Material Design of Citric Acid-Modified Cellulose Composite Polymeric Materials with Both Tough and Sustainable Enhancement by Multiple Noncovalent Bonds

To achieve a carbon circulation society, petroleum-derived resources must be replaced with cellulose and other bioderived resources. Although cellulose serving as a filler enhances the mechanical properties of polymeric materials upon mixing, it remains a challenge to increase the contents of cellulose fillers while maintaining the enhanced mechanical properties. Regarding mechanical properties, polymer composites containing cellulose fillers can usually be improved by adding a small percentage of cellulose fillers. Unfortunately, mixing large amounts of cellulose fillers creates brittle polymer composites. Herein, we report polymer composites containing large amounts of citric acid-modified cellulose. Moreover, the polymeric matrices consist of reversible cross-links formed by β-cyclodextrin and adamantane and secondary linear polymers. By optimizing the ratios of the reversible cross-links and the secondary linear polymers, we successfully increase the content of cellulose fillers to 10%, which is 1 order of magnitude higher than the conventional cellulose filler contents, maintaining high toughness and Young’s modulus values. In addition, utilizing hydrogen bonds is appropriately advantageous in the reinforcing effect of citric acid-modified cellulose compared to native cellulose.