Benzoxazine studies with Gaussian simulation

OHASHI, SEISHI; GIL, PHWEY; HEYL, TYLER R.; ISHIDA, HATSUO; ARZA, CARLOS R.; IGUCHI, DANIELA; LACKS, DANIEL J.; SEDWICK, VICTORIA M.; HAN, LU

Nueva Orleans

Simposio; 255th ACS National Meeting & Exposition; 2018

American Chemical Society

After 25 years of research on benzoxazine, there are still fundamental questions that have not been answered. The complex structure and polymerization mechanism of benzoxazine can be blamed. Gaussian simulation of benzoxazine, along with experimental results can start to answer some of these questions. For example, polymerization of benzoxazine can be detected by the disappearance of a 960-900 cm-1 band in FTIR. Researchers widely excepted that this peak was assigned to C-H out of plane bending of the benzene ring. However, after a potential energy distribution analysis concluded via a Gaussian simulation, that backbone vibrations from the oxazine ring is the primary contribution along with phenol ring torsion. Also using a Gaussian simulation, the natural charge of each element can also be calculated. When summing the natural charges of the phenol benzene ring and plotting it against the polymerization temperature of different substituted phenol benzoxazine monomers there is a noticeable trend. At around 265°C there is a horizontal asymptote with decreasing negativity. Then the trend decreases exponentially with increasing negativity of the natural charges. This suggests that in the benzoxazine polymerization mechanism the phenol plays a role in initiating the ring open polymerization. With Gaussian simulations, researchers are able to obtain a more fundamental understanding of such a complex molecule.