Abstract
Statistical copolymers of methacrylic acid and methyl methacrylate were synthesised via free radical catalytic chain transfer polymerisation (CCTP) in emulsion to form a hydrophilic emulsifier/surfactant. The vinyl-terminated oligomers were in turn utilised as chain transfer agents, with no further purification, for the formation of diblock copolymers with butyl and methyl methacrylate which constitutes the emulsifier via sulfur-free reversible addition–fragmentation chain transfer polymerisation (SF-RAFT). In turn these polymers were solubilized with various concentrations of ammonium hydroxide and utilised in the surfactant-free emulsion polymerization of butyl methacrylate using persulfate initiators, which also stabilized the polymer particles with observed no coagulation, with solid contents as high as 40%.
Highlights
Emulsion polymerisation in the absence of added emulsifier, or surfactant, has received significant attention as a technique for synthesising monodisperse spherical particles and clean lattices [1,2]
We focused on statistical co-oligomers of MMA (85 wt%) and MAA (15 wt%) as prepared using catalytic chain transfer polymerisation (CCTP) in emulsion polymerisation with bis [(difluoroboryl)dimethylglyoximato] cobalt(II), (CoBF) as the catalyst, which has been previously reported as an effective CTA for the emulsion CCTP of methacrylates [32,48]
Increasing the acid concentration within the co-oligomers resulted in an increases in the particle size of the polymers resulting in phase separation ascribed to the particles becoming very hydrophilic and in turn causing water to enter the particles over time giving rise to latex destabilisation, whereas when MAA15%MMA85% was used particle sizes < 310 nm were obtained giving stable latex’s with long shelf life
Summary
Emulsion polymerisation in the absence of added emulsifier, or surfactant, has received significant attention as a technique for synthesising monodisperse spherical particles and clean lattices [1,2]. For reaction A′ (Fig. 2) post polymerisation with BMA monomer with 0 equivalents of NH4OH, both the diblock poly(MMA-co-MAA-bBMA10) and subsequent pseudo tri-block copolymers resulted in monomodal particles of 614 nm, according to DLS and SEM.
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