On the compatibility and thermally induced blending of poly(styrene phosphonate diethyl ester) with cellulose acetate

Abstract The miscibility of poly(styrene phosphonate diethyl ester) (PSP) with cellulose acetate (CA) was studied. Experiments were designed to prove that these polymers are a miscible pair. The study revealed that when blends were prepared from a solution with partially phosphorylated polystyrene, favourable conditions for crystallization of the cellulose acetate prevailed. Upon conversion of the crystalline regions into amorphous domains—as done by heating the sample in a differential scanning calorimeter—an amorphous homogeneous blend spontaneously formed. The merger of the CA- and PSP-rich phases in the temperature range 190–200°C (slightly above T g of CA) was recorded to yield the plot of the corresponding changes in the glass transition temperature vs. time. Computation of the corresponding values for the changes in specific heats clearly indicated the exchange of matter between the two merging phases. However, it also showed that prolonged exposure of the sample to this temperature results in chemical changes (i.e. degradation and crosslinking) in the CA-rich phase. The results of this study revealed that PSP is miscible with CA at a lower degree of phosphorylation than previously thought; thus, one phosphoryl ester per six styrene units in PSP will still render this polymer miscible with cellulose acetate.