Edward Bryan Coughlin

As renewable electricity becomes less and less expensive and it's use becomes more widespread, there is a need for electrical energy-to-chemical energy conversion for both storage and for the use of electrons as reagents. Current electrolysis applications focus on large-scale alkaline water electrolysis (\ or proton exchange membrane water electrolyzers, featuring well-developed technology and industrial equivalent current densities. However, significant drawbacks, such as high overpotential, poor design, inherent environmental risks, reliance on hard-to-access chemicals, and poor understanding of membrane and electrode properties, have constrained opportunities for improvement. We have been working on anion exchange membranes for a number of years and we are now addressing the cationic ionomers and electrocatlysts needed for device fabrication. To address this we are investigating the interaction of ionomers on metal substrates and the use of structured ionomers as templates to produce nano-structured metal particles as heterogeneous electrocatlayt/ionomer compose materials . We use a series of random and structured block co-polymers with unsaturated hydrophobic components that can be hydrogenated to rubbery polymethylbutylene or semi-crystalline polyethylene. Co-polymerized with these components we use vinyl benzyl chloride which once polymerized can be quaternized with a large variety of amines to systematically vary the size and nature of the organic cation in the polymer. Initial studies using commercial Ag nano-particles or flat Ag substrates indicated that we could vary the interaction of the ionomer with the metal surfaced by changing the polymer chemistry. Unsaturated unquaternized polymers showed very strong orthogonal alignment on flat Ag surfaces. When quaternized the material became less ordered but still maintained vertical transport channels to the catalysts surface. Ag nano-particle effected the crystal city of the polyethylene component of the block co-polymers via interaction with the cations. We have recently been extending these studies to Nickel foam electrodes and studying the effect if ionomer and ionomer/Ag composites on electrochemical processes important to electrolysis.

Polyelectrolyte complexation is an entropically driven, associative phase separation that has been leveraged to produce aqueously processed plastics known as polyelectrolyte complexes (PECs). Previously, we showed that their affinity to water and their chain mobility are important aspects to consider when designing PEC materials. To establish a more complete picture of influencing parameters, we examined the effect of polymer chemistry, specifically chain length and the side chain and backbone chemistry, on both the phase behavior and mechanical properties of homopolymer PECs. We combined compositional studies of PEC phase behavior with analyses of PEC dynamics and mechanics to understand how these aspects of polymer chemistry affect material performance. We observed that the identity of the ionizable groups heavily affected ion solvation, where PECs with lower water affinities had higher glass transition humidities and were generally more brittle, compared to PECs with higher water affinities. In contrast, backbone chemistry affected chain mobility, allowing acryloyl chemistries to have lower glass transition humidities compared to methacryloyl. Finally, chain length effects depended on the degree of match/mismatch of the polymer’s lengths, with matched PEC systems having higher glass transition humidities than mismatched. Comparisons of the phase behavior and glass transitions revealed that side chain and backbone chemistry effects are universal across different mediums, while length effects are medium specific. These results establish fundamental structure–property relationships for the rational design of functional PEC materials.

The evolution of crystallinity resulting from stress imposed on a melt, known as flow-induced crystallinity, can strongly influence the mechanical and physical properties of semicrystalline polymers. This study investigates shear-induced crystallization by applying an ultrasonic field to the melt flow as it passes through dies with various geometries. A custom-built sonication die is employed for controlling the dynamic temperature and shear environment, resulting in molecular alignment and potential for flow-induced crystallization. Application of both conventional and ultrasonic shear rates at the equilibrium melt temperature of high-density polyethylene (HDPE) was investigated to accelerate crystallinity and manipulate the crystal morphology across the film in pursuit of improved mechanical and gas barrier properties without the need for additives or other polymer layers. The relationships among ultrasonic-assisted extrusion processing, polymer structure, and performance were analyzed using wide- and small-angle X-ray scattering (WAXS and SAXS), tensile testing, and oxygen transmission rate (OTR) analysis. Multiple linear regression models were implemented to predict the correlation among HDPE structure, process, and properties. Structural analysis revealed that both conventional and ultrasonic shear rates had the most significant influence on lamellar spacing and redistribution of rigid and soft amorphous fractions within the crystalline domains, ultimately dictating the mechanical and physical properties of the films. The goal is to explore the potential of the ultrasonic-assisted high crystallinity monolayer that can replace some of the functionality of complex, heterogeneous multilayer packaging with a single-material film having enhanced oxygen barrier properties.

Functionalization of CC in unsaturated polyolefins by hydroboration/oxidation successfully generates linear poly­(ethylene-co-vinyl alcohol) (LEVOH) polymers. This postpolymerization modification expands upon previously reported chemistry to control the extent of functionalization through reagent stoichiometry. Partial functionalization (24–92% of CC) of polycyclooctene produces materials with both CC in the backbone and pendant OH and subsequent hydrogenation generate a LEVOH. We explore the thermal, structural, surface, and adhesive properties of these LEVOH and the partially unsaturated intermediate and find they are impacted by both the extent of OH incorporation and saturation. The presence of CC significantly reduces the melting temperature and crystallinity while increasing surface polarity and adhesive strength compared with saturated polymers at equivalent functionalization. This investigation demonstrates linear analogs of EVOH with a wide range of properties tuned by extent of hydroxylation and presence of unsaturation.