Humidity-Adaptive Behaviors of Alginate/Chitosan Complex Fiber

Humidity is a critical environmental parameter that greatly affects the performance of many materials. Alginate (ALG) and chitosan (CHI) are abundant naturally occurring polymers, and their complex based on electrostatic interaction is widely used in various fields, especially in the biomedical area. Due to the strong hygroscopicity of ALG and CHI, the mechanical properties of ALG/CHI complex are significantly influenced by humidity; however, there remains a lack of quantitative understanding regarding this phenomenon. Here, we prepared ALG/CHI complex fiber and systematically studied the humidity effect. The humidity-adaptive behaviors of ALG/CHI fiber were investigated by tensile test, stress relaxation, and creep. Time–water superposition (TWSP) and time–temperature superposition (TTSP) principles were applied to elucidate the mechanical behaviors in a long-time scale using the dynamic mechanical analysis (DMA) data of frequency sweep at different humidity and temperature. The cyclic humidification and dehumidification test demonstrated that ALG/CHI fiber quickly and reversibly responds to environmental humidity variation. The study provides fundamental understanding on humidity adaptability of ALG/CHI fiber, which can facilitate further development of ALG/CHI complex as an advanced responsive and adaptive material.