Intrinsic water-soluble benzoxazine-functionalized cyclodextrin and its formation of inclusion complex with polymer

In this study a new water-soluble benzoxazine-functionalized cyclodextrin monomer (beta-CD-BZ) was synthesized through monoazido-functionalized beta-cyclodextrin (N3-CD) with 3,4-dihydro-3-(prop-2-ynyl)-2H-benzoxazine (Ppa) by Huisgen [2 + 3] cycloadditions (click reaction) based on H-1 NMR and FTIR spectroscopy. Its thermal curing polymerization and thermal stability were monitored by DSC and TGA displaying the ring-opening polymerization of benzoxazine units. Incorporation of beta-CD into the benzoxazine monomer could improve the thermal stability and water-solubility because of the highly hydroxyl contents of the cyclodextrin unit. Furthermore, the presence of the beta-CD cavity could allow the benzoxazine monomer to form inclusion complex (IC) with poly(propylene glycol) (PPG) based on XRD, H-1 NMR, FTIR and TGA. From the XRD results, the PPG were confined into the beta-CD-BZ channels and then form the columnar crystalline structures where the stoichiometries of repeat unit of PPG: beta-CD-BZ - 2 : 1 were determined by H-1 NMR analysis. More importantly, the benzoxazine units in beta-CD-BZ/PPG inclusion complex could further provide the thermal curing polymerization behavior to improve their thermal properties that could not be observed in typical inclusion complex system.

Automated summary

A new water-soluble benzoxazine-functionalized cyclodextrin monomer was synthesized and confirmed to improve thermal stability and water-solubility when incorporating cyclodextrin into the benzoxazine monomer. Furthermore, investigation on the beta-CD-BZ/PPG inclusion complex showed that the benzoxazine units could provide thermal curing polymerization behavior to enhance their thermal properties.