Synthesis and properties of a rod-g-rod bottlebrush with a semirigid mesogen-jacketed polymer as the side chain

A series of bottlebrushes, poly(γ-3-azidopropanyl-L-glutamate)-g-poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene (PPLG-g-PMPCS), with an α-helical rigid backbone and mesogen-jacketed rigid side chains were synthesized by the “grafting onto” method from yne-terminated PMPCS (side chain) and poly(γ-azide propanyl-L-glutamate) (backbone) by a Cu(I)-catalyzed 1,3-dipolar cycloaddition click reaction. The chemical structures of the bottlebrushes were confirmed by 1H NMR, gel permeation chromatography (GPC), GPC coupled with multi-angle laser light scattering and differential refractive index detection, and Fourier-transform infrared spectroscopy. The bottlebrushes were obtained with high grafting densities (>85%). The properties of the bottlebrushes were studied by small-angle X-ray scattering and atomic force microscopy. And the results show that the conformation of the bottlebrush changes from a cylinder to an ellipsoid as the degree of polymerization of the side chain increases from 14 to 65.