Temperature jump light scattering

Fig. 18 Scattered light intensity (a) as a function of temperature in aqueous solution of PEP-PPO-PEO block copolymers, including the location of a typical temperature-jump (b) as a function of time at the target temperature. Reprinted with permission from [127]. Copyright (1997) American Chemical Society...

The kinetics of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers have been intensively studied by T-jump experiments with light scattering detection [115, 126-130]. PEO-PPO-PEO triblock copolymers form micelles in aqueous solution, with PPO as the core forming hydrophobic block. Above the critical micelle concentration (cmc) and critical micelle temperature there exists a transition region of AT 10-15 C where... 

In 1991, Basche and Moerner included perylene in polyethylene [71]. The small and rigid perylene molecule has good emission and triplet properties, but absorbs in a difficult spectral region, around 445 nm. Because the spectral jumps we discuss here are mainly consequences of matrix dynamics, we must shortly discuss sample preparation. The samples of [71] were made from low-density polyethylene (crystallinity 25%), doped at low concentration with perylene, and were quickly quenched from the melt to liquid nitrogen temperature to reduce light scattering. The thin films thus obtained were 10 to 20 pm thick. The polymer structure is thus expected to be dominantly amorphous. 

Fig. 3.28. Time dependent light scattering experiments, conducted on a (0.3 0.7)-mixture of PS (M = 1.5 10 ) and PVME (M = 4.6 10 ) subsequent to a rapid transfer from a temperature in the region of homogeneous states to the temperature Tf = 101 °C located in the two-phase region. Numbers give the time passed after the jump (in seconds). Data from Hashimoto et al. [19]...

Figure 4.2 Time dependence of the relative change of intensity of the light scattered by a 1.5 wt% L64 solution at a final temperature of 40°C after a T-jump of 0.3°C. (A) scattering angle 90° relaxation times 30 10 ps and 1.40 0.15 ms (B) scattering angle 20° relaxation times 170 60 ps and 1.37 0.15 ms. Reproduced from Reference 31 with permission of the American Chemical Society.

The time-resolved light scattering experiment was carried out to evaluate the spherulitic growth rate as a function of Tc. When is above the Tc,max 200 °C, where SPS crystallizes with a maximum rate, the crystallization was induced by the rapid temperature drop from 300°C to Tc (T-drop). On the other hand, when Tc is below Tc x, the amorphous samples, which were obtained by quenching the samples from 300 to 0°C, were heated up to Tc to be crystallized (T-jump). 

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