Study of the Effect of Montmorillonite Nanolayers on the Kinetics of Styrene Atom Transfer Radical Polymerization

Modified nanoclay with a double bond on its modifier structure was employed to study the confinement effect of nanoclay in the atom transfer radical polymerization of styrene. The clay-attached and free polystyrene chains were used as evidence to such a kinetic study. The variations of monomer conversion and the linearity of semi-logarithmic kinetic plot, evidence of the living polymerization and constant radical concentration in the reaction medium, were revealed by the use of gas chromatography technique (GC). Number- and weight- average molecular weights and polydispersity index of polymers were also derived from GPC data. According to the gel permeation chromatography (GPC) results, the number-average molecular weight increases linearly against the monomer conversion indicating the living nature of the polymerization. Free chains which showed higher molecular weights than the attached ones exhibited closer molecular weights values to the theoretical ones. In addition, lower PDI values were obtained in free polystyrene chains. In the case of free polystyrene chains, the initiator efficiency was lower than 1 and by increasing clay content, higher molecular weights were obtained. Attached chains revealed lower molecular weights and their initiator efficiency was higher than 1. By adding clay content, an increase of PDI value and a decrease of molecular weight were observed in attached polystyrene chains. Moreover, all the samples experienced a falling of PDI value from nearly 2 to almost 1.2 as the reaction progressed. FTIR results revealed an interaction between clay surface and monomer causing acceleration in the polymerization kinetic.