Abstract:

Objective Polyvinyl alcohol (PVA) fibers hold great potential for smart textiles by virtue of their excellent biocompatibility, processability, and moisture responsiveness. However, conventional chemical crosslinking for mechanical reinforcement typically compromises hydrophilicity and moisture actuation performance, hindering their use in dynamic wearable systems. Therefore, asymmetric bicomponent PVA fiber was prepared by dual-nozzle wet-spinning, and the mechanical strength and humidity responsiveness of fiber was improved, thereby achieving high-performance moisture actuation smart textiles.

Method PVA spinning solutions were prepared with varying glutaraldehyde (GA) crosslinking ratios(0.1%, 0.125%, 0.15%, 0.2%), single-component PVA fiber and PVA/GA(PG) fibers were fabricated using a conventional wet-spinning setup. Asymmetric two-component PVA/PG (PPG) fibers were fabricated using a dual-nozzle wet-spinning setup. Fiber morphology chemical structure and mechanical properties surface wettability was analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), water contact angle measurement, and tensile testing, respectively. Moisture response time was quantified upon water exposure.

Results The results show that the dosage of the crosslinking agent has a significant impact on the microstructure, chemical structure, mechanical properties, hydrophilicity and wet stimulus response performance of PVA fibers. The dosage of the crosslinking agent significantly increases the tensile stress and strain of single-component PVA fibers. As the proportion of the crosslinking agent increases, the hydrophilicity of PVA decreases. The water contact angle of the PVA film is 47.28°, while that of the crosslinked PG film increases to 70.39°. The PVA and PG were utilized to prepare two-component PVA fibers, which not only overcomes the shortcoming of decreased hydrophilicity, but also solve the problem of incompatibility in different phases. The PVA fiber with asymmetric structure was successfully obtained continuous and structurally stable by dual-nozzle wet-spinning. The mechanical properties of the two-component PVA fibers are excellent, which is attributed to a more uniform structure, a more balanced stress distribution, and the synergistic stabilizing effect of the two components. The wet stimulation response performance is jointly regulated by the crosslinking degree and structure of the fibers. For single-component fibers, as the dosage of the crosslinking agent increases, the response time increases from 26 s to 49 s. This is because the densification of the crosslinking network reduces the hydrophilic groups and limits the movement of molecular chains. In contrast, the two-component asymmetric PVA fiber shows better response performance, especially at high crosslinking degrees, such as an average response time of 27 s, which is 44.9% faster than that of the single-component PVA fibers. The improved responsibility attributes to the asymmetric structure of fiber, which can generate internal stress through different swelling behaviors of the components, thereby compensating for the decrease in hydrophilicity caused by high crosslinking degrees. Moreover, the fabric prepared using asymmetric structure fibers exhibits significant and reversible deformation under wet stimulus. When the fabric absorbs 100% of the water, its length change rate reaches 50%, and it remains stable after three cycles. This is attributed to the strong hydrogen bond interaction between the hydroxyl groups in PVA and water molecules, as well as the promoting effect of the asymmetric structure on the differential penetration of water molecules and the movement of molecular chains.

Conclusion This study provides a new viewpoint to the asymmetric moisture-responsive PVA fiber. The results showed that increasing the crosslinking agent content enhances the tensile strength of the single-component fibers, but reduces their hydrophilicity and prolong the moisture response time. The bicomponent asymmetric structure of fiber not only preserves high mechanical strength but also improves structural stability while significantly shortening the moisture response time. Moreover, the resulting fabric exhibits excellent moisture-actuation shape memory with excellent reversibility. Therefore, this work provides both a material platform and a technical basis for developing high-performance smart textiles, particularly for applications in intelligent thermo-moisture-responsive clothing and adaptive protective materials.

Key words: polyvinyl alcohol, wet spinning, wet stimulation response, two-component asymmetric structure, shape memory, smart textiles, moisture-driven fiber