The influence of total monomer concentration on the ?reactivity? of ?-(p-vinylbenzyl ether) macromonomers of poly(2,6-dimethyl-1,4-phenylene oxide) determined from radiacal copolymerization experiments with butyl methacrylate

Abstract

The influence of the total monomer concentration on the radical reactivity ratio r1 of butyl methacrylate (BMA) (M1)-ω-(p-vinylbenzyl ether) macromonomer of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO-VBE) (M2) monomer pair was investigated. For two different molecular weights of the PPO-VBE macromonomer (\(\bar M_n = 14,000\),\({{\bar M_w } \mathord{\left/ {\vphantom {{\bar M_w } {\bar M_n }}} \right. \kern-\nulldelimiterspace} {\bar M_n }} = 1.25\) and\(\bar M_n = 5,300\)\({{\bar M_w } \mathord{\left/ {\vphantom {{\bar M_w } {\bar M_n }}} \right. \kern-\nulldelimiterspace} {\bar M_n }} = 1.26\)), the determined reactivity ratio r1 decreases with the increase of the macromonomer concentration. Therefore, the reactivity of the macromonomer, 1/r1, follows the opposite trend. This dependence is due to micelles formation during copolymerization. This microsegregation process partitionates the comonomer concentrations between the bulk of solvent and around the growing chain and therefore, the experimental r1 is actually a product of the true reactivity ratio r10 and a partition coefficient k.