Effects of Molecular Structure on the Physical Properties of Fully Substituted Cellulose Esters of Aliphatic Acids

According to the literature, mainly in relation to mixed cellulose esters (MCEs) with two types of acyl group, the solubility parameter (SP) is a measure of certain physical properties of MCE that is helpful for property prediction; contrary to expectations, it has been implied by different studies that simple cellulose esters (SCEs) with only one type of acyl group do not altogether follow the empirical relationship. In this study, MCE and SCE were systematically prepared to verify the SP-property relationship. It was revealed that the correlation between SP and physical properties exists only for MCE. Thermal analysis revealed that MCEs possess remarkable unidentified endothermic transition depending on the ratio of two acyl groups, suggesting that the formation of such a stable structure could contribute to the difference between MCE and SCE. It was also revealed that, even for MCE, the empirical relationship involving SP varies from acyl group to acyl group; there is no universal relationship. In spite of aforementioned limitation, the empirical relationship with SP was verified to be useful for the property prediction of MCE. We demonstrated that the Fox equation and Voigt model are also useful for this prediction.