New Insights into the Strengthening Mechanism of Nanofillers in Terminally Functionalized Polyisoprene Rubbers

To overcome the problems of reduced elasticity and increased energy consumption resulting from large amounts of nanofillers, the reinforcement mechanism of low loading nanofillers is quite attractive but still obscure, especially considering the interactions with special polymer structures. Herein, two special nanofillers with low loading levels were used to interact noncovalently with polar end groups to form distinct aggregates. Nonpolar olefin-rich groups were introduced into the other end of the rubber chain to provide an anchoring effect and restrain the network. The analysis of the viscoelastic behavior and the evolution process of the secondary structure showed a difference between the two polar aggregates. The sample containing the nanofiller pentaalanine (5A) showed viscoelastic behavior similar to that of nonfilled rubber, with very low hysteresis loss, excellent resilience, and improved dimensional stability because of its relatively stable aggregate structures. The samples containing the HMWCNT nanofiller significantly improved the mechanical properties and strain-induced crystallization behavior due to their strong orientation ability. Besides, the 5A composite showed certain recyclability and presented excellent mechanical strengths of recycled samples compared to the reported ones, which are much superior to the HMWCNT composites.