Polyelectrolyte Hydrogel Formed by UV Photopolymerization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for applying super-absorbent polymers as coatings on substrates face limitations, including inconsistent swelling degrees, structural inconsistencies, and safety concerns due to the use of volatile and toxic monomers like acrylic acid, which affect the absorption capacity and stability of the hydrogels.
Innovation Solution
An aqueous polyelectrolyte composition comprising a first monomer selected from vinylic sulphonic acids or their salts, a second monomer with an acid group and a spacer group, and a photochemical radical initiator, which polymerizes under UV radiation to form a water-insoluble hydrogel with high swelling capacity and stability, eliminating the need for neutralization and reducing the risk of polymerization during storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acrylic acid monomers are used for polymerization, then the hydrogel can be formed, but the monomers are volatile and toxic, creating safety concerns and affecting stability
Solution Approach 1:
The patent extracts and removes the harmful acrylic acid monomer from the system, replacing it with safe, non-volatile alternatives such as acryliclamide and 2-acrylamido-2-methylpropanesulphonic acid. This substitution eliminates the toxicity and volatility issues while preserving the hydrogel-forming capability.
Solution Approach 2:
The patent changes the chemical parameters of the monomers used, transitioning from volatile carboxylic acids to non-volatile amides and sulphonic acids. This parameter change maintains the polymerization functionality and hydrogel formation while eliminating the harmful properties of the original monomers.
2Ease of manufacture
If neutralization step is used in polymerization process, then the polymer can be formed, but it adds process complexity and time
Solution Approach 1:
The patent applies preliminary action by pre-selecting monomers that do not require neutralization. The chosen monomers (acrylamide and 2-acrylamido-2-methylpropanesulphonic acid) can be directly polymerized without acid-base neutralization, eliminating this intermediate step from the process.
Solution Approach 2:
The neutralization step is completely extracted and removed from the polymerization process. The patent achieves direct polymerization of the monomer mixture without requiring conversion to salt forms, thereby simplifying the manufacturing process and reducing time consumption.
3Strength
If high crosslinking degree is used, then the gel strength is contained and form is retained, but the absorption capacity and swelling are reduced
Solution Approach 1:
The patent changes the crosslinking parameters by using a low crosslinking degree (0.1-5% of total monomer mass) combined with specific monomer selection. This parameter optimization achieves sufficient gel strength while maximizing water absorption capacity and swelling, resolving the trade-off between strength and absorption.
Solution Approach 2:
The patent creates a composite polymer system combining acrylamide and 2-acrylamido-2-methylpropanesulphonic acid with controlled crosslinking. This composite structure provides both mechanical integrity and high absorption capacity, balancing strength and swelling properties.
4Use of energy by moving object
If thermal polymerization initiator is used, then polymerization can occur, but energy consumption is high and safety risks increase
Solution Approach 1:
The patent substitutes thermal initiation with photochemical initiation using UV light. This replacement eliminates the need for high-temperature heating, significantly reducing energy consumption and eliminating safety risks associated with thermal runaway and monomer volatility during heating.
Solution Approach 2:
The patent utilizes photochemical phase transition (from monomer to polymer via UV-induced radical formation) instead of thermal activation. This phase transition approach allows polymerization to proceed at ambient temperatures, improving safety and reducing energy requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a high swelling degree of at least 150, improved stability across a wider pH range, and safer, energy-efficient polymerization conditions, with the resulting hydrogels being non-toxic to the aquatic environment and suitable for industrial applications.
Implementation Method 1
an aqueous polyelectrolyte composition comprising a first monomer selected from vinylic sulphonic acids or their salts, a second monomer with an acid group and a spacer group, and a photochemical radical initiator, which polymerizes under UV radiation to form a water-insoluble hydrogel
Implementation Method 2
The network is herein capable of absorbing and retaining quantities of water that are large in comparison to its own mass. The water is herein retained in the network by means of osmotic pressure.
Data Source
AI summary
A poly-electrolyte composition for forming a water insoluble copolymer suitable as a hydrogel, wherein the copolymer is formed by means of free radical polymerization of at least a first and a second hydrophilic monomer, wherein the first monomer is selected from vinylic sulphonic acids, vinylic phosphonic acids or a water soluble salt thereof, and wherein the second monomer is a vinylic monomer with an electron-withdrawing spacer between the double bond and an acidic group, at least one compound selected from the group consisting of monomers comprising an acidic group either in the free acid form or in the form of a water soluble salt, and of which the logarithm of the acid dissociation constant (pKa) in the free acid form has a value smaller than 3.5.