Polymerization of miniemulsions containing predissolved polystyrene and using hexadecane as costabilizer

The effect on the polymerization kinetics of predissolving polystyrene poly mers that have various molecular weights and end groups in styrene miniemul sions prepared using hexadecane as costabilizer was studied. It was noted t hat the rate of polymerization and number of droplets nucleated were affect ed by the molecular weight of the polymer that was predissolved. This depen dence was attributed to a change in the number of droplets formed during ho mogenization as the molecular weight of the polymer was varied. However, th e end group of the predissolved polymer did not have an affect on the kinet ics. In all cases, predissolving polymer into a miniemulsion stabilized usi ng hexadecane as costabilizer resulted in a much lower degree of enhancemen t in the kinetics compared to similar miniemulsion systems using cetyl alco hol as costabilizer. Since droplet sizes in miniemulsions containing hexade cane have been shown to be stable with time, unlike miniemulsions containin g cetyl alcohol, these experiments were taken as evidence that the dominant cause for "enhanced droplet nucleation" is the preservation of droplet num ber prior to the addition of initiator.