Rapid Synthesis of Silk-Like Polymers Facilitated by Microwave Irradiation and Click Chemistry
Amrita Sarkar, Cody B. Edson, Ding Tian, Tanner D. Fink, Katherine Cianciotti, Richard A. Gross, Chulsung Bae, R. Helen Zha
Abstract
Silk is a natural fiber that surpasses most man-made polymers in its combination of strength and toughness. Silk fibroin, the primary protein component of silk, can be synthetically mimicked by a linear copolymer with alternating rigid and soft segments. Strategies for chemical synthesis of such silk-like polymers have persistently resulted in poor sequence control, long reaction times, and low molecular weights. Here, we present a two-stage approach for rapidly synthesizing silk-like polymers with precisely defined rigid blocks. This approach utilizes solid-phase peptide synthesis to create uniform oligoalanine “prepolymers”, followed by microwave-assisted step-growth polymerization with bifunctional poly(ethylene glycol). Multiple coupling chemistries and reaction conditions were explored, with microwave-assisted click chemistry yielding polymers with Mw ∼ 14 kg/mol in less than 20 min. These polymers formed antiparallel β-sheets and nanofibers, which is consistent with the structure of natural silk fibroin. Thus, our strategy demonstrates a promising modular approach for synthesizing silk-like polymers.