Polymerization of Styrene in Presence of Polybutadiene: Determination of Molecular Structure

ESTENOZ, D. A.; GONZALEZ, I M; OLIVA, H. M.; MEIRA, G. R.

JOURNAL OF APPLIED POLYMER SCIENCE

Año: 1999 vol. 74 p. 1950 - 1961

0021-8995

This work experimentally and theoretically determines the molecular macrostructure of the polymer mixture that is developed (at relatively low conversions in a solution polymerization of styrene (St) in presence of polybutadiene (PB). The reaction was carried out at 70°C in a batch-stirred tank reactor. From samples taken along the reaction, the three polymeric components of high-impact polystyrene (HPS) (i.e., polystyrene-PS-, residual PB, and graft copolymer) were first separated from each other by solvent extraction. Then, the graft copolymer was ozonized to isolate the St branches. The molecular weight distributions (MWDs) of the total HIPS, the three HIPS components, and the grated St branches were determined by the size exclusion chromatography (SEC). For the graft copolymer and the total HIPS, the variation of the St mass fraction with molecular weights was also determined by SEC. All measurements were compared with theoretical estimates, and a reasonable agreement is observed. For the theoretical estimates, the mathematical model of Estenoz, D.A.; Valdez E.; Oliva, H.M.; Meira, G.R. (J Polym Sci 1996, 59, 861) was extended to compare the MWD of the St branches with the MWD of the free PS. For the sought experimental conditions, these two distributions had very similar results but in a bulk industrial process, larger discrepancies are to be expected.