Polyvinylpyridine-Grafted Block Copolymers by an Iterative All-Anionic Polymerization Strategy

摘要

Functional block copolymers are a highly relevant material platform for many potential applications in fields of nanolithography, drug delivery, and separation technologies. Here, poly(2-vinylpyridine) (P2VP)-grafted diblock copolymers consisting of polystyrene-block-polyisoprene (PS-b-PI) backbone are synthesized via an iterative anionic grafting-to polymerization strategy. P2VP macro anions having molar masses of 1.1, 3.6, and 9.9 kDa are grafted to PS-b-PI block copolymers featuring 37 mol 1,2-polyisoprene moieties. Prior to the grafting-to strategy, the PS-b-PI is subjected to platinum-catalyzed hydrosilylation reaction for the introduction of chlorosilane groups. The Si-Cl moieties are advantageously used for nucleophilic reaction of the P2VP macro anions with PS-b-PI yielding grafted block copolymers having a final P2VP volume fraction of 73, 87, and 93 vol. Micellization of the P2VP-grafted block copolymers in polar solvents and in water (after protonation of the pyridine moieties) is studied by dynamic light scattering experiments and transmission electron microscopy (TEM). As a focus of this work, the influence on microphase separation in the bulk state is noted to be tremendously influenced by introducing P2VP segments. This is confirmed by TEM measurements and small angle X-ray scattering experiments, which reveal a good control over morphologies at the nanometer length scale.