Charge Transfer Dye in Various Polymers with Different Polarity: Synthesis, Photophysical Properties, and Unusual Aggregation-Induced Fluorescence Changes

A new pyran-based CTD monomer, allyl 2-(2,6-bis(( E )-4-(dimethylamino)styryl)-4 H -pyran-4-ylidene)-2-cyanoacetate ( 2 ), was successfully synthesized by Knoevenagel reaction. Copolymerization of 2 with styrene (St), methyl methacrylate (MMA), and acrylonitrile (AN) afforded copolymers with different polarity, P(St- co - 2 ), P(MMA- co - 2 ), and P(AN- co - 2 ), respectively. IR and UV−vis absorption spectra revealed that 2 is incorporated into the copolymers. The 2 in the copolymers exhibited absorption and fluorescence properties which are completely different from 2 . All these copolymers showed significant blue shifts in emission relative to 2 . Also, their λ max,abs and λ max,em increased with an increase in dielectric constant (ε) of the polymer matrix in order PAN (ε = 5.5) > PMMA (3.3) > PSt (2.5). The copolymers in DMF showed blue shifts in emission along with aggregation by addition of methanol while copolymers in 1,4-dioxane showed a red shift. The fluorescence intensity of P(St- co - 2 ) and P(MMA- co - 2 ) decreased by aggregation while that of P(AN- co - 2 ) increased.