixture comprises reacting the mixture in an inert atmosphere of N2.

[0099] In some embodiments, the method step of reacting the mixture comprises heating the mixture. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 20°C to about 100°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 30°C to about 100°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 40°C to about 100°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 50°C to about 100°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 60°C to about 100°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 70°C to about 100°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 20°C to about 90°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 30°C to about 80°C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 40°C to about 70°C.

[0100] In some embodiments, the method step of reacting the mixture comprises heating the mixture to a temperature in the range of about 20° C. to about 40° C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to about 40° C. In some embodiments, the method step of reacting the mixture comprises heating the mixture to about 70° C.

[0101] In some embodiments, the method further comprises drying the reaction product. In some embodiments, the method further comprises drying the reaction product in an oven. In some embodiments, the method further comprises drying the reaction product at a temperature in the range of about 50°C to about 100°C. In some embodiments, the method further comprises drying the reaction product at a temperature in the range of about 60°C to about 100°C. In some embodiments, the method further comprises drying the reaction product at a temperature in the range of about 70°C to about 100°C. In some embodiments, the method further comprises drying the reaction product at a temperature in the range of about 80°C to about 100°C. In some embodiments, the method further comprises drying the reaction product at a temperature in the range of about 60°C to about 90°C. In some embodiments, the method further comprises drying the reaction product at a temperature in the range of about 70°C to about 90°C.

[0102] In some embodiments, the method further comprises drying the reaction product at a temperature of about 85°C.

[0103] In some embodiments, the method further comprises grinding the reaction product.In some embodiments, the method further comprises grinding the reaction product with a grinding device selected from the group consisting of a mechanical stirrer, a coffee grinder, a crusher, a pulverizer, a grinder, a mill, and combinations thereof.

[0104] In some embodiments, the ability of a polymer to absorb fluid under a static load can be measured as the Absorbency Under Load (AUL).A typical AUL test format can be used.

[0105] In some embodiments, the ability of a pre-swollen polymer to retain water under force can be measured as the Centrifuge Retention Capacity (CRC). A typical CRC test format can be used.

[0106] In some embodiments, superabsorbent polymers are used in consumer products or superabsorbent materials. In some embodiments, consumer products or superabsorbent materials comprise superabsorbent polymers.

[0107] In some embodiments, methods of using superabsorbent polymers include using the superabsorbent polymers in consumer products or superabsorbent materials.

[0108] In some embodiments, the consumer product is selected from the group consisting of cloth products, diapers, feminine hygiene napkins, and disposable mattress pads.

[0109] Example

[0110] Without further elaboration, it is believed that one skilled in the art using the preceding description can utilize the present invention to its fullest extent.Therefore, the following examples are to be construed as illustrative only, and not limiting of the present disclosure in any way whatsoever.

[0111] Material.

[0112] Unless otherwise stated, the following materials were used in the examples: acrylic acid (AA), 99%; acrylamido-2-methylpropane sulfonic acid (AMPS), 2-hydroxyethyl methacrylate (HEMA), 97%; methoxyethyl acrylate (MEA); vinyl sulfonic acid sodium salt (VSA), 25% in water, technical grade; poly(ethylene glycol) methyl ether methacrylate (PEGMMA), Mw=300-500 g / mol; poly(ethylene glycol) methacrylate (PEGMA), Mn=360 g / mol ; Poly(ethylene glycol) diacrylate (PEGDA), Mw=250; Ethylene glycol dimethacrylate (EGDMA), Mw=198.22 g / mol; Poly(ethylene glycol) dimethacrylate (PEGDMA), Mn=550 g / mol; Potassium persulfate (KPS), ≥99%; N,N-methylene (bis)acrylamide (MBAA), ≥99%; and ammonium persulfate (APS), ≥98%; N,N,N',N'-tetramethylethylenediamine (TEMED), ≥99.5%.

[0113] Comparative Example 1. Preparation of AA-based SAM particles.

[0114] 17g milli-Q water was added to a high 200mL reaction flask, and 1.94g 97% NaOH pellets (or 2.08g in the case of 75% neutralization) for 70% neutralization were dissolved in an ice bath. 5g AA (anhydrous, containing 200ppm MEHQ as an inhibitor, 99%) was added. 25mg>99% MBAA was dissolved in 2mL water and added to the above solution. The solution was stirred at 600rpm with a magnetic stirring bar throughout the reaction. The reaction flask was purged with N2 gas for 10 minutes, and the reaction temperature was increased to 40°C. 15mg APS (redox initiator) was dissolved in 1mL water and added to the reaction mixture with 10μL TEMED. The reaction flask was sealed with paraffin film and kept under low flow N2. Gelation began within 10-20min. After gelation, the reaction tank was capped and kept at 40°C for another 4 hours. The gelled reaction product was cut into small pieces and dried at 85°C for 48 hours. The dried sample was ground using a coffee grinder. The dried gel particle size fraction between 300-600 microns was isolated using a suitable sieve and dried overnight.

[0115] Comparative Example 2. Preparation of SAM particles based on AA 90% / PEGMMA 10%.

[0116] 14g milli-Q water is added to a high 200mL beaker. 2.08g 97% NaOH pellets are dissolved in water on an ice bath. 4.5g AA (anhydrous, containing 200ppm MEHQ as an inhibitor, 99%) is added. 2.07g PEGMMA is mixed with 3ml milliQ water and added dropwise through a dropping funnel. 25mg>99% MBAA is completely dissolved in 2mL water and added to the above solution. The solution is stirred with a magnetic stirrer at about 600rpm during the entire reaction. The reaction flask is purged with N2 gas for 5-10 minutes, and the temperature is increased to 40°C. 15mg APS (redox initiator) is dissolved in 1mL water and added to the reaction mixture together with 40μLTEMED. The reaction flask is sealed with paraffin film and kept under low flow N2. Gelation begins within 5-15min, and the reaction tank is capped and kept at 40°C for another 4 hours. The gelled reaction product was cut and dried in an oven at 85°C for 48 hours. The dried sample was ground using a coffee grinder. The dried gel particle size fraction between 300-600 microns was isolated using a suitable sieve and dried overnight.

[0117] Example 1. Preparation of AMPS / MEA and AMPS / HEMA based SAM particles.

[0118] Three bottles were designated as bottle 1, bottle 2, and bottle 3, respectively. 10 g, 8 g, and 8 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were added to bottles 1, 2, and 3, respectively. 1.121 g of hydroxyethyl acrylate (HEA) was added to bottle 2. 1.256 g of methoxyethyl acrylate (MEA) was added to bottle 3. 34 mL, 27.2 mL, and 27.2 mL of NaOH aqueous solution (0.05684 g / mL) were added to bottles 1, 2, and 3, respectively, in an ice bath. 6.8 mL of water was added to each of bottles 2 and 3. The pH of the mixture in each bottle was adjusted to 6.5 by NaOH solution or HCl solution. 2 mL of N,N'-methylenebisacrylamide (MBAA) solution (8.695 mg / mL) was added to each bottle. In an ice bath, the mixture in each bottle was purged with a N2 stream for 15 min. Then, 2 mL of an aqueous solution of ammonium persulfate (APS) (17.39 mg / mL) was added to each bottle, followed by 2 mL of an aqueous solution of tetramethylethylenediamine (TEMED) (13.9 μl / mL). The bottles were capped and transferred to a 40°C water bath with stirring. Generally, a hydrogel was formed after about 15 to 30 minutes. The gel was further incubated at 40°C for 4 hours. The gels from AMPS and AMPS / MEA were relatively rigid, while the gel from AMPS / HEA was soft and sticky. The cured hydrogel was cut into small pieces and dried at 85°C for 48 hours. The dried hydrogel was ground with a food grinder and sieved into 300 to 600 um particles. These particles were designated as AMPS, AMPS / HEA and AMPS / MEA from bottles 1, 2 and 3, respectively.

[0119] Example 2. AUL measurements of SAM particles.

[0120] AUL measures the ability of a polymer to absorb fluid under a static load and can be considered a measurement of gel swelling combined with gel strength. A typical AUL test format is used, which consists of a simple cylindrical device with a macroporous sintered filter plate at one end of a sintered plastic cylinder. For the sample tested, 160 mg (W1) of dried SAP sample is weighed and evenly placed on the surface of a polyester gauze, which is placed on top of the sintered plastic. The desired load (0.3 PSI, 0.6 PSI, or 0.9 PSI) is then placed on top of the dry SAP particles, where the load is designed to allow it to move freely in the plastic cylinder. The device is placed in a culture dish of 0.9% saline solution on top of the screen (to ensure that water can access the bottom of the sintered plastic) for 1 hour. The swollen sample (W2) is weighed and AUL is calculated using equation (1)

[0121]

[0122] About 0.2 g of each of the SAM particles prepared according to Comparative Example 1, Comparative Example 2, and Example 1 was placed in an AUL measuring cup and covered with a lid and a 100 g steel cylinder. The pressure on the SAM particles was 0.3 PSI. The cups were placed in 0.9% saline for 24 hours. The absorbed water was weighed for each cup. The AUL was then calculated by dividing the absorbed water by the weight of the SAM particles. The 24-hour AUL of AMPS / MEA was about 15% higher than that of AMPS, while the AUL of AMPS / HEA was about 8% lower than that of AMPS.

[0123] These results demonstrate that the AUL of the AMPS / MEA copolymer-based SAM particles is improved compared to the AMPS-only-based SAM particles and the AMPS / HEA copolymer-based SAM particles.

[0124] Example 3. Salt sensitivity.

[0125] Six AUL cups were divided into two groups. Each sample of the first group (3 cups) contained about 0.2g of AMPS SAM particles for AUL measurement at 0.3PSI. Each sample of the second group (3 cups) contained about 0.2g of AMPS / MEA SAM particles for AUL measurement at 0.3PSI. They were placed in aqueous solutions of different NaCl concentrations (0.225%, 0.45% and 0.9%, respectively). The 3-hour AUL of AMPS SAM particles in 0.9% NaCl solution was 20% lower than the AUL in 0.225% NaCl solution. In contrast, the 3-hour AUL of AMPS / MEA SAM particles in 0.9% NaCl solution was 12% lower than the AUL in 0.225% NaCl solution.

[0126] These results demonstrate that the salt sensitivity of SAM particles based on the copolymer of AMPS / MEA is reduced compared to SAM particles based on AMPS alone.

[0127] Example 4. Synthesis of copolymer compositions.

[0128] A variety of novel copolymer compositions were synthesized by replacing a portion of AA and / or AMPS (5, 10, 15, 20, 25, or 30 mol % of the total monomers present in the backbone) with different monomers using free radical polymerization in water to prepare copolymer hydrogels. Unless otherwise stated, acrylic acid was partially neutralized (70%), N,N′-methylene (bis) acrylamide (99% purity) was used as a crosslinker (0.21-0.23 mol % relative to total monomers), and potassium persulfate (≥99.0% purity) was used as a thermal initiator (0.08-0.1 mol % relative to total monomers).

[0129] Each polymerization reaction was performed according to the following procedure. A 200 mL glass reaction jar was immersed in an ice bath. NaOH pellets were dissolved in milli-Q water and AA or AMPS was added. For each series of reactions, stock solutions of defined concentrations of cross-linking agents (10 mg / ml) and (20 mg / ml) were freshly prepared before each synthesis. The required amount of cross-linking agent was added to each reaction mixture. The reaction mixture was purged with nitrogen for 5-10 minutes and the temperature was increased to 40°C. The beaker was sealed and kept under a low flow of nitrogen to ensure inert conditions throughout the polymerization process. After gelation occurred, the reaction was allowed to proceed for about another 4 hours, although macroscopic gelation of most samples was observed within 10-15 minutes. The prepared gel was cut into smaller pieces and dried in an oven at 85°C for 48 hours. The dried gel was ground and sieved, and all particles used for subsequent testing were collected between 600 μm and 300 μm standard sieves.

[0130] The specific motivations for the selected comonomers and details of their respective syntheses are as follows.

[0131] AMPS

[0132] AMPS are inexpensive and commercially available hydrophilic sulfonic acid-based monomers that have a permanent charge at pH values ​​well below physiological pH, providing highly hydrophilic and anionic properties over a wide pH range.

[0133] The hydrogels were prepared using the general conditions described above. Since AMPS is a strong acid, the calculation of the copolymerization with AA (AMPS+AA, corresponding to all AMPS and based on the pK of the two monomers) was a The amount of NaOH required to achieve 70% total ionization during the reaction (part of the residual AA). After the NaOH pellets and acrylic acid were completely dissolved in water, AMPS was added to the neutralized mixture. Gelation occurred in less than 10 minutes, although the reaction was continued for an additional 4 hours. All prepared gels appeared transparent and were neither sticky nor too brittle. The gels remained transparent when dry, although a slight yellow tint was observed, which disappeared when the gel was rehydrated.

[0134] HEMA

[0135] HEMA is a hydrophilic monomer widely used in commercial applications such as contact lenses. Based on the physical and chemical structure of the polymer, HEMA hydrogels have been reported to absorb 10% to 600% of water relative to the dry weight without charged residues, making the resulting swelling significantly less sensitive to salt (as needed). First, using the same conditions as described above, 10, 15, and 20 mol% of AA monomers were replaced with HEMA. However, even after increasing the amount of cross-linking agent or initiator by 10%, no gel formation was observed after 2 hours. Replacing potassium persulfate with ammonium persulfate as an initiator resulted in gelation within 15 minutes. The transparent gels were neither overly viscous nor brittle, and they remained transparent, although they were light yellow when dry.

[0136] VSA

[0137] Vinylsulfonic acid is a highly reactive unsaturated sulfonic acid. It is a colorless, water-soluble liquid, although commercial samples may appear yellow or even red. Polyvinylsulfonic acid (PVSA; as the sodium salt) is a blood-compatible polyelectrolyte with negatively charged sulfonate groups.

[0138] The hydrogel was prepared using the general conditions described above. Gelation occurred quickly (in about 15 minutes) to produce a clear but extremely viscous gel that was difficult to remove from the beaker. During the drying process, the gel remained viscous and turned pale yellow while remaining transparent. Due to its viscous nature, the gel was also difficult to grind.

[0139] PEGMMA (Mn = 300-500 g / mol)

[0140] PEGMMA is a highly hydrophilic, uncharged biocompatible monomer with a comb-like structure consisting of hydrophilic side chains containing ethylene oxide (EO) repeating units. The length of the side chain can be adjusted by using PEGMMA with different numbers of ethylene oxide (EO) groups, where short chains (n ​​= 2 repeating units) exhibit thermoresponsive properties, while long chains (n>8) exhibit high hydrophilicity. Poly (ethylene glycol) (PEG) is commonly used in biomaterials as a highly water-binding polymer that repels protein adsorption, and its high water binding (about 3-4 water molecules / ethylene oxide repeating unit) is attributed to hydrogen bonding with ether oxygen in the repeating unit and the steric flexibility of the polymer. When PEG of sufficient length is incorporated into PEGMMA as a side chain, it is expected to retain these similar water-binding properties that are relatively independent of salt concentration in the absence of charge, as well as the possibility of spatial screening of charge interactions between adjacent acrylic acid residues.

[0141] The hydrogels were prepared using the general conditions described above. However, phase separation was observed when the pre-gel mixture was heated to the 70°C set point temperature required for persulfate-based initiation. To prevent this phenomenon, the initiator was changed from a thermal initiator to a redox initiator, combining ammonium persulfate (APS) with a redox promoter N,N,N',N'-tetramethylethylenediamine (TEMED). Compared with other redox systems for low-temperature polymerization reactions, this system can provide lower induction periods and higher conversions at lower temperatures. By using this initiator, the polymerization of PEGMMA / AA was successfully carried out at both 40°C and room temperature without any visible phase separation. The monomer addition strategy was also changed to ensure that phase separation was avoided. The NaOH pellets were first dissolved in water, and a mixture of AA / PEGMMA monomers was added dropwise to a reaction flask using a dropping funnel on an ice bath. The reaction mixture was purged with N2 for 5-10 minutes, and then APS / TEMED was added to the reaction. Then, the temperature was increased to 40°C and the polymerization was continued for 4 hours, with gelation observed in about 10-15 min. Finally, the gel was cut, dried in an oven at 85°C, ground, and sieved as previously described. For some gels, a thin opaque layer formed on the outside of the gel after drying; however, most gels remained transparent as previously described for other comonomer systems. Samples were prepared using PEG side chains of different lengths (n=4, 9) and by replacing different mole % of AA with PEGMMA (10, 15 or 20 mole %).

[0142] PEGMA (Mn = 360 g / mol)

[0143] PEGMA is a highly hydrophilic biocompatible monomer with the same basic properties as PEGMMA, but the side chains are terminated with OH groups instead of methyl groups. In this context, PEGMA represents a direct analog of HEMA, in which the hydrophilic -OH group is further tethered to the polymer backbone; and a direct analog of PEGMMA, in which the ends of the PEG chains can be hydrogen bonds. Polymerization is performed using the same method as PEGMMA described above to obtain a similar transparent but very brittle gel with a PEGMA content in the range of 10-15 mol%. Hydrogels based on different combinations of AA / PEGMMA / PEGMA and PEGMA / VSA have also been synthesized to evaluate the potential of mixing monomers with different properties for swelling properties. In this context, hydrogels containing 90-75 mol% AA, 7, 10, 12, 15 or 20 mol% PEGMMA, 5, 8 or 10 mol% PEGMA and 2-5 mol% VS are prepared to evaluate relative swelling. Acrylic acid-only control samples were synthesized by each initiation system (ie, potassium persulfate at 70°C and ammonium persulfate / TEMED at 40°C) to ensure proper interpretation of the effect of comonomer content on the swelling response.

[0144] AMPS-PEGMMA copolymer hydrogel

[0145] To evaluate the possibility of using a mixture of strong acid comonomers and neutral high water binding comonomers, copolymer hydrogels of AMPS and PEGMMA were prepared using the same APS / TEMED redox initiation protocol used to formulate AA-PEGMMA hydrogels. PEGMMA contents in the range of 10-15 mol% were used, with AMPS constituting the remainder of the formulation. All other methods and chemical variables used were consistent with the general protocol.

[0146] Example 5. AUL and CRC results for copolymer compositions.

[0147] The swelling results, ie, the absorption under load (AUL) and the centrifuge retention capacity (CRC), for the copolymer composition prepared according to Example 4 are presented in Table 1 .

[0148] AUL was measured according to the procedure of Example 2.

[0149] In contrast to the AUL test in which a dry powder of SAP is hydrated under load, the CRC test measures the ability of a pre-swollen SAP to retain water under force. For the test, approximately 100 mg (W1) of dry SAP sample was weighed into a pre-weighed tea bag. The tea bag was immersed in a 0.9 saline solution for 1 hour to swell the SAP. Subsequently, the tea bag was placed in a cylindrical centrifuge tube containing a porous interior to allow drainage and centrifuged at 1600 rpm for 3 minutes. As a control, an empty tea bag was also placed in saline and centrifuged at the same speed. After centrifugation, the tea bag was weighed again (W2) and the difference between the dry sample and the swollen sample was calculated. The CRC amount was calculated by equation (2):

[0150]

[0151] All AUL measurements reported represent the average of 2-3 replicates per batch. Where more than one AUL number is reported, the second number represents an independent replicate batch. CRC was measured using a 100 g weight.

[0152] Table 1. AUL and CRC results of copolymer superabsorbent hydrogels prepared with different functional comonomers.

[0153]

[0154] The swelling results showed that the AUL was increased using most of the synthesized copolymers compared to the control hydrogels. This clearly demonstrates the benefit of copolymerizing monomers with different water binding mechanisms (PEGMMA, PEGMA, HEMA) into AA-based SAPs.

[0155] Copolymerization appeared to reduce the CRC of most hydrogels, with most copolymers resulting in a reduction in CRC of approximately 5%-26%. This opposite trend of CRC and AUL is consistent with conventional observations, although minimizing this CRC reduction is desirable.

[0156] The copolymerization of PEGMMA is unique in that the PEGMMA monomer phase separates directly upon addition to AA or during polymerization. Under such conditions (70°C, KPS initiation), very high increases in AUL were observed in some cases, up to twice that of the AA control. However, some of these formulations phase separated too much before gelation and subsequently failed to form a gel at all.

[0157] Example 6. PEGMMA-based hydrogel synthesized using APS / TEMED.

[0158] The high AUL values ​​and the small reduction in CRC relative to those achieved with AMPS or HEMA alone prompted the development of a reliable copolymerization strategy for PEGMMA-based hydrogels using an APS / TEMED system that can be polymerized at 40°C and avoids the need to heat the monomers above the temperature at which phase separation occurs. The results of such copolymerizations of AUL and CRC with PEGMMA, alone with AA and with some other potentially interesting comonomers such as PEGMA and VSA are shown in Table 2.

[0159] Table 1. AUL and CRC results of PEGMMA-based copolymer superabsorbent hydrogels prepared with different functional comonomers using a redox initiator system (APS / TEMED; temperature: 40°C).

[0160]

[0161] Using the APS / TEMED method, reproducible and visually more homogeneous hydrogels were obtained that maintained high increases in AUL of about 9%-33% relative to the AA-only control. The change in initiator system from KPS 70°C to APS / TEMED 40°C did not change the AUL or CRC measured for the AA-only control gels (e.g., compare row 1 of Table 1 with row 1 of Table 2). Thus, the new initiator system did not affect gel properties other than changing the degree of phase separation observed with the PEGMMA system.

[0162] Mixing PEGMMA (methyl-terminated side chains) and PEGMA (OH-terminated side chains) had minimal benefit in increasing AUL relative to PEGMMA alone, although gels prepared using PEGMA alone showed only a small increase in AUL and a larger decrease in CRC relative to either PEGMMA alone or PEGMA-co-PEGMMA copolymers.

[0163] Incorporation of small amounts of VSA into PEGMMA copolymer formulations significantly reduced the AUL but significantly increased the CRC relative to the PEGMMA-only formulation. However, these hydrogels remained somewhat viscous.

[0164] Replacing more than 15% of the acrylic acid with PEGMMA or any PEG derivative reduced the AUL benefit associated with the copolymer while (especially at 25% total monomer substitution) significantly reducing the CRC in all cases; similar trends were observed in several test formulations using 80% or less AA mole percentages in Table 1.

[0165] Example 7.

[0166] The significant reduction in CRC observed with the AA copolymer formulation that provided the best AUL results prompted investigation of the potential of using the strong acid AMPS as the primary charged monomer coupled with PEGMMA as the neutral water-binding monomer.

[0167] Table 3. AUL and CRC results of AMPS-PEGMMA superabsorbent hydrogels prepared using a redox initiation system (APS / TEMED; temperature: 40°C).

[0168]

[0169] Polymerization and gelation in poly(AMPS-co-PEGMMA) occurred very rapidly, even at room temperature. All samples began to exhibit easy gelation between about 27°C and 40°C. The samples appeared completely transparent and white, with good AUL (high 15%-20%) but very low CRC (35%-45%). In part, this result can be attributed to the challenges inherent in estimating the proper degree of neutralization of strong acids such as AMPS. Gelation did not occur unless an equivalent of at least 70% neutralized NaOH was added, and adding NaCl salt of the same molar concentration in place of NaOH did not promote gelation. Therefore, NaOH is a key factor in the success of this reaction, and therefore also a key factor in the performance of the resulting SAP.

[0170] Example 8.

[0171] Figure 1 Shown is the appearance of the AMPS-co-PEGMMA sample after swelling compared to the commercial (surface cross-linked) sample and the control (AA only, no surface cross-linking) sample.

[0172] The swelling kinetics of the AMPS-PEGMMA samples were measured using the ElastoSens Bio, a device that non-destructively measures the viscoelastic (complex Young's modulus) properties of soft biomaterials. Pre-weighed SAP was loaded into a removable sample holder, after which saline was added and the measurement started to continuously observe the long-term changes in the hydrogel modulus (and therefore water binding) during the swelling process. Figure 2 Shown is the shear storage modulus of each hydrogel as a function of time during the swelling process as measured with the ElastoSens Bio.

[0173] Based on the physical appearance of the samples, the AMPS-PEGMMA samples showed better performance in terms of water permeability and gel strength after swelling relative to the AA-only control, even in the absence of any surface cross-linking. These results present potential advantages in the practical application of copolymer hydrogels as SAPs.

[0174] Quantitative measurements of swelling indicated similar effects, with the AMPS-PEGMMA samples swelling significantly faster and with an increase in modulus more similar to surface cross-linked commercial SAPs. These results suggest that modified formulations can be engineered to have properties similar to existing commercial samples while avoiding the additional cost and leaching issues inherent to surface cross-linking.

[0175] Example 9.

[0176] AA-PEGMMA hydrogels were prepared using PEG di(meth)acrylate crosslinkers with different numbers of ethylene oxide groups (EGDMA-1 PEG unit; PEGDA-5 PEG units; PEGDMA-7 PEG units) to explore the effects of the hydrophilicity and flexibility of the crosslinker on swelling. Table 4 shows the resulting AUL and CRC values ​​for this test.

[0177] Table 4. AUL and CRC results showing superabsorbent hydrogels synthesized using PEG di(meth)acrylate crosslinkers containing different numbers of PEG groups prepared with a redox initiator system (APS / TEMED; temperature: 40°C).

[0178]

[0179] Hydrogels with similar swelling properties to the MBAA control can be prepared with n=1 EGDMA crosslinkers and n=5 PEGDA crosslinkers, although the AUL achieved with the PEGDA crosslinker is significantly higher than with the EGDMA crosslinker. However, the longer chain n=7 PEGDMA crosslinker, while successful in producing hydrogels, resulted in very sticky hydrogels that could not be ground into powders. This result is attributed to the increased steric flexibility of the longer PEG chains within the crosslinker.

[0180] Example 10.

[0181] AA-PEGMMA hydrogels were prepared using different molecular weights of PEGMMA (Mn=188-2 PEG units; Mn=300-4-5 PEG units; Mn=500-7-8 PEG units) to evaluate the effect of PEG side chain length and hydrophilicity on the resulting swelling response. Table 5 shows the resulting AUL and CRC values.

[0182] Table 5. AUL and CRC results of AA-co-PEGMMA superabsorbent hydrogels synthesized with PEGMMA monomers containing PEG side chains of different lengths prepared with a redox initiator system (APS / TEMED; temperature: 40°C).

[0183]

[0184] While each PEGMMA chain length tested gave similar CRC values ​​(about 25% lower than the AA control), only the PEGMMA 300 comonomer provided significantly higher AUL values ​​relative to the AA-only control. Longer PEGMMA 500 monomers produce hydrogels with long side chains that can adopt more brush-like structures; in addition, the enhanced steric inhibition associated with copolymerization of longer side chain comonomers can lead to lower crosslinker density and thus lower AUL values. Shorter PEGMMA 188 monomers produce polymers with lower critical solution temperatures of about room temperature when homopolymerized; therefore, the lower AUL can be attributed to the introduction of some hydrophobicity into the hydrogel network, thereby offsetting the entropic contribution of swelling associated with adding more chain ends within the hydrogel volume. For PEGMMA 188 and some PEGMMA 300, the resulting dried hydrogels appear white and sometimes opaque, indicating phase separation even at the lower 40°C reaction temperature.

[0185] Example 11. Effect of cross-linker length.

[0186] To evaluate the effect of cross-linker length on SAP performance, the performance of hydrogels prepared with PEG diacrylate-based cross-linkers with various PEG chain lengths was analyzed for AA-co-AMPS copolymers. An AA-only control was also prepared using the same cross-linker type / amount to enable direct comparison of the observed swelling responses.

[0187] Hydrogels were prepared using the same protocol generally used for each comonomer mixture, but replacing the MBAA content with PEGDA, EGDMA, or PEGDMA at the same molar ratio. Gelation occurred within a few minutes to produce clear gels, although the hydrogels crosslinked by EGDMA and PEGDMA were slightly more viscous than the control.

[0188] It was determined that higher AUL values ​​can be achieved by using higher crosslink density. However, at 70%, 75%, or 80% neutralization, consistently high AULs were observed. This relative independence of the degree of neutralization is a process-related benefit of formulating SAPs using the AMPS copolymerization process, as hydrogels containing only AA are more sensitive to the degree of neutralization of the reaction mixture.

[0189] Example 12. Comparison between PEGMMA-based and PEGMA-based PAMs.

[0190] Table 6 compares the AUL and CRC data of many AA, AA / PEGMMA (with terminal hydroxyl terminated by methyl) and AA / PEGMA (with terminal hydroxyl) PAMs. The only difference between PEGMMA and PEGMA is that the terminal hydroxyl of PEGMMA is terminated by methyl, and PEGMA has terminal hydroxyl. Both average molecular weights are 300g / mol. For AA monomer units, all SAM particles have the same molar cross-linking agent density of 0.2% and the neutralization level of 70%. By using the same procedure to prepare polymerization conditions and particles under the same conditions. Obtain AUL and CRC measurements under the same conditions.

[0191] Pure PEGMMA and PEGMA SAM particles were not obtained due to the stickiness of pure PEGMMA and PEGMA hydrogels. AA / PEGMMA SAM particles with higher than 15% PEGMMA were obtained due to the lack of compatibility of PEGMMA in high concentrations of PEGMMA.

[0192] The data in Table 6 demonstrate that incorporation of a minor portion of methyl-terminated neutral PEGMMA significantly increases the AUL compared to PAA without PEGMMA. Incorporation of a small amount of PEGMA into PAA has no significant effect on the AUL. However, too much PEGMA has a significant negative effect on the AUL.

[0193] Table 6. AUL results of AA-co-PEGMMA and AA-co-PEGMA superabsorbent hydrogels.

[0194] composition AUL (1 hour) AA 100% 12.5 AA 95% / PEGMMA 5% 13.6 AA 90% / PEGMMA 10% 16.5 AA 85% / PEGMMA 15% 16.8 AA 90% / PEGMA 10% 12.2 AA 85% / PEGMA 15% 11.1 AA 80% / PEGMA 20% 10.1 AA 70% / PEGMA 30% 7.5

[0195] Table 7 compares the absorption properties of AMPS, AMPS / MEA, and AMPS / HEMA based SAM particles. All SAMs have the same molar crosslinker density of 0.24% MBAA and have the same neutralization during polymerization. Incorporation of a minor portion of MEA into AMPS based SAMs increases the AUL, while incorporation of HEA into AMPS based SAMs decreases the AUL. Methylation of the hydroxyl groups in HEA converts HEA to MEA. Therefore, methyl capping of the hydroxyl groups in HEA improves the absorption properties. The hydrogels of pure HEA and MEA were too viscous to be processed into SAM particles. AUL data were collected at 1 hour and 24 hours at 0.3 PSI in 0.9% saline.

[0196] Table 7. AUL results of AA-co-MEA and AA-co-HEA superabsorbent hydrogels.

[0197] SAM Composition 1 hour AUL 24-hour AUL AMPS 5.9 18.1 AMPS 80% / MEA 20% 7.7 23.3 AMPS 70% / MEA 30% 7.1 22.0 AMPS 60% / MEA 40% 6.1 19.6 AMPS 80% / HEA 20% 4.9 16.2 AMPS 70% / MEA 30% 4.7 15.1

[0198] The results herein demonstrate that copolymerization of monomers with different mechanisms for binding water significantly alters the absorbency of AA-based hydrogels. AA-PEGMMA and AMPS-PEGMMA copolymer hydrogels show particularly good AUL responses.

[0199] This written description uses examples to illustrate the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any compositions or systems and performing any included methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have elements that do not differ from the literal language of the claims, or if they have equivalent elements with insubstantial differences from the literal language of the claims.

[0200] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," "characterized by," or any other variation thereof, are intended to cover a non-exclusive inclusion, subject to any expressly indicated limitation. For example, a composition, mixture, process, or method that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, mixture, process, or method.

[0201] The transitional phrase "consisting of" excludes any elements, steps, or ingredients not specified. If in a claim, this would make the claim close to including materials other than those recited in addition to the impurities normally associated therewith. When the phrase "consisting of" appears in a clause in the body of a claim, rather than immediately following a preamble, it is limited only to the elements set forth in that clause; other elements are not excluded from the claim as a whole.

[0202] The transitional phrase "consisting essentially of is used to define a composition or method that includes materials, steps, features, components, or elements in addition to those literally disclosed, provided that such additional materials, steps, features, components, or elements do not materially affect the basic and novel characteristics of the claimed invention. The term "consisting essentially of occupies an intermediate position between "comprising" and "consisting of."

[0203] When an invention or a portion thereof is defined using an open-ended term such as "comprising," it should be readily understood that (unless otherwise indicated) the specification should be interpreted as also describing the invention using the term "consisting essentially of" or "consisting of."

[0204] In addition, unless expressly stated to the contrary, "or" refers to an inclusive or rather than an exclusive or. For example, the condition A or B satisfies any of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist).

[0205] In addition, the indefinite articles "a" and "an" before the elements or components of the present invention are intended to be non-restrictive with respect to the number of instances (i.e., occurrences) of the elements or components. Therefore, "a" or "an" should be understood to include one or at least one, and the singular word form of an element or component also includes the plural, unless the number obviously means the singular.

[0206] As used herein, the term "about" means plus or minus 10% of a value.

Claims

1. A superabsorbent polymer, comprising A copolymer comprising The main part of the charged monomer; a minor portion of alkyl- or aryl-terminated neutral and hydrophilic monomers; as well as optional cross-linking agent; wherein the alkyl or aryl terminated neutral and hydrophilic monomer contains no free hydroxyl groups and has a water solubility of at least 200 mg / mL; wherein the major portion is present in an amount greater than 50 mole % of the copolymer, and the minor portion is present in an amount greater than 5 mole % and less than 50 mole % of the copolymer; wherein the minor portion comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight of less than 1000 g / mol; wherein said copolymer is free of a structured ordered arrangement of said charged monomers and said alkyl or aryl terminated neutral and hydrophilic monomers; wherein the charged monomer is selected from the group consisting of acrylic acid, vinyl sulfonic acid, vinyl phosphoric acid, partially hydrolyzed maleic anhydride; and wherein the alkyl or aryl terminated neutral and hydrophilic monomer is selected from the group consisting of polyethylene glycol monomethyl ether monomethacrylate, methoxyethyl acrylate, a compound according to formula I: Where n is a number in the range of 1-50 and R 1 and R 2 Each is independently selected from the group consisting of hydrogen, a linear or branched C1-C6 alkyl group, and combinations thereof.

2. The superabsorbent polymer of claim 1, wherein the major portion is present in an amount greater than 65% by weight of the copolymer and the minor portion is present in an amount less than 35% by weight of the copolymer.

3. The super absorbent polymer of claim 1, wherein the super absorbent polymer is in a form selected from the group consisting of particles, gels, fibers, beads, liquids, solids, pastes, or combinations thereof.

4. The super absorbent polymer of claim 1, wherein the super absorbent polymer is in the form of particles having a diameter ranging from 100 μm to 1000 μm.

5. The superabsorbent polymer of claim 1, wherein the superabsorbent polymer is surface cross-linked.

6. The superabsorbent polymer of claim 1, wherein the crosslinking agent density is in the range of 0.05 wt% to 1 wt%.

7. The superabsorbent polymer of any one of claims 1 to 6, wherein the minor portion of alkyl or aryl terminated neutral and hydrophilic monomers comprises alkyl or aryl terminated neutral and hydrophilic monomers having a water solubility in the range of 200 mg / mL to 500 mg / mL.

8. A method for preparing a superabsorbent polymer, the superabsorbent polymer comprising A copolymer comprising The main part of the charged monomer; a minor portion of alkyl or aryl terminated neutral and hydrophilic monomers; and optional cross-linking agent; wherein the alkyl or aryl terminated neutral and hydrophilic monomers are free of free hydroxyl groups and have a water solubility of at least 200 mg / mL, wherein the major portion is present in an amount greater than 50 mol% of the copolymer, and the minor portion is present in an amount greater than 5 mol% and less than 50 mol% of the copolymer; wherein the minor portion comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight less than 1000 g / mol; and wherein the copolymer is free of a structured ordered arrangement of the charged monomers and the alkyl or aryl terminated neutral and hydrophilic monomers, the method comprising forming a mixture comprising Solvents Charged monomer; Alkyl or aryl terminated neutral and hydrophilic monomers; and Optional cross-linking agent Provoke a reaction; and reacting the mixture, wherein the charged monomer is selected from the group consisting of acrylic acid, vinyl sulfonic acid, vinyl phosphoric acid, partially hydrolyzed maleic anhydride; and wherein the alkyl or aryl terminated neutral and hydrophilic monomer is selected from the group consisting of polyethylene glycol monomethyl ether monomethacrylate, methoxyethyl acrylate, a compound according to formula I: Where n is a number in the range of 1-50 and R 1 and R 2 Each is independently selected from the group consisting of hydrogen, a linear or branched C1-C6 alkyl group, and combinations thereof.

9. The method of claim 8, wherein the method step of initiating a reaction comprises adding an initiator, a accelerator, or a combination thereof to the mixture.

10. The method of claim 8, wherein the method step of reacting the mixture comprises reacting the mixture in an inert atmosphere.

11. The method of claim 8, wherein the method step of reacting the mixture comprises heating the mixture.

12. The method of claim 8, wherein the method further comprises drying the produced superabsorbent polymer.

13. The method of claim 8, wherein the method further comprises grinding the produced superabsorbent polymer.

14. A method of using a superabsorbent polymer, the superabsorbent polymer comprising A copolymer comprising The main part of the charged monomer; a minor portion of alkyl or aryl terminated neutral and hydrophilic monomers; and optional cross-linking agent; wherein the alkyl or aryl terminated neutral and hydrophilic monomers are free of free hydroxyl groups and have a water solubility of at least 200 mg / mL, wherein the major portion is present in an amount greater than 50 mol % of the copolymer, and the minor portion is present in an amount greater than 5 mol % and less than 50 mol % of the copolymer; wherein the minor portion comprises alkyl or aryl terminated neutral and hydrophilic monomers having a molecular weight less than 1000 g / mol; and wherein the copolymer is free of a structured ordered arrangement of the charged monomers and the alkyl or aryl terminated neutral and hydrophilic monomers, the method comprising using the superabsorbent polymer in a consumer product, wherein the charged monomer is selected from the group consisting of acrylic acid, vinyl sulfonic acid, vinyl phosphoric acid, partially hydrolyzed maleic anhydride; and wherein the alkyl or aryl terminated neutral and hydrophilic monomer is selected from the group consisting of polyethylene glycol monomethyl ether monomethacrylate, methoxyethyl acrylate, a compound according to formula I: Where n is a number in the range of 1-50 and R 1 and R 2 Each is independently selected from the group consisting of hydrogen, a linear or branched C1-C6 alkyl group, and combinations thereof.

15. The method of claim 14, wherein the superabsorbent polymer is in the form of particles having a diameter ranging from 100 μm to 1000 μm.

16. The method of claim 14 or 15, wherein the consumer product is selected from the group consisting of cloth products, diapers, feminine hygiene napkins and disposable mattress pads.

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