Intrinsic fluorescence studies of compatibility in thermoplastic phenol formaldehyde resin / poly(ε-caprolactone) blends

Abstract

Intrinsic fluorescence method was applied to study the miscibility and interactions of thermoplastic phenol formaldehyde resin (TPF) / poly(!-caprolactone) (PCL) blends. The characteristic intrinsic fluorescence emission of TPF at 313 nm showed the very good sensitivity to monitor the macromolecular chain motion in the TPF/PCL blends. The glass transition (Tg), crystallization (Tc), and melting transition point (Tm) of TPF/PCL blends were measured by the temperature dependence of intrinsic fluorescence intensities upon heating or cooling process. Interestingly, when TPF/PCL 5/5, besides a Tg for the amorphous phase of blend, another transition at temperature a little higher than Tg of PCL can be observed by intrinsic fluorescence method. This microheterogeneity can be explained by the so-called 'rigid amorphous phase' (RAP) due to the good flexibility and the strong self-association of PCL chains in amorphous phase. Besides, the analysis of the dependence of Tg on the content of PCL suggests that this microheterogeneity can attenuate the interactions between TPF and PCL chains and result in a lowering of Tgs of blends. In view of the simplicity and sensitivity of measurement as well as affordability of instrument, intrinsic fluorescence proved to be an effective means for characterization of microstructural variation in polymer blends.