高分子结晶临界核尺寸的测定

成核是高分子结晶基础研究中的难点，也是影响高分子结晶材料性质的关键因素。目前，高分子结晶临界核尺寸的实验测定还是困难重重。即使通过理论计算，不同的结晶理论或模型也会计算出不同的临界核尺寸。本申请提出了基于结晶过程成核速率对结晶单元浓度依赖性来直接获得临界核尺寸的方法。测定一系列无规共聚物的球晶径向生长速率随结晶单元浓度的变化，可获得二次临界核中结晶单元的数目。测定熔体相容的结晶均聚物/无定型聚合物共混物的球晶径向生长速率随结晶组分浓度的变化，又可以获得二次临界核中聚合物分子链的数目。同理，也可测定主成核时临界核的尺寸。这一计算临界核尺寸的方法适用于多种聚合物，且不依赖于结晶过程的具体微观路径。拟测定聚丁二酸丁二酯和聚乳酸等聚合物结晶时二次成核和主成核的临界核尺寸，研究其随结晶条件的变化。本研究有望解决结晶临界核尺寸实验测定这一难题，为设计新型成核剂和调控聚合物结晶结构提供理论指导。

Nucleation considerably affects the crystallization rate and the final performance of crystalline polymers. However, elucidating the mechanism of nucleation is still a great challenge in the field of polymer crystallization. On one hand, it is very difficult to observe the exact size of the critical nuclei. On the other hand, theoretical calculation based on different models may lead to different results. Our project proposes a novel method to obtain the size of the critical nuclei based on the microscopic kinetics model of polymer crystallization, which is applicable to various polymers and independent of the microscopic pathway of crystallization. The number of monomer units in the critical secondary nuclei can be obtained from the variation of the spherulite radial growth rate with the concentration of the crystallization units in the random copolymers. The number of polymer chains in the critical secondary nuclei can be calculated from the dependence of the spherulite radial growth rate on the blend ratio in the crystalline homopolymer/amorphous polymer blends miscible in the melt. Similarly, the size of the critical primary nuclei can be figured out. Based on the method, we will carry out experiments on poly(butylene succinate) and polylactide to determine the critical nuclei sizes and their variance with crystallization conditions. The research will not only deepen our understanding of polymer crystallization but also benefit the design of novel nucleating agent and controlling the crystalline structure of polymer materials.