# Prerequisites for Developing a Classification of Phase Transitions in Systems Based on Thermosensitive Polymers: Use of a Semi-Empirical Model

## TL;DR

This paper introduces a new classification system for phase transitions in thermosensitive polymers using a semi-empirical model and phase portraits.

## Contribution

The novel contribution is a semi-empirical model that classifies phase transitions in thermosensitive polymers using phase portraits and equivalent chemical reactions.

## Key findings

- Phase transitions in thermosensitive polymers can be described through equivalent chemical reactions of first and second orders.
- The proposed model explains why phase portraits often show parabolic and linear segments.
- The approach enables automatic systematisation of experimental data using image recognition.

## Abstract

It is shown that the extensive experimental material available in the literature reflecting the behaviour of thermosensitive hydrogels and solutions of thermosensitive polymers requires systematisation and generalisation. Additional evidence is given that the method of forward and reverse phase portraits is an important tool for the systematisation of such data. It is shown that using this method makes it possible to refine the characteristics of the phase transition, as well as to classify thermosensitive hydrogels and solutions according to such classification criteria as the number of phase transition stages. Based on the developed classification, a new semi-empirical theory of phase transitions is proposed. Using this model, it is shown for the first time that phase transitions can be described through equivalent chemical reactions of the first and second orders. The proposed model allows us to explain the fact that the phase portraits obtained from experimental data often contain segments corresponding to parabolic and linear dependences. It is shown that the proposed approach creates a basis for systematisation of the results accumulated in the field of study of thermosensitive polymers in automatic mode by means of image recognition technologies.