Fu Zhen-Zhen, Guo Sheng-Jie, Li Chen-Xi, Wang Ke, Zhang Qin, Fu Qiang
College of Polymer Science and Engineering, Sichuan University, State Key Laboratory of Polymer Materials Engineering, Chengdu 610065, People's Republic of China.
Phys Chem Chem Phys. 2022 Jan 19;24(3):1885-1895. doi: 10.1039/d1cp03893a.
Hydrogen bonds (H-bonds) in poly(vinyl alcohol) (PVA) play a crucial role in macroscopic mechanical properties, particularly for stretchability. However, there is still some ambiguity about the quantitative dependence of H-bond interactions on the mechanical performance, mainly attributed to the difficulty in the discrimination of various H-bond types. Herein, small molecular chemicals as plasticizers were incorporated into the PVA matrix to tailor the H-bonding interactions. By altering the PVA molecular weight, plasticizer type and loading, both the stretchability and H-bond content were regulated on a large scale. By a combination of DMA, IR spectroscopy, MD simulation and solid-state C-NMR, every sort of H-bond in PVA was assigned, and their relative fractions were ascertained quantitatively. After correlating the elongation ratio with the relative fraction of the different types of H-bonding interaction, it was found that all the pairs of elongation intermolecular H-bond content derived from different series of PVA/plasticizer films could be plotted into a master curve and exhibited good linearity, indicating that intermolecular H-bonds dominate the mechanical stretchability in PVA films. Our efforts contribute towards an in-depth understanding of performance optimization induced by H-bond manipulation from empirical, phenomenological aspects to intrinsic, numerical insights.
聚乙烯醇（PVA）中的氢键（H键）在宏观机械性能尤其是拉伸性方面起着至关重要的作用。然而，H键相互作用对机械性能的定量依赖性仍存在一些不明确之处，这主要归因于区分各种H键类型存在困难。在此，将小分子化学物质作为增塑剂引入PVA基体中以调整H键相互作用。通过改变PVA分子量、增塑剂类型和负载量，拉伸性和H键含量都得到了大规模调控。通过动态热机械分析（DMA）、红外光谱（IR）、分子动力学（MD）模拟和固态碳核磁共振（C-NMR）相结合的方法，确定了PVA中每种H键，并定量确定了它们的相对比例。将伸长率与不同类型H键相互作用的相对比例相关联后，发现源自不同系列PVA/增塑剂薄膜的伸长率与分子间H键含量的所有数据对都可以绘制成一条主曲线，并且呈现出良好的线性关系，这表明分子间H键主导了PVA薄膜的机械拉伸性。我们的工作有助于从经验、现象学层面到内在、数值洞察等方面深入理解由H键操控引起的性能优化。
