Tailored Chain Sequences of Pendant Functional Groups and Resulting Phase Behavior of Gel-State Functionalized Blocky Copolymers

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 are made up of two different chains (blocks) attached together at one of their ends. If the blocks possess distinctly different chemical properties, then they may be capable of self-assembling into well-ordered physical structures that impart material properties that are very different, and often better, than the properties of the individual blocks alone. Unfortunately, the chemical synthesis of block copolymers is generally much more complicated, energy intensive, and expensive compared to that employed in synthesizing a typical commodity polymer of just one block. While polymer chemists have made remarkable progress in developing new ways to synthesize block copolymers, commercial success has been limited and often relegated to applications in high-cost fields such as advanced medical devices or semiconductor manufacture. In this project, a new physical approach will be used to create blocky copolymers in a straightforward, economically-attractive fashion by selectively modifying specific sequences of units along the chains of commercially available polymers. The breakthrough approach here involves performing chemistry in the gel state, whereby specific portions of the chains are essentially hidden from the modifying chemistry. This research will provide significant advancements in accelerating the creation of tailored block copolymer assemblies and enhance fundamental insight toward next-generation membrane technologies. With respect to the grand challenges facing our society, this project will provide cost-effective, readily available alternative materials needed to meet critical demands for water purification membranes, fuel cell membranes for clean energy conversion, and environmentally-friendly materials for the medical and healthcare industries. The interdisciplinary nature of research activities in this project, ranging from pure chemistry to materials structure and properties, will provide a plethora of educational opportunities to a diverse community of students and researchers eager to contribute to our nation's leadership in a scientifically and technologically advanced 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 reactions 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. Building upon recent discoveries that semi-crystalline polymers, such as syndiotactic polystyrene and poly(ether ether ketone), can be brominated in the heterogeneous gel-state as a simple way to create blocky copolymers with tailored sequence distributions, this project aims to engage a wealth of substitution chemistries available with brominated aromatic templates to create a wide variety of new blocky copolymers as a means to systematically manipulate phase behavior and thus the formation of ordered morphologies with tailored properties. In addition to the substitution chemistries, the morphological parameters of the semi-crystalline gel will be altered by controlled temperature, concentration, and solvent to precisely affect the sequences of functionalized and non-functionalized chain segments. The grand challenge to be addressed in this project will be: Can we now direct the formation of ordered phase-separated domains, similar to that observed with conventional block copolymers, by tailoring the chemical composition of these new, gel-state functionalized, blocky copolymer systems? Membranes of the blocky copolymers will be architecturally tailored for energy conversion and water purification applications. The interdisciplinary nature of research activities in this project, ranging from pure chemistry to materials structure and properties, will help to educate 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. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.