The influence of the initiator component removal method from atriethylboron-hexamethylendiamine complex on the copolymers butylacrylate - vinyl butyl ether molecular-mass characteristics at the compensation copolymerization in the boiling monomer

A radical compensatory copolymerization of butyl acrylate with vinyl butyl ether was carried out when the latter boiled in the presence of triethylboron. Under the circumstances present in the system the residual air oxygen acts as a co-initiator. As it turned out, in boiling vinylbutyl ether the amount of oxygen is sufficient for the oxidation of triethylboron and the copolymerization. Triethylboron from the complex with hexamethylenediamine was isolated directly in the reaction medium by the addition of methacrylic acid in two ways: together with butyl acrylate (method 1) or simultaneously before the addition of butyl acrylate (method 2). The active monomer was portioned during 20 min, then the reaction mixture was stirred for the necessary time. Unreacted monomers were removed under low pressure (about 0.5 torr). The polymer was dried to constant weight at Т=20-25 °. It has been shown that in the both cases the formation of macromolecules occurs along two chain growth centers, oligomeric and low molecular weight, and with the growth of conversion the molecular weight distribution of the former shifts to the larger molecular weight range. The signs of the oligomeric mode formation have been noted, with the participation of boroxyl radical formed during the triethylboron oxidation by the reversible inhibition mechanism. A study was carried out of the dependence of monomer conversion on the synthesis time of copolymers of butyl acrylate and vinyl butyl ether, synthesized by the compensatory method in the presence of triethylboron. It should be noted that the yield of the active monomer at the beginning of the process when metacrylic acid is dosed together with butyl acrylate (method 1) increases more slowly than in the case of methacrylic acid dosing prior to butyl acrylate (method 2). This can be explained by oxidation of triethylboron in the very beginning of the process if acid is added before butyl acrylate, while it requires 20 min with simultaneous addition of the components. In the case of method 2 a much larger amount of non-living polymer is formed. Analysis of the composition of copolymers by IR spectroscopy has shown that copolymers of butyl acrylate with vinylbutyl ether have a composition near to equimolar in both cases. Molecular weight parameters of the copolymers were studied by gel permeation chromatography. The values of the number-average molecular weight Mn increase uniformly with the conversion growth (Mn is worth considering for unimodal molecular weight distribution starting from 50 min for the first method and 60 min for the second method after the start of the synthesis). This dependence is a characteristic feature of the pseudoliving processes.