Surface modification and characterization of polystyrene formed via admicellar polymerization on precipitated silica : water soluble vs insoluble initiator and application of RAFT agent via admicellar polymerization

Abstract

Since the late 1980's, researchers have been investigating uses of polymerization carried out in the adsorbed surfactant aggregates on substrates. This process, known as admicellar polymerization (AP), has been proven useful in several applications where the modification of an inorganic surface by an organic polymer film is desirable. This study aimed at characterizing the polystyrene film formed on precipitated nonporous silica Aersoil OX50 surface using CTAB surfactant, and both water soluble (VA-044) and insoluble (AIBN) initiator via admicellar polymerization. The adsorption of CTAB on Aerosil OX50 is 130 umol/g of silica while the adsolubilization of styrene into CTAB bilayer increased with increasing styrene loading. The reaction time to complete the admicellar polymerization for the given reaction conditions is two hours. Eight ratios of monomer to initiator loading were examined for both initiators. Results from experiments suggested that the water soluble initiator (VA-044) could from polymer film with much higher molecular weight polymer than that of the water insoluble initiator (AIBN), and the thickness of the polymer film obtained between 2-15 nm. The application of RAFT to AP demonstrates the ability to apply new emulsion polymerization techniques to the process, opening doors for novel surface modification processes.