磁场影响聚合物本体结晶动力学的机理分析

在经典的热力学理论基础上,探讨了磁场对聚合物本体结晶过程的成核与生长的影响,建立了相关结晶动力学理论方程.初步认为,磁场产生的＂磁结晶效应＂可能是由于晶相与非晶相之间磁化率差异导致了两相之间磁化能的差异,也可能由于聚合物体系在结晶前会形成一种有序相,减小了体系的熵值,进而改变了结晶过程中的体系自由能,影响其成核与晶体生长,乃至整个结晶动力学方程.利用Matlab软件结合PLLA的各结晶参数值,绘制了结晶自由能与各成核临界参数之间的函数图像.结果表明,在低过冷度下,较小的自由能扰动可能导致较大的晶核临界参数变化.

A theory of polymer crystallization kinetics influenced by magnetic field

The mechanism of the magnetic field influence on polymer bulk crystallization has been discussed,which included nucleation and crystal growth.We have constructed relative equations of crystallization kinetics based on the classic thermodynamic theory.The equations show that the ＂magnetocrystallization effect＂（MCE） caused by the difference of magnetic energy between crystal and amorphous phases.It came from the difference of magnetic susceptibilities between crystal and amorphous phases.The ＂like-liquid-crystal phase＂ induced by magnetic field in some polymer is another possible reason of MCE,which have low entropy and change the free energy in crystallization.They could affect the process of nucleation,crystal growth,the entire formula of crystal kinetics.We used ＂Matlab＂ software to figure the function of nucleation critical parameters and crystal free energy,the pictures indicated that small free energy changed by the temperature or magnetic field could greatly impact on the values of nucleation critical parameter with low degree of supercooling.