pH响应木质素基胶体球的制备和表征

以造纸制浆废液中的松木碱木质素（AL）为原料，通过季铵化改性，制备了季铵化碱木质素（QAL）.QAL与十二烷基苯磺酸钠（SDBS）通过静电作用形成QAL/SDBS复配物，将QAL/SDBS复配物在乙醇/水混合溶剂中进行自组装得到具有pH响应性的胶体球.采用X射线光电子能谱（XPS）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、元素分析和静态接触角研究了胶体球的形成过程和结构.研究结果表明，QAL/SDBS复配物通过疏水聚集作用形成具有较疏水的“核”和较亲水的“壳”结构的规整胶体球.在pH=3.0时，由于QAL与SDBS间的静电作用和疏水作用使胶体球能够稳定存在.当pH>7.5时，季铵化碱木质素上的羧基电离，由于静电斥力的作用使胶体球开始解聚，当pH=10.5时，季铵化碱木质素上的酚羟基的电离使得QAL与SDBS间的静电斥力增大，胶体球完全解聚.这种在酸性条件下稳定，中性条件下解聚的胶体球在药物缓释方面具有潜在的应用.

Preparation and Characterization of pH-Responsive Lignin-based Colloidal Spheres

The quaternary ammonium of lignin(QAL) was synthesized by chemical conversion of alkali lignin(AL).The complex was formed based on electrostatic interactions by QAL with sodium dodecyl benzenesulfonate(SDBS) and the pH-response colloidal spheres were prepared with complex in ethanol-water solution via self-assembly.The structure and formation process of colloidal spheres were investigated by XPS, SEM, TEM, elemental analysis, and contact angle measurements.The results showed that pH-responsive colloidal spheres are obtained from gradual hydrophobic aggregation of QAL/SDBS complex molecules, and the colloidal spheres have hydrophobic cores and hydrophilic shells.At pH=3, the colloidal spheres are stable due to the hydrophobic and electrostatic interactions between QAL and SDBS.At pH=7.5, the carboxylic acid groups on the QAL become progressively ionized.In this case, the colloidal spheres start disaggregated due to electrostatic repulsion.At pH=10.5, the electrostatic repulsion between the QAL and SDBS molecule increases because of the ionization of carboxyl and phenolic hydroxyl groups on the QAL.Therefore, the colloid spheres disaggregation completely.The colloidalsphere are stable under the acidic condition and disaggregates under the neutral condition, so it has the potential for used in drug delivery systems.