Crystallization Mechanizm of Polymers

1)从熔体中结晶：发现聚合物单晶是通过新的增厚生长和众所周知的横向生长机制形成的。增厚生长速率(U)随过冷度的增加而增大。这些结果表明，高分子链的滑动扩散在聚合物结晶机理中起着重要作用。用成核速率和成核速度的竞争来解释单晶形状的结晶温度变化。2)溶液结晶：聚合物链的吸附在结晶过程中的重要作用，以及形成三维形核的可能性。3)球晶的结晶：球晶的形成是由于不同取向褶皱的两个扇区之间的错配导致的螺位错的产生。在很高的过冷度下观察到了横向生长速度，这不能用传统的形核理论来很好地解释，这需要一些新的解释。4)其他研究：研究了多组分体系的共晶和结晶，发现结晶竞争和组分分离减少了各种形貌。研究发现，晶化和随后的固-固相变在晶体中引入了“冻结”缺陷。

1) Crystalizathion from the melt : It is found that polymer single crystlas are formed through new thickening growth and well known lateral growth mechanisms. Thickening growth rate (U) increased with increase of degree of supercooling. These findings indicates that sliding diffusion of polymer chains takes important role in polymer crystallization mechanism. Crystallization temperature deyiendence of shape of single crystals was explained by competing of nucleation rate and traveling velocity of a nucleus.2) Crystallization from the solution : Important role of absorption of polymer chains in crystallization and possibility of nucleation of three dimensional nucleus were shown.3) Crystallization of spherulites : Origin of spherulite formation was explained by generation of screw dislocation induced by misfit between two sectors with differently oriented folds. Lateral growth rate at very high degree of supercooling was observed and it could not be well explained by conventional nucleation theory, which requires some new explanation.4) Other studies : Co-crystallization and crystalization of multi-component system were studied, which showed that competition of crystallization and segregation of components reduces various morphologies. It is found that crystallization and subsequent solid-solid phase transformation introduces "frozed" defects within a crystal.