Accelerated heterogenous ring-opening polymerization towards well-defined helical poly(N-allyl alanine) with clickable side chains

Well-defined poly(N-allyl alanine) has been synthesized by heterogenous ring-opening polymerization (HROP) of less reactive N-allyl-alanine N-carboxyanhydride, using acetic acid as the catalyst and benzylamine as the initiator, in non-polar n-hexane. Interestingly, the polymerization exhibited typical features of living polymerization though both monomer (liquid) and polymer (solid) have minimal solubility in n-hexane. The obtained polymer showed a stable helix structure independent of the temperatures screened, as evidenced by circular dichroism analysis. Also, the preliminary study demonstrated that the side chains can be post-functionalized through thiol-ene click chemistry with quantitative conversion. Together, this work provides guidance for the development of accelerated HROP of other liquid monomers bearing low reactivity. Besides, the helical and functionalizable poly(N-allyl alanine) could be a useful “clickable platform” for the design of variable biomaterials via efficient click chemistry.