I. Capek et al., DISPERSION COPOLYMERIZATION OF POLYOXYETHYLENE MACROMONOMER AND STYRENE .2. EFFECT OF INITIATOR TYPE AND CONCENTRATION ON THE POLYMERIZATION PROCESS, European Polymer Journal, 31(9), 1995, pp. 895-902
The dispersion copolymerization of methacryloyl-terminated polyoxyethy
lene (PEG-MA) macromonomer and styrene initiated by a water/ethanol-so
luble (2, 2'-azobis(N,N-dimethyleneisobutyramide, VA) and oil-soluble
(dibenzoyl peroxide, DBP) initiators was investigated at 60 degrees C.
The rate of polymerization and the number of particles were found to
increase with increasing concentration of initiator. The initial rate
of polymerization was found to be proportional to the 0.6 and 0.8th po
wer of IVA] and [DBP], respectively. The rate per particle was observe
d to be proportional to the 0.17th and 23rd power of [VA] and [DBP], r
espectively. In the VA systems the polymerizations were faster and the
molecular weights of graft copolymers larger. The dependence of the p
article number was described by a curve with a minimum at ca 15 or 20%
conversion. The partition of DBP molecules between the continuous pha
se and the polymer particles causes the formation of radicals in both
phases. The DBP molecules or DBP radical fragments located in polymer
particles take part in both initiation and termination events. The lat
ter is suggested to be responsible for the low rates and molecular wei
ghts of graft copolymers.