Influence of conformational parameters on physical properties of copolyimides containing pendant diphenylphosphine oxide units

Modification or designing new molecular architectures are the key strategies to obtain materials with improved/tunable properties able to address environmental restrictions and public needs. Herein, a series of copolyimides containing bulky diphenylphosphine oxide pendant units was synthesized and the physical properties were studied and correlated with the conformational parameters, such as Kuhn segments, Van der Waals and free volumes. It is shown that conformational rigidity determines the packing of macromolecules in glass state, and therefore the free volume, glass transition and dielectric permittivity. The Kuhn segment of the synthesized random copolyimides calculated by Monte Carlo method exhibited a nonlinear dependence on chemical composition. The use of correlations between the chemical structure and conformational parameters is the key to achieve polymers with tailored physicochemical characteristics by varying the comonomers' ratio.