A New Strategy To Synthesize Temperature- and pH-Sensitive Multicompartment Block Copolymer Nanoparticles by Two Macro-RAFT Agents Comediated Dispersion Polymerization

Multicompartment block copolymer nanoparticles (MCBNs) arouse great interest due to their special structure and wide application. However, synthesis of MCBNs suffers from great inconvenience and difficulty. In this contribution, an efficient strategy to prepare well-defined temperature- and pH-sensitive MCBNs constructed with two diblock copolymers of poly(4-vinylpyridine)-b-polystyrene (P4VP-b-PS) and poly(N-isopropylacrylamide)-b-polystyrene (PNIPAM-b-PS) through the two macro-RAFT agents comediated dispersion polymerization is proposed. In this two macro-RAFT agents comediated dispersion polymerization, two macro-RAFT agents having similar polymerization degree are simultaneously adopted, and onset micellization of PNIPAM-b-PS and P4VP-b-PS occurs simultaneously to form mixed coronacore nanoparticles containing a PNIPAM/P4VP mixed corona and a PS core. In neutral water at room temperature, the corona-forming P4VP block deposits on the PS core to form MCBNs, which contain a solvophobic PS core, discrete P4VP nodules on the PS core, and a solvophilic PNIPAM corona. The parameters affecting the MCBNs structure are investigated. It is found that the higher percent of the poly(4-vinylpyridine) trithiocarbonate (P4VP-TTC) macro-RAFT agent and the shorter PS block, the larger the size of the P4VP nodules on MCBNs. The synthesized MCBNs are temperature- and pH-responsive. Through the phase transition of the temperature-responsive PNIPAM block and the pH-responsive P4VP block, the morphology of MCBNs can be changed. Our strategy of the two macro-RAFT agents comediated dispersion polymerization is believed sufficiently to overcome the inconvenience and difficulty in synthesis of well-defined MCBNs.