Dey Shantanu, Adhikari Aniruddha, Mandal Ujjwal, Ghosh Subhadip, Bhattacharyya Kankan
Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.
J Phys Chem B. 2008 Apr 24;112(16):5020-6. doi: 10.1021/jp8002257. Epub 2008 Apr 3.
Solvation dynamics and anisotropy decay of coumarin 480 (C480) in a supramolecular assembly containing a triblock copolymer, PEO20-PPO70-PEO20 (Pluronic P123) and a surfactant, CTAC (cetyl trimethylammonium chloride) are studied by femtosecond up-conversion. In a P123-CTAC complex, C480 displays a significant (22 nm) red edge excitation shift (REES) in the emission maximum as lambda ex increases from 335 to 445 nm. This suggests that the P123-CTAC aggregate is quite heterogeneous. The average rotational relaxation time (tau rot) of C480 in a P123-CTAC complex decreases by a factor of 2 from 2500 ps at lambda ex = 375 nm to 1200 ps at lambda ex = 435 nm. For lambda ex = 375 nm, the probe molecules in the buried core region of P123-CTAC are excited and the solvation dynamics displays three components, 2, 60, and 4000 ps. It is argued that insertion of CTAC in P123 micelle affects the polymer chain dynamics, and this leads to reduction of the 130 ps component of P123 micelle to 60 ps in P123-CTAC. For lambda ex = 435 nm, which selects the peripheral highly polar corona region, solvation dynamics in P123-CTAC and P123 are extremely fast with a major component of <0.3 ps ( approximately 80%) and a 2 ps ( approximately 20%) component.
采用飞秒上转换技术研究了香豆素480（C480）在包含三嵌段共聚物PEO20-PPO70-PEO20（普朗尼克P123）和表面活性剂十六烷基三甲基氯化铵（CTAC）的超分子聚集体中的溶剂化动力学和各向异性衰减。在P123-CTAC复合物中，随着激发波长λex从335 nm增加到445 nm，C480的发射最大值出现显著的（22 nm）红边激发位移（REES）。这表明P123-CTAC聚集体具有相当的不均匀性。C480在P123-CTAC复合物中的平均旋转弛豫时间（τrot）从λex = 375 nm时的2500 ps减小到λex = 435 nm时的1200 ps，减小了2倍。对于λex = 375 nm，P123-CTAC埋藏核心区域中的探针分子被激发，溶剂化动力学表现出三个组分，分别为2、60和4000 ps。有人认为CTAC插入P123胶束会影响聚合物链动力学，这导致P123-CTAC中P123胶束的130 ps组分减小到60 ps。对于选择外围高极性冠层区域的λex = 435 nm，P123-CTAC和P123中的溶剂化动力学极快，主要组分为<0.3 ps（约80%）和2 ps（约20%）组分。
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