RAFT Emulsion Polymerization: MacroRAFT Agent Self-Assembly Investigated Using a Solvachromatic Dye

摘要

Polymerization-induced self-assembly (PISA) and amphiphilic-macroRAFT-mediated emulsion polymerization are commonly used approaches for synthesis of well-defined polymers and sophisticated particle morphologies. One aspect of these systems that remains relatively unexplored is the conformational state of macroRAFT agents in aqueous solution. To redress this deficiency, we have used fluorescence spectrometry experiments to conduct detailed investigations of the coil conformation across a wide range of pH values for a series of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) macroRAFT agents with different Z-groups (-S-(CH_(2))_(2)-COOH, -S-(CH_(2))_(3)-CH_(3), and -S-(CH_(2))_(11)-CH_(3)), as well as amphiphilic macroRAFT agents (PMAA-b -poly(methyl methacrylate)(PMMA) and PAA-b -polystyrene(PS)). The critical aggregate concentrations (CAC) or critical micelle concentrations (CMC) for all systems ranged from 7.48 × 10~(–7) to 2.57 × 10~(–3) mol L~(–1). Overall, an extensive library of CAC/CMC values has been compiled for PAA- and PMAA-based macroRAFT agents at different pH conditions, providing important information related to the mechanistic understanding and optimization of macroRAFT-assisted emulsion polymerization.