Synthesis and Characterization of Cylindrical Polymer Brushes with Cyclic Side-chains

Cylindrical polymer brushes with densely grafted cyclic side-chains are synthesized via the grafting onto method. The structure and composition of the polymers are well characterized. Linear polynorbornylene derivative (l-PND) backbones containing alkynyl groups are prepared by ring opening metathesis polymerization (ROMP), and cyclic poly (tert-butyl acrylate) side-chains (c-PtBA) containing azide groups are synthesized by the combination of atom transfer radical polymerization (ATRP) and copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Then, the cyclic side-chains are grafted densely onto the backbone by CuAAC reaction to form a cylindrical polymer brush. The structures of the polymers were characterized by H-1-NMR, gel permeation chromatography (GPC) and infrared (IR) spectroscopy. The obtained polymer brush has a long backbone of 400 degree of polymerization. The densely grafted side-chains lead to extension of the backbone. A single molecule of the polymer brush shows a wormlike (cylindrical) morphology observed by the atomic force microscopy (AFM). The length of the polymer brush is 200 nm, and the diameter is 30 nm. The polymer brush with cyclic side-chains is observed as a wormlike molecule for the first time, which has great reference value to study the influence of the topological structure (backbone and side-chains) on the morphology of the polymer brushes.