Structuring Polymer Crystals through Macromolecular Architecture

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。即使是简单的均聚物在结晶时也显示出分级结构，不同的性质主要由不同的结构特征控制，例如，熔点取决于晶体厚度，刚度取决于晶体连续性和取向。通常，只能对这些关键结构特征进行粗略控制。我们的研究目标是合成聚合物，这些聚合物将自发地自组装以产生晶体，这些晶体的介观结构（厚度和取向）可以精确地定向，并且通过合成来改变大分子结构而在宽范围内进行调谐。为此，我们将利用活性开环易位聚合（ROMP）提供的结构控制。我们不寻求将晶体限制在离散的微区（球体或圆柱体）内，而是建立微区支架，通过结晶或通过熔体中的嵌段间排斥形成，这允许晶体像常规均聚物结晶那样生长延长的距离，但对最终结构具有相当大的控制。活性ROMP提供了两种全烃，高度结晶的嵌段（氢化聚苯乙烯，hPN，和线性聚乙烯，LPE），这是熔融混溶与一系列其他非结晶饱和烃嵌段在高分子量。此外，无定形嵌段的物理性质可以在玻璃化转变温度的200 ° C范围内进行调节，例如通过由Promerus Electronic Materials的合作者提供的烷基双烯（aN）和四环十二烯（TD）库。hPN-hPaN-hPN三嵌段共聚物，其应显示可通过hPN和hPaN嵌段长度调节的平衡晶体厚度，以及可与目前的全无定形嵌段共聚物相媲美或超过其的热塑性弹性体行为;玻璃-结晶hPTD-hPN和hPTD-LPE二嵌段，其中我们将阐明决定晶体厚度和熔点的特征;堆叠结晶hPN-LPE二嵌段，其中我们寻求在介观尺度上证明晶体多晶型;和ABC三嵌段共聚物，其中各个嵌段可以是橡胶状的、玻璃状的或高度结晶的，作为产生具有非对称表面的微晶和控制微晶相对于微区界面的取向的手段。拟议的工作将在年期间为两到三名研究生和三到六名本科生提供综合研究和教育经验。该奖项，特别是包括代表性不足的群体的成员。学生将在内部和外部展示他们的工作，而研究生将同时担任研究人员，学生和导师的角色，从而确保研究和教育之间的整合。PI和学生将通过在自由科学中心（泽西城，新泽西州）的科学推广活动，通过开发和展示展示聚合物材料的不寻常和有用的特性，吸引公众。PI和学生还将支持美世县3-8年级基于工具包的科学教育，并寻求引入一个围绕有机和聚合材料的工具包，遵循县和州的教育目标。

Crystallization of polymers has a profound impact on their properties, and underpins many of their applications. Even simple homopolymers show a hierarchical structure when they crystallize, with different properties principally controlled by different structural features, e.g., melting point dependent on crystal thickness, stiffness dependent on crystal continuity and orientation. Ordinarily, only coarse control can be exerted over these key structural features. Our research aim is to synthesize polymers which will spontaneously self-assemble to give crystals whose mesoscopic structure (thickness and orientation) can be precisely directed, and tuned over broad ranges by altering the macromolecular architecture through synthesis. To this end, we will avail ourselves of the architectural control afforded by living ring-opening metathesis polymerization (ROMP). We seek not to confine crystals within discrete microdomains (spheres or cylinders), but rather to establish microdomain scaffolds, formed either by crystallization or through interblock repulsion in the melt, which permit the crystals to grow for extended distances as in conventional homopolymer crystallization, but with considerably greater control over the final structure. Living ROMP provided access to two allhydrocarbon, highly-crystalline blocks (hydrogenated polynorbornene, hPN, and linear polyethylene, LPE) which are melt-miscible with a range of other noncrystallizable saturated hydrocarbon blocks at high molecular weights. Moreover, the physical properties of the amorphous block can be tuned over a wide range a 200oC range in glass transition temperature, for example via a library of alkylnorbornenes (aN) and tetracyclododecenes (TD) provided by collaborators at Promerus Electronic Materials. Some of the architectures which we propose to explore, and the unusual features which we anticipate, are: hPN-hPaN-hPN triblock copolymers, which should show equilibrium crystal thicknesses tunable through the hPN and hPaN block lengths, as well as thermoplastic elastomer behavior which could rival or surpass that of current all-amorphous block copolymers; glassy-crystalline hPTD-hPN and hPTD-LPE diblocks, where we will elucidate the features which dictate the crystal thickness and melting point; crystallinecrystalline hPN-LPE diblocks, where we seek to demonstrate crystal polymorphism at the mesoscale; and ABC triblock copolymers, where the individual blocks may be rubbery, glassy, or highly crystalline, as a means to generate crystallites with asymmetric surfaces and to control the orientation of the crystallites relative to the microdomain interfaces.The proposed work will provide an integrated research and educational experience for two to three graduate students and three to six undergraduates over the period of the award, especially including members of underrepresented groups. Students will present their work both internally and externally, while graduate students will have concurrent roles as researchers, students, and mentors, thus ensuring integration between research and education. The PI and students will engage the general public through science outreach at the Liberty Science Center (Jersey City, NJ), by developing and presenting demonstrations illustrating the unusual and useful properties of polymeric materials. The PI and students will also support of kit-based science education for Grades 3-8 in Mercer County, and seek to introduce a kit revolving around organic and polymeric materials, following county and state educational objectives.