Lower critical solution temperature field

Both PNIPAAm and PVME exhibit unique thermo-shrinking properties. Thus, as an aqueous solution is heated beyond a certain point, the polymer shrinks and a phase separation occurs. This temperature is commonly referred to as the lower critical solution temperature (LCST). For PNIPAAm, it lies between ca. 30 and 35°C, the exact temperature being a function of the detailed microstructure of the macromolecule. Below LCST, the polymer is soluble in the aqueous phase, as the chains are extended and surrounded by water molecules. Above the LCST, the polymer becomes insoluble and phase separation occurs. Because of the abrupt nature of these transitions and their reversibility (which allows repeated thermal switching) these polymers have stirred up particular interest in the field of science and engineering since their first appearance in the open literature in 1956. 

We have studied critical density fluctuations of water-in-oil droplets in AOT/water/n-decane system that has a lower critical solution temperature (LCST) decomposing at higher temperature by SANS below and near the phase boundary of decomposition into two phases [6, 7]. We observed critical scattering I q) growing toward the phase boundary at small q. From the extrapolation of I q) to zero of q, we get I (0) which is proportional to the susceptibility So- The observed behavior of Sq revealed a crossover from mean field to 3D Ising and is well described in terms of asymptotic expression Eq. (8) as depicted... 

Two examples of binary homopolymer blends exhibiting a crossover from mean-field to 3D-lsing critical behavior will be presented. The first blend is a lower critical solution temperature (LCST) blend of high-molar-volume dPS and PVME at... 

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