Copolymerization of Styrene with Dodecyl Methacrylate and Octadecyl Methacrylate

Sa？etak Styrene (Sty) was copolymerized with dodecyl methacrylate (DDMA) and with octadecyl methacrylate (ODMA) in toluene solution using 2,2'-azobis(isobutyronitrile) (AIBN) as a free radical initiator over a wide composition and conversion range. The copolymer composi-tion was determined from NMR spectra. The copolymerization reactivity ratios were found to be r1 = 0.52 (Sty) and r2 = 0.42 (DDMA) for the Sty-DDMA system, and r1 = 0.58 (Sty) and r2 = 0.45 (ODMA) for the Sty-ODMA system, showing a tendency toward ideal copolymerization reactions. The Q and e values were also calculated according to the Greenly method. The initial poly-merization rate, Rv, was found to be in the order ODMA > DDMA ？ Sty and sharply decreased for both copolymerization systems as the content of Sty in the monomer mixture increased. Similar behaviour was also recorded for the molecular weights and intrinsic viscosities of the copolymers as their values significantly decreased with increasing the Sty fraction in the monomer mixture. Polymer viscosity in toluene solution determined at 30 to 90 °C slightly increased with the temperature for homopolymers of the alkyl methacrylates and reached the local maximum value at higher temperature, showing a constant value for the polystyrene, whereas the co-polymer values were intermediate between those of homopolymers. Also, the copolymers showed an increase in thermal stability with increasing the Sty content