Reaction kinetics of graft copolymerization and thermochemical studies of the degradation of poly(vinyl alcohol) graft copolymer

Poly(vinyl alcohol) (PVA) is a water-soluble and biomedical polymer. 2-Acrylamido-2-methyl-1-propanesulfonic acid was grafted onto PVA using ammonium persulfate as radical initiator. The influences of synthesis conditions such as temperature, concentrations of initiator, PVA and monomer were investigated. Both the initial rate of grafting and the final percentage of grafting were increased by an increase in reaction temperature. The reaction kinetics were studied to determine the rate constants of the first-order reactions. An activation energy of 16.3 kJ mol(-1) was found for the grafting reaction. The graft copolymers were characterized by IR and intrinsic viscosity measurements. A proposed mechanism of the grafting reaction is discussed. Kinetics of the thermal degradation were studied using a thermogravimetric method and the order of thermal stabilities are given. The apparent activation thermodynamic parameters, E-a, DeltaH*, DeltaS* and DeltaG* were determined and correlated to the thermal stabilities of the homo- and grafted polymers. (C) 2001 Society of Chemical Industry.