Poly(vinyl alcohol) (PVA) is an attractive polymer for various applications based on membranes. To increase water resistance, PVA material has to be adequately crosslinked. However, crosslinking behavior on the whole PVA membrane generally leads to obviously increased brittleness and deteriorated transparency. In the present research, a kind of glutaraldehyde crosslinked PVA membrane with gradient structure has been successfully designed and prepared by the casting membrane of pure PVA aqueous solution and the following surface post-crosslinking processes. The method can endow the PVA membrane with the gradiently decreased crosslinking degree from the surface to inside. Such gradient cross-linked PVA membrane not only keeps good flexibility and transparency, but also possesses satisfactory water-proof property. The structure and properties of the prepared the gradient acetalized PVA (GAPVA) membranes were analyzed and characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscope (SEM), tensile measurement, water resistance test and transparency observation, etc. Compared with pure PVA membrane and uniform acetalized PVA (UAPVA) one, such GAPVA membrane displays excellent performance including good water resistance, transparency and mechanical properties, much higher than those of UAPVA membrane.

聚乙烯醇（PVA）是一种有吸引力的聚合物，可用于各种基于膜的应用。为了增加耐水性，PVA材料必须充分交联。然而，在整个PVA膜上的交联行为通常导致明显的脆性增加和透明性下降。本研究通过纯PVA水溶液的流延膜和随后的表面后交联工艺，成功设计和制备了一种具有梯度结构的戊二醛交联PVA膜。该方法可以赋予PVA膜从表面到内部梯度降低的交联度。这种梯度交联的PVA膜不仅保持良好的柔韧性和透明性，而且具有令人满意的防水性能。