Crystallizable Block Copolymers

该项目围绕材料-半晶嵌段共聚物-表现出半晶均聚物和传统非晶嵌段共聚物的特性。这些材料可以形成一系列长度尺度的结构，从可结晶块的单细胞结构，到微畴长度尺度，再到球晶尺度。提出了两类互补的材料和现象进行研究：1)流体中间相模板化结晶；2)具有无缺陷结晶块的新型聚合物。第一种情况是基于最近的一项发现，即至少在某些情况下，由嵌段共聚物形成的众所周知的中间相（例如，圆柱体和球体）能够将结晶限制在中间相的特定部分内（例如，圆柱体内的结晶，其中圆柱体直径为几十纳米），即使对于在结晶过程中基体保持流体并且材料在常规加工条件下结晶的材料也是如此。本文的目的是确定熔体中间相在模板结晶中有效的条件，并阐明这种受限结晶的机制和起源。在第二种情况下，将研究环丁烯和降冰片烯的开环复分解聚合（ROMP）制备的新聚合物。聚（环丁烯）氢化反应得到线性（无支化的高密度）聚乙烯。最后，通过使用一个非常活跃的饱和催化剂，将有可能饱和降冰片烯和环丁烯块。因此，这种材料将是结晶-结晶双块，其中结构形成和材料特性裁剪的可能性是相当多样化的。这些半结晶嵌段共聚物主要用作可熔融加工的橡胶，与传统的硫化橡胶不同，它们可以回收利用（简单地重塑成新制品）。与现有的熔融可加工橡胶相比，这些新型聚合物具有更高的温度（例如，汽车应用），更高的光学清晰度（例如，医疗应用），以及出色的耐油和溶剂性。＊＊＊

9711436 Register This project revolves around materials - semicrystalline block copolymers - which exhibit characteristics of both semicrystalline homopolymers and conventional amorphous block copolymers. These materials can develop structure over a range of length scales, from the unit cell structure of the crystallizable block, to the microdomain length scale, to the spherulite scale. Two complementary classes of materials and phenomena are proposed for investigation: 1) crystallization templated by fluid mesophases, and 2) new polymers with a defect-free crystallizable block. The first case builds on a recent discovery that in at least some cases, the well-known mesophases formed by block copolymers (e.g., cylinders and spheres) are able to restrict crystallization to within a particular part of the mesophase (e.g., crystallization within cylinders, where the cylinder diameter is a few tens of nanometers), even for materials where the matrix remains fluid during crystallization and the material is crystallized under conventional processing conditions. The objective here is to determine the conditions under which the melt mesophases are effective at templating crystallization, and to elucidate the mechanism and origin of this restricted crystallization. In the second case, new polymers made by ring-opening metathesis polymerization (ROMP) of cyclobutene and norbornene will be studied. Hydrogenation of poly(cyclobutene) yields a linear (unbranched, high-density) polyethylene. Finally, by using a very active saturation catalyst, it will be possible to saturate the norbornene block as well as the cyclobutene block. Such materials would thus be crystalline-crystalline diblocks, where the possibilities for structure formation and the tailoring of material properties are quite diverse. %%% These semicrystalline block copolymers are principally intended for use as melt-processible rubbers, where unlike conventional vulcanized rubbers, they can be recycled (simply remolded into new articles). In comparison with existing melt-processible rubbers, these new polymers offer higher temperatures (e.g., automotive applications), improved optical clarity (e.g., medical applications), and excellent resistance to oil and solvents. ***