Hydrophobically modified pullulans: Characterization and physicochemical properties
Hydrophobically modified pullulans: Characterization and physicochemical properties
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DOI：
10.1021/jp048068e
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发表时间：
2004-12-09
影响因子：
3.3
通讯作者：
La Mesa, C
中科院分区：
文献类型：
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作者：
Sallustio, S;Galantini, L;La Mesa, C
通过与十二烷酸反应对普鲁兰进行疏水改性，调节聚合物与酸的比例。所得产物称为PULAU(N)，对其进行了表征，并报道了其在25℃水溶液中的物理化学性质。疏水取代是通过傅里叶变换红外，FTIR和核磁共振分析确定。采用核磁共振定量表征了取代度N，粘度、表面张力、准弹性光散射、QELS和凝胶渗透色谱等方法表征了PULAU(N)的溶液性质。根据聚合物浓度和N的不同，PULAU(N)形成胶束状聚集体。临界胶束浓度cmc随氮的增加而降低，加入十二烷基硫酸钠SDS可形成混合胶束。在所研究的浓度范围内，将PULAU(N)与SDS混合，没有形成聚合物表面活性剂基凝胶。根据核磁共振自扩散和QELS结果，PULAU(N)胶束的数-平均聚集数取决于浓度和取代度。在替换率更高的PULAU中观察到较大的数值（5.0）。PULAU（5.0）在空气-溶液界面的吸附动力学非常缓慢（数天）。在低于cmc的浓度下观察到的效果是由疏水改性聚合物的浓度调节的。吸附动力学与不同作用的组合有关。建立了一个热力学模型来解释上述行为。考虑到PULAU（5.0）链的表面扩散、自扩散和弹性特性，对该工艺进行了合理化。
Pullulan was hydrophobically modified by reaction with dodecanoic acid, modulating the polymer-to-acid ratio. The resulting products, termed PULAU(N), have been characterized, and their physicochemical properties in aqueous solution, at 25 degreesC, are reported. The hydrophobic substitution was determined by Fourier transform infrared, FTIR, and NMR analyses. NMR also quantifies the substitution degree, N. Viscosity, surface tension, quasi-elastic light scattering, QELS, and gel permeation chromatography, GPC, methods were used to characterize the solution properties of PULAU(N). Depending on the polymer concentration and N, PULAU(N) form micelle-like aggregates. The critical micelle concentration, cmc, decreases with increasing N. Addition of sodium dodecyl sulfate, SDS, results in the formation of mixed micelles. In the investigated concentration range, no polymer- surfactant-based gels are formed by mixing PULAU(N) and SDS. According to NMR self-diffusion and QELS findings, the number-average aggregation numbers of PULAU(N) micelles, , depend on the concentration and substitution degree. Large values are observed in the more substituted PULAU(5.0). A very slow kinetics of adsorption at the air-solution interface (some days long) is observed for PULAU(5.0). The effect, observed at concentrations below the cmc, is modulated by the concentration of hydrophobically modified polymer. The kinetics of adsorption is related to the combination of different effects. A thermodynamic model was developed to account for the above behavior. The process was rationalized by taking into account terms due to the surface spreading, self-diffusion, and elastic properties of the PULAU(5.0) chains.