Molecular fluorene contains two benzene rings linked with a five-membered ring and provides high overlaps of p-orbitals.Polymers containing fluorenyl structure in the backbone have many excellent improved properties, such as good heat-resistance, high char yield, high limited oxygen index, good flame-retardant, etc. In previous studies, researches on synthesis, polymerization behavior, curing kinetics, and thermal properties of fluorene bisphenol and diamine-based benzoxazines have been reported. However, bifunctional fluorene-based polybenzoxazines generally exhibited brittleness and poor processability attributed to lower crosslinking density and higher rigidity of polymer chains. In this study, we synthesized a novel phenolic compound with four phenolic hydroxyl groups, 2,7-dihydroxy-9,9-bis(4-hydroxy-phenyl) fluorene (THPF), through the condensation reaction between phenol and 2,7-dihydroxy-9-fluorenone. Then, a series of tetra-functional benzoxazine monomers were obtained from the reaction of THPF with paraformaldehyde and primary amines such as aniline, butylamine, and octylamine. Their chemical structures were characterized with FT-IR and NMR. The curing behavior of benzoxazine monomers was studied by differential scanning calorimetry (DSC) and FT-IR. The thermal properties of cured polybenzoxazines were measured by DSC and thermogravimetric analysis (TGA). The results suggest that the glass transition temperature and thermal stability of tetrafunctional fluorene-based polybenzoxazines are much higher than those of corresponding bifunctional fluorene-based polybenzoxazines and traditional bisphenol A-aniline-based polybenzoxazines due to the increase of crosslinking density of polymer. Tetra-octylamine-fluorene-based benzoxazine, viscous liquid at room temperature, displayed excellent processability, toughness, and higher thermal properties.

Synthesis and thermal properties of novel tetra-functional fluorene-based benzoxazines

246th National Meeting (2013)

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