Effect of room temperature ionic liquids on femtosecond solvation dynamics in a triblock copolymer (P123) gel

Abstract

Effect of two room temperature ionic liquids (RTIL, [pmim][Br] and [pmim][BF₄]) on the solvation dynamics and anisotropy decay of coumarin 480 (C480) in P123 gel has been studied using femtosecond up-conversion. In P123 gel, C480 displays a significant excitation wavelength dependence of emission maximum (red edge excitation shift, REES of 18 nm) and solvation dynamics, which suggest heterogeneous structure of the P123 gel. Dynamics of different regions of the P123 gel-RTIL is probed by the variation of excitation wavelength (<img src='/image/spc_char/lamda.gif' border=0>_ex). For <img src='/image/spc_char/lamda.gif' border=0>_ex = 435 nm, the polar peripheral region of the P123-RTIL gel is preferentially excited with a very small contribution of the non-polar region. At <img src='/image/spc_char/lamda.gif' border=0>_ex = 375 nm, contribution of the non-polar region is very large. The solvation dynamics in both the core and corona regions of P123 gel-RTIL is faster than that in P123 gel. The anisotropy decay of C480 in the P123 gel-RTIL phase is about two times faster as compared to P123 gel. The results are compared with a recent fluorescence correlation spectroscopic study on diffusion in RTIL-P123 gel.<span style="mso-bidi-font-style:italic">

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