Silent elongation of polyrotaxane and its composites

Polyrotaxanes (PR) have attracted great interest due to their unique mechanical properties, exhibiting the pulley effect, via their slide-ring topological structure. Flexible and functional composite materials consisting of PR and inorganic particles, particularly those with plasma-surface modifications, have also shown higher toughness, even with large amounts of inorganic particles present. In this study, we verified the effect of neat PR and its composites with graphene nanoplates or carbon nanofibers by measuring acoustic emission (AE). Simultaneous AE and tensile measurements were tested several times for each sample, and AE signals during elongation were acquired. It revealed that the conventional fixed cross-linked elastomer materials showed AE signals in the entire tensile region, while the movable-cross-linked materials of PR showed almost no AE signal counts. This suggests that neat PR had almost no microscopic fracture before final breakage via the pulley effect. PR composites with plasma-surface-modified fillers showed a lower number of AE signals than that with unmodified fillers. This might be due to the surface modification of fillers, which improved filler dispersibility and/or prevented a large drop in the mobility of cross-linking points.