PDF(Pubmed)
Abstract：
The dilational modulus (E) of polymer films has been commonly measured using the oscillating ring/bubble/drop methods with an external force, and often without specifying the state of the adsorbed film. This study explores an approach where E was determined from the relaxations of surface tension (ST) and surface area (SA) of natural perturbations, in which ST and SA were monitored using a pendant bubble tensiometer. The E of the adsorbed film of PAA (polyacrylic acid) was evaluated for aqueous solutions at CPAA = 5 × 10-4 g/cm3, [MW = 5, 25, and 250 (kDa)]. The E (=dγ/dlnA) was estimated from the surface dilational rate (dlnA/dt) and the rate of ST change (dγ/dt) of the bubble surface from the natural perturbation caused by minute variations in ambient temperature. The data revealed that (i) a considerable time is required to reach the equilibrium-ST (γeq) and to attain the saturated dilational modulus (Esat) of the adsorbed PAA film, (ii) both γeq and Esat of PAA solutions increase with MW of PAA, (iii) a lower MW solution requires a longer time to reach its γeq and Esat, and (iv) this approach is workable for evaluating the E of adsorbed polymer films.
摘要：
聚合物薄膜的扩张模量（E）通常使用振荡环/气泡/液滴方法在外力下测量，并且通常没有指定吸附膜的状态。这项研究探索了一种方法，其中E是由自然扰动的表面张力（ST）和表面积（SA）的弛豫确定的，其中使用悬吊式气泡张力计监测ST和SA。对于CPAA=5×10-4g/cm3，[MW=5、25和250（kDa）]的水溶液，评估了PAA（聚丙烯酸）吸附膜的E。E（=dγ/dlnA）是根据环境温度微小变化引起的自然扰动，根据气泡表面的表面扩张速率（dlnA/dt）和ST变化率（dγ/dt）估算的。数据显示（i）达到平衡ST（γeq）和达到吸附的PAA膜的饱和扩张模量（Esat）需要相当长的时间，（ii）PAA溶液的γeq和Esat均随PAA的MW增加，（iii）较低的MW解决方案需要更长的时间才能达到其γeq和Esat，和（iv）该方法可用于评估吸附的聚合物膜的E。
