CREPEC, Department of Chemical Engineering, Polytechnique Montréal, P. O. Box 6079, Station Centre-Ville, Montreal, Quebec, H3C 3A7, Canada.
Soft Matter. 2022 Jun 15;18(23):4437-4444. doi: 10.1039/d2sm00421f.
PNIPAM (poly(-isopropylacrylamide)), a well-studied thermo-responsive polymer, undergoes conformational transition around 32 °C. On the other hand, cellulose nanocrystals (CNCs), as a promising and biocompatible material, has rarely been introduced to the PNIPAM-based fibrous hydrogel system. CNCs' impact on the temperature responsive behaviors of hydrogels, either in single layer or bilayer hydrogel systems, is yet to be investigated. In this work, stable well dispersed PNIPAM/CNC suspensions (with various CNC proportions) are prepared and electrospun into nanofiber membranes. The corresponding hydrogels are then obtained UV-induced crosslinking. CNCs are found to exert a significant constraint effect on hydrogel swelling when it exceeded 5 wt% but a negligible effect on contraction. The difference between hydrogels with various CNC proportions regarding their temperature responsive behaviors is utilized to fabricate bilayer hydrogels. These bilayer samples are capable of generating 3D geometries when they come into contact with water for the first time anisotropic swelling between the two layers and changing their dimension reversibly in the following swelling and contraction. In addition, these geometries are found to be highly tunable the finely tuned thickness ratio between the two layers. This promising feature would significantly extend the application of these materials in tissue engineering where a controllable geometry of the culture substrate is of great importance.
聚 N-异丙基丙烯酰胺（PNIPAM）是一种研究广泛的温敏聚合物，在 32°C 左右发生构象转变。另一方面，纤维素纳米晶体（CNC）作为一种有前途且生物相容的材料，很少被引入到基于 PNIPAM 的纤维水凝胶系统中。CNC 对水凝胶的温度响应行为的影响，无论是在单层还是双层水凝胶系统中，都尚未被研究过。在这项工作中，我们制备了稳定且分散良好的 PNIPAM/CNC 悬浮液（具有不同 CNC 比例），并通过静电纺丝将其制成纳米纤维膜。然后通过 UV 交联得到相应的水凝胶。当 CNC 含量超过 5wt%时，CNC 对水凝胶溶胀会产生显著的限制作用，但对收缩的影响可以忽略不计。利用不同 CNC 比例的水凝胶在温度响应行为上的差异，制备了双层水凝胶。这些双层样品在第一次接触水时能够形成 3D 形状，表现出两层之间的各向异性溶胀，并在随后的溶胀和收缩过程中可逆地改变其尺寸。此外，这些形状具有高度可调性，可以通过精细调整两层之间的厚度比来实现。这一有前景的特性将极大地扩展这些材料在组织工程中的应用，因为在组织工程中，培养基底的可控形状非常重要。
