Double-helical polymer brushes consisting of helical polyacetylene main chain and helical poly(n-hexyl isocyanate) side chains

Abstract

4-Ethynylbenzyloxy-containing poly(n-hexyl isocyanate)s (defined as M-PHICs) were synthesized via coordination polymerization by using organotitanium catalyst. The M-PHICs were characterized by GPC, FT-IR, NMR, mass spectrometry (MALDI-TOF MS) and elemental analysis techniques. UV–vis spectra demonstrated that the M-PHICs adopted reversible helical structures in solution. The obtained M-PHICs were then used as macromonomers and subjected to Rh-catalyzed coordination polymerization to form helical polymer brushes composed of helical polyacetylene backbones and meanwhile helical poly(n-hexyl isocyanate) pendants. Additionally, the M-PHICs underwent catalytic copolymerizations with chiral N-propargyl-(S)-camphanamide (M1), to form copolymer brushes consisting of polyacetylene backbones and PHIC pendants. GPC, FT-IR and NMR confirmed the formation of the two types of helical polymer brushes. UV–vis spectra indicated that both the polyacetylene backbones and the PHIC pendants in the (co)polymer brushes adopted dynamic helical structures. Circular dichroism effects demonstrated that the presence of chiral M1 units led to preferred-handed helical conformations in the polyacetylene backbones in the copolymer brushes. The copolymer brushes recognized (S)-(−)-1-phenylethylamine in the two enantiomers, demonstrating the potentials of such copolymer brushes in chiral recognition and chiral resolution.