Gianni Paolo, Bernazzani Luca, Carosi Rita, Mollica Vincenzo
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56100 Pisa, Italy.
Langmuir. 2007 Aug 14;23(17):8752-9. doi: 10.1021/la701190g. Epub 2007 Jul 24.
The interaction of lithium perfluoroheptanoate (LiPFHep) with poly(ethylene glycol) (PEG) of different molecular weights (300 < MW < 20 000 Da) was investigated in water at 298.15 and 308.15 K by the isothermal titration calorimetry (ITC). Density and sound velocity measurements were also performed at 288.15, 298.15, and 308.15 K, while viscosity and conductivity data were only collected at 298.15 K. The aggregation process of this surfactant on the PEG polymeric chain was found to be very similar to the process exhibited by the two homologous perfluorooctanoate and perfluorononanoate. Viscosity and ITC data indicated that the formation of polymer-surfactant complexes between PEG and LiPFHep also leads to a conformational change in the polymer. The aggregation of micelles of the lithium perfluoro surfactants on the PEG polymeric chain is characterized by a comparable thermodynamic stability, which results from a balance of enthalpy and entropy contributions, which both increase with the length of the surfactant hydrophobic chain.
在298.15 K和308.15 K的水中，采用等温滴定量热法（ITC）研究了全氟庚酸锂（LiPFHep）与不同分子量（300 < MW < 20 000 Da）的聚乙二醇（PEG）之间的相互作用。在288.15 K、298.15 K和308.15 K下进行了密度和声速测量，而粘度和电导率数据仅在298.15 K下收集。发现该表面活性剂在PEG聚合物链上的聚集过程与两种同系物全氟辛酸酯和全氟壬酸酯所表现出的过程非常相似。粘度和ITC数据表明，PEG与LiPFHep之间形成聚合物 - 表面活性剂复合物也会导致聚合物的构象变化。全氟锂表面活性剂胶束在PEG聚合物链上的聚集具有相当的热力学稳定性，这是由焓和熵贡献的平衡导致的，两者都随着表面活性剂疏水链长度的增加而增加。
