Chiral, thermal-responsive hydrogels containing helical hydrophilic polyacetylene: preparation and enantio-differentiating release ability

Abstract

In this contribution, a chiral N-propargylamide monomer (R and S) was synthesized and used as a comonomer to prepare hydrophilic polyacetylene (HPA) bearing polymerizable vinyl groups in the presence of (nbd)Rh⁺B⁻(C₆H₅)₄. The obtained HPA chains could form a single-handed helical structure in water and showed intense optical activity. Taking advantage of the hydrophilic and polymerizable moieties, HPA was further used as a macromer to prepare hydrogels in deionized water via free radical polymerization, using N-isopropylacrylamide (NIPAm) as a co-monomer, N,N-methylenebisacrylamide (BIS) as a crosslinker, and ammonium persulphate (APS) and N,N,N,N-tetramethylethylenediamine (TEMEDA) as redox initiators. The as-prepared hydrogels exhibited optical activity, thermal responsivity and biocompatibility. More interestingly, the hydrogels showed enantio-differentiating release ability towards mandelic acid enantiomers, demonstrating the potential applications of these novel optically active hydrogels in chiral drug delivery fields.