Physical Sciences and Mathematics Commons^™

Effect Of Network Structure On Free Volume And Gas Transport Properties Of Thiol-Ene And Epoxy-Amine Networks, Ramesh Krishnan Ramakrishnan

Dissertations

Network parameters such as cross-link density or intermolecular interactions were used as effective parameters to control polymer chain packing or free volume and thereby control the mass transport properties of networks.

A series of polyethylene glycol (PEG) based thiol-ene elastomeric networks having a broad range of molecular weight between cross-links, M_c, (inverse of cross-link density) was prepared. The specific volume of the networks was studied as a function of temperature and pressure using high pressure dilatometry, and the obtained PVT data was fit using Simha-Somcynsky equation of state (S-S eos) analysis. Fractional free volume, quantified through S-S eos …

Photopolymerized Thiol-Ene Networks For Gas Barrier And Membrane Applications, Luke Kwisnek

Dissertations

Gas transport and free volume properties of photopolymerized thiol-ene networks for various applications are reported. For basic, commercially-available thiol-ene formulations, oxygen permeation was strictly dependent on the difference between T_test (room temperature for this work) and network T_g. Networks with T_g near T_test demonstrated the lowest values of permeability, diffusivity, and solubility. A robust, high-barrier network was selected for further modification. New networks with embedded functionality were formed using a two-step approach. Thio-Michael addition of a tetrathiol to monofunctional acrylates formed new functional thiol monomers. These functional thiols were combined with an isocyanurate-based triene and …

The Influence Of Nanoporous Crystalline Structure On Low Molecular Weight Mass Transport In Syndiotactic Polystyrene, Justin Paul Brandt

Dissertations

Solid-state structure, crystalline morphology, crystallization kinetics, thermal, free volume, and gas transport properties of semicrystalline syndiotactic polystyrene (sPS) and ethylene vinyl alcohol copolymers (EVOH) have been investigated. Solid-state structure of sPS after crystallization from the melt and glassy state was examined by differential scanning calorimetry (DSC), density and wide angle x-ray diffraction analysis (WAXD). The measurements confirmed low density of syndiotactic polystyrene crystalline forms, which in the case of α and δe was smaller and in the case of β and γ crystalline forms was slightly larger than the density of the glassy amorphous sPS. Positron annihilation lifetime spectroscopy (PALS) …