UC Santa Barbara

Polymers have revolutionized modern life, finding countless applications due to their low production cost, tunable material properties, and long-term stability. However, this ubiquity and durability present global sustainability challenges necessitating the development of next-generation polymers capable of closed-loop recycling. Currently, sorting and recycling most consumer plastic products is not economically feasible due to the complexity of plastic types, resulting in only 5% of plastics in the United States being recycled. Promising strategies to enhance our recycling capabilities and transform plastics into a sustainable commodity include improving the blending of different polymers, incorporating degradable comonomers, and upcycling unwanted plastic products.To further explore polymer blending, Chapter 2 and Appendix A discussed improving polymer blending by developing polymers end-functionalized with complementary quadruple hydrogen-bonding end groups for improved miscibility. 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (Napy) functionalized polymers reduced macrophase separation through the formation of the UPy-Napy heterocomplex in solution and thin film studies. This approach enables the creation of challenging silicone-based blends, benefiting both industrial applications and fundamental research. To expand upon the utility of degradable comonomers, Chapter 3 and Appendix B presented a platform to access vinyl-based α,ω-dithiol oligomers by degradation of copolymers derived from α-lipoic acid or ethyl lipoate with various vinyl comonomers. Structurally diverse polymeric α,ω-dithiols are synthesized by incorporating and then reducing disulfide bonds within the vinyl polymer backbone, demonstrating controllable molecular weights and tunable glass-transition temperatures (Tg). The utility of these α,ω-dithiol oligomers is highlighted for use as building blocks or crosslinkers in efficiently photocrosslinked networks. Further expansion of these α,ω-dithiol polymers for facile access to customizable random multiblock copolymers (MBC) was discussed in Chapter 4 and Appendix C. By oxidizing the thiols of low and high Tg dithiol polymers, a diverse range of random MBCs with high molecular weights and modulated mechanical properties were synthesized. This approach enabled precise control over MBC block molecular weight, tunable composition, and added chemical degradability. The versatility and scalability of this approach paves the way for future studies on telechelic thiol vinyl-based polymers and random MBCs.