Freeze dried, highly porous materials made from cellulose nanofibrils (CNF) hydrogels are capable of absorbing and storing a significant quantity of liquid inside their 3D structure, with total absorption capacity increasing linearly with porosity. One of the challenges of freeze dried high porosity CNF gels is their propensity to break down rapidly in aqueous environments. Here we explore a method to overcome this deficiency by incorporating methacrylate functionalized carboxymethyl cellulose (MetCMC) into the CNF system followed by UV irradiation leading to crosslinking of the methacrylate groups of MetCMC. The resultant polymer composite matrix successfully maintains a robust 3D structure, without collapsing, even when rewetted and stored in water. When freeze dried, the CNF-MetCMC composite maintains its size and shape whereas air drying induces significant shrinkage. In contrast, air dried CNF-MetCMC hydrogels swell when rewetted. Swelling and shrinkage of CNF-MetCMC hydrogels were tuned by controlling the ratio between CNF and MetCMC in the composite. The crosslinking between the methacrylate groups of MetCMC also enhances the dry and wet modulus of CNF-MetCMC gels significantly. We invoke a simple model involving a balance between hydrogen bonding and crosslinking to explain these data.

由纤维素纳米原纤维（CNF）水凝胶制成的干燥，高度多孔的冷冻材料能够在其3D结构内部吸收和存储大量液体，总吸收能力随孔隙度线性增加。冷冻干燥的高孔隙度CNF凝胶的挑战之一是它们在水性环境中易于迅速分解的倾向。在这里，我们探索了一种通过将甲基丙烯酸酯官能化的羧甲基纤维素（MetCMC）掺入CNF系统中，然后进行UV辐射导致MetCMC的甲基丙烯酸酯基团交联的方法来克服这一缺陷。所得的聚合物复合材料基质即使在重新润湿并储存在水中时也能成功保持稳固的3D结构，而不会塌陷。冻干后 CNF-MetCMC复合材料保持其尺寸和形状，而空气干燥则引起明显的收缩。相反，重新湿润时，风干的CNF-MetCMC水凝胶溶胀。通过控制复合材料中CNF和MetCMC之间的比例，可以调节CNF-MetCMC水凝胶的溶胀和收缩。MetCMC的甲基丙烯酸酯基团之间的交联也显着提高了CNF-MetCMC凝胶的干模和湿模量。我们调用一个涉及氢键和交联之间平衡的简单模型来解释这些数据。MetCMC的甲基丙烯酸酯基团之间的交联也显着提高了CNF-MetCMC凝胶的干模和湿模量。我们调用一个涉及氢键和交联之间平衡的简单模型来解释这些数据。MetCMC的甲基丙烯酸酯基团之间的交联也显着提高了CNF-MetCMC凝胶的干模和湿模量。我们调用一个涉及氢键和交联之间平衡的简单模型来解释这些数据。