Maradiaga Rivas Johann Eduardo, Chen Li-Jen, Lin Shi-Yow, Hussain Siam
Department of Chemical Engineering, National Taiwan University of Science and Technology, 43, Sec. 4, Keelung Road, Taipei 106, Taiwan.
Department of Chemical Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei City 106, Taiwan.
Polymers (Basel). 2024 May 10;16(10):1359. doi: 10.3390/polym16101359.
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 C = 5 × 10 g/cm, [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 (γ) and to attain the saturated dilational modulus (E) of the adsorbed PAA film, (ii) both γ and E of PAA solutions increase with MW of PAA, (iii) a lower MW solution requires a longer time to reach its γ and E, and (iv) this approach is workable for evaluating the E of adsorbed polymer films.
聚合物薄膜的拉伸模量（E）通常使用外力作用下的振荡环/气泡/液滴法进行测量，而且常常未明确吸附膜的状态。本研究探索了一种方法，即根据自然扰动下表面张力（ST）和表面积（SA）的弛豫来确定E，其中ST和SA使用悬滴气泡张力仪进行监测。针对浓度C = 5×10 g/cm、分子量[MW = 5、25和250（kDa）]的聚丙烯酸（PAA）水溶液，评估了其吸附膜的E。E（=dγ/dlnA）是根据由环境温度的微小变化引起的自然扰动下气泡表面的表面拉伸速率（dlnA/dt）和ST变化速率（dγ/dt）估算得出的。数据表明：（i）达到平衡表面张力（γ）并获得吸附的PAA膜的饱和拉伸模量（E）需要相当长的时间；（ii）PAA溶液的γ和E均随PAA分子量的增加而增大；（iii）较低分子量的溶液达到其γ和E所需的时间更长；（iv）这种方法对于评估吸附聚合物薄膜的E是可行的。
