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The development of facile and cost-effective strategies for hydrogels with multifunctionality is of great scientific interest. In this work, a series of poly (vinyl alcohol)/tannic acid (PVA/TA) composite hydrogels were facilely prepared by gamma radiation of a PVA solution and subsequent soaking treatment in TA solutions. The chemical composition, transparency, microstructure, mechanical property and antibacterial activity of the resulting composite hydrogels were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis spectroscopy, SEM, tensile measurements and an antibacterial test, respectively. The introduction of TA into the gamma radiation-induced chemically cross-linked networks of PVA hydrogels via the soaking treatment, which forms the second physically cross-linked networks, endows the PVA hydrogels with improved mechanical performance. The tensile strength, toughness and elongation at break of the composite hydrogel were increased by 1500 % (from 18 kPa to 254 kPa), 3600 % (from 8.5 kJ m−3 to 315 kJ m−3) and 360 % (from 87 to 403 %), respectively. Meanwhile, high transparency of the neat irradiated PVA hydrogels was maintained in the obtained composite hydrogels (transmittance over 60 % at 660 nm). The strong hydrogen bonding interaction between PVA and TA within the networks serves as sacrificial bonds and suppresses the crystallinity of the PVA hydrogels. In addition, the composite hydrogels also possess superior antibacterial activity against both gram-negative and gram-positive bacteria. This work provided a simple approach for the construction of multifunctional hydrogels on large-scale preparation, thus would hopefully promote their applications in biomedicine, wound dressings and soft devices.

Polyamide 1010 (PA1010) is a representative of long-chain polyamides, used in applications requiring good mechanical, thermal and chemical properties. It has a lower melting point and slightly higher flexible properties compared to nylon 66. Very few reports have been focused on the structures and properties of long-chain polyamides, which brings some troubles on their processing and applications. For the purpose of understanding mechanical changes within different temperature interval, dynamic structure transition of PA1010 was investigated by wide-angle X-ray diffractometer (WAXD) equipped with a hot stretching stage. During the process of the simultaneous thermal stretched, in addition to the Brill transition phenomenon, it was also accompanied by changes in crystallinity, orientation and tensile force. Both annealing and stretching can promote crystallization, in addition, stretching can also induce and destroy crystallization. With stretch ratios increasing, the crystallinity increases firstly, reaches the maximum when stretch ratio is 2.25 times and then decreases. The degree of orientation increase firstly but increase poorly after 2.50 times. The stretch force increase gradually too. The stretch force has a stronger ability than temperature to induce the PA1010 undergo the Brill transition. The presented results show that Brill transition is completed and the α-crystal structure completely transformed into γ-crystal structure when the stretch ratio is 2.50 times.