Research Theme
Supramolecular Composite Materials
Toughening Cellulose Composites by Designing Polymer Cross-linking and Surface Modification of Cellulose
Compositing naturally occurring cellulose with polymeric materials leads to a reduction in the use of petroleum-derived materials, thereby reducing environmental impact. Toughening was achieved by introducing a unique cross-linking design to the polymers in the cellulose composite.
Citric acid-modified cellulose composites have high toughness and recyclability due to hydrogen bonding
In this study, we developed a new composite material with a high weight ratio (33 wt%) of citric acid modified cellulose (CAC) in order to reduce the use of petroleum-derived polymer materials, which are a contributing factor to environmental problems. To elucidate the mechanism of toughness enhancement by hydrogen bonding between polymer matrix and filler, acrylate polymers with different side chain structures such as PHPA, PHEA, and PMEA were used, and the interaction was evaluated by glass transition temperature, FT-IR, and first principle calculation. It was found that hydrogen bonds formed between polymers with hydroxy groups and CAC fillers significantly increase the toughness of the composites despite their high cellulose content. Furthermore, the non-covalent interactions enabled mechanical recycling and material reclamation through fracture and remolding. This achievement is expected to reduce petroleum dependence and extend the service life of materials.
Toughening Cellulose Composites by Designing Polymer Cross-linking and Surface Modification of Cellulose
Composites of naturally occurring cellulose with polymeric materials lead to a reduction in the use of petroleum-derived materials, thereby reducing environmental impact. Toughening was achieved by introducing a unique cross-linking design to the polymer in the cellulose composite: a mixture of primary and secondary linear polymers (SCP) with reversible cross-linking consisting of β-cyclodextrin (βCD) and adamantane (Ad) was composited with citrate modified cellulose (CAC) ( SCP/CAC(w)) (Figure a). the breaking strain of SCP/CAC(w) increased as the amount of CAC added w (wt%) increased. In particular, high toughness was maintained at w = 5 wt% and 10 wt% (Figure b), and SCP/CAC(10) exhibited more than twice higher elongation than the material composited with unmodified cellulose (SCP/Cellulose(10)) (Figure c). In general, the addition of cellulose to polymers results in brittleness, but the cross-linking design of the polymer and surface modification of cellulose achieved improved toughness.
Development of Strain Sensing Devices Using Carbon Composite Movable Crosslinked Polymer Materials
Strain-sensing materials were prepared by compositing a movable crosslinked polymer with conductive carbon filler (KB) to achieve both toughness and conductivity (Figure a).A movable crosslinked polymer with polyethyl acrylate (PEA) penetrating the CD ring in CD-modified polystyrene (PSCD) and KB ⊃ PEA/KB(10)), the sliding motion of the CD rings along the PEA during stretching improved the stretching property. Furthermore, the conductive path of the KB changed as it was stretched, and the strain of the material was successfully detected as a change in electrical resistance. The composite material attached to the finger becomes a remote actuation system in which the servomotor performs the same action in response to the change in electrical resistance (ΔR/R0%), and is expected to be applied to a robot teleoperation system (Figure b)
(b) material design of carbon composite movable crosslinked polymer materials.
Supramolecular materials composited with cellulose
Although we have focused on host-guest interaction as a reversible bonding, we considered it important to introduce multiple reversible cross-linking points and fillers to achieve high toughness in a stronger material. Therefore, we attempted composites of cellulose with citric acid in the side chain (provided by Dr. Uyama, Osaka University) and supramolecular elastomers. The resulting composite material exhibited strength, toughness, and cut surface-selective adhesion not found in single supramolecular elastomers (see Figure a below).
