Adding a solvophilic comonomer to the polymerization-induced self-assembly of block copolymer and homopolymer: a cooperative strategy for preparing large compound vesicles

摘要

We report a reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of styrene (St) and 4-vinylpyridine (4VP) in methanol/water at 70 °C. The polymerization was mediated by a binary mixture of S-1-dodecyl-S′-(α,α′-dimethyl-α′′-acetic acid) trithiocarbonate (DDMAT) and monomethoxy poly(ethylene glycol)-based macromolecular RAFT agent (mPEG₄₅-DDMAT). By varying the molar ratio of [St]₀/[4VP]₀, polymer nano-objects of different morphologies (porous vesicles, large compound vesicles (LCVs), and lamellae) were formed. Transmission electron microscopy (TEM) observations demonstrated that LCVs were formed by further aggregation and reorganization of vesicles during the process. Effects of [mPEG₄₅-DDMAT]/[DDMAT] molar ratio, methanol/water ratio, and degree of polymerization (DP) of the core-forming block on the assemblies were also studied in detail. Ag@mPEG₄₅-P(St₁₀₈-co-4VP₂₄)/P(St₁₀₈-co-4VP₂₄) LCVs were prepared by in situ reduction of AgNO₃, as confirmed by TEM and UV-vis measurements. The obtained Ag@mPEG₄₅-P(St₁₀₈-co-4VP₂₄)/P(St₁₀₈-co-4VP₂₄) LCVs exhibited catalytic activity for the catalysis of methylene blue (MB) using NaBH₄.