D'Errico Gerardino, Paduano Luigi, Khan Ali
Dipartimento di Chimica, Università di Napoli Federico II, via Cynthia, Naples I 80126, Italy.
J Colloid Interface Sci. 2004 Nov 15;279(2):379-90. doi: 10.1016/j.jcis.2004.06.063.
The phase behavior (temperature vs composition) and microstructure for the two binary systems Pluronic 25R4 [(PO)19(EO)33(PO)19]-water and Pluronic 25R2 [(PO)21(EO)14(PO)21]-water have been studied by a combined experimental approach in the whole concentration range and from 5 to 80 degrees C. The general phase behavior has been identified by inspection under polarized light. Precise phase boundaries have been determined by analyzing 2H NMR line shape. The identification and microstructural characterization of the liquid crystalline phases have been achieved using small-angle X-ray scattering (SAXS). The isotropic liquid solution phases have been investigated by self-diffusion measurements (PGSE-NMR method). 25R2 does not form liquid crystals and is miscible with water in the whole concentration range; with increasing temperature, the mixtures split into water-rich and a copolymer-rich solutions in equilibrium. 25R4 shows rich phase behavior, passing, with increasing copolymer concentration, from a water-rich solution to a lamellar and copolymer-rich solution. A small hexagonal phase, completely encircled in the stability region of the water-rich solution, is also present. In water-rich solutions, at low temperatures and low copolymer concentrations, the copolymers are dissolved as independent macromolecules. With increasing copolymer concentrations an interconnected network of micelles is formed in which micellar cores of hydrophobic poly(propylene oxide) are interconnected by poly(ethylene oxide) strands. In copolymer-rich solutions water is molecularly dissolved in the copolymer. The factors influencing the self-aggregation of Pluronic R copolymers (PPO-PEO-PPO sequence) are discussed, and their behavior in water is compared to that of Pluronic copolymers (PEO-PPO-PEO sequence).
通过一种组合实验方法，在整个浓度范围以及5至80摄氏度的温度区间内，研究了两种二元体系，即普朗尼克25R4[（PO）19（EO）33（PO）19]-水体系和普朗尼克25R2[（PO）21（EO）14（PO）21]-水体系的相行为（温度与组成关系）和微观结构。通过偏光下的观察确定了一般相行为。通过分析2H NMR线形确定了精确的相边界。利用小角X射线散射（SAXS）实现了液晶相的识别和微观结构表征。通过自扩散测量（PGSE-NMR方法）研究了各向同性液体溶液相。25R2不形成液晶，在整个浓度范围内与水互溶；随着温度升高，混合物会分成富含水和富含共聚物的平衡溶液。25R4表现出丰富的相行为，随着共聚物浓度增加，从富水溶液转变为层状且富含共聚物的溶液。还存在一个小的六方相，它完全被富水溶液的稳定区域包围。在富水溶液中，低温和低共聚物浓度下，共聚物以独立大分子形式溶解。随着共聚物浓度增加，形成了由胶束组成的相互连接网络，其中疏水性聚环氧丙烷的胶束核通过聚环氧乙烷链相互连接。在富含共聚物的溶液中，水以分子形式溶解在共聚物中。讨论了影响普朗尼克R共聚物（PPO-PEO-PPO序列）自聚集的因素，并将它们在水中的行为与普朗尼克共聚物（PEO-PPO-PEO序列）的行为进行了比较。
