A MODEL FOR CHEMICAL-VAPOR COPOLYMERIZATION OF P-XYLYLENES WITH VINYLIC COMONOMERS - ORDER OF INITIATION AND REACTIVITY RATIOS

A model for chemical vapor homo- and copolymerization is presented in two dimensions, allowing determination of order of initiation in homop olymers and reactivity ratios in copolymers. The model assumes a linea r pressure gradient along the flow direction and allows calculation of the order of initiation if thickness vs position are known, and r(1) and r(2) if the gas flow rates, final film thickness, and film composi tion vs distance are known. Experiments indicate the number, Lambda, o f p-xylylene molecules required to initiate polymerization: For poly(p -xylylene) and poly(p-chloroxylylene), Lambda = 3; for poly(p-dichloro xylylene), Lambda = 4. Tentative values for the reactivity ratios of p oly(p-chloroxylylene) with perfluorooctyl methacrylate have been deter mined at different temperatures. At 20 degrees C, r(1) = 13.04 and r(2 ) approximate to 0; r(1) increases with increasing temperature, while r(2) remains vanishingly small.