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

Abstract

In this study a new water-soluble benzoxazine-functionalized cyclodextrin monomer (β-CD-BZ) was synthesized through monoazido-functionalized β-cyclodextrin (N 3 -CD) with 3,4-dihydro-3-(prop-2-ynyl)-2H-benzoxazine (Ppa) by Huisgen [2 + 3] cycloadditions (click reaction) based on 1 H 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 β-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 β-CD cavity could allow the benzoxazine monomer to form inclusion complex (IC) with poly(propylene glycol) (PPG) based on XRD, 1 H NMR, FTIR and TGA. From the XRD results, the PPG were confined into the β-CD-BZ channels and then form the columnar crystalline structures where the stoichiometries of repeat unit of PPG: β-CD-BZ = 2 : 1 were determined by 1 H NMR analysis. More importantly, the benzoxazine units in β-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. • A new water-soluble benzoxazine-functionalized cyclodextrin monomer (β-CD-BZ) was successfully synthesized. • Incorporation of β-CD into the benzoxazine monomer could improve the thermal stability and water-solubility of BZ monomer. • Formation inclusion complex (IC) between β-CD-BZ) and poly(propylene glycol) (PPG). • The thermal properties of β-CD-BZ/PPG inclusion complex significantly improved.