The Phase-field Simulation Of Phase Separation Of Polymer Blends

The macromolecule alloy has excellent combination property including physicalproperties, mechanical properties which can satisfy modern people’s pursuit of betterquality of life.In the mean time,it relieves the contradiction between the singleness of theperformance of traditional single polymer material and the production also living demands.One kind of the macromolecule alloy with the characteristics of phase separation hasattracted a great amount of attention because it generates a special micro structure duringphase separation,thereby giving the alloy superior features.Therefore, how to control theforms of micro structure by studying the mechanism of phase separation and thecharacteristics of different polymer blends is the focus of obtaining polymer alloys whichhave the excellent performance and use value.This article was based on the phase-field theory, and summarized the thermodynamicsand dynamics during the phase separation. By Combining the Ginzburg-Landau freeenergy with the classical diffusion law, we deduced the binary phase-field model under theinfluence of the molecular weight and gradient energy coefficient and also the ternaryphase-field model. Keeping the molecular weight of one component a constant, we studiedhow the variation of molecular weight in the other component affect the phase separation.It turned out that the molecular weight plays a dual role in phase separation, andultimately brought a kind of regular pattern to phase separation. We studied the influenceof gradient energy coefficient on the phase separation from the perspective ofone-dimensional and two-dimensional, and the result indicated that the introducing of theentropy contribution of coefficient slowed the rate of phase separation in the early andmiddle stage and reduced the growth index of the late stage. On the basis of the ternarymodel, we summarized the results and described the phase structure with a phaseclassification by changing the composition of the system and the interaction parametersbetween the components. What’s more, we proposed the judgment of the final structure ofthe ternary system, by extracting18kinds of structures as the most representative ones toanalyze the formation mechanism of each structure and the causes of different types. Inaddition, based on compositional quenching, we prepared the membrane of the binarysystem via the spin-coating as a result of phase separation. Then we observed the form of the membrane, which was followed by the comparison with the simulation results. Itturned out that the two results are highly similar to each other, which proved the accuracyof the phase-field model.