Polystyrene Polyampholyte Composition for Stable UCST Response

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Solution Overview

Problem

Conventional thermoresponsive polymers with upper critical solution temperature (UCST) behavior are prone to hydrolysis due to hydrolyzable ester or amide groups, and they often have low osmotic pressure, making them unsuitable for durable applications in drug delivery and forward osmosis membrane water treatment systems.

Innovation Solution

Development of a polystyrene-based polyampholyte comprising specific cationic and anionic monomer components, such as halogenated 4-vinylbenzyltrialkylammonium, vinylpyridine, and 4-vinylbenzenesulfonate, with controlled molecular weight and molar ratios, exhibiting UCST-type thermoresponsiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional thermoresponsive polymers with UCST behavior are used, then they can provide temperature-responsive functionality, but they are prone to hydrolysis due to hydrolyzable ester or amide groups, reducing durability

Engineering Contradiction:

ImprovedurabilityVSAvoidhydrolytic stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical composition parameters by using polyampholytes with specific cationic and anionic monomer ratios (36-64 mol% cationic, 36-64 mol% anionic) to achieve UCST behavior without hydrolyzable groups, resolving the contradiction between durability and hydrolytic stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite polyampholyte structure combining cationic monomers (vinylpyridine, quaternized vinylpyridine) with anionic monomers (4-vinylbenzenesulfonate) to achieve both UCST functionality and hydrolytic stability, eliminating the need for hydrolyzable ester or amide groups

Inventive Principle:

Principle #40Composite materials

2Reliability

If nonionic thermoresponsive polymers are used, then they can provide temperature-responsive behavior, but they have excessively low osmotic pressure for forward osmosis applications

Engineering Contradiction:

Improveosmotic pressureVSAvoidthermoresponsive behavior

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces ionic groups (cationic and anionic) into the polymer structure, changing the electrical charge parameter to generate sufficient osmotic pressure while maintaining UCST-type thermoresponsiveness through the balanced polyampholyte composition

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates local ionic interactions within the polymer chains through cationic and anionic monomers, enabling both high osmotic pressure for forward osmosis and temperature-responsive phase transition behavior at specific composition ratios

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If polymers with hydrolyzable ester or amide groups are used to achieve UCST behavior, then they can provide thermoresponsiveness, but the thermoresponsiveness is likely to disappear by hydrolysis

Engineering Contradiction:

ImprovethermoresponsivenessVSAvoidfunctional stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the chemical stability parameter by selecting monomers without hydrolyzable groups (vinylpyridine, quaternized vinylpyridine, 4-vinylbenzenesulfonate), ensuring long-term functional stability while maintaining UCST-type thermoresponsiveness through ionic interactions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces unstable hydrolyzable groups with stable non-hydrolyzable ionic groups, creating a durable polyampholyte that maintains its thermoresponsive functionality over time without degradation

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 polystyrene-based polyampholyte provides durable UCST-type thermoresponsiveness, suitable for biomedical applications and effective as a draw solution in forward osmosis membrane water treatment systems, particularly for desalination and food concentration, without the issues of hydrolysis and low osmotic pressure.

Implementation Method 1

polymers having upper critical solution temperature (UCST) behavior depending on phase change due to temperature

Methodology Applied

Scientific EffectUpper critical solution temperature (UCST): Phase Change

Implementation Method 2

zwitterionic polymers including both a cation and an anion on a side chain are known to exhibit a UCST

Methodology Applied

Scientific EffectOsmotic pressure: Osmotic Pressure

Data Source

PatentUS12516143B2Polystyrene-based polyampholyte having upper critical solution temperature, and application for same

Publication Date: 2026.01.06 TOSOH FINECHEM CORP

AI summary

Provided is a novel polystyrene-based polyampholyte having upper critical solution temperature (UCST)-type thermoresponsiveness and a method for producing the same. When monomers having halogenated vinylbenzyl trialkyl ammonium and p-styrenesulfonate as main components are radically polymerized in an aqueous solvent, a polyampholyte having an upper critical solution temperature is produced by optimizing the mole ratio between cationic groups and anionic groups and the amount of a radical initiator and a chain transfer agent to be added to thereby control the copolymer composition and the molecular weight.