The Effect of Polymerization Conditions on the Density and Tg of Bisphenol-A and Hexafluoroisopropylidene-Containing Polybenzoxazines

The volumetric expansion of bisphenol-A and aniline-based benzoxazine (BA-a) has been studied by comparing the room temperature density of the cured BA-a under different polymerization conditions with the amorphous BA-a monomer. The glass transition temperatures (Tg) of BA-a at various degrees of polymerization have been investigated by differential scanning calorimetry (DSC). The degrees of conversion at different polymerization temperatures were compared with the respective glass transition temperatures. It was found that substantial development of Tg occurs at low degrees of conversion. A fluorinated polybenzoxazine was synthesized from the ring-opening polymerization of hexafluoroisopropylidene-containing benzoxazine monomer. The properties of the fluorine-containing polymer were compared to those of nonfluorinated polybenzoxazine. Fluorine incorporation had a profound effect on the glass transition temperature of polybenzoxazine. The thermal stability also improved upon fluorination.