長鏈正高級醇類及其環氧乙烷加成物單分子膜之展佈現象與蒸發比阻之研究

Spreading Phenomena and Specific Evaporation Resistance of Monolayers of Long Chain n-Alcohols and their Oxyethylene Derivatives

羅瑛錫(Eng-Si Lo) ； 呂銘坤(Meng-Kun Lu)

《化學》 64年4期 (1975/12) Pp. 98-107

https://doi.org/10.6623/chem.1975016

摘要

以鏈碳數十八，二十及二十二之正高級醇及正二十二醇環氧乙烷加成物爲單分子膜物質，使用Wilhelmy浸板型膜壓計，在15℃至30℃之溫度範圍內研究分子面積與膜壓關係，平衡展佈膜壓，展佈速率及水分蒸發抑制效果等，以研討各種分子膜之展佈現象及蒸發比阻，並比較其經濟價值。由實驗結果得知，正高級醇類之蒸發比阻隨碳數及膜壓之增加而遞增，但其平衡展佈膜壓則隨碳數之增加而遞減，正二十二醇環氧乙烷加成物在高膜壓下之蒸發比阻高於二十醇而略低於二十二醇，但其平衡展佈膜壓則較醇類爲高，展佈速率亦較快。爲瞭解單分子膜之狀態，對醇類之分子面積與膜壓之關係曾詳細討論。單分子膜展佈過程中之展佈熱及熵，自由能，焓等之變化亦加以計算。

並列摘要

The influence of the monolayers of octadecanoI, eicosanol, docosanol and oxyethylene do-casanol on the rate of evaporation of water have been studied by measuring the rate of absorption of water vapor by a solid desiccant supported above the water surface. The data was reported as the specific resistance to the evaporation of water. The equilibrium spreading pressure, the rate of formation of monolayer and surface pressure-area isotherms of monolayers under the temperature range of 15-30℃ were also investigated. All of the works were conducted by using a precisely developed Wilhelmy dipping plate-type surface balance. The balance consists of movable Teflon barriers and Teflon lined trough. It was found that the specific resistance of normal long chain alcohols increases as the surface pressure and chain length increased, while the equilibrium spreading pressure decreases with the increasing of chain length. Oxyethylene docosanol has higher specific resistance than eicosanol and smaller than docosanol monolayer, but its equilibrium spreading pressure and the rate of formation of monolayers are higher than all of the alcohols used. The states of monolayers were discussed from surface pressure-area isotherms. And energy changes in the formation of equilibrium monolayer were also calculated from the relation between the molecular area and equilibrium spreading pressure.