Abstract: The paper first introduced phase transitions among gas, liquid and solid states in the single component substance, then introduced how to apply the method of transplantation in the scientific research of binary mixtures according to their resemblance to the singlecomponent substance. The method was also applied in the study of polymer phase separation and crystallization in multicomponent systems. The interplay of two phase transitions reveals the complexity of polymer phase transitions.

Key words: polymers, thermodynamics, phase separation, crystallization, complexity