Abstract This report investigates viscoelastic and mechanical behavior of hybrid polyvinyl alcohol (PVA)-cellulose nanofibers (CNC) hydrogel aggregated with sodium chloride (NaCl) salt. In almost all samples, wide distribution of pores with roughly equal average pore size was observed, denoting that the average porosity is independent from CNC concentration. To assess dispersion quality of CNCs in CNC-PVA/salt hybrid network, transmission electron microscopy (TEM) was employed. Small and large amplitude oscillatory shear (SAOS and LAOS) measurements were also performed on CNC-loaded PVA-salt hydrogels to further characterize their microstructure via monitoring viscoelastic parameters. At CNC loadings near the percolation threshold (15 g/L), a sudden jump in storage modulus versus frequency curve was observed, attributing to polymer-CNC 3D network formation. Interestingly, appearance of a more dramatic jump in the value of the rheological parameters at higher CNC concentrations (30 g/L) indicates the establishment of a secondary network structure upon formation of a direct contact between individual CNC particles and/or clusters. The viscoelastic behavior of the hydrogels was further investigated via LAOS approach based on Lissajous-Bowditch plots and sequence of physical process method. In addition, through a wide range of rheological characterizations, we demonstrated successful fabrication of a healable hydrogel able to regain original strength after disruption of the structure at sufficiently large deformations. Afterward, to explore the interactions between CNC-CNC and PVA-CNC, the Foglar-Tucker model, designed to account for modeling the orientation of CNC particles within the matrix, was fitted on stress-overshoot experiments. The present study on PVA-CNC hydrogels opens avenues for further developing advanced materials with tunable microstructures for tissue engineering and regenerative medicine applications.

中文翻译：

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通过添加氯化钠制备的具有纤维素纳米晶体的聚乙烯醇水凝胶的粘弹性：双网络形成的流变学证据

摘要 本报告研究了与氯化钠 (NaCl) 盐聚合的混合聚乙烯醇 (PVA)-纤维素纳米纤维 (CNC) 水凝胶的粘弹性和机械性能。在几乎所有样品中，观察到具有大致相等平均孔径的广泛分布的孔隙，表明平均孔隙率与 CNC 浓度无关。为了评估 CNC-PVA/盐混合网络中 CNC 的分散质量，采用透射电子显微镜 (TEM)。还对装载 CNC 的 PVA 盐水凝胶进行了小振幅和大振幅振荡剪切（SAOS 和 LAOS）测量，以通过监测粘弹性参数进一步表征其微观结构。在接近渗透阈值 (15 g/L) 的 CNC 负载下，观察到储能模量与频率曲线的突然跳跃，归因于聚合物-CNC 3D 网络的形成。有趣的是，在更高的 CNC 浓度 (30 g/L) 下，流变参数值出现更显着的跳跃表明在单个 CNC 颗粒和/或簇之间形成直接接触后建立了二级网络结构。通过基于 Lissajous-Bowditch 图和物理过程序列方法的 LAOS 方法进一步研究了水凝胶的粘弹性行为。此外，通过广泛的流变学表征，我们证明了可修复水凝胶的成功制造，能够在足够大的变形下破坏结构后恢复原始强度。之后，为了探索 CNC-CNC 和 PVA-CNC 之间的相互作用，Foglar-Tucker 模型，设计用于模拟矩阵内 CNC 粒子的方向，适合应力超调实验。目前对 PVA-CNC 水凝胶的研究为进一步开发用于组织工程和再生医学应用的具有可调微结构的先进材料开辟了道路。