ANIONIC DISPERSION POLYMERIZATION OF 1,4-DIVINYLBENZENE

Highly cross-linked 1,4-divinylbenzene (1,4-DVB) microgels with a shell of poly(4-tert-butylstyrene) (PtBS) chains were prepared by anionic dispersion polymerization in n-heptane at 50°C. ″Living″ PtBS chains with various lengths were used as the initiator of the DVB polymerization and also as steric stabilizers for the phase-separated particles. The effect of the polymerization parameters such as the length of PtBS chains and the DVB concentration on the properties of the microgels was studied using static and dynamic light-scattering techniques and viscosimetry. As the DVB concentration in the reaction medium increases, both the molecular weight of the microgels and their intrinsic viscosities increased, at first slowly and then abruptly at about 30-35 mol % DVB, corresponding to the transition from the microgel to the macrogel region. It was also found that the length of PtBS chains at the nuclei surface controls the intrinsic viscosities of the microgels. The calculations indicate that the solvated PtBS chains are close-packed on the surface of the nuclei.