Strengthening and toughening of polybenzoxazine by incorporation of polyrotaxane molecules

A mechanically interlocked supramolecule polyrotaxane (PR) was utilized as a functional additive to modify the hydrogen bonding (H-bonding) and cross-linking network of polybenzoxazine (PBa). Epoxide and hydroxyl groups at the terminal end of polycaprolactone grafted on CDs were chosen to investigate how these functional groups influence H-bonding, morphology, and mechanical properties of PBa matrix. Fourier transform infrared spectroscopy and differential scanning calorimetry results show evidence of successful manipulation of H-bonding and curing kinetics of PBa in the presence of the functionalized PR. After curing, epoxide functionalized PR (EPR) shows a strong interaction with PBa, leading to molecular level dispersion in PBa compared to PR with the hydroxyl functional group. By introducing only 4 wt% of EPR in PBa, the ductility and fracture toughness of PBa are greatly improved without a noticeable drop in Young's Modulus, which is attractive for aerospace and microelectronic applications.