Chain transfer agents and methods of preparing the same

Abstract

A polymer including a residue of a chain transfer agent and a polymerized monomer is provided. The monomer can include (meth / eth / prop)acrylamide or derivative thereof; (meth / eth / prop)acrylic acid or acidic derivative thereof; C1-C18 alkyl (meth / eth / prop)acrylate; hydroxy-functional C1-C18 alkyl (meth / eth / prop)acrylate; or a combination thereof. The chain transfer agent can be water compatible. The chain transfer agent can include homocysteine or derivatives thereof; C2-C18 mono- and di-thiols; C3-C12 ethylene glycol-based mono- and di-thiols; thioglycolic acid or derivative thereof; or the like; or a combination thereof. At least one polymer terminal end of the polymer can include the residue of the chain transfer agent. A link between the polymer terminal end and the residue of the chain transfer agent can include a sulfur atom. A method of preparing such a polymer is also provided.

Description

[0001] CHAIN TRANSFER AGENTS AND METHODS OF PREPARING THE SAME

[0002] FIELD

[0003] The invention is related to molecular weight regulation of polymers using thiofunctional chain transfer agents.

[0004] BACKGROUND

[0005] Low molecular weight water soluble or water swellable polymers, especially poly(meth)acrylamide or derivatives thereof, poly(meth)acrylic acid, or mixtures or copolymers thereof have many useful attributes. However, preparation of low molecular weight polymers having controlled properties can require large amounts of chain transfer agent, which can adversely affect the properties of the resulting polymer. For example, due to undesirable side reactions, bimodal and multi modal polymers may inadvertently be formed. Certain chain transfer agents can also impart odor to the resulting polymer. In addition, low or no odor polymers are especially desirable for many applications.

[0006] Previous attempts to prepare such materials are described below.

[0007] U.S. Patent Application Publication No. 2020383896 discloses functionalized polymers and processes for preparing them.

[0008] U.S. Patent No. 5,916,985 discloses functionalized hydrophobic polymer.

[0009] U.S. Patent No. 6,433,061 discloses a rheology modifying copolymer composition containing a cross-linked copolymer of unsaturated carboxylic acid, a hydrophobic monomer, a hydrophobic chain transfer agent, a cross linking agent, and, optionally, a steric stabilizer. The composition provides increased viscosity in aqueous electrolyte containing environments.

[0010] U.S. Patent No. 5,298,585 discloses polymers having amine sulfide terminal moieties. Amine thiols are used as chain transfer agents.

[0011] C. Henriquez, et al. Polymer, 44 (2003), 5559-5561, discloses the behavior of thiophenol and aliphatic thiols of different structure as chain transfer agents in the polymerization of acrylamide and l-vinyl-2-pyrrolidone in aqueous solution at 25°C. Mahdavian, Ali-Reza, et al., Journal of Applied Polymer Science, 93(5), (2004): 2007-

[0012] 2013, describes measurement of kinetics of polyacrylamide formation;

[0013] There remains a need for chain transfer agents useful for providing low odor or no odor, low molecular weight water soluble or water swellable polymers, especially homo- and copolymers of (meth)acrylamide and / or derivatives thereof and homo- and co-polymers of (meth)acrylic acid and / or derivatives thereof. There also remains a need for polymers produced using such chain transfer reagents.

[0014] SUMMARY

[0015] It has been found that homocysteine and certain derivatives thereof can be excellent chain transfer agents for preparation of low molecular weight homo- and co-polymers of (meth)acrylamide and / or derivatives thereof and homo- and co-polymers of (metli / eth / prop)acrylic acid and / or acidic derivatives thereof. Unexpectedly, homocysteine and certain of its derivatives can perform significantly better as chain transfer agents than other similar thiol-functional chain transfer agents. For example, cysteine, which differs from homocysteine by merely a single methylene is typically not as effective a chain transfer reagent as homocysteine. Also importantly, homocysteine, when used as a chain transfer agent, does not impart unpleasant, nor indeed any, odor to the resulting polymer in appropriate quantities.

[0016] Aqueous (solution / emulsion) polymerization of (meth)acrylamide and derivatives thereof is a well-known procedure to produce low molecular weight poly(meth)acrylamide to date. Chain transfer agents such as sodium hypophosphite have been used to control molecular weight of these polymers. Mercaptans may be useful chain transfer agents that are comparable to sodium hypophosphite for producing low molecular weight polymers, especially polyacrylamide, but the sulfur-containing nature of mercaptan compounds can tend to provide polymer having an unpleasant odor.

[0017] Advantageously, at concentrations typically used for polymer chain transfer agents, homocysteine is typically an odor-free component. Therefore, free-radical polymerized polymers with odor sensitive applications may be beneficially produced using homocysteine as a chain transfer agent. In addition, homocysteine could be useful when phosphorous and its derivatives are undesirable for the final application of the polymer. According to an embodiment, L-homocysteine, D-homocysteine or a D / L homocysteine mixture (such as a racemic mixture), or derivatives thereof may be suitable as chain transfer agent(s) for poly((meth / eth / prop)acrylic acid) or acidic derivatives thereof in order to reduce the molecular weight of these polymers.

[0018] A polymer including a residue of a chain transfer agent and a polymerized monomer is described. The monomer can include: (meth)acrylamide or derivative thereof, (meth / eth / prop)acrylic acid or acidic derivative thereof, or any combination thereof. The chain transfer agent can advantageously be water-compatible (e.g., water soluble or water miscible). The chain transfer agent can include homocysteine or derivatives thereof; C2-C 18 mono- and di- thiols; C3-C 12 ethylene glycol-based mono- and di- thiols; thioglycolic acid or derivative thereof; compounds of Formula (I) (below'); or any combination thereof. At least one polymer terminal end of the polymer can include the residue of the chain transfer agent. A link between the polymer terminal end and the residue of the chain transfer agent can include a sulfur atom (S).

[0019] A method of preparing a polymer is also provided. The method can include the following steps:

[0020] First, combining the following to form a reaction mixture:

[0021] • Monomer comprising (meth)acrylamide or derivative thereof; (meth / eth / prop)acrylic acid or acidic derivative thereof ; or combination thereof;

[0022] • a free-radical initiator;

[0023] • a water compatible chain transfer agent comprising at least one of homocysteine or derivatives thereof; C2-C18 mono- and di- thiols; C3-C10 ethylene glycol-based mono- and di- thiols; thioglycolic acid or derivative thereof; compounds of Formula (I); and a combination thereof; and

[0024] • an optional carrier, preferably comprising water.

[0025] Second, reacting the reaction mixture to form the polymer.

[0026] The polymer thus formed can include the (meth)acrylamide or derivative thereof; (meth)acrylic acid or derivative thereof; or combination thereof as polymerized monomer, and a residue of the chain transfer agent. At least one polymer terminal end of the polymer can include the residue of the chain transfer agent, wherein a link between the polymer terminal end and the residue of the chain transfer agent can include a sulfur atom (S).

[0027] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0030] Figure 1 shows a reactor set up for polymerization;

[0031] Figure 2 shows an NMR spectrum used for determining monomer conversion in Example 1;

[0032] Figure 3 shows GPC results of polyacrylamide produced without chain transfer agent (Example 1, run 5) compared to polyacrylamide produced with L -homocysteine as chain transfer reagent (Example 1, run 8);

[0033] Figure 4 shows the plot of the Mayo equation used to determine the chain transfer constant for L-homocysteine;

[0034] Figure 5 shows the GPC chromatograms of polyacrylamides prepared in Example 2;

[0035] Figure 6 shows the number average molecular weight of polyacrylamide prepared using various levels of L-homocysteine.

[0036] Figure 7 shows1H NMR spectra of L-homocysteine (top) and polyacrylamide at various L-homocysteine loadings; and

[0037] Figure 8 shows1H NMR spectra of L-homocysteine (top), as reacted polyacrylamide (middle) and purified polyacrylamide (bottom).

[0038] DETAILED DESCRIPTION

[0039] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. The present disclosure is directed to the use of certain chain transfer agents to form low molecular weight polymers. It has been found that homocysteine can be used in relatively large amounts as an effective chain transfer agent to provide relatively low molecular weight polymers. Poly(meth)acrylamide and co-polymers thereof can particularly advantageously be formed. The present disclosure is also directed to methods of preparing polymers, especially poly (meth)acrylamide and co-polymers thereof, as well as poly(meth / eth / prop)acrylic acid and acidic derivatives thereof.

[0040] A polymer comprising a residue of a chain transfer agent and a polymerized monomer is described herein. The monomer to be polymerized can include: (meth)acrylamide or derivative thereof, (meth / eth / prop)acrylic acid or acidic derivatives thereof, or any combination thereof. The chain transfer agent can be water-compatible (e.g. , water soluble or water miscible). Additionally or alternatively, the polymer itself can be water-compatible. As used herein, the term ‘"water soluble” should be understood to mean resulting in no suspended or settled particulates when combined with essentially pure distilled water at room temperature -20-25°C, as determined by human visual observation after stirring for -60 minutes at -500 rpm and after remaining quiescent thereafter for -5 minutes. As used herein, the term “water miscible” should be understood to mean resulting in no settled particulates when combined with (a) essentially pure distilled water, or (b) a single phase of distilled water combined with up to 50 wt% of a cosolvent having a dielectric constant (relative permittivity) of at least 4.0, at room temperature ~20-25°C, as determined by human visual observation after stirring for -60 minutes at -500 rpm and after remaining quiescent thereafter for -5 minutes. As used herein, the term “water compatible” encompasses at least “water soluble” and “water miscible”, potentially as well as other situations in which (i) both initiation and propagation can occur in a medium comprising at least 1 wt% of water, and (ii) chain transfer by functional mercaptan CTAs in such a medium is sufficient / effective to control polymer molecular weight.

[0041] The chain transfer agent can include homocysteine or derivatives thereof; compounds according to Formula (I) herein; C2-C18 mono- and di- thiols; C3-C12 ethylene glycol-based mono- and di- thiols; thioglycolic acid or derivative thereof; or any combination thereof (in particular, homocysteine, derivatives thereof, and compounds according to Formula (I)). At least one polymer terminal end of the polymer can include the residue of the chain transfer agent. In some embodiments, the chain transfer agent can comprise substantially no, or no intentionally added, C2-C18 mono- and di- thiols, C3-C12 ethylene glycol-based mono- and di- thiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine. A link between the polymer terminal end and the residue of the chain transfer agent can advantageously include a sulfur atom (S).

[0042] A method of preparing a (e.g, water-compatible) polymer is also provided. The method includes the steps:

[0043] Combining the following to form a reaction mixture.

[0044] • (Meth)acrylamide or derivative thereof; (meth / eth / prop)acrylic acid or acidic derivative thereof; or combination thereof;

[0045] • A free-radical initiator;

[0046] • A water compatible chain transfer agent comprising at least one of homocysteine or derivative thereof; a compound according to Formula (I); C2-C18 mono- and di- thiols; C3-C 10 ethylene glycol-based mono- and di- thiols; thioglycolic acid or derivative thereof; or a combination thereof (in particular, homocysteine, a derivative thereof, and / or a compound of Formula(I); additionally or alternatively, comprising substantially no, or no intentionally added, C2-C18 mono- and di- thiols, C3-C12 ethylene glycol-based mono- and di- thiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine); and

[0047] • An optional carrier, preferably comprising water.

[0048] The next step is reacting the reaction mixture to form the (e.g, water-compatible) polymer. However, although reaction is referred to herein as the “next step," it is both possible and contemplated for the combination step to overlap the reaction step, instead of serially following completion of the combination step, such as in (semi-)continuous reactors and / or where portions of one or more of initiator, monomer, and / or chain transfer agent (and / or optionally also carrier) may be added after reaction begins (but typically before it is complete).

[0049] The (e.g. , water-compatible) polymer thus formed can include the (meth)acrylamide or derivative thereof; (meth / eth / prop)acrylic acid or acidic derivative thereof; or combination thereof as polymerized monomer, and a residue of the chain transfer agent. At least one polymer terminal end of the polymer can include the residue of the chain transfer agent, wherein a link between the polymer terminal end and the residue of the chain transfer agent can include a sulfur atom (S).

[0050] Chain transfer agents:

[0051] Suitable chain transfer agents can be water-compatible (typically water soluble or water miscible). The chain transfer agent can include at least one of homocysteine or derivatives thereof; C2-C18 mono- and di- thiols; C3-C12 ethylene glycol-based mono- and di- thiols such as 1,8- dimercapto-3,6-dioxaoctane; thioglycolic acid or derivatives thereof; and compounds of Formula

[0052] (I)-

[0053] General formula (I) is shown below: (I) where C* is a chiral carbon and where: R1and R7are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms (but, when n 1, preferably wherein neither R1nor R7are acetyl groups or in particular wherein neither R1nor R7form an amide group with the attached nitrogen); X is selected from: >C( =O), -CH2- or -CN; R2is selected from: (i) absent when X represents -CN, (ii) a hydrogen atom, (iii) -OR3, where: R3is a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms, or (iv) -NR4R5, where: R4and R5are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms; and n is an integer from 1 to 4.

[0054] When R1= R7= H, R2-OH (with R3being H), X = >C-O, and n - 2, Formula (I) is homocysteine. When Rl= R7= H, R2= -OH (with R3being H), X = >C-O. and n = 1 , Formula (I) is cysteine. As a result, and because cysteine is typically not an effective CTA and because homocysteine is separately itemized, the text following Formula (I) is written such that cysteine and homocysteine are excluded.

[0055] According to certain embodiments, the chain transfer agent can advantageously include homocysteine or derivative thereof, specifically L-homocysteine, D-homocysteine, or racemic mixtures of homocysteine. Typically, at least L-homocysteine can be present.

[0056] Chemical derivatives of homocysteine can be useful as chain transfer agent, according to some embodiments. Non-limiting examples include converting the COOH to NH2 or other functional groups, for example according to Formula I. Additionally or alternatively, the chain transfer agent can comprise substantially no, or no intentionally added, C2-C18 mono- and dithiols, C3-C12 ethylene glycol-based mono- and di- thiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine.

[0057] Cysteine, homocysteine, and the other mercaptans of Formula (I) are referred to as functionalized mercaptans, because, in addition to the -SH moiety, they also comprise at least one amine moiety, such as -NR1R7.

[0058] Additionally or alternatively, in embodiments of Formula (I), one or more of the following may be satisfied:

[0059] • n can be from 1 to 3, for example 1 or 2, or 2 or 3. or in particular n can be 2;

[0060] • X can be >C-O;

[0061] • R2can be OR3, and R3may be a hydrogen atom or a linear or branched, saturated hydrocarbon moiety of 1 to 10 carbon atoms, such as 1 to 5 carbon atoms, optionally comprising one or more heteroatoms, or in particular R3may be H: and

[0062] • R1and R7may individually be a hydrogen atom or a linear or branched, saturated hydrocarbon moiety of 1 to 10 carbon atoms, such as 1 to 5 carbon atoms, optionally comprising one or more heteroatoms (but typically not so as to form an amide group with the attached nitrogen atom and preferably not comprising an acetyl group), or in particular R1and R7are both H,

[0063] • with the proviso that Formula (I) does not include cysteine or acetylcysteine.

[0064] According to some embodiments, mixtures of chain transfer agents in combination with the chain transfer agent homocysteine and / or its derivatives as described above are contemplated. For example, combinations of homocysteine with l,8-dimercapto-3,6-dioxaoctane can be used to achieve acceptable chain transfer activity. According to an embodiment, other water-soluble chain transfer agents may be used in combination with the homocysteine and / or its derivatives or in combination with one or more compounds according to Formula (I). Non-limiting examples of chain transfer agents that may be blended in this way can include thioglycolic acid, C2-C 18 mono- and di- thiols: C3-C12 ethylene glycol-based mono- and di- thiols such as l,8-dimercapto-3,6- dioxaoctane; optionally sodium hypophosphite; or combinations thereof.

[0065] According to some embodiments, the chain transfer agent may include at least 10, 20, 30, 40, 50, 60, 70, 80, or at least 90 % by weight of homocysteine and / or a derivative thereof. According to some embodiments, the chain transfer agent includes at least 10, 20, 30, 40, 50, 60, 70, 80, or at least 90 % by weight of homocysteine. According to some embodiments, the chain transfer agent includes at least 10, 20, 30, 40, 50, 60, 70, 80, or at least 90 % by weight of L- homocysteine and / or a derivative thereof. According to some embodiments, the chain transfer agent includes at least 10, 20, 30, 40, 50, 60, 70, 80, or at least 90 % by weight of L-homocysteine.

[0066] According to some embodiments, the chain transfer agent may include at most 100%, 90, 80, 70, 60, 50, 40, 30, or at most 20 % by weight of homocysteine and / or a derivative thereof. According to some embodiments, the chain transfer agent may include at most 100%, 90, 80, 70, 60, 50, 40, 30, or at most 20 % by weight of homocysteine. According to some embodiments, the chain transfer agent may include at most 100%, 90, 80, 70, 60, 50, 40, 30, or at most 20 % by weight of L-homocysteine and / or a derivative thereof. According to some embodiments, the chain transfer agent may include at most 100%, 90, 80, 70, 60, 50, 40, 30, or at most 20 % by weight of L-homocysteine.

[0067] According to an embodiment, the chain transfer agent does not include cysteine. Additionally or alternatively, the chain transfer agent can comprise substantially no, or no intentionally added, C2-C18 mono- and di- thiols, C3-C12 ethylene glycol-based mono- and dithiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine.

[0068] Monomers:

[0069] The monomer(s) can include at least one of (meth / eth / prop)acrylamide or derivative thereof, (meth / eth / prop)acrylic acid or acidic derivatives thereof, C1-C18 alkyl (meth / eth / prop)acrylates, hydroxy-functional C1 -C18 alkyl (meth / eth / prop)acrylates, and any combination thereof. The monomer(s) can advantageously include (meth)acrylamide, (meth)acrylic acid, Cl -Cl 4 alkyl (meth)acrylates, and / or hydroxy-functional C1-C6 alkyl (meth)aciylates. As is known in the art, the term, "(meth / eth / prop)” in “(meth / eth / prop)acrylamide'‘ and the like is understood to encompass acrylamide and methacrylamide and ethacrylamide and propacrylamide, for example. This convention applies to all such uses of the terms "(meth / 'eth / prop)" and "(meth)” in compounds recited herein.

[0070] Nonlimiting examples of suitable derivatives of (meth / eth / prop)acrylamide can include acrylamide, methacrylamide, phosphoalkyl (meth / eth / prop)acrylamides N-(3- dimethylaminopropyl)acrylamide, N-(3-dimethylaminopropyl)-methacrylamide, N- dimethylaminoethylacrylamide, N-diethylaminoethyl-methacry lamide, N- diethylaminoethylacrylamide, N -diethy laminoethy 1-methacry lamide, N-(4 morpho linomethy 1 )acry lamide , N-(4 morpholinomethyl)methacrylamide, N-[3-(l,3- diazacryclohexan)-2-one-propyl]methacrylamide, and combinations thereof.

[0071] The at least one of (meth / eth / prop)acrylamide or derivative thereof, (meth / eth / prop)acrylic acid or acidic derivatives thereof, C1 -C18 alkyl (meth / eth / prop)acrylates. hydroxy-functional Cl- C18 alkyl (meth / eth / prop)acrylates, and combinations thereof may be polymerized itself / copolymerized themselves, or may be copolymerized with one or more other co-monomers, to form a (di-, tri-, multi-) block, alternating, random, gradient, branched, linear, crosslinked, grafted, syndiotactic, isotactic, atactic, and / or other type of copolymer. Non-limiting examples of such other co-monomers, can include styrene or derivatives thereof; acrylonitrile or derivatives thereof; other vinylic esters: or combinations thereof. Additional and / or alternative non-limiting examples of suitable co-monomers can include other vinyl monomers, e.g., vinyl cyanide monomers / acrylonitrile, vinyl alcohol, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, n-butylacrylate, n- butylmethacrylate, tert-butylacrylate, tert-butylmethacrylate, n-pentyl acrylate, n-pentyl methacrylate, isopentyl acrylate, isopentyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, isohexyl acrylate, isohexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, iso-octyl methacrylate, iso-octyl acrylate, n-decyl acrylate, n-decyl methacrylate, isodecyl acrylate, isodecyl methacrylate, lauryl acrylate, lauryl methacrylate, myristyl acrylate, myristyl methacrylate, palmityl acrylate, palmityl methacrylate, n-stearyl acrylate, n-stearyl methacrylate, isostearyl acrylate, isostearyl methacrylate, eicosanoyl acrylate, eicosanoyl methacrylate, docosanoyl acrylate, docosanoyl methacrylate, tetracosanoyl acrylate, tetracosanoyl methacrylate, isobomyl acrylate, isobomyl methacrylate, phenyl acrylate, phenyl methacrylate, naphthyl acrylate, naphthyl methacrylate, benzyl acrylate, benzyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, ethoxyethyl acrylate, ethoxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, methoxypropyl acrylate, methoxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl methacrylate, maleic anhydride, full and / or partial esters of maleic anhydride, other (meth / eth / prop)acrylate monomers, various esters of versatic acid, styrene, styrenic derivatives (including but not limited to divinylbenzene, divinylnaphthalene, vinyl phenol, vinyl toluene, and the like), and combinations thereof. Additional and / or alternative non-limiting examples of comonomers can include maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, cinnamic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, tetrabromophthalic acid, trimellitic acid, pyromellitic acid, 1, 4, 5, 6,7,7- hexachloro-5-norbomene-2,3-dicarboxylic acid, succinic acid, 2,6-naphthalenedicarboxylic acid, glutaric acid, sebacic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3- cyclohexanedicarbocylic acid, full and / or partial hydrocarbonaceous (eg., alkyl) esters thereof, and combinations thereof.

[0072] Polymers:

[0073] Importantly, the (e.g., water- compatible) polymer includes at least one terminal end and the at least one terminal end includes a residue of the chain transfer agent, wherein a link between the polymer terminal end and the residue of the chain transfer agent can advantageously include an S (sulfur) atom. According to certain embodiments, the polymer can include a molecular weight distribution containing at least one mode / peak having a number average molecular weight (Mn) of from 500 g / mol to 250,000 g / mol, in particular from 800 g / mol to 100.000 g / mol, from 800 g / mol to 8000 g / mol, or from 1000 g / mol to 5000 g / mol. For example, the polymer molecular weight distribution can include at least one mode / peak having an Mn of at least 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4500, or 5000 g / mol, and additionally or alternatively can have an Mn of at most 250,000, 200,000, 150,000, 100,000, 75,000, 50.000, 25,000, 20.000, 15,000, 10,000, 8000, or 5000 g / mol. In some embodiments, the polymer can have a molecular weight distribution with two modes / peaks (bimodal), typically each of which modes can have an Mn within the range(s) disclosed, but at least one of which two modes can have an Mn within the range(s) disclosed). In some embodiments, the polymer can have a molecular weight distribution with more than two modes (polymodal). In such polymodal embodiments, at least one or at least two of the modes / peaks (but typically not all of the modes / peaks) can exhibit an Mn within the range(s) disclosed. According to an embodiment, the polymer can include from 50wt% to 100wt%. such as from 75wt% to 100%, from 90wt% to 100wt%, or about 100wt% of (meth)acrylamide, (meth)acrylic acid, C1 -C18 alkyl (meth)acrylate, hydroxyl-functional C1 -C18 alkyl (meth)acrylate, or a combination thereof, as polymerized monomer(s) by total weight of the polymer, excluding the terminal end. Additionally or alternatively, the polymer can further include, as polymerized monomer(s), in addition to the (meth)acrylamide, (meth)acrylic acid, alkyl (meth)acrylate, and / or hydroxyl-functional C1 -C18 alkyl (meth)acrylate, at least one of styrene or derivatives thereof; acrylonitrile or derivatives thereof; other vinylic esters; or combinations thereof.

[0074] Polymerization Method: Without wishing to be bound by any particular theory, the polymerization reaction may proceed as shown below, using acrylamide as the exemplary propagating monomer.

[0075] R-S-H (from L-homocysteine or isomer / derivative / Formula (I) substitute) + Pn* -> Pn-H + R-S* (where Pn* is the growing polymer chain)

[0076]

[0077] Similarly, radical initiator can activate L-homocysteine as shown below.

[0078] Depending upon the desired average molecular weight of the polymer chains, the reaction mixture may include from 500 ppm by weight (wppm) to 500,000 ppm by weight, such as from 10,000 wppm to 100,000 wppm, from 10,000 wppm to 50,000 wppm, or from 15,000 wppm to 30,000 wppm of the chain transfer agent, based on the weight of the monomers.

[0079] In some embodiments, simple feeding of the chain transfer agent, which may include homocysteine (such as L -homocysteine) or derivatives thereof, or compounds of Formula (I) as described above, may be used; i.e., the chain transfer agent may be added all at once at the initial polymerization stage. In other embodiments, particularly when polymerization kinetics are important, continuous feeding of the chain transfer agent may be advantageous to controlling molecular weight of polymers.

[0080] According to some embodiments, any suitable aqueous / water-based polymerization technique may employ the chain transfer agents disclosed herein. Non-limiting examples can include emulsion polymerization of alkyl (meth)acrylates, styrene, their derivatives, and / or mixtures thereof. According to other embodiments, other polymerization systems (e.g. , non- aqueous / solvent-based, as well as including other non- water-soluble monomers and / or forming other non-water-swellable polymer compositions) and methods (e.g, emulsion / suspension / latex polymerizations) may also be used. Various polymerization processes such as batch, semi-batch, semi-continuous, and continuous processes may be suitable for using the chain transfer agents disclosed herein.

[0081] A range of temperatures may be used to produce the (e.g., water-compatible) polymers mediated by the chain transfer agents disclosed herein and / or including chain ends comprising (sulfur-containing) residues of the chain transfer agents disclosed herein. The chain transfer agent(s) may be used to control the molecular weight of a radical initiated polymerization such as photopolymerization, thermally-activated radical polymerization, redox initiation, or free radical initiated polymerization.

[0082] According to some embodiments, various functional mercaptan chain transfer agent loadings may be used for controlling the molecular weight of (e.g., water-compatible) polymers. For example, in the case of homocysteine, loadings of〜3,000 wppm (by weight ofthe monomer(s)) may produce polymers having an Mn of approximately 100,000 g / mol. Higher loadings of homocysteine or derivative thereof, e.g.,〜10,000 wppm can further reduce molecular weight.

[0083] Any initiator suitable for radical -based polymerization may be used. Non-limiting examples of suitable initiators can include water-soluble / water-compatible azo initiators, peroxides, redox initiators, UV activated initiators, or combinations, complexes and / or reaction products thereof. Examples of free radical initiators can include, but are not necessarily limited to, hydrogen peroxide, organic peroxides such as tert-butyl peroxide, alkali metal persulfates such as potassium peroxydisulfate (a.k.a. potassium persulfate), sodium peroxydisulfate (a.k.a. sodium persulfate), and lithium peroxy disulfate (a. k. a. lithium persulfate), other persulfates such as ammonium persulfate, and mixtures of such initiators optionally with a reducing agent. Nonlimiting examples azo initiators can include V-501 (4,4’-azobis(4-cyanovaleric acid)), VA-086 (2,2’-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]), VA-057 (2,2’-azobis[N-(2- carboxyethyl)-2-methylpropionamidine]tetrahydrate), V-50 (2,2’-azobis(2- methylpropionamidine)dihydrochloride), VA-061 (2,2-’azobis[2-(2-imidazolin-2-yl)propane]), VA-044 (2,2’-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride), or combinations thereof. The V-series and VA-series initiators listed herein are commercially available from Fujifilm Wako Chemicals of Richmond, VA (USA). The amount of initiator may be chosen as desired for, among other things, a target polymer molecular weight, for example, from 0.01wt% to 3wt% or from 0.01wt% to lwt%, based on the total weight of monomer.

[0084] When a redox polymerization initiator system is used, a reducing agent may be used in conjunction with an oxidant. Reducing agents suitable for aqueous / water-based emulsion polymerization can include sulfites (e.g., alkali metal metabisulfite, hydrosulfite, and / or hyposulfite), ascorbic acid derivatives (including ascorbic acid, isoascorbic acid, or an alkali metal (iso)ascorbate salt), or the like, or combinations thereof. In a redox system, the amount of reducing agent may be chosen as desired, for example, from 0.01wt% to 3wt% based on the total amount of monomer. In such redox systems, when desired / present. oxidizing agents (oxidants) can include, for example, water-compatible oxidants such as hydrogen peroxide, alkali metal persulfates, perborates, peracetates, peroxides, and / or percarbonates, other inorganic (such as ammonia) persulfates, perborates, peracetates, peroxides, and / or percarbonates, and combinations thereof, optionally including a water-insoluble / water-immiscible oxidizing agent such as, for example, benzoyl peroxide, lauryl peroxide, t-butyl peroxide, t-butyl hydroperoxide, 2,2'- azobisisobutyronitrile, t-amyl hydroperoxide, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, or the like, or a combination thereof. The amount of oxidizing agent(s) may be collectively or individually chosen as desired, for example, from 0.01wt% to 3wt% collectively, based on the total amount of monomer.

[0085] In radical initiated systems, the polymerization temperature can typically be from about 10°C to about 100°C. In the case of persulfate systems, the temperature may be from about 60°C to about 100°C. In redox systems, the temperature may be from about 30°C to about 100°C, such as from about 30°C to about 60°C or from about 30° C to about 45° C.

[0086] The carrier used in the polymerization may comprise or be water or an aqueous composition that is suitable to dissolve, disperse, or suspend the chain transfer agents.

[0087] Additionally or alternatively, the invention may include, but is not necessarily limited to, the following non-limiting embodiments.

[0088] Embodiment 1. A water-compatible polymer comprising: a residue of a chain transfer agent and a polymerized monomer comprising at least one of (meth / eth / prop)acrylamide or derivative thereof, (meth / eth / prop)acrylic acid or acidic derivative thereof. C1 -C18 alkyl (meth / eth / prop)acrylate, hydroxyl-functional C1 -C18 alkyl (meth / eth / prop)acrylate, and a combination thereof; wherein at least one terminal end of the water-compatible polymer comprises the residue of the chain transfer agent, wherein a link between the polymer terminal end and the residue of the chain transfer agent comprises a sulfur atom; and wherein the chain transfer agent is water compatible and comprises homocysteine or derivatives thereof; compounds of Formula (I) below; or any combination thereof: Formula (I) where C* is a chiral carbon and where:

[0089] R1and R7are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms but not so as to form an amide group with attached nitrogen;

[0090] X is selected from: >C(=O), -CH2- or -CN;

[0091] R2is selected from:

[0092] (i) absent when X represents -CN,

[0093] (ii) a hydrogen atom,

[0094] (iii) -OR3, where: R3is a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms, or (iv) NR4R5, where: R4and R5are identical or different, and are selected from: a hydrogen atom: or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms; and n is an integer from 1 to 4, provided that, when X is >C(-O), when R2is -OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2.

[0095] Embodiment 2. The water-compatible polymer of embodiment 1, wherein the chain transfer agent comprises D-homocysteine, L-homocysteine, a derivative thereof, or a compound according to Formula I.

[0096] Embodiment 3. The water-compatible polymer of embodiment 1 or embodiment 2, wherein the chain transfer agent comprises homocysteine, in particular L-homocysteine.

[0097] Embodiment 4. The water-compatible polymer of any of embodiments 1-3, wherein the homocysteine comprises at least 90% L-homocysteine.

[0098] Embodiment 5. The water- compatible polymer of any of embodiments 1-4, wherein the chain transfer agent comprises no intentionally added C2-C 18 mono- and di- thiols, C3-C 12 ethylene glycol-based mono- and di- thiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine.

[0099] Embodiment 6. The w'ater-compatible polymer of any of embodiments 1-5, wherein the polymer exhibits a molecular weight distribution comprising at least one mode having a number average molecular weight (Mn) from 500 g / mol to 250,000 g / mol, from 800 g / mol to 100,000 g / mol, from 800 g / mol to 8000 g / mol, or from 1000 g / mol to 5000 g / mol.

[0100] Embodiment 7. The water-compatible polymer of any of embodiments 1-6, wherein the polymer molecular weight distribution is monomodal.

[0101] Embodiment 8. The water-compatible polymer of any of embodiment 1-7, wherein the polymer comprises from 50wt% to 100wt%, from 75wt% to 100wt%, from 90wt% to 100wt%, or about 100wt% of (meth)acrylamide, (meth)acrylic acid, Cl -Cl 4 alkyl (meth)acrylate, hydroxy-functional C 1-C6 alkyl (meth)acrylate, or a combination thereof, as a polymerized monomer by total weight of the polymer, excluding the terminal end. Embodiment 9. The water-compatible polymer of any of embodiments 1-8, wherein the polymer further comprises, as polymerized monomers, at least one of styrene or derivatives thereof; acrylonitrile or derivatives thereof; other vinylic esters; or combinations thereof.

[0102] Embodiment 10. A method of preparing a water-compatible polymer comprising: combining to form a reaction mixture: at least one monomer comprising (meth / eth / prop)acrylamide or derivative thereof; (meth / eth / 'prop)acrylic acid or acidic derivative thereof; C1 -C18 alkyl (meth / eth?prop)acrylate; hydroxyl-functional C1 -C18 alkyl (meth / eth / prop)acrylate, or a combination thereof; a free-radical initiator; a water compatible chain transfer agent comprising at least one of homocysteine or derivative thereof; C2-C12 dithiols; C3-C10 ethylene glycol-based dithiols; thioglycolic acid or derivative thereof; a compound of Formula (I); or a combination thereof:

[0103] Formula (1) where C* is a chiral carbon and where:

[0104] R1and R7are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms but not so as to form an amide group with attached nitrogen;

[0105] X is selected from: -C(=O)-, -CH2- or-CN;

[0106] R2is selected from:

[0107] (i) absent when X represents -CN, (ii) a hydrogen atom,

[0108] (iii) -OR3, where: R3is a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms, or

[0109] (iv) NR4R5, where; R4and R5are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms; and n is an integer from 1 to 4, provided that, when X is >C(=O), when R2is - OH, and when R!and R7are each hydrogen, n is not equal to 1 or 2; and an optional carrier, preferably comprising water; and reacting the reaction mixture to form a water-compatible polymer, wherein the water-compatible polymer comprises the at least one monomer comprising ((meth / eth / prop)acrylamide or derivative thereof: (meth / eth / prop)acrylic acid or acidic derivative thereof; C1 -C18 alkyl (meth / eth / prop)acrylate; hydroxyl -functional C1 -C18 alkyl (meth / eth / prop)acrylate, or a combination thereof, as polymerized monomer, and a residue of the chain transfer agent; and wherein at least one terminal end of the water-compatible polymer comprises the residue of the chain transfer agent, wherein a link between the polymer terminal end and the residue of the chain transfer agent comprises a sulfur atom.

[0110] Embodiment 11. The method of embodiment 10, wherein the chain transfer agent comprises D-homocysteine, L-homocysteine, a derivative thereof, or a compound according to Formula I:

[0111] Embodiment 12. The method of embodiment 10 or embodiment 11, wherein the chain transfer agent comprises homocysteine, in particular L-homocysteine. Embodiment 13. The method of any of embodiments 10-12, wherein the homocysteine comprises at least 90% L-homocysteine.

[0112] Embodiment 14. The method of any of embodiments 10-13, wherein the chain transfer agent comprises substantially no, or no intentionally added, C2-C18 mono- and di- thiols, C3- C12 ethylene glycol-based mono- and di- thiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine.

[0113] Embodiment 15. The method of any of embodiments 10-14, wherein the watercompatible polymer exhibits a molecular weight distribution comprising at least one mode having a number average molecular weight (Mn) from 500 g / mol to 250,000 g / mol, from 800 g / mol to 100,000 g / mol, from 800 g / mol to 8000 g / mol, or from 1000 g / mol to 5000 g / mol.

[0114] Embodiment 16. The method of any of embodiments 10-15, wherein the polymer molecular weight distribution is monomodal.

[0115] Embodiment 17. The method of any of embodiments 10-16, wherein the watercompatible polymer comprises from 50wt% to 100wt%, from 75wt% to 100wt%, from 90wt% to 100wt%, or about 100wt% of (meth)acrylamide, (meth)acrylic acid, C1 -C18 alkyl (meth)acrylate, hydroxyl-functional C 1 -C 18 alkyl (meth)acrylate, or a combination thereof, as polymerized monomer(s) by total weight of the polymer, excluding the terminal end.

[0116] Embodiment 18. The method of any of embodiments 10-17, wherein the watercompatible polymer further comprises, as polymerized monomers, at least one of styrene or derivatives thereof; acrylonitrile or derivatives thereof; other vinylic esters; or combinations thereof.

[0117] Embodiment 19. The method of any of embodiments 10-18, wherein the reaction mixture comprises from 500 wppm to 500,000 wppm, from 10,000 wppm to 100.000 wppm. from 10,000 wppm to 50,000 wppm, or from 15,000 wppm weight to 30,000 wppm of the chain transfer agent, by weight of the monomer(s).

[0118] EXAMPLES The following examples are mainly focused on acrylamide monomer, but any water-borne polymers (radical mediated) are applicable, such as emulsion polymerization of acrylates / styrenics, aqueous polymerization of (mcth)acrylic acids, etc., could be suitable.

[0119] Materials:

[0120] Acrylamide, D / L homocysteine (racemic mixture) and cysteine were purchased from Sigma. L-homocysteine was received from Arkema and was used as-is. All commercial chemicals were used as received without any purifications.

[0121] Methods:

[0122] Nuclear Magnetic Resonance Spectroscopy (NMR)) was performed on a Bruker 300 MHz NMR Spectroscope. The software was TopSpin (ver. 3.6.3, Bruker).1H NMR was conducted with DiO. Conversion was determined by peak area comparison - C=C (-5.6-6.4 ppm) vs. C-C (polymeric backbone, -1.2-2.4 ppm).

[0123] Gel permeation chromatography (GPC) was conducted on a Waters Alliance 2695, Wyatt t-REX differential refractometer using the following parameters.

[0124] Columns: Two PSS SUPREMA 30A columns (-3, -5, -10 pm) and a guard column (-7.8 mm I.D. x 50 cm, -10 pm).

[0125] Solvent: Water with -0.2 g / L sodium azide and -0.1 M sodium nitrate.

[0126] Temperature: ~35°C.

[0127] Flow rate: -1.0 mL / min.

[0128] Injection volume: -100 pL.

[0129] Sample Concentration: -1 -2 mg / mL of provided sample in water with -0.2 g / L sodium azide and -0.1 M sodium nitrate.

[0130] Standards: Seven poly(ethylene oxide) standards ranging in Mp (peak molecular weight) from -26,000 to -969,000 g / mol.

[0131] Analysis: ASTRA Calibration data was fitted to a linear polynomial with R2 of at least 0.99. Liquid chromatography using a mass spectrometer detector was conducted as follows.

[0132] Approximately 0.05 g sample was diluted into -3 g water and analyzed with LC-MS2 under the following conditions:

[0133] Figure 1 illustrates a lab scale setup for polymerization of acrylamide. As shown, a -250 or -500 ml of round bottom flask with 2- or 3-neck reactor was equipped with a magnetic bar stirrer. A nitrogen blanket was applied to create a relatively inert atmosphere in which to run the reaction.

[0134] Example 1 : Comparison of racemic mixture of homocysteine, cysteine, L-homocysteine and no chain transfer agent Table 1 shows the detailed reaction parameters for producing poly (acrylamide) using various chain transfer agents (CTA). The reaction conditions for all the runs in Table 1 were: -20 grams of acrylamide, -45 grams of water, -0.05 gram of potassium peroxydisulfate (potassium persulfate) as initiator (-2,500 ppm weight based on weight of acrylamide), -0.1 gram of chain transfer agent (CTA) (-5,000 ppm weight based on weight of acrylamide).

[0135] After polymerization, the products were additionally diluted with - 70-100 grams of water.

[0136] Aliquot amounts of each sample were taken for GPC and NMR samples. Weight average molecular weight (Mw) and polydispersity (PDI ~= Mw / Mn) were measured by aqueous GPC with polyethylene oxide (PEG) standards (7 standards with Mw range of from -26,000 to -969,000 g / mol, conducted as described above. Monomer conversion was determined by 'H NMR, by comparing the peak areas of unsaturated hydrocarbon to those of the backbone, as shown in Figure 2.

[0137] Results:

[0138] The results of the polymerizations and characterization of the polymers are shown in Table

[0139] > > > > >

[0140] 'Could not be measured due to gelation.

[0141] *Close to upper limit of calibration range.

[0142] Control polymerizations were conducted without chain transfer agent. Reactions at ~80°C led to gelation (Table 2, runs 1 and 2), and these polymers were not soluble in water. Because of the poor solubility to water, molecular weights were not measured (presumably, gelation resulted in very high Mw). Lowering the reaction temperature to ~60°C showed slightly better results, but gelation was not universally avoidable. A small portion of the polymers that exhibited varying levels of gelation were dissolved in water for GPC analysis. The results for these polymers indicated that the molecular' weights of even the soluble portion of the polymers were very high and approached the calibration limit of the GPC standards (Table 2 entries 5 and 6). The results indicated that polymerizations without any chain transfer agent and with cysteine had poorly controlled molecular weight distributions.

[0143] On the other hand, appreciable differences were observed when using various homocysteine enantiomeric forms as the chain transfer agent for polymerizations of acrylamide. Both L-homocysteine and D / L homocysteine as chain transfer agent produced substantially transparent and moderately viscous liquid acrylamide polymers. In addition, these acrylamide products appeared to be fully soluble in water. Higher reaction temperature (-80°C) also seemed to produce water-soluble products (Table 2, runs 3-4) while control samples (either no chain transfer agent or cysteine as chain transfer agent) at the same temperature led to some level of gelation of the resulting polymers, indicating poor control of the molecular weight. GPC results indicated that polyacrylamide produced by both types of homocysteine (L-homocysteine or D / L homocysteine racemic mixture) successful reduced the molecular weights and the polymers fell within the Mn range of 85,000 g / mol to 150,000 g / mol, as shown in Figure 3. The molecular weight values for polymers made using homocysteine as the chain transfer agent were five to ten times lower than those of polymers produced either without chain transfer agent or with cysteine as the chain transfer agent. All samples were observed to be free from odor. According to the results, L- homocysteine can be used for polymerization of acrylamide by batch or continuous process polymerizations.

[0144] Example 2: Effect of L-homocysteine loading on molecular weight of polyacrylamide

[0145] The same experimental set up as was used in Example 1 was utilized for these experiments, as shown in Figure 1. The reaction conditions for the runs shown in Table 3 are as follows. -20 grams of acrylamide, -45 grams of water, and -0.05 grams of potassium peroxydisulfate as the initiator. The reactions were carried out at ~80°C for -4 hours.

[0146] Table 3 shows the loading of L-homocysteine used for each run in Example 2. The polyacrylamides in each of the runs shown in Table 3 were worked up as follows. After polymerization, each polymer was diluted with about 50 grams of water. Then an excess of methanol (about 350 mL) was slowly added to the aqueous mixture of polymer with vigorous stirring to form a white precipitate. The white precipitate was collected by filtration and dried under vacuum. The samples were re-dissolved in deionized water and the above procedure (diluting with an excess of methanol, etc.) was repeated once more to obtain a purified polymer.

[0147] Characterization: NMR analysis was conducted for determining monomer conversion by comparison of peak areas of vinyl (seen at about 5.6-6.4ppm on the spectra) and polymeric backbone (seen at about 1.2-2,4 ppm on the spectra). For chain-end analysis, each sample of purified polyacrylamide was re-dissolved in deuterium oxide and an NMR analysis was conducted. Mw, Mn and poly dispersity (Mw / Mn) were measured by aqueous GPC with polyethylene oxide standards (7 standards having Mw range of -26,000 g / mol to -969.000 g / mol as described above.

[0148] The chain transfer constant (Ctr = ktr / kp) was determined by the Mayo equation using Runs 1-4 in Table 3. where DP is degree of polymerization, (DP = Mn / 71.08), [CTA] is molar concentration of the chain transfer agent, [AM] is the mole concentration of the acrylamide monomer. The plot used to determine the chain transfer constant Ctrof -2.33 according to the Mayo equation is shown in Figure 4.

[0149] The residue of the homocysteine remaining after reaction was completed was determined by liquid chromatography using a mass spectrometer detector. The calibration curve was built using Extracted ion chromatography for -136.04 ([M+H]+~ 136.04) and a representative MS2 (secondary ion fragments) mass spectroscopy spectrum of L-homocysteine was used as validation of identity. In particular, 136.04 ~ L-homocysteine (~135) + H+ (~1 ). More details are described above. The targeted ion mass range was 136.04 and detected only m / z = 136.04 molecule to identify L-homocysteine residue. These results are shown in Table 5 below.

[0150] Table 4 shows a summary of the polyacrylamides made using various levels of L- homocysteine as the chain transfer agent for Example 2. > > >

[0151] Summary: Various L-homocysteine loadings were used for synthesizing low molecular weight (Mw and Mn) polyacrylamides (PAMs). The targeted Mn range was -1000 to 5000 g / mol.

[0152] Optimal L-homocysteine loading was -10,000-50,000 wppm based on the weight of the acrylamide monomer. The observed Mn were below -5000 g / mol. The polymers were worked up the same way as described in Example 1. The GPC results are shown in Figure 5.

[0153] Chain-end functionality was determined by1H NMR. L-homocysteine showed three characteristic peaks, at -2.2. -2.7 and -3.8 ppm (Figure 7). Higher L-homocysteine levels showed higher peak intensities at -2.7 and -3.3 ppm, believed to be from non-purified polyacrylamide. The peak at 5:::-2.2 ppm overlapped with the polymeric backbone. The purified polyacrylamide also seemed to show L-homocysteine characteristic peaks (Figure 8). The polymer chains each appeared to contain approximately one L-homocysteine residue chain end (determined by numberaverage molecular weight Mn). According to LC-MS and NMR results, the majority of L- homocysteine was successfully incorporated in polyacrylamide.

[0154] The residual chain transfer reagent in the reaction mixtures for four different runs were determined by liquid chromatography with a mass spectrometer detector. Reaction temperature and conversion were varied. No significant differences were observed by reaction temperature (-60 or -80 °C). Similarly, different monomer conversions showed a similar level of L- homocysteine residue (about 300 ppm weight by total weight of polymer and any unreacted monomer). According to GPC and LC-MS results, L-homocysteine seems to exhibit a high Ctrvalue and effectively reacted to propagating species (growing polymer chain).

[0155] The results are shown in Table 5.

[0156] Three key findings were:

[0157] (1) The lowest Mw was -2300 g / mol using -25,000 ppm weight L-homocysteine loading based on the weight of the acrylamide;

[0158] (2) The residual L-homocysteine was about 300 ppm weight based on the weight of the polyacrylamide. This concentration level was comparable to that of other chain transfer agents left in conventional free radical polymer systems (e.g., n-dodecyl mercaptan used as the chain transfer agent when polymerizing styrene acrylonitrile-grafted polymeric polyol).

[0159] (3) The obtained polymers appeared to contain L-homocysteine chain ends indicating the expected high chain end functionality.

[0160] L-homocysteine loading ranges between about 10,000 and 50,000 wppm by weight of the acrylamide seemed to be suitable to produce polyacrylamide polymers having Mn below -5000 g / mol. The lowest Mn observed was at -25,000 ppm L-homocysteine loading (-2300 g / mol). L- homocysteine loading above -100,000 ppm seemed to provide a bimodal distribution (by GPC), which might be indicative of side reactions.

[0161] Unreacted L-homocysteine chain transfer agent concentrations were determined by liquid chromatography with a mass spectrometer detector. Approximately 300 wppm by weight of residual L-homocysteine was confirmed, which is comparable to that of other polymer systems which typically have a residual chain transfer reagent content of -500-5,000 wppm. Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

[0162] The foregoing description of various forms of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

CLAIMSWhat is claimed is:

1. A water-compatible polymer comprising: a residue of a chain transfer agent and a polymerized monomer comprising at least one of (meth / eth / prop)acrylamide or derivative thereof, (meth / eth / prop)acrylic acid or acidic derivative thereof, C1 -C18 alkyl (meth / eth / prop)acrylate, hydroxy-functional C1 -C18 alkyl (meth / eth / prop)acrylate, or a combination thereof; wherein at least one polymer terminal end of the water-compatible polymer comprises the residue of the chain transfer agent, wherein a link between the polymer terminal end and the residue of the chain transfer agent comprises a sulfur atom; and wherein the chain transfer agent is water compatible and comprises homocysteine or derivatives thereof; C2-C12 dithiols; C3-C12 ethylene glycol-based dithiols; thioglycolic acid or derivative thereof; compounds of Formula (I) below; or any combination thereof:where C* is a chiral carbon and where:R1and R7are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms but not so as to form an amide group with attached nitrogen;X is selected from: >C(^O), -CHj- or-CN;R2is selected from:(i) absent when X represents -CN,(ii) a hydrogen atom,(iii) -OR3, where: R3is a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms, or(iv) -NR4R5, where: R4and R5are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms; and n is an integer from 1 to 4, provided that, when X is >C(=O), when R2is ・ OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2.

2. The water-compatible polymer of claim 1, wherein the chain transfer agent comprises D- homocysteine, L-homocysteine, a derivative thereof, or a compound according to Formula I.

3. The water-compatible polymer of claim 1 or claim 2, wherein the chain transfer agent comprises homocysteine, in particular L-homocysteine.

4. The water-compatible polymer of any of claims 1-3, wherein the homocysteine comprises at least 90% L-homocysteine.

5. The water-compatible polymer of any of claims 1-4, wherein the chain transfer agent comprises no intentionally added C2-C18 mono- and di- thiols, C3-C12 ethylene glycol-based mono- and di- thiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine.

6. The water-compatible polymer of any of claims 1-5, wherein the polymer exhibits a molecular weight distribution comprising at least one mode having a number average molecular weight (Mn) from 500 g / mol to 250,000 g / mol, from 800 g / mol to 100,000 g / mol, from 800 g / mol to 8000 g / mol, or from 1000 g / mol to 5000 g / mol.

7. The water-compatible polymer of any of claims 1-6, wherein the polymer molecular weight distribution is monomodal.

8. The water-compatible polymer of any of claims 1-7, wherein the polymer comprises from 50wt% to 100wt%, from 75wt% to 100wt%, from 90wt% to 100wt%, or about 100wt% of (meth)acrylamide, (meth)acrylic acid, C1 -C18 alkyl (meth)acrylate, hydroxy-functional C1 -C18alkyl (meth)acrylate, or a combination thereof, as a polymerized monomer by total weight of the polymer, excluding the terminal end.

9. The water-compatible polymer of any of claims 1-8, wherein the polymer further comprises, as polymerized monomers at least one of styrene or derivatives thereof; acrylonitrile or derivatives thereof; other vinylic esters; or combinations thereof.

10. A method of preparing a water-compatible polymer comprising: combining: at least one monomer comprising (meth / eth / prop)acrylamide or derivative thereof; (meth / cth / prop)acrylic acid or acidic derivative thereof; CT -Cl 8 alkyl (meth / eth / prop)acrylate; hydroxy-functional Cl -Cl 8 alkyl (meth / eth / prop)acrylate, and a combination thereof; a free-radical initiator; a water compatible chain transfer agent comprising at least one of homocysteine or derivative thereof; C2-C12 dithiols; C3-C10 ethylene glycol-based dithiols; thioglycolic acid or derivative thereof; a compound of Formula (I); or a combination thereof:Formula (I)where C* is a chiral carbon and where:Rland R7are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms but not so as to form an amide group with attached nitrogen;X is selected from: -C(=O)-, -CH2- or -CN;R2is selected from:(i) absent when X represents -CN,(ii) a hydrogen atom,(iii) -OR3, where: R3is a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms, or(iv) -NR4R5, where: R4and R5are identical or different, and are selected from: a hydrogen atom; or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety of 1 to 20 carbon atoms optionally comprising one or more heteroatoms; and n is an integer from 1 to 4, provided that, when X is >C(=O), when R2is - OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2; and an optional carrier, preferably comprising water; and reacting the reaction mixture; wherein the water-compatible polymer comprises the monomer comprising (meth)acrylamide or derivative thereof: (meth)acrylic acid or acidic derivative thereof; or combination thereof as polymerized monomer, and a residue of the chain transfer agent; and wherein at least one polymer terminal end of the water-compatible polymer comprises the residue of the chain transfer agent, wherein a link between the polymer terminal end and the residue of the chain transfer agent comprises an S.

11. The method of claim 10, wherein the chain transfer agent comprises D-homocysteine, L- homocysteine, a derivative thereof, or a compound according to Formula I.

12. The method of claim 10 or claim 11, wherein the chain transfer agent comprises homocysteine, in particular L-homocysteine.

13. The method of any of claims 10-12, wherein the homocysteine comprises at least 90% L- homocysteine.

14. The method of any of claims 10-13, wherein the chain transfer agent comprises no intentionally added C2-C18 mono- and di- thiols, C3-C12 ethylene glycol-based mono- and dithiols, thioglycolic acid or derivative thereof, cysteine, or acetylcysteine.

15. The method of any of claims 10-14, wherein the water-compatible polymer exhibits a molecular weight distribution comprising at least one mode having a number average molecular weight (Mn) from 500 g / mol to 250,000 g / mol, from 800 g / mol to 100,000 g / mol, from 800 g / mol to 8000 g / mol, or from 1000 g / mol to 5000 g / mol.

16. The method of any of claims 10-15, wherein the polymer molecular weight distribution is monomodal.

17. The method of any of claims 10-16, wherein the water-compatible polymer comprises from 50wt% to 100wt%, from 75wt% to 100wt%, from 90wt% to 100wt%, or about 100wt% of (meth)acrylamide, (meth)acrylic acid. C1 -C18 alkyl (meth)acrylate, hydroxy- functional C1 -C18 alkyl (meth)acrylate, , or a combination thereof, as polymerized monomer(s) by total weight of the polymer, excluding the terminal end.

18. The method of any of claims 10-17, wherein the water-compatible polymer further comprises, as polymerized monomers at least one of styrene or derivatives thereof; acrylonitrile or derivatives thereof; other vinylic esters; or combinations thereof.

19. The method of any of claims 10-18, wherein the reaction mixture comprises from 500 wppm to 500,000 wppm, from 10,000 wppm to 100,000 wppm, from 10,000 wppm to 50,000 wppm, or from 15,000 wppm weight to 30,000 wppm of the chain transfer agent, by weight of the monomer(s).

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