Monolayers of Cellulose Ethers at the Air−Water Interface
Monolayers of Cellulose Ethers at the Air−Water Interface
复制标题
空气-水界面处的单层纤维素醚
作者：
Patricia Basque;Anémone de Gunzbourg;Andréanne Rondeau;A. Ritcey
纤维素的脂肪族醚在空气-水界面上从稀氯仿溶液中铺展时能形成稳定的单分子膜。单层的压力-面积等温线表现出一个类似液体的相，然后是一个在恒定压力下相对较高压缩的过渡区。发现限制分子面积取决于侧链长度，表明烃取代基不采用严格垂直于水面的取向。平均每个重复单元含有单个长链取代基的混合醚的单层在与脱水葡萄糖环的面积相等的分子面积处形成液体类似相。因此得出结论，纤维素主链平放在水面上。压缩后观察到的过渡区超出液体类似相是由于形成的双或多层，与分子离开水面。这种解释与观察到的平台压力随温度升高而降低的情况一致。
Aliphatic ethers of cellulose are found to form stable monolayers when spread from dilute chloroform solution at the air-water interface. Monolayer pressure-area isotherms exhibit a liquid analogous phase followed by a transition region of relatively high compression at constant pressure. Limiting molecular areas are found to depend on side-chain length, indicating that the hydrocarbon substituents do not adopt an orientation strictly perpendicular to the water surface. Monolayers of mixed ethers containing, on average, a single long chain substituent per repeat unit, form liquid analogous phases at molecular areas equivalent to the area of the anhydroglucose ring. It is thus concluded that the cellulose backbone lies flat on the water surface. The transition region observed upon compression beyond the liquid analogous phase is attributed to the formation of bi- or multilayers, with molecules leaving the water surface. This interpretation is consistent with the observed decrease in plateau pressure with increasing temperature.