Ultrasonically initiated emulsion polymerization of n-butyl acrylate

Ultrasonically initiated emulsion polymerization of n-butyl acrylate (13A) without added initiator has been studied. The experimental results show that high conversion of BA can be reached in a short time by employing an ultrasonic irradiation technique with a high purge rate of N-2. The viscosity average molecular weight of poly(n-butyl acrylate) (PBA) obtained reaches 5.24 x 10(6) g mol(-1). The ultrasonically initiated emulsion polymerization is dynamic and complicated, with polymerization of monomer and degradation of polymer occurring simultaneously. An increase in ultrasound intensity leads to an increase in polymerization rate in the range of cavitation threshold and cavitation peak values. Lower monomer concentration favours enhancement of the polymerization rate. H-1 NMR, C-13 NMR and FTIR spectroscopies reveal that there are some branches and slight crosslinking, and also carboxyl groups in PBA. Ultrasonically initiated emulsion polymerization offers a new route for the preparation of nanosized latex particles; the particle size of PBA prepared is around 50-200 nm as measured by transmission electron microscopy. (C) 2001 Society of Chemical Industry.