ε-Poly-L-lysine-graft-oligo(3-hexylthiophene) Copolymers as Antibacterial and Biodegradable Polymer Electronics

Biodegradable polymer electronics offer an innovative solution to the growing challenge of electronic waste, which are engineered to disintegrate after a defined functional period. Here, a new class of graft copolymer is presented, ε-poly-L-lysine-graft-oligo(3-hexylthiophene) (EPL-g-O3HTs), synthesized by covalently grafting oligo(3-hexylthiophene) onto the biopolymer ε-poly-L-lysine at three grafting densities, resulting in copolymers containing 43, 65 and 90 wt.% O3HT (EPL-g-O3HT-1, EPL-g-O3HT-2 and EPL-g-O3HT-3, respectively). Benefiting from the "guidance" of ε-poly-L-lysine on O3HT chains alignment, the graft copolymer with optimized grafting density exhibits an extended conjugation length and increased crystallite size of O3HT. Thin films of three copolymers, upon doping, demonstrate appreciable conductivity under ambient conditions. EPL-g-O3HT-1 could be fully break down over 12 days by enzymatic degradation. EPL-g-O3HT-1 also displays excellent broad-spectrum antibacterial activity against Gram-negative and Gram-positive bacteria, attributed to its high ɛ-poly-L-lysine content. It is further demonstrated the versatility of EPL-g-O3HTs in transient electronics for electromyography sensors for muscle signal acquisition and as the channel material in organic electrochemical transistors. Combining tunable conductivity, controlled biodegradability, and antimicrobial properties, EPL-g-O3HT copolymers hold significant potential for diverse transient electronic applications, including skin and implantable electronics, where degradable electronics with antimicrobial properties are highly desirable.