Huber Tim, Feast Sean, Dimartino Simone, Cen Wanwen, Fee Conan
Department of Chemical and Process Engineering and Biomolecular Interaction Centre, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand.
School of Product Design, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand.
Materials (Basel). 2019 Apr 1;12(7):1066. doi: 10.3390/ma12071066.
Cellulose-based hydrogels were prepared by dissolving cellulose in aqueous sodium hydroxide (NaOH)/urea solutions and casting it into complex shapes by the use of sacrificial templates followed by thermal gelation of the solution. Both the gelling temperatures used (40⁻80 °C), as well as the method of heating by either induction in the form of a water bath and hot press or radiation by microwaves could be shown to have a significant effect on the compressive strength and modulus of the prepared hydrogels. Lower gelling temperatures and shorter heating times were found to result in stronger and stiffer gels. Both the effect of physical cross-linking via the introduction of additional non-dissolving cellulosic material, as well as chemical cross-linking by the introduction of epichlorohydrin (ECH), and a combination of both applied during the gelation process could be shown to affect both the mechanical properties and microstructure of the hydrogels. The added cellulose acts as a physical-cross-linking agent strengthening the hydrogen-bond network as well as a reinforcing phase improving the mechanical properties. However, chemical cross-linking of an unreinforced gel leads to unfavourable bonding and cellulose network formation, resulting in drastically increased pore sizes and reduced mechanical properties. In both cases, chemical cross-linking leads to larger internal pores.
基于纤维素的水凝胶是通过将纤维素溶解在氢氧化钠（NaOH）/尿素水溶液中，并利用牺牲模板将其浇铸成型，随后对溶液进行热凝胶化而制备的。所使用的凝胶化温度（40⁻80 °C）以及通过水浴和热压形式的感应加热或微波辐射的加热方法，都被证明对所制备水凝胶的抗压强度和模量有显著影响。较低的凝胶化温度和较短的加热时间会导致凝胶更强更硬。在凝胶化过程中，通过引入额外的不溶性纤维素材料进行物理交联的效果，以及通过引入环氧氯丙烷（ECH）进行化学交联的效果，还有两者结合的效果，都被证明会影响水凝胶的力学性能和微观结构。添加的纤维素充当物理交联剂，强化氢键网络，同时作为增强相改善力学性能。然而，未增强凝胶的化学交联会导致不利的键合和纤维素网络形成，从而导致孔径大幅增加和力学性能降低。在这两种情况下，化学交联都会导致内部孔隙更大。
