2 research outputs found
Study on the Ring-Opening Polymerization of Benzoxazine through Multisubstituted Polybenzoxazine Precursors
To
discuss the mechanism of ring-opening polymerization (ROP) of
benzoxazine, a bisphenol A/diaminodiphenylmethane-based polybenzoxazine
precursor (PBz-0M), <i>o</i>-dimethylbisphenol A/diaminodiphenylmethane-based
polybenzoxazine precursor (PBz-2M), and <i>o</i>-dimethylbisphenol
A/<i>o</i>-tetramethyldiaminodiphenylmethane-based polybenzoxazine
precursor (PBz-6M) were prepared. Among the polybenzoxazine precursors,
free ortho positions to the O of oxazine are available for PBz-0M.
No free ortho or para position to the O of oxazine is available for
PBz-2M, but free ortho position to the N of oxazine is available.
No free ortho positions to the O or N of oxazine are available for
PBz-6M. According to DSC, IR, and thermal analysis, we found that
the ROP of PBz-2M can be carried out even though no free ortho or
para position to the O of oxazine is available. We conclude that the
ROP is carried out through the ortho position to the N of oxazine
and propose a reaction mechanism to explain the polymerization
Origin of the Rapid Trimerization of Cyanate Ester in a Benzoxazine/Cyanate Ester Blend
Blends
of cyanate ester and benzoxazine have been independently
studied by several researchers, and different reaction mechanisms
were reported. Recently, we unexpectedly observe that gelation occurred
in a 50 wt % methyl ethyl ketone solution of P-oda/BACY (1/1 mol/mol)
blend after 24 h at 30 °C, in which P-oda is a 4,4′-oxyaniline/phenol-based
benzoxazine and BACY is a dicyanate ester of bisphenol A. Previous
studies suggest that the rapid trimerization of cyanate ester in the
blend is related to the ring-opened structure of benzoxazine. However,
the possibility of ring-opening polymerization for benzoxazine at
30 °C is rare. Therefore, it is highly likely that the catalytic
effect results from the benzoxazine itself, not from the ring-opened
structure of benzoxazine. Through IR and DSC analyses, we conclude
that the tertiary amine of benzoxazine catalyzes the trimerization
of cyanate ester, and we propose a three-step catalytic mechanism
of benzoxazine for the trimerization of cyanate ester