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Polymers with an amidinothio end group (-S-eNH are easily obtained1v2) by polymerization of a vinyl monomer with redox initiators involving thiourea (TU) as the reductant. Such end groups are reported to hydrolyse readily under alkaline conditions forming mercapto end groups. In the presence of air, intermolecular oxidative coupling of these chain ends takes place leading to an appreciable increase in intrinsic viscosity or molecular weight I). This sequence of reactions was employed in the pesent work with the objective of preparing block copolymers from a mixture of poly(methy1 methacrylate) and polystyrene, prepared separately from the respective monomers by Fei3-TU as redox initiator. NH, Nn CH3 NH II

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Benzophenone (BP)‐sensitized photopolymerization of methyl methacrylate (MMA) in near UV/visible light was studied at 40°C using dimethylaniline maleic acid (DMA—MA) combination as the photoinitiator. An instantaneous 1:1 complexation between DMA and MA takes place when they are mixed together in acetonitrile. Also, instantaneous complex formation occurs between DMA and MMA and between MA and MMA when they are dissolved in MMA in low concentrations, separately. Interestingly, when equimolar proportions of DMA and MA are mixed together in MMA, there is indication for further instantaneous complexation between (DMA—MMA) complex and (MA—MMA) complex forming the actual initiating species in the photopolymerization system. Initiator exponent was 0.28 and monomer exponent varied between 0.0 to 1.8 depending on the nature of the solvent and range of dilution used. Analysis of kinetic data indicates a free radical mechanism for the polymerization with initiator‐dependent termination. Chain termination via degradative initiator transfer is quite significant; but the degradative effect becomes much less prominent in the higher range of initiator concentration indicating that the reinitiation reaction following the initiator transfer process assumes more proportionate significance as the initiator concentration is increased, probably as a result of higher reinitiation efficiency. Polymers obtained gave evidence for the incorporation of aromatic (amine) end groups in them.

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