FRG: Synthesis, Characterization, and Simulation of Tailored Inhomogeneous Elastomers

Cornell University, Ithaca NY

Investigators

Abstract

Intellectual Merits. Much progress has been accomplished recently in understanding the role of the structure on the physical properties of homogeneous elastomers composed of neutral flexible polymer chains. Carefully tailored syntheses, new analyses of physical measurements, and new computer simulation methods have been developed to study these polymer networks. It is now possible to address the more challenging task of understanding the properties of inhomogeneous elastomers. The presence of a discontinuous phase (made up of microdomains that either spontaneously form or are purposely introduced) is known or expected to dramatically affect the network mechanical properties. Two examples of such situations are polar domains formed in ionomers and densily-crosslinked domains formed in bimodal networks. Two types of inhomogeneous elastomers will be investigated by synthesizing model systems that will allow the identification of the molecular basis of the observed properties using NMR, X-ray, and neutron scattering measurements. Computer simulation of these systems will provide comparison with experimental results. Specific areas of research include: 1) the flow properties of precursor polysiloxane chains with interacting groups at regular intervals along their backbone; 2) the macroscopic and microscopic properties of endlinked networks synthesized from these precursor chains and the development of kinetic and equilibrium Monte Carlo simulations for comparison with experimental results; 3) the study of the properties of bimodal networks to test a recently proposed scaling that predicts the onset of short chain clustering that dramatically affect the properties of the elastomer. Broader Impacts. The particular materials to be investigated have potential applications in the area of conducting elastomers (in the case of ionomer networks), and in high-strength rubber fibers (in the case of bimodal networks). Scientific results will be disseminated through professional meetings and an industrial outreach program organized by Cornell Center for Material Research. Both graduate and undergraduate students will be working on the project; they will gain a good understanding of the synthesis and the chemical and physical properties of polymers and elastomers in particular. They will acquire a general appreciation for the coupling of experimental analysis and computer simulation that is becoming increasingly important for industry as the materials being engineered to benefit society become more complex.