Crystallization Mechanizm of Polymers

1)熔融结晶：发现聚合物单晶是通过新的增厚生长和已知的侧向生长机制形成的。增稠生长速率(U)随过冷度的增大而增大。这些发现表明聚合物链的滑动扩散在聚合物结晶机理中起着重要作用。用成核速率和原子核运动速度的竞争来解释结晶温度对单晶形状的影响。2)溶液结晶：聚合物链的吸收在结晶过程中的重要作用和三维核成核的可能性。3)球晶的结晶：球晶形成的原因是由于两个不同取向褶皱的扇区不匹配导致螺位错的产生。在过冷度非常高时观察到横向生长速率，常规的成核理论不能很好地解释这一现象，需要一些新的解释。4)其他研究：对多组分体系的共结晶和结晶进行了研究，表明结晶的竞争和组分的偏析减少了各种形态。发现结晶和随后的固-固相变在晶体内引入了“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.