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

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.