Phase Behavior and Network Morphologies in ABC Triblock Copolymers

合成聚合物占据着化工行业最大的商业市场之一，其产品从足够的垃圾袋到用于精细血管成形的球囊导管。越来越多的聚合物材料必须结合多种功能（例如，韧性，硬度，耐溶剂性，渗透性，透明度等），同时优化加工特性和最小化成本。嵌段共聚物是通过连接两个或多个化学性质不同的大分子而形成的，它提供了对纳米级形态的无与伦比的控制，并为制造具有竞争性质的先进材料提供了前景。线性双单体嵌段共聚物（AB， ABA， ABABA等）的热力学性质已得到很好的了解；在通用相图的框架内，从理论和实验两方面建立了四种微相分离状态。三单体三块体（ABC、ABCBA等）提供了更丰富的材料设计组合、相行为和功能谱，但人们对它们的理解却明显不足。本提案针对几种模型ABC三嵌段共聚物体系，战略性地选择用于基本相行为研究，并用于离子导电膜的开发。也许连接ABC三嵌段共聚物理论和实践的最大限制是一系列令人望而生畏的实验变量。通过模拟苯乙烯(S)、异戊二烯(I)和环氧乙烷(O)的阴离子聚合，确定了一种系统和精确的方法来改变组成和块序，从而能够基于小角度x射线和中子散射（SAXS和SANS）、动态机械光谱（DMS）、透射电子显微镜（TEM）和其他方法有组织地评估相行为。ISO和SIO三块体材料将在弱和强偏析极限下进行评估，重点是识别多连续和三周期结构，并与领先的理论计划协调。通过阴离子聚合和催化加氢获得的模型聚烯烃的合成和结构表征将补充这一基本推力，同时为聚合物工业中最重要的部门提供新材料。玻璃状聚（二己基乙烯）(C)、橡胶状聚（乙烯）(E)和半晶状聚（乙烯）(E)将被配置成互补序列（CEE E、CEE E和E ECE）和模型纳米结构，并评估熔体状态下对剪切的响应和固态下相关的机械性能。膜为嵌段共聚物提供了诱人的发展机会。选择性运输特性可以结合强大的机械性能，化学稳定性和优越的可加工性。离子传导膜在固态电解质和质子传导燃料电池膜方面的应用具有特别的吸引力。离子电导率将被确定为使用锂掺杂的ISO和SIO三块体的形态函数。多种连续的形态，如陀螺，有望在没有畴对齐的情况下提供方便的离子传导。含有酸性基团（如羧酸或磺酸）的新三嵌段将使用阴离子或活性自由基聚合方法制备，并通过聚合后功能化加以增强。与氟化聚（丁二烯）和聚（苯乙烯）结合的聚（丙烯酸）是最初的目标化合物。这些质子导电材料将通过SAXS， SANS， DMS和TEM进行表征，从而建立常规非极性嵌段共聚物与含有离子取代基的共聚物之间相行为的对应关系

Synthetic polymers command one of the largest commercial markets in the chemical industry with products ranging from ough trash bags to balloon catheters used in delicate angioplaty. Increasingly, polymeric materials must combine multiple functions (e.g., toughness, hardness, solvent resistance, permeability, clarity, etc.), while optimizing processing characteristics and minimizing cost. Block copolymers, formed by joining two or more chemically distinct macromolecules, provide unparalleled control over nanoscale morphology and the prospect for creating advanced materials with competitive properties. Linear two-monomer block copolymers (AB, ABA, ABABA, etc) are well understood thermodynamically; four microphase separated states have been established within the framework of a universal phase diagram, both theoretically and experimentally. Three-monomer triblocks (ABC, ABCBA, etc.), which offer a much richer spectrum of materials design combinations, phase behavior, and functionality, are significantly less well understood. This proposal targets several model ABC triblock copolymer systems, strategically selected for fundamental phase behavior studies, and for development as ion conducting membranes. Perhaps the greatest limitation in connecting ABC triblock copolymer theory and practice is a daunting array of experimental variables. A systematic and precise approach to varying composition and block sequencing through model anionic polymerization of styrene (S), isoprene (I), and ethylene oxide (O) is identified, thereby enabling an organized evaluation of phase behavior based on small-angle X-ray and neutron scattering (SAXS and SANS), dynamic mechanical spectroscopy (DMS), transmission electron miscoscopy (TEM), and other methods. ISO and SIO triblock materials will be assessed in the weak and strong segregation limits with an emphasis on identifying multicontinuous and triply periodic structures in coordination with a leading theoretical program. Synthesis and structural characterization of model polyolefins, obtained by anionic polymerization and catalytic hydrogenation, will compliment this fundamental thrust while contributing new materials to this most important sector of the polymer industry. Glassy poly(dyclohexylethylene) (C), rubbery poly(ethylethylene) (E), and semicrystalline poly(ethylene) (E) will be configured into complimentary sequences (CEE E, CE E E, and E ECE) and model nanostructures and evaluated for response to shear in the melt state and the associated mechanical properties in the solid state.Membranes present an attractive development opportunity for block copolymers. Selective transport characteristics can be combined with robust mechanical properties, chemical stability, and superior processability. Ion conduction membranes are identified as particularly attractive with applications as solid-state electrolytes and proton conducting fuel cell membranes. Ion conductivity will be determined as a function of morphology using lithium doped ISO and SIO triblocks. Multiply continuous morphologies, such as the gyroid, are anticipated to provide facile ion conduction without domain alignment. New triblocks containing acidic moieties (e.g., carboxylic or sulfonic acid) will be prepared using anionic or living free-radical polymerization methods, augmented by post polymerization functionalization. Poly(acrylic acid) in combination with fluorinated poly(butadiene) and poly(styrene) is an initial target compound. These proton-conducting materials will be characterized by SAXS, SANS, DMS, and TEM, thereby establishing the correspondence in phase behavior between conventional non-polar block copolymers and those containing ionic substituents