High‐Performance Polybenzoxazine Derived from Polyfunctional Benzoxazine Composed of an Oligonuclear Phenolic Compound Having a 4,4′‐Dimethylenebiphenyl Linker

• Published in: Macromolecular chemistry and physics Vol. 220; no. 1
• Main Authors: Kawauchi, Takehiro, Osawa, Tsubasa, Matsumura, Shunichiro, Mori, Takuto, Furukawa, Nobuyuki, Ishikawa, Kazunori, Iwasaki, Koju, Takeichi, Tsutomu
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.01.2019
• Subjects: Aniline; Benzoxazines; Dynamic mechanical analysis; Elongation; Glass transition temperature; phenolic resins; Phenols; polybenzoxazine; Polybenzoxazines; polyfunctional benzoxazine; ring‐opening polymerization; Storage modulus; Temperature; Tensile tests; Thermal stability; Thermodynamic properties; Thermogravimetric analysis; Thermosetting resins
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/macp.201800317

A novel polyfunctional benzoxazine monomer, OP‐a, is synthesized from aniline, formaldehyde, and an oligonuclear phenolic compound (OP) with a 4,4′‐dimethylenebiphenyl group as the phenol linker. After thermal curing of OP‐a up to 240 °C, a brown‐colored, transparent polybenzoxazine (POP‐a) film is obtained. The mechanical and thermal properties of the POP‐a film are investigated by tensile test, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The POP‐a film is extremely tough compared with a typical polybenzoxazine (PB‐a) film. The elongation at break of the POP‐a film is 7.6%, which is surprisingly large for the highly cross‐linked thermoset. The high cross‐link density is suggested from the very high storage modulus (over 1 GPa) above the glass transition temperature (T g) observed by DMA. The T g of POP‐a is also improved significantly to T g = 223 °C, which is approximately 50 °C higher than that of PB‐a. Moreover, TGA reveals that the thermal stability of POP‐a is also enhanced. A newly designed polyfunctional benzoxazine is reported to yield a remarkably tough polybenzoxazine film with much improved thermal properties. The monomer is synthesized using an oligonuclear phenolic compound with a 4,4′‐dimethylenebiphenyl group as the phenol linker, which is commercially available as a curing agent for epoxy resin.