Fu Zhen-Zhen, Yao Yi-Hang, Guo Sheng-Jie, Wang Ke, Zhang Qin, Fu Qiang
College of Polymer Science and Engineering, Sichuan University, State Key Laboratory of Polymer Materials Engineering, Chengdu, 610065, P. R. China.
Macromol Rapid Commun. 2023 Jan;44(1):e2200296. doi: 10.1002/marc.202200296. Epub 2022 Jul 3.
Adding small molecular plasticizers is the most common route to tailor the stretchability of poly(vinyl alcohol) (PVA). However, how the plasticization along with the nature of the plasticizer governs the structural homogeneity during stretching remains an open question to answer. Herein, two representative plasticizers, glycerol (GLY) and water, are chosen to endow the PVA films with ductility. It is found that large strain cavitations cause obvious stress whitening in the PVA/H O films; on the contrary, most of the PVA/GLY films maintain transparent undergoing tensile deformation. Through a combination of experimental inspections and molecular dynamic simulation, it is revealed that partial water molecules that behave as free water will aggregate into microdomains, which serve as mechanical defects responsible for yielding voids. Whereas, the GLY plasticizer homogeneously disperses at a molecular level and interacts with PVA chains through strong hydrogen bonds. More interestingly, it is illustrated that the dispersion and bound states of plasticizers are closely related to the mechanical character of the plasticized PVA films. These findings offer new insight into the working mechanism of plasticization on the structural stability during stretching, and guide the design of PVA/plasticizer system to obtain excellent comprehensive mechanics.
添加小分子增塑剂是调节聚乙烯醇（PVA）拉伸性最常用的方法。然而，增塑作用以及增塑剂的性质如何在拉伸过程中控制结构均匀性仍是一个有待解答的开放性问题。在此，选择两种具有代表性的增塑剂，甘油（GLY）和水，赋予PVA薄膜延展性。研究发现，大应变空化在PVA/H₂O薄膜中导致明显的应力发白；相反，大多数PVA/GLY薄膜在拉伸变形过程中保持透明。通过实验检测和分子动力学模拟相结合，揭示出作为自由水的部分水分子会聚集形成微区，这些微区作为导致产生空隙的力学缺陷。而GLY增塑剂在分子水平上均匀分散，并通过强氢键与PVA链相互作用。更有趣的是，结果表明增塑剂的分散和结合状态与增塑PVA薄膜的力学特性密切相关。这些发现为拉伸过程中增塑作用对结构稳定性的作用机制提供了新的见解，并指导PVA/增塑剂体系的设计以获得优异的综合力学性能。
