Three-dimensional free-radical copolymerization of methyl methacrylate with diunsaturated monomers in the presence of an aromatic polyimide

The three-dimensional free-radical copolymerization of MMA with diunsaturated comonomers of various natures in the absence and in the presence of 4 wt % aromatic polyimide (eta(inh) = 0.38-1.02 dl/g) has been studied by isothermal calorimetry. It has been shown that, depending on the chemical nature of spacers separating double bonds of the comonomers, the kinetic curves of copolymerization may be divided into two groups, one of which is characterized by an almost complete absence of stationary portions. It has been demonstrated that the effects of the polyimide on the initial rate of copolymerization and on the parameters of the gel effect depend on the nature of diunsaturated comonomers and the molecular mass of the aromatic polyimide. The swelling of the polymer systems under study in toluene has been investigated, and the parameters of their network structure have been estimated. The irreversible flow deformation of the MMA copolymers with diunsaturated comonomers does not manifest itself up to a temperature corresponding to the onset of degradation of the copolymers. The incorporation of polyimide units improves the thermal stability of the copolymers.