Polymer adsorption studies at the solid/liquid interface using gel permeation chromatography. II. Influence of molecular weight on the adsorption of poly(vinyl chloride) from chlorobenzene onto calcium carbonate

Abstract

Abstract Adsorption of both high molecular weight (M̄ w = 114,000) and low molecular weight (M̄ w = 42,800) poly(vinyl chloride) resins were followed from chlorobenzene solution onto CaCO 3 at room temperature, and compared with data obtained previously for an inter‐mediate molecular weight resin (M̄ w = 80,600). At increase in the adsorption saturation capacity (ASC) was observed for increasing M̄ w (31.6 mg‐g −1 to 41.7 mg‐g −1 ) as was a corresponding decrease in the number of molecules adsorbed (9.0 × 10 −7 mol‐g −1 to 6.3 × 10 −7 mol‐g −1 ). Preferential adsorption of high molecular weight polymer was noted for all resins. The average molecular weight of polymer adsorbed at ASC increased with increasing M̄ w . Fractionation of the adsorbed polymer was also evident and improved with decreasing M̄ w . Within the molecular weight distribution (MWD) of all three resins an increase in the amount of polymer adsorbed (described by an adsorption efficiency factor) with increasing molecular weight occurred up to a molecular weight near 75,000. Above a molecular weight of 75,000 the adsorption efficiency factor continued to increase with the low molecular weight resin but stayed fairly constant for the intermediate and high molecular weight resins. Competition of high molecular weight polymer for surface sites was cited as an ex‐planation. The polymer molecules were thought to adsorb as interpenetrating or compressed coils with relatively few points of surface contact.