Banks Simon R, Sammon Chris, Melia Colin D, Timmins Peter
Formulation Insights, School of Pharmaceutical Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
Appl Spectrosc. 2005 Apr;59(4):452-9. doi: 10.1366/0003702053641496.
In this work attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to probe the thermal gelation behavior of aqueous solutions of hydroxypropyl methylcellulose (HPMC), specifically thermal gelation and accompanying precipitation. Cloud point measurements are usually evaluated through turbidity in dilute solutions but the method cannot readily be applied to more concentrated or highly viscous solutions. From the ATR-FTIR data, intensity changes of the nu(CO) band marked the onset of gelation and information about the temperature of gelation and the effect of the gel structure on the water hydrogen bonding network was elucidated. Changes in the relative intensities of bands associated with the methoxyl groups and hydrogen-bond-forming secondary alcohol groups indicated that hydrophobic polymer chain interactions were involved in the gelation process. The dominance of inter-molecular H bonding over intra-molecular H bonding within the cellulose ether in solution was also observed. The ATR-FTIR data was in good agreement with measurements of turbidity conducted on the same systems. The work indicates significant potential for the use of ATR-FTIR for the investigation of gelation and cloud point measurements in viscous cellulosic formulations.
在本研究中，采用衰减全反射傅里叶变换红外（ATR-FTIR）光谱法探究羟丙基甲基纤维素（HPMC）水溶液的热凝胶化行为，特别是热凝胶化及伴随的沉淀过程。浊点测量通常通过稀溶液中的浊度进行评估，但该方法不适用于更浓或高粘度溶液。从ATR-FTIR数据可知，ν(CO)带的强度变化标志着凝胶化的开始，阐明了凝胶化温度及凝胶结构对水氢键网络的影响。与甲氧基和形成氢键的仲醇基团相关的谱带相对强度变化表明，疏水聚合物链相互作用参与了凝胶化过程。还观察到溶液中纤维素醚内分子间氢键比分子内氢键占主导。ATR-FTIR数据与对相同体系进行的浊度测量结果吻合良好。该研究表明，ATR-FTIR在研究粘性纤维素制剂中的凝胶化和浊点测量方面具有巨大潜力。
