Excimer fluorescence as a probe of miscibility in styrene copolymer blends

The miscibility of styrene‐alt‐maleic anhydride (SMA) and a series of styrene‐acrylonitrile (SAN) copolymers in blends with either PMMA or PVC were examined by fluorescence and FTIR spectroscopic techniques. In the case of the alternating copolymer intra‐molecular excimer formation is precluded and changes in the excimer/monomer fluorescence intensity (IE/IM) reflect changes in the amount of inter‐chain excimer formation. The value of IE/IM in blends, therefore, provides a sensitive measure of phase separation (miscibility). In the case of the acrylonitrile copolymers the IE/IM of the blend had to be corrected to account for intra‐molecular excimers formed between adjacent chromophores in the SAN. These results compared favourably with observed frequency shifts in the phenyl C—H out‐of‐plane bend (∼700 cm−1).