Dispersion polymerization of styrene in an aqueous medium using poly(vinyl alcohol)-copper(II) chloride (PVA-CuCI2) produces grafted chains on PVA in addition to the dispersion of polystyrene. The polymerization kinetics are found to be greatly affected by the amount of poly(vinyl alcohol), the amount of carbon tetrachloride, the pH of the initial solution and the reaction temperature. A typical plot of percentage weight increase of polymer versus time of polymerization shows a rapid increase after an induction time. This induction time is postulated to occur because of the formation of PVA-9-polystyrene, which, owing to thermodynamic factors, diffuses to the monomer droplet or polymer particle interphase. We determined the molecular weights of the homopolymers and the grafted polystyrene and it was found that the molecular weight of the latter is always higher. The particle size distribution undergoes a drastic narrowing owing to the formation of the grafted copolymer. Existing theories for dispersion and emulsion polymerization fail to explain the experimental data, and the complexity of the mathematical modelling of this process is indicated.
Посилання на статтю:
Grafting of polystyrene on to poly(vinyl alcohol) (PVA) by a PVA-CuCI2 complex initiating system in an aqueous medium / Sanjay Nigam, Ramkrishna Bandopadhyay, Aditya Joshi and Anil Kumar // Polymer. – 1993. – Vol 34. – P. 4213-4220.