Polymeric materials are economically produced from a variety of chemical feedstocks for applications ranging from commodity packaging and structural materials to value-added materials for microelectronic and biomedical applications. Copolymers, resulting from linking two or more monomer units into a single polymer chain, exhibit a variety of properties depending on the molecular structures of the monomers, the order in which they are enchained, and the manner in which the functional groups in the monomers interact to alter the solid state structure ("morphology") and bulk properties of the material. Numerous studies have established that various monomer structures and the exact copolymer sequences sensitively influence the properties and the potential applications of polymers in applications that require selective ion permeability, toughness, and mechanical strength. The discovery of copolymeric materials with new and useful properties therefore depends sensitively on the ability to synthesize polymer architectures with precise control over functional group incorporation, chain architecture, and comonomer sequences in order to control solid-state structure and to tune materials properties and processabilities.
Efficient development of new and useful polymeric materials requires two synergistic skills sets:
(i) the ability to develop and to exploit new synthetic methods to produce new molecular structures with precise control over chain structure, functional group placement, and monomer sequence, and
(ii) the ability to physically characterize materials as ensembles of molecules to effectively evaluate their supramolecular structures (morphology), properties, and ultimate utility in applications.
Based on my group's unique combination of skills in synthetic methods development to make new polymer structures and in characterization of the resulting soft materials, our group synthesizes and fully characterizes new polymeric materials in order to discover new means for controlling polymer morphology to achieve unusual physical properties. In order to maximize the potential applications of these new materials, our research focuses on energy efficient ("green") syntheses amenable to large-scale production using inexpensive chemical feedstocks. Through this powerful combination of skills within my group, we rapidly identify novel materials targets and develop and optimize their flexible and scalable syntheses.
Research projects in my group focus on three significant challenges in polymer science that leverage the synthesis and characterization of new materials within the confines of a single research group:
Project Area 1. Degradable and Biodegradable Block Copolymers. Block copolymers are unique macromolecules comprised of two chemically distinct homopolymer segments that are covalently linked. Due to the chemical incompatibility of the homopolymer blocks (immiscibility), these polymers spontaneously self-assemble into a variety of well-defined structures (Figure 2) with unique physical properties. We have recently developed the syntheses of a new class of block copolymers that are expected to be (bio)degradable in the environment and in vivo. We are examining structure-property relationships therein toward the development of degradable commodity plastics, surfactants, and value-added tissue scaffolding and biomedical materials.
Project Area 2. Polydispersity effects in block copolymer phase behavior. We are probing the phase behavior of new multiblock copolymers that contain polydisperse segments to understand the implications of broadening polymer molecular weight distributions (chain length distributions) on the physics of self-assembly, processability, and properties of these materials.
Project Area 3. Lyotropic liquid crystals derived from small molecule surfactants. We are exploring efficient methods for generating small molecule surfactants that form liquid crystalline phases upon solvation with water. The resulting self-assembled media possess interpenetrating porous networks with sub-nanometer dimensions that are filled with water, which may be useful in size-selective chemical separations such as water desalination and ultrafiltration.
Each of these project areas develops and exploits new synthetic methods in organic and polymer chemistry to gain a molecular level understanding and control over polymer morphology, bulk materials properties, and polymer processabilities toward the development of new and useful commodity polymers for widespread applications.