IMPROVING THE KNOWLEDGE AND DESIGN OF END-GROUPS IN POLYMERS PRODUCEDBY FREE-RADICAL POLYMERIZATION

Several techniques have been used to probe polymer end groups. The nit roxide radical trapping technique has been used (i) to show that initi ator-derived unsaturated end groups in polymethyl methacrylate can be minimized by using t-hexyl peroxypivalate as the initiator (ii) to pre dict the end and penultimate groups in acrylonitrile/ethyl vinyl ether copolymer produced by t-butoxyl initiation by analogy with the initia tion mechanism (iii) to predict probable end groups in polyacrylonitri le and polystyrene produced by cyanoisopropyl initiation in the presen ce of adventitious oxygen. NMR techniques have been used to show that the end groups of functionalized oligomers, made from styrene and meth acrylonitrile by the addition-fragmentation chain transfer technique w ith allylic sulphides, conform to the expected structures. (C) 1998 Jo hn Wiley & Sons, Ltd.