Sugosh Prabhu - Can Critical Packing Parameter Depict Probe Rotation in Block-Copolymer Reverse Micelles?

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      Publication Details (including relevant citation   information):

        Radiation & Photochemistry Division, Bhabha Atomic Research     Centre, Trombay, Mumbai 400 085, India  
    J. Phys. Chem. B, 2013, 117 (19), pp 5868–5874
    Publication Date (Web): April 19, 2013
    Copyright © 2013 American Chemical Society


        Rotational diffusion of two ionic probes, cationic rhodamine 110   (R110) and anionic fluorescein (FL), has been examined in reverse   micelles formed with the triblock copolymer   (EO)13–(PO)30–(EO)13    (L64), where EO and PO represent ethylene oxide and propylene   oxide units, respectively, with small amounts of water in   p-xylene.   This study has essentially been undertaken to explore the   influence of mole ratio of water to copolymer (W)   as well as copolymer concentration on probe rotation. On the   basis of fluorescence lifetimes and reorientation times, it has   been established that both R110 and FL are located in the   interfacial region of L64/water/p-xylene   reverse micellar system. The average reorientation time decreases   by 10–35% with an increase in W    for both the probes at a given copolymer concentration. However,   for a particular W,   the average reorientation time increases by 10–30% as the   concentration of the copolymer is enhanced. From the micellar   structural parameters available in the literature, critical   packing parameters have been calculated for the   L64/water/p-xylene   reverse micellar system, and it has been noticed that the average   reorientation times of both the probes scale linearly with the   critical packing parameter. In essence, the results of this study   indicate that the probe mobility in the interfacial region of   block copolymer reverse micelles is governed by the micellar   packing.

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