Modelling of size‐exclusion chromatograms from molecular weight distribution calculations. Application to the grafting of polymers onto functionalized silica

Abstract

AbstractThe objective of this paper is the modelling of the molecular weight distribution (MWD) and the polydispersity index (P. I.) of polystyrene grafted on porous silica beads prefunctionalized by a thiosilane molecule. Grafting occurs by a transfer reaction to the fixed mercapto groups. We have analysed the MWD of both grafted and ungrafted polymers by size‐exclusion chromatography (SEC). A good agreement between the experimental SEC diagrams and those calculated from the reaction rate constants is obtained with the following hypotheses: (1) the medium is a two‐phase system constituted of an interparticle phase and a porous intraparticle phase with a high local mercapto group concentration in the pores; (2) a higher transfer efficiency of the transfer agent in the pores (what could be attributed to a higher mobility of the very short chains inside the pores); (3) a lower termination rate in the pores, which results in a higher rate of polymerization than in the interparticle phase (probably due to an increase of the medium viscosity).