Photophysical Study in Blends of Poly(alkyl methacrylate-co-styrene)/Polystyrene

The morphology of blends of poly(alkyl methacrylate-co-styrene)/polystyrene [XMAS/PS; X = M (methyl), E (ethyl)] was studied at the microscopic level (micrometric scale) by differential scanning calorimetry (DSC), dynamic-mechanical analysis (DMA), and epifluorescence microscopy (EFM) and at the nanoscopic scale by steady-state and time-resolved fluorescence emission spectroscopy (FES). Time-resolved energy transfer analysis was used to probe the interpenetration of molecular chains. The copolymers MMAS and EMAS (approximate content in mol %:  78% of methacrylate units; 22% of styrene units) covalently labeled with 9-vinylanthracene units (≤0.1%), as fluorescent comonomer (fluorophore), were synthesized by emulsion polymerization and were characterized by FTIR, ¹H NMR, ¹³C NMR, TGA, GPC, DSC, DMA, UV−vis, and FES. Films of copolymer blends were prepared by casting from dilute chloroform solutions with compositions of 5, 20, 50, 80, and 95 wt % of copolymer. Some miscibility was observed for the blends of XMAS/PS containing 5, 20, and 95 wt % of copolymer. Interaction strength in blends increased with the size of aliphatic chain of the ester group in the copolymer. Blends with 50 wt % of copolymer are always immiscible. Two values of glass transition temperatures were observed by DSC and DMTA. MMAS/PS and EMAS/PS blends of copolymer-richer compositions (95 and 80 wt %) show fluorescence lifetimes with broader distributions, suggesting a wider distance distribution of interlumophoric groups.