Cell & Developmental Biology

Cell & Developmental Biology
Open Access

ISSN: 2168-9296

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Weiss RA

Weiss RA

 Professor of Polymer Engineering, University of Akron, USA

Robert Weiss  has done his Ph.D. in Chem. Engineering at the University of Massachusetts, Amherst (1976) followed by his B.S. in Chem. Engineering at Northwestern University (1972). He has been the recipient of many national and international awards and grants. He has served as an Editor, Associate editor, Editor in chief for various journals and he has been a member of advisory board for many books. He is currently working as a Associate Dean of Research in College of Polymer Science & Polymer Engineering in the University of Akron, USA    
Research Interest

Manufacture of Controlled Microstructure Proton Exchange Membranes
The objective of this research is to solution and melt processing to control the microstructure of multicomponent, multiphase polymer membranes and to understand the effect of the controlled microstructure on the transport and mechanical properties of a PEM. The polymer systems of interest include polymer blends, block copolymers and polymer nanocomposites. Methods are being developed for manufacturing membranes while simultaneously orienting a conductive phase in the direction of proton transport using external electrical and magnetic fields. Controlling the ionic micro- or nano-phase structure allows the optimization of the membrane's conductivity, durability and resistance to fuel crossover.

Functional Polymers from Renewable Resources
This research involves the synthesis and characterization of ionomers from renewable and sustainable resources. Current work is focused on ionomers based on lactic acid, which is derived from corn, and itaconic anhydride (ITA), which is derived from citric acid. One approach is to use preformed polymers, such as poly(lactic acid) and incorporate a carboxylic acid or sulfonic acid species randomly into the chain or specifically at the chain ends (telechelic polymer) using melt transesterification reactions. These materials materials will be assessed for a variety of applications - e.g., hydrogels, compatibilizers, coatings and adhesives.

Shape Memory Elastomers
Shape memory polymers (SMP) are being developed from compounds of a fatty acid or fatty acid salt (FAS) combined with an ionomer, such as sulfonated poly{ethylene-r-propylene-r-(5-ethylidene-2-norbornene) ionomer (SEPDM) The ionic interactions within the ionomer phase provid a permanent crosslinked network due to the extremely long relaxation times of the physical crosslinks produced from nanophase separation of ion-rich domains. The novelty of this type of SMP is that the fatty acid crystals form the temporary network, due to strong intermolecular interactions between the metal sulfonate groups of the ionomer and the carboxylate groups of the FAS. The surprising result is that the ionic or dipolar interactions between the FAS and the ionomer is strong enough to allow the dispersed FAS crystals to support stress, thus providing a robust physical crosslink. The advantage of this approach for making a SMP is that the critical temperature for fixing the temporary network or allowing shape recovery can be easily varied by varying the fixing temperature (in this case, the melting point of the FAS) by judicious choice of the FAS - thus, providing a family of SMPs with a single host elastomer.

Rheology of Ionomers
Ionomers are a genre of associating polymers, i.e., polymers with strong attractive intermolecular forces. The strength and relaxation times of the associations in ionomers significantly influence their fluid dynamics. To what extent is dependent on the nature of the ionic groups, the counterion used to neutralize the fixed charges, the concentration of such charges and the time, temperature and amplitude of the deformation of these fluids. This research focuses on the rheological behavior of lightly sulfonated, low molecular weight polystyrene ionomers. The objectives of this research are to 1) develop an understanding of how the nature of the ionomer counterion affects the rheology, specifically the relaxation times of the chain and the ionic associations; 2) how is elasticity developed in unentangled ionomers, 3) what is the origin of shear-thickening that is observed in ionomer melts and 4) how can one engineer the rheology of ionomer melts by the addition of low molecular weight additives. The research includes the synthesis and characterization of ionomers, steady state and dynamic shear rheology of the ionomer melts and real-time, small angle neutron scattering (SANS) evaluation of the melts during shear deformation.

Controlling Surface Morphology of Thin Films
Wettability of surfaces plays an important role in many biological and industrial applications. Non-wettable surfaces have important applications, for example in self-cleaning, anti-sticking, stain resistance and anti-contamination surfaces in technologies such as biomedical, transportation, textiles, electronics and coatings. We recently discovered a facile method for introducing nano- and micro-scale roughness during the manufacture of thin polymer films. The goal of this research is understand the mechanism of the roughness formation, which is thought to be a spinodal decomposition of the surface during solvent evaporation. The research involves experimental, theoretical, and computational components. Applications of this work that are being separately studied include manufacturing methods of forming superhydrophobic surfaces by solvent casting and the development of scaffolds for tissue engineering. 

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