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Abstract：
To afford an intact double network (sample abbr.: DN) hydrogel, two-step crosslinking reactions of poly(2-acrylamido-2-methylpropanesulfonic acid) (i.e., PAMPS first network) and then poly(acrylic acid) (i.e., PAA second network) were conducted both in the presence of crosslinker (N,N\'-methylenebisacrylamide (MBAA)). Similar to the two-step processes, different contents of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) oxidized cellulose nanofibers (TOCN: 1, 2, and 3 wt.%) were initially dispersed in the first network solutions and then crosslinked. The TOCN-containing PAMPS first networks subsequently soaked in AA and crosslinker and conducted the second network crosslinking reactions (TOCN was then abbreviated as T for DN samples). As the third step, various (T-)DN hydrogels were then treated with different concentrations of FeCl3(aq) solutions (5, 50, 100, and 200 mM). Through incorporations of ferric ions into (T-)DN hydrogels, notably, three purposes are targeted: (i) strengthen the (T-)DN hydrogels through ionic bonding, (ii) significantly render ionic conductivity of hydrogels, and (iii) serve as a catalyst for the forth step to proceed with in situ chemical oxidative polymerizations of pyrroles to afford polypyrrole-containing (sample abbr.: Py) hydrogels [i.e., (T-)Py-DN samples]. The characteristic functional groups of PAMPS, PAA, and Py were confirmed by FT-IR. Uniform microstructures were observed by cryo scanning electron microscopy (cryo-SEM). These results indicated that homogeneous composites of T-Py-DN hydrogels were obtained through the four-step process. All dry samples showed similar thermal degradation behaviors from the thermogravimetric analysis (TGA). The T2-Py5-DN sample (i.e., containing 2 wt.% TOCN with 5 mM FeCl3(aq) treatment) showed the best tensile strength and strain at breaking properties (i.e., σTb = 450 kPa and εTb = 106%). With the same compositions, a high conductivity of 3.34 × 10-3 S/cm was acquired. The tough T2-Py5-DN hydrogel displayed good conductive reversibility during several \"stretching-and-releasing\" cycles of 50-100-0%, demonstrating a promising candidate for bioelectronic or biomaterial applications.
摘要：
提供完整的双网络(样本缩写。:DN)水凝胶，聚（2-丙烯酰胺基-2-甲基丙磺酸）的两步交联反应（即，PAMPS首先网络)，然后是聚(丙烯酸)(即，PAA第二网络)在交联剂存在下进行(N，N'-亚甲基双丙烯酰胺(MBAA)。类似于两步过程，不同含量的2,2,6,6-四甲基-1-哌啶基氧基（TEMPO）氧化纤维素纳米纤维（TOCN：1、2和3wt。％）最初分散在第一网络溶液中，然后交联。随后将含TOCN的PAMPS第一网络浸泡在AA和交联剂中并进行第二网络交联反应(对于DN样品,TOCN缩写为T)。作为第三步，然后用不同浓度的FeCl3(aq)溶液(5、50、100和200mM)处理各种(T-)DN水凝胶。通过将三价铁离子掺入（T-）DN水凝胶中，特别是,有三个目的：（i）通过离子键合增强（T-）DN水凝胶，（ii）显着赋予水凝胶的离子电导率，和（iii）用作第四步骤的催化剂，以进行吡咯的原位化学氧化聚合，以提供含聚吡咯的（样品摘要。：Py)水凝胶[即，(T-)Py-DN样品]。PAMPS的特征官能团，PAA,和Py经FT-IR确证。通过低温扫描电子显微镜（cryo-SEM）观察到均匀的微观结构。这些结果表明，通过四步法获得了T-Py-DN水凝胶的均匀复合材料。根据热重分析（TGA），所有干燥样品均显示出相似的热降解行为。T2-Py5-DN样本(即，含有2wt。％TOCN用5mMFeCl3（aq）处理）显示出最佳的拉伸强度和断裂性能应变（即，σTb=450kPa和εTb=106%)。用相同的构图，获得3.34×10-3S/cm的高电导率。坚韧的T2-Py5-DN水凝胶在50-100-0%的几个“拉伸和释放”循环中显示出良好的导电可逆性，展示了生物电子或生物材料应用的有前途的候选者。
