A novel high performance oxazine derivative: design of tetrafunctional monomer, step-wise ring-opening polymerization, improved thermal property and broadened processing window

A novel tetraphenol fluorene, 2,7-dihydroxy-9,9-bis-(4-hydroxyphenyl) fluorene (THPF), was synthesized via the condensation reaction of 2,7-dihydroxy-9-fluorenone and phenol in the presence of a strong acidic cation exchange resin and 3-mercaptopropionic acid. Thus, a novel tetrafunctional oxazine monomer containing benzoxazine and fluorene-oxazine (t-BF-b) was prepared for the first time using a Mannich condensation reaction of THPF with paraformaldehyde and n-butylamine. The chemical structures of THPF and t-BF-b were characterized by Fourier transform infrared (FTIR) spectroscopy, elemental analysis, H-1 and C-13 nuclear magnetic resonance (NMR). The viscosity-temperature properties and the polymerization behavior of t-BF-b as well as the thermal and mechanical properties of its cured polymer (poly(t-BF-b)) were studied by rheometry, FTIR, H-1 NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The results show that poly(t-BF-b) displays a lower melting point and wider processing window. The oxazine rings of fluorene-oxazine possess higher reactivity and lower polymerization temperature than those of benzoxazine. Also, its cured poly(t-BF-b) exhibits a higher glass transition temperature than its corresponding bifunctional polybenzoxazines without sacrificing any thermal properties in spite of the introduction of more flexible aliphatic groups into polymer chains.