Linking-reaction kinetics of star shaped polystyrene by temperature gradient interaction chromatography

Abstract

The linking reaction kinetics of a chlorosilane-linked polystyrene six-arm star was investigated by temperature gradient interaction chromatography using a light scattering detector. The precursor arm material (M-w = 83 000) was made by anionic polymerization and end capped with isoprene, and 1,2-bis(trichlorosilyl)ethane was used as the linking agent. All the reaction intermediates, from unlinked arm to six-arm star, were successfully resolved from the aliquots taken from the reactor at various linking reaction times. From the time-varying relative abundance of the star molecules with different numbers of arms, Linking reaction rate constants were determined. It was found that the linking reaction rate becomes progressively slower as the number of attached arms increases. We were able to extract the quantitative ratio of the linking rate constants, k(5)/k(4) = 0.097 and k(6)/k(5) = 0.30,where k(i) stands for the rate constant of the reaction incorporating the ith arm to an (i - 1)-arm star to form an i arm star. The larger Value of k(6)/k(5) than k(5)/k(4) can be interpreted from the molecular structures of the linking agent and polymeric anions.