Department of Physics and Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.
J Chem Phys. 2013 Apr 21;138(15):154904. doi: 10.1063/1.4798462.
The effects of aligning fields on models of polymer liquid crystals were simulated using the dissipative particle dynamics method. Exposing a liquid crystal of rod-like particles to a directional field causes a stabilization of the phases with orientational order, shifts the isotropic-nematic and nematic-smectic-A phase transitions to higher temperatures, makes the transitions continuous beyond a critical field strength, and induces weak para-nematic alignment in the zero-field isotropic phase. The interplay of liquid-crystalline ordering, microphase separation, and an alignment field endows the diblock and triblock copolymers studied here with rich phase behavior. The simulations suggest that field-induced orientational ordering can give rise to positional ordering. Reversely, positional ordering resulting from rod-coil demixing may be accompanied by orientational ordering, which is enhanced by external fields. For highly asymmetric rod-coil copolymers, the microphase separation pattern formed by the rigid segments can be altered by an aligning field.
使用耗散粒子动力学方法模拟了场对齐效应对聚合物液晶模型的影响。将棒状粒子的液晶暴露于定向场中会导致具有取向有序的相稳定化，将各向同性-向列相和向列-近晶 A 相转变推向更高的温度，使转变在超过临界场强时连续，并在零场各向同性相中诱导弱的准向列排列。液晶有序、微相分离和取向场的相互作用赋予了这里研究的两嵌段和三嵌段共聚物丰富的相行为。模拟表明，场诱导的取向有序可能导致位置有序。相反，由于棒状-线圈的混合而产生的位置有序可能伴随着取向有序，而外部场会增强这种有序。对于高度不对称的棒状-线圈共聚物，由刚性段形成的微相分离模式可以通过取向场来改变。
