Title

Preparation and characterization of thiol based polymeric materials

Author

Junghwan Shin

Date of Award

2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Charles E. Hoyle

Advisor Department

Polymers and High Performance Materials

Abstract

In this dissertation, three major thiol click-type reactions, i.e. thiol-electron rich double bonds by free radical, thiol-electron poor double bonds by nucleophile catalyzed hetero-Michael addition, and tertiary amine catalyzed thiol-isocyanate nucleophilic coupling reactions, were studied in terms of the efficiency of thiol click-type reactions for the fabrication of materials and their physical/mechanical properties. Also, sub- Tg aging of thiol-ene photopolymerized network films monitored by enthalpy relaxation was investigated in terms of fundamental molecular parameters such as network density, rigidity, uniformity, and polar/non-polar side chains. In Chapter III, highly elastic segmented polythiourethanes linear polymers were synthesized through sequential thiol click-type reactions involving the phosphine catalyzed thiol-acrylate hetero-Michael addition and triethylamine catalyzed thiol-isocyanate nucleophilic coupling reactions. Real-time FTIR and NMR showed that both the thiol-acrylate hetero-Michael addition and the thiol-isocyanate coupling reactions are very fast and efficient with no side products. In Chapter IV, thiol-ene-isocyanate ternary networks were studied as a new approach to modify classic thiol-ene networks by incorporating thiourethane linkages through sequential and simultaneous two thiol click-type reactions. The thiol-isocyanate coupling reaction providing strong hydrogen bonding in thiol-ene networks was triggered thermally and photolytically in order to control the sequence with the thiol-ene photo-polymerization. The kinetics of the ternary networks was investigated for both sequential and simultaneous processes. In Chapter V∼VIII, sub-Tg aging behavior of thiol-ene networks measured by the extent of enthalpy relaxation was extensively investigated. The fundamental enthalpy relaxation study on thiol-ene networks was accomplished in Chapter V. The highly dense and uniform network structure of the thiol-ene networks, exhibiting narrow glass transition temperature ranges, showed characteristic temperature and time dependency relationships for enthalpy relaxation. In Chapter VI, the effect of chemical modification of thiol-ene networks on enthalpy relaxation was investigated as an unprecedented methodology to control sub-Tg aging process. Flexible alkyl side chains and hydrogen bonding were incorporated into thiol-ene networks without sacrificing network uniformity using the phosphine catalyzed Michael addition reaction. Overall both the rate and extent of enthalpy relaxation slightly decreased as a function of the flexible n-alkyl chain length, while hydrogen bonding resulted in enhanced enthalpy relaxation. In Chapter VII, as an extended study of the modification of thiol-ene networks in order to control sub-Tg aging process described in Chapter VI, the degree of restriction effect of the rigid TMPTA homopolymer domains and gold nanoparticles on thiol-ene networks was quantitatively determined by calculating the apparent activation energy (Δh *) for enthalpy relaxation. Finally, in Chapter VIII, 10- and 32-layered thiol-ene based films with different components were fabricated to investigate sub-T g aging of multi-layered thiol-ene network films. The distinctive glass transition temperatures of each component were observed at corresponding transition regions of each bulk sample. (Abstract shortened by UMI.)