• 文献标题:   pH-Dependent Morphology Control of Cellulose Nanofiber/Graphene Oxide Cryogels
  • 文献类型:   Article, Early Access
  • 作  者:   PAN ZZ, GOVEDARICA A, NISHIHARA H, TANG R, WANG C, LUO Y, LV W, KANG FY, TRIFKOVIC M, YANG QH
  • 作者关键词:   graphene oxide, micro #8208, honeycomb, ph adjustment, tempo cellulose nanofiber, unidirectional freeze #8208, drying ice templating
  • 出版物名称:   SMALL
  • ISSN:   1613-6810 EI 1613-6829
  • 通讯作者地址:   Tohoku Univ
  • 被引频次:   0
  • DOI:   10.1002/smll.202005564 EA DEC 2020
  • 出版年:  

▎ 摘  要

The precise control of the ice crystal growth during a freezing process is of essential importance for achieving porous cryogels with desired architectures. The present work reports a systematic study on the achievement of multi-structural cryogels from a binary dispersion containing 50 wt% 2,2,6,6-tetramethylpiperidin-1-oxyl, radical-mediated oxidized cellulose nanofibers (TOCNs), and 50 wt% graphene oxide (GO) via the unidirectional freeze-drying (UDF) approach. It is found that the increase in the sol's pH imparts better dispersion of the two components through increased electrostatic repulsion, while also causing progressively weaker gel networks leading to micro-lamella cryogels from the UDF process. At the pH of 5.2, an optimum between TOCN and GO self-aggregation and dispersion is achieved, leading to the strongest TOCN-GO interactions and their templating into the regular micro-honeycomb structures. A two-faceted mechanism for explaining the cryogel formation is proposed and it is shown that the interplay of the maximized TOCN-GO interactions and the high affinity of the dispersoid complexes for the ice crystals are necessary for obtaining a micro-honeycomb morphology along the freezing direction. Further, by linking the microstructure and rheology of the corresponding precursor sols, a diagram for predicting the microstructure of TOCN-GO cryogels obtained through the UDF process is proposed.