Study of the characterization and curing of a phenyl benzoxazine using15N solid-state nuclear magnetic resonance spectroscopy

Abstract

ABSTRACT:A difunctional 1,3-benzoxazine compound, 2,2Ј-(3-phenyl-4-dihydro-1,3,2-benzoxazine)propane (B-a), derived from bisphenol-A, 15 N-enriched aniline, and formaldehyde was synthesized and characterized using 15 N-NMR and 13 C-NMR spectroscopies. The observed resonances in the solid-state 15 N-and 13 C-NMR spectra showed good agreement with the calculated chemical shifts which are based on the chemical structure. The B-a samples were cured at 150 and 200°C. The polymerization inspired peak intensity changes and line-width broadenings in the NMR spectra.

Improved thermal and mechanical properties of polybenzoxazines based on alkyl-substituted aromatic amines

“…This was confirmed with the solid-state 13 C and 15 N nuclear magnetic resonance (NMR) spectroscopy by Russell et al 22,23 and through pyrolytic gas chromatography-mass spectrometry (GC/MS). 24 It was hypothesized that crosslinking the pendent aromatic rings would stabilize the Mannich bridge from thermal degradation and prevent the pendant rings from volatilizing.…”

“…40 Koenig et al also proposed the formation of this bisphenolic methylene species during the later stages of cure above 200°C. 22 The number of methylene bridges appears to be These results may not be totally indicative of the initial network structure since crosslinking of the arylamine rings (and the subsequent delay of the thermal degradation process) increases the residence time of the various fragmented species in the char. This would allow the fragmented species greater opportunity to undergo secondary crosslinking reactions, such as the formation of additional methylene-bridged structures.…”

“…While several works have suggested what the crosslinked structure of polybenzoxazine may be, 13,19,22,23,[35][36][37] more study is needed to fully understand the crosslinking mechanism of the aromatic amine-based polybenzoxazines. Some questions remain as to whether the structure is fully crosslinked, hyperbranched, or consists of highly crosslinked domains that are more loosely connected.…”

Examining the influence of bisphenol A on the polymerisation and network properties of an aromatic benzoxazine

“…The kinetics and mechanism of the monomer to form the homopolymer have been studied in detail using predominantly spectroscopic 5,6,7 and thermal analysis 8,9 techniques.…”

Synthesis and properties of organo-gels by thiol-benzoxazine chemistry

“…These materials offer low water absorption, high char yield and resistance against flame, high modulus, high strength, high glass transition temperatures, chemical resistance, long shelf life and dimensional stability upon curing. [1][2][3][4][5][6][7][8][9][10][11] Thus, polybenzoxazines have become one of a rare few new polymers developed and commercialized in the past 20 years. Another reason for that is benzoxazine monomers have enormous molecular design flexibility.…”