Pikina Elena S, Ostrovskii Boris I
Landau Institute for Theoretical Physics of the RAS, 142432, Chernogolovka, Russia.
Oil and Gas Research Institute, Russian Academy of Sciences, Gubkin str. 3, 119333, Moscow, Russia.
Eur Phys J E Soft Matter. 2017 Mar;40(3):24. doi: 10.1140/epje/i2017-11509-5. Epub 2017 Mar 2.
We present a theoretical explanation for the formation of nematic droplets in free-standing smectic films (FSSF) overheated above the temperature of the bulk smectic - nematic transition. The conditions for the formation of the nematic droplets in smectic films are studied on the basis of the general thermodynamic approach to the stability of FSSF. It is shown that the formation of droplets in overheated FSSF is only possible in the presence of a certain amount of thermally generated dislocation loops. We determined the gain in the free energy related with the formation of the nematic droplets, the value of the critical work and the critical size of the drops. The initial increase of the drops size is due to release of material from the growing dislocation loops. At the second stage the drops growth occurs through coalescence of the smaller drops with the larger ones. The droplets attract each other by means of capillary forces arising due to gradients of the surface energy in the area between them. Drops size evolution, the dynamics of their growth and merging are in good agreement with experiments.
我们给出了一个理论解释，用于说明在高于体相近晶 - 向列相转变温度的独立近晶薄膜（FSSF）中向列液滴的形成。基于FSSF稳定性的一般热力学方法，研究了近晶薄膜中向列液滴形成的条件。结果表明，过热的FSSF中液滴的形成仅在存在一定数量热生成的位错环时才有可能。我们确定了与向列液滴形成相关的自由能增益、临界功的值和液滴的临界尺寸。液滴尺寸的初始增加是由于生长的位错环释放出物质。在第二阶段，液滴通过较小液滴与较大液滴的合并而生长。液滴通过它们之间区域表面能梯度产生的毛细力相互吸引。液滴尺寸的演变、它们生长和合并的动力学与实验结果吻合良好。
