Riley R G, Smart J D, Tsibouklis J, Dettmar P W, Hampson F, Davis J A, Kelly G, Wilber W R
Biomaterials and Drug Delivery Group, Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, White Swan Road, PO1 2DT, Portsmouth, UK.
Int J Pharm. 2001 Apr 17;217(1-2):87-100. doi: 10.1016/s0378-5173(01)00592-0.
A range of poly(acrylic acid)s with different average degrees of polymerisation and cross-linking densities were synthesised using a solution polymerisation process. The rheological characteristics of aqueous dispersions of these materials and those of mixtures with homogenised pigs gastric mucus were investigated using dynamic oscillatory rheology, and compared to the known mucoadhesive Carbopol 934P. From the storage moduli, the rheological synergy and relative rheological synergy were calculated, and the effects of concentration and pH on this considered. Generally, the larger the molecular weight (and degree of cross-linking), the greater the rheological synergy, with Carbopol 934P giving the most pronounced effect. Rheological synergy was seen to be concentration-dependent, and a maximum concentration to produce an optimum effect was evident. Acid pHs were seen to favour synergy, although in marked contrast to previous literature reports, the optimum mucus-polymer interaction was not observed at the half ionised value (pH = pKa) but at pH regimes that were unique to each polymer type. This could be influenced by the structural constrains imposed on potential hydrogen bonded interactions. It was concluded that synthesising poly(acrylic acid)s with better defined physicochemical properties than commercially available polymers will advance the study of the phenomenon of rheological synergy.
采用溶液聚合工艺合成了一系列具有不同平均聚合度和交联密度的聚丙烯酸。使用动态振荡流变学研究了这些材料的水分散体以及与均质猪胃黏液混合物的流变特性，并与已知的黏膜黏附剂卡波姆934P进行了比较。根据储能模量计算了流变协同作用和相对流变协同作用，并考虑了浓度和pH值对其的影响。一般来说，分子量（和交联度）越大，流变协同作用越大，卡波姆934P的效果最为显著。流变协同作用表现出浓度依赖性，并且存在产生最佳效果的最大浓度。酸性pH值有利于协同作用，尽管与先前的文献报道形成鲜明对比的是，在半电离值（pH = pKa）时未观察到最佳的黏液 - 聚合物相互作用，而是在每种聚合物类型特有的pH范围内观察到。这可能受到潜在氢键相互作用所施加的结构限制的影响。得出的结论是，合成具有比市售聚合物更明确物理化学性质的聚丙烯酸将推动流变协同现象的研究。
