The fluorescent quantum efficiency of copolymers containing coumarin-6 at the side-chain

Abstract

Coumarin-6 containing acrylates (CA) with different spacers were synthesized. Copolymers of CA with methyl methacrylate (MMA) in CA/MMA in the weight ratios of 1/20, 1/40 and 1/60 were prepared by using AIBN as initiator. The copolymer compositions were determined from uv-visible spectroscopic analyses, according to Beer's law. UV absorption and photoluminescence (PL) spectra indicated a concentration quenching, which increased with increasing coumarin-6 concentration in the copolymer compositions and also increasing the spacer length from the copolymer to coumarin-6 moiety, leading to a decreased fluorescence efficiency (phi(s)/phi(o)) as well as a red shift of lambda(max). Furthermore, as the spacer, n in -(CH2)(n)-, increases from n = 2, 3 to 6, excimers formed due to overlap of chromophores, resulting in the splitting of the PL emission band and lowering the PL intensity. Experimental results revealed that when the ratio of CA/MMA = 1/60 and the spacer n = 2, the copolymer film showed an optimized fluorescent quantum efficiency.