Controlled Crystallization in Novel Block Copolymers

该奖项将研究嵌段共聚物直接聚合物结晶的能力。 具有无缺陷可结晶嵌段的二嵌段和三嵌段共聚物将测试结晶-无定形嵌段共聚物中链折叠的平衡程度的预测，这与通常由均聚物表现出的动力学诱导的链折叠形成鲜明对比。 通过结晶和无定形嵌段长度控制微晶厚度或添加非挥发性稀释剂将产生具有窄且可调的熔融范围的材料。 具有可结晶端块的稀释三嵌段将代表具有低模量和良好尺寸稳定性的新型热塑性弹性体凝胶-大变形致动器的理想候选者。 在这项工作的第二个方面，通过结合开环复分解和阴离子聚合合成的新型嵌段共聚物将解决线性和短支链聚乙烯之间的共结晶的长期存在的问题。 这些聚合物将含有线性聚乙烯PE和聚（乙烯-共-丁烯）PEB的嵌段，其由可变长度的无定形嵌段隔开。 当这种“连接体”运行较短时，聚合物基本上是PE-PEB二嵌段，预期其显示出令人感兴趣的晶体异质性。 当连接体链段具有中等长度（足够长以与其它嵌段微相分离）时，则PE和PEB嵌段被束缚到无定形结构域，有利于PE/PEB共结晶。 最后，当连接体运行是主要组分时，混合的PE + PEB链将在离散的微区中分离，其中它们将仅在深过冷下结晶并且具有广泛的共结晶。 这为系统研究PE/PEB共晶的结构和性能提供了一条途径。 聚合物的结晶对其性能有着深远的影响，并支撑着它们的许多应用。 在从纳米到微米的尺寸尺度上，一个典型的聚合物的晶体结构强烈地依赖于用于结晶it. In这项工作中，我们提出了强大的控制结晶过程中的细节方法，因此结构，通过分子功能内置到聚合物-所谓的“块架构”-在合成过程中。 拟议的工作将为两名研究生和大约六名本科生提供综合研究和教育经验，他们将能够在内部和外部传播他们的工作成果。 PI和研究生将继续通过开发新的教育材料和教师培训，积极支持美世县的K-6科学教育。

This award will investigate the ability of block copolymers to direct polymer crystallization. Diblock and triblock copolymers with defect-free crystallizable blocks will test the prediction of an equilibrium degree of chain folding in crystalline-amorphous block copolymers, which contrasts sharply with the kinetically-induced chain folding typically exhibited by homopolymers. Control of crystallite thickness through crystalline and amorphous block lengths or the addition of a nonvolatile diluent will yield materials with narrow and tunable melting ranges. Diluted triblocks having crystallizable endblocks will represent a new type of thermoplastic elastomer gel with low modulus and good dimensional stability-desirable candidates for large-deformation actuators. In the second aspect of this work, novel block copolymers synthesized by combining ring-opening metathesis and anionic polymerizations will address the long-standing issue of cocrystallization between linear and short-branched polyethylenes. These polymers will contain blocks of linear polyethylene, PE, and poly(ethylene-co-butene), PEB, separated by an amorphous block of variable length. When this "linker" run is short, the polymers are essentially PE-PEB diblocks, which are expected to show an interesting crystal heterogeneity. When the linker run is of medium length (long enough to microphase-separate from the other blocks), then the PE and PEB blocks are tethered to amorphous domains, favoring PE/PEB cocrystallization. Finally, when the linker run is the majority component, the mixed PE + PEB chains will be segregated within discrete microdomains, where they will crystallize only at deep undercoolings and with extensive cocrystallization. This provides a route to the preparation of PE/PEB cocrystals for systematic examination of their structure and properties. Crystallization of polymers has a profound impact on their properties, and underpins many of their applications. At size scales ranging from nanometers to microns, a typical polymer's crystalline structure depends strongly upon details of method used to crystallize it. In this work, we propose to robustly control the crystallization process, and hence the structure, through molecular features built into the polymers-the so-called "block architecture"-during synthesis. The proposed work will provide an integrated research and educational experience for two graduate students and approximately six undergraduates, who will be able to disseminate results from their work both internally and externally. The PI and the graduate students will continue their active work in support of K-6 science education in Mercer County, both through the development of new educational materials and through teacher training.