Blocky Copolymers via Gel-State Functionalization of Semi-Crystalline Polymers

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY Block copolymers are a unique class of long-chain molecules (polymers) that can be designed to contain well-ordered physical structures in thin films capable of efficiently separating the passage of molecules based on discriminating chemical attractions. Due to the ability to precisely control the size and chemical make-up of these physical structures, emerging applications of block copolymers include membranes for water purification and energy-efficient fuel cell vehicles. While polymer chemists have made remarkable progress in developing new ways to synthesize block copolymers for these applications, commercial success has been limited due to the complex chemical procedures needed to control the block-like growth of the molecular chains. In this project, a new physical approach will be used to create blocky polymers in a straightforward, economically attractive fashion by selectively modifying commercially available polymers in the gel state. This research will provide significant advancements in accelerating the creation of tailored block copolymer assemblies and enhance fundamental insight needed to enable next-generation membrane technologies and broaden the base of advanced materials available. The interdisciplinary nature of research activities in this project, ranging from materials chemistry to membrane properties, will provide many educational opportunities to a diverse community of citizens and researchers eager to contribute to our nation's leadership in ensuring a healthier, more energy-efficient global society. PART 2: TECHNICAL SUMMARY This project will focus on a new way to create blocky copolymers using straightforward, post polymerization chemistries on semi-crystalline homopolymers in the gel state. With the introduction of reactants capable of functionalizing the homopolymer, the desired chemistry is restricted to reaction upon only the accessible amorphous chain segments within the semi-crystalline network. This new physical process yields a non-random, blocky incorporation of functionality, and is a simple alternative to the complex polymerization mechanisms that are conventionally employed in the synthesis of block copolymers. The technical advancement of this approach is rooted in the fundamentals of pure physical polymer chemistry, and clearly transforms our way of thinking with respect to the creation of blocky copolymer architectures. By tailoring the morphological parameters of the semi-crystalline gel, the content and dimensions of functionalized and non-functionalized chain segments will be altered in the creation of new blocky ionomers from commercially important polymers for mechanically robust membranes targeted for water purification and fuel cell applications. The goals of this project are to develop a fundamental understanding of the physical, chemical, and compositional parameters needed to control the gel-state functionalization chemistry. In comparison to random copolymer analogs, the blocky architecture of gel-state sulfonated ionomers will be controlled with respect to ion content, block length distribution, crystallization conditions, and processing parameters. Membranes of the blocky copolymers will be prepared and compared to model membrane systems in order to facilitate the design of architecturally tailored membranes for energy conversion and water purification applications. The interdisciplinary nature of research activities in this project, ranging from materials chemistry to membrane properties, has proven to be attractive to a diverse community of researchers, including underrepresented groups. Educational outreach activities will engage citizens of all ages through the focus on cutting-edge research aimed at ensuring a healthier, more energy-efficient global society.