The structure and physicochemical properties of polyvinyl alcohol (PVA) and PVA/glycerol films have been investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA), and advanced scanning probe microscopy (SPM). In the pure PVA films, SPM allowed us to observe ribbon-shaped domains with a different frictional and elastic contrast, which apparently originated from a correlated growth or assembly of PVA crystalline nuclei located within individual PVA clusters. The incorporation of 22% w/w glycerol led to modification in shape of those domains from ribbon-like in pure PVA to rounded in PVA/glycerol 22% w/w films; changes in the relative intensities of the XRD peaks and a decrease in the amorphous halo in the XRD pattern were also detected, while the DTA peak corresponding to the melting point remained at almost the same temperature. For higher glycerol content, FT-IR revealed additional glycerol-characteristic peaks presumably related to the formation of glycerol aggregates, and XRD, FT-IR, and DTA all indicated a reduction in crystallinity. For more than 36% w/w glycerol, the plasticization of the films complicated the acquisition of SPM images without tip-induced surface modification. Our study contributes to the understanding of crystallinity in PVA and how it is altered by a plasticizer such as glycerol.

中文翻译：

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甘油对聚乙烯醇薄膜表面形貌和结晶度的影响


通过傅里叶变换红外光谱 (FT-IR)、X 射线衍射 (XRD)、热重/差热分析 (TG/DTA) 和先进的扫描探针显微镜（SPM）。在纯 PVA 薄膜中，SPM 使我们能够观察到具有不同摩擦力和弹性对比的带状区域，这显然源自位于各个 PVA 簇内的 PVA 晶核的相关生长或组装。 22% w/w 甘油的加入导致这些区域的形状发生变化，从纯 PVA 中的带状变为 PVA/甘油 22% w/w 薄膜中的圆形；还检测到 XRD 峰相对强度的变化以及 XRD 图案中非晶晕的减少，而与熔点对应的 DTA 峰几乎保持在相同的温度。对于较高的甘油含量，FT-IR 显示了额外的甘油特征峰，可能与甘油聚集体的形成有关，并且 XRD、FT-IR 和 DTA 均表明结晶度降低。对于超过 36% w/w 的甘油，薄膜的塑化使 SPM 图像的采集变得复杂，而无需尖端诱导的表面修饰。我们的研究有助于了解 PVA 的结晶度以及甘油等增塑剂如何改变结晶度。