| The exploration of re-mending and self-healing of polymeric materials has become increasingly more exciting in the recent past. However, no highly cross-linked polymeric material could be healed in the absence of additional ingredients such as a catalyst, additional monomer, or special surface treatment of the fractured interface until the materials that are the subject of this dissertation were discovered.; Thermally reversible Diels-Alder (DA) cycloadditions of multi-dienes and multi-dienophiles were used as cross-linking to prepare thermally re-mendable highly cross-linked polymers, in which the thermal reversibility can be accomplished by the retro DA reaction. The bulk polymeric materials are tough solids at room temperature but at temperatures above 90 to 120°C, a number of “intermonomer” linkages disconnect, yet reconnect upon cooling. This process is fully reversible and can be used to restore a fractured part multiple times.; DSC, TMDSC, TMA, DMA and solid state NMR were applied to study the thermal and mechanical properties of the polymers. To determine the fracture-healing efficiencies of these polymers, tests were performed using compact tension specimens. Representative recoveries were obtained between 57% and 83% of the original fracture load, after the thermal treatment of failed pieces. Scanning electron microscope (SEM) was also used to characterize healing efficiency. Efficient multiple-time healing was also observed.; Novel shape memory materials with Diels-Alder groups were also developed. The shapes of materials can be changed and restored after being heated to elevated temperatures (60 to 80°C).; Water-soluble cationic poly(p-phenylene vinylene) were synthesized for bio-sensing purposes. |
