Specific features of coupling reactions of polystyrene in the presence α-dinitrones based on glyoxal

Bromine-containing polystyrene synthesized by atom transfer radical polymerization was used as a model to study coupling reactions in the presence of such free radical acceptors as conjugated dinitrones (N, N-dimethylglyoxaldinitrone, N, N-di-tert-butylglyoxaldinitrone, and N, N-diphenylglyoxaldinitrone). The influence of the reaction conditions, including the ratio of reagents, on the molecular weight characteristics of resulting products and the kinetics of the process was evaluated. It was shown that the proposed method allows one to synthesize polystyrene which contains in the middle of the chain an alkoxyamine functional group with a labile >C-ON< bond capable of further functionalization. The specified bond in the polymer modified by the coupling reaction in the presence of dinitrones cleaves at elevated temperatures, and the molecular weight of the polymer returns to the values characteristic of the original monobrominated polystyrene. It was found that in the case of the formation of dimeric products through recombination of macroradicals catalyzed by the system based on copper bromide and metallic copper in the absence of nitrones, the process follows the head-to-head pattern with the formation of a C-C bond. In this case, the polymer chain does not contain a nitroxyl functional group, which makes it inert to thermolysis under the conditions causing the >C-ON< bond cleavage formed in the presence of α-dinitrones.