Crystallizable Block Copolymers

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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. ***