Prameela G K S, Phani Kumar B V N, Pan A, Aswal V K, Subramanian J, Mandal A B, Moulik S P
Chemical Physics Laboratory and Chemical Laboratory, CSIR - Central Leather Research Institute, Adayar, Chennai-600020, India.
Centre for Surface Science, Department of Chemistry, Jadavpur University, Kolkata 700032, India.
Phys Chem Chem Phys. 2015 Nov 11;17(45):30560-9. doi: 10.1039/c5cp04910e.
The influence of the water soluble non-ionic tri-block copolymer PEO-PPO-PEO [poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] i.e., E2P16E2 (L31) on the microstructure and self-aggregation dynamics of the anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution was investigated using cloud point (CP), isothermal titration calorimetry (ITC), high resolution nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and small-angle neutron scattering (SANS) measurements. CP provided the thermodynamic information on the Gibbs free energy, enthalpy, entropy and heat capacity changes pertaining to the phase separation of the system at elevated temperature. The ITC and NMR self-diffusion measurements helped to understand the nature of the binding isotherms of SDS in the presence of L31 in terms of the formation of mixed aggregates and free SDS micelles in solution. EPR analysis provided the micro-viscosity of the spin probe 5-DSA in terms of rotational correlation time. The SANS study indicated the presence of prolate ellipsoidal mixed aggregates, whose size increased with the increasing addition of L31. At a large [L31], SANS also revealed the progressive decreasing size of the ellipsoidal mixed aggregates of SDS-L31 into nearly globular forms with the increasing SDS addition. Wrapping of the spherical SDS micelles by L31 was also corroborated from (13)C NMR and SANS measurements.
采用浊点（CP）、等温滴定量热法（ITC）、高分辨率核磁共振（NMR）、电子顺磁共振（EPR）和小角中子散射（SANS）测量，研究了水溶性非离子三嵌段共聚物聚环氧乙烷-聚环氧丙烷-聚环氧乙烷[poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)]，即E2P16E2（L31）对水溶液中阴离子表面活性剂十二烷基硫酸钠（SDS）微观结构和自聚集动力学的影响。CP提供了关于高温下系统相分离的吉布斯自由能、焓、熵和热容变化的热力学信息。ITC和NMR自扩散测量有助于从溶液中混合聚集体和游离SDS胶束的形成方面理解L31存在下SDS结合等温线的性质。EPR分析根据旋转相关时间提供了自旋探针5-DSA的微观粘度。SANS研究表明存在长椭球形混合聚集体，其尺寸随着L31添加量的增加而增大。在高[L31]时，SANS还显示随着SDS添加量的增加，SDS-L31的椭球形混合聚集体尺寸逐渐减小为近乎球形。(13)C NMR和SANS测量也证实了L31对球形SDS胶束的包裹作用。
