Synthesis of High Molecular Weight Poly(glycerol monomethacrylate)via RAFT Emulsion Polymerization of Isopropylideneglycerol Methacrylate

摘要

High molecular weight water-soluble polymers are widely used as flocculants or thickeners. However, synthesis of such polymers via solution polymerization invariably results in highly viscous fluids, which makes subsequent processing somewhat problematic. Alternatively, such polymers can be prepared as colloidal dispersions; in principle, this is advantageous because the particulate nature of the polymer chains ensures a much lower fluid viscosity. Herein we exemplify the latter approach by reporting the convenient one-pot synthesis of high molecular weight poly(glycerol monomethacrylate) (PGMA) via the reversible addition–fragmentation chain transfer (RAFT) aqueous emulsion polymerization of a water-immiscible protected monomer precursor, isopropylideneglycerol methacrylate (IPGMA) at 70 °C, using a water-soluble poly(glycerol monomethacrylate) (PGMA) chain transfer agent as a steric stabilizer. This formulation produces a low-viscosity aqueous dispersion of PGMA–PIPGMA diblock copolymer nanoparticles at 20% solids. Subsequent acid deprotection of the hydrophobic core-formingPIPGMA block leads to particle dissolution and affords a viscous aqueoussolution comprising high molecular weight PGMA homopolymer chainswith a relatively narrow molecular weight distribution. Moreover,it is shown that this latex precursor route offers an important advantagecompared to the RAFT aqueous solution polymerization of glycerol monomethacrylatesince it provides a significantly faster rate of polymerization (andhence higher monomer conversion) under comparable conditions.