Investigations toward tunability of mechanical, thermal, and impact properties of thiol-ene networks for novel high energy absorbing materials
The UV polymerization of thiols with electron rich alkenes is a highly resourceful reaction that has been utilized by scientists within various disciplines to produce an even more versatile display of applications. This dissertation focuses on a newer application, thiol-ene network (TEN) materials for energy absorption devices. TEN networks display a host of positive polymer properties such as low stress, high optical clarity and uniformity, but they also suffer from unfavorable mechanical properties such as low toughness and elongation at break. The poor mechanical properties demonstrated by TENs prohibit them as choice materials for applications requiring thicker material forms, including energy damping devices. The chapters in this dissertation focus on enhancing the toughness of TENs via urethane or thiourethane incorporation wherein toughness is enhanced by either hydrogen bonding or underlying network morphologies. Impact behaviors of base systems were investigated and correlated to polymer glass transition temperature. The tunability of the temperature associated with viscoelastic relaxation was also investigated by developing hybrid networks containing two thiol components. The relevance of the works performed is highlighted by the major contributions realized by understanding structure-property relationships and network morphology on underlying principles of energy absorption.