Ordering and potential appearance of a phase transition in low-tenperature liquid confined within meso-pores

用绝热量热法研究了液态环己烷和苯的低温热性能。发现有三个特征被指出。第一，玻璃化转变温度和导致玻璃化转变的基本过程随孔径变化不大。二是热容曲线呈现平缓的峰值，峰值温度随直径的增大而减小，说明散装液体中的峰值将出现在玻璃化转变温度以下。这被理解为由于聚集体允许的分子构型数量的空间限制所引起的。三是环己烷在直径2.1 nm左右的孔中出现相变。这意味着一种固有于液体基本结构的特殊结构将在包括分子与孔壁之间的原子间相互作用的孔隙中稳定下来。

Low-temperature thermal properties of liquid cyclohexane and benzene were studied by adiabatic calorimetry. Three features were found to be pointed out. The first is that the glass transition temperature and therefore the elementary process causing the transition reveal no big change with the pore diameter. The second is, the heat capacity curve displays a gentle peak and the peak temperature decreases with increasing the diameter, indicating that the peak in bulk liquid would appear below the glass transition temperature. This is understood as caused by the spatial restriction in the number of the permitted molecular configurations of the aggregates. The third is, in the case of cyclohexane, a phase transition appears in the pores with diameter around 2.1 nm. This implies that a special structure inherent to the liquid elementary one would be stabilized within the pores with including the inter-atomic interactions between the molecules and pore wall.