Drogoz Alexandre, David Laurent, Rochas Cyrille, Domard Alain, Delair Thierry
Unité mixte CNRS-BioMérieux, UMR 2714, ENS Lyon, 46, allée d'Italie, 69364 Lyon Cedex 07, France.
Langmuir. 2007 Oct 23;23(22):10950-8. doi: 10.1021/la7008545. Epub 2007 Sep 20.
Colloids were obtained from non-stoichiometric polyelectrolyte complexes with two polysaccharides of opposite charge: chitosan and dextran sulfate (DS) as the polycation and polyanion, respectively. The complexes were elaborated by a one-shot addition of the polymer in default to the one in excess. The colloids were positively or negatively charged according to the nature of the polymer in excess. Dynamic light scattering (DLS) demonstrated that particles were formed at a very early stage in the complexation process. The consumption of the excess polyelectrolyte was monitored with a dye assay specific for dextran sulfate (toluidine blue) or chitosan (orange II). From these experiments, two different mechanisms of colloidal PEC formation were evidenced, according to the nature of the polymer in excess. On adding chitosan to DS in excess, regular consumption of the polyanion was observed at a constant stoichiometry, in the 1.5 to 1.85 range (sulfate residues for one glucosamine group), according to the molar mass of the polycation. When DS was added to chitosan in excess, the overall stoichiometry varied from ca. 6 (glucosamine residues for one sulfate group) down to 1 as the charge molar mixing ratio R=n+/n- decreased from 20 to 1. The existence of various mechanisms, according to the nature of the polymer in excess, could be attributed to the differences in chemical reactivity (strong vs low) of the ion in excess and the conformation and flexibility of the macromolecular chains related to their electrostatic potential.
胶体是由非化学计量的聚电解质复合物制备而成，该复合物由两种带相反电荷的多糖组成：壳聚糖和硫酸葡聚糖（DS），分别作为聚阳离子和聚阴离子。通过将一种聚合物一次性加入到过量的另一种聚合物中来制备复合物。根据过量聚合物的性质，胶体带正电荷或负电荷。动态光散射（DLS）表明，在络合过程的早期阶段就形成了颗粒。用针对硫酸葡聚糖（甲苯胺蓝）或壳聚糖（橙黄II）的染料测定法监测过量聚电解质的消耗情况。从这些实验中可以看出，根据过量聚合物的性质，胶体PEC形成存在两种不同的机制。当向过量的DS中加入壳聚糖时，观察到聚阴离子以恒定的化学计量比被规律地消耗，根据聚阳离子的摩尔质量，该化学计量比在1.5至1.85范围内（一个葡糖胺基团对应一个硫酸根残基）。当向过量的壳聚糖中加入DS时，随着电荷摩尔混合比R = n+/n-从20降至1，总化学计量比从约6（一个硫酸根对应六个葡糖胺残基）降至1。根据过量聚合物的性质存在多种机制，这可能归因于过量离子的化学反应性差异（强与弱）以及与大分子链静电势相关的构象和柔韧性差异。
