Phase Behavior and Network Morphologies in ABC Triblock Copolymers

合成聚合物主宰着化工行业最大的商业市场之一，产品范围从生硬的垃圾袋到用于精致血管支架的气囊导管。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、透气性、透明度等)，同时优化加工特性并将成本降至最低。嵌段共聚物由两个或更多化学上不同的大分子连接而成，提供了对纳米级形态的无与伦比的控制，并为创造具有竞争性能的先进材料提供了前景。线型双单体嵌段共聚物(AB、ABA、ABABA等)在热力学上是很好理解的，在通用相图的框架内，从理论上和实验上都建立了四种微相分离状态。三单体三嵌段(ABC、ABCBA等)提供了更丰富的材料设计组合、相行为和功能，但人们对它们的了解明显较少。这项建议针对几个模型ABC三嵌段共聚物系统，战略地选择用于基本相行为研究，并作为离子导电膜的开发。连接ABC三嵌段共聚物理论和实践的最大限制可能是一系列令人望而生畏的实验变量。确定了一种通过模型阴离子聚合苯乙烯(S)、异戊二烯(I)和环氧乙烷(O)改变组成和嵌段排序的系统和精确的方法，从而能够基于小角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)和其他方法对相行为进行有组织的评估。ISO和SiO三块材料将在弱偏析和强偏析限制下进行评估，重点是与领先的理论计划相协调地识别多连续和三周期结构。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动力，并为聚合物工业这一最重要的部门提供新材料。玻璃态聚(二环己基乙烯)(C)、橡胶聚(乙基乙烯)(E)和半晶聚(乙烯)(E)将被配置成互补序列(CEE、CE E E和E ECES)和模型纳米结构，并评估其在熔融状态下的剪切响应和在固态下的相关力学性能。选择性传输特性可以与坚固的机械性能、化学稳定性和卓越的加工性相结合。离子导电膜在固体电解质和质子传导燃料电池膜方面的应用被认为是特别有吸引力的。使用锂掺杂的ISO和SiO三组分，离子电导率将被确定为形貌的函数。多重连续形态，如陀螺体，有望在没有磁区对齐的情况下提供容易的离子传导。含有酸性部分(例如，羧酸或磺酸)的新三嵌段将通过阴离子或活性自由基聚合方法制备，并通过聚合后官能化来增强。聚丙烯酸、含氟聚丁二烯和聚苯乙烯是一种初始的目标化合物。这些质子导电材料将用SAXS、SANS、DMS和TEM进行表征，从而在传统的非极性嵌段共聚物和那些含有离子取代基的聚合物之间建立相行为的对应关系

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