ELECTRONIC-STRUCTURE AND OPTICAL-SPECTRA OF MDF-2 OLIGOETHERACRYLATE

The molecular spatial structure and electronic energy levels of MDF-2 oligoetheracrylate have been theoretically investigated using a Hyperc hem 4.5 computer package. We have optimized the MDF-2 geometry, obtain ing a non-linear structure with one benzene ring situated near one of the molecule ends. The electron charge density of the MDF-2 photopolym er is distributed non-uniformly, showing the highest absolute values i n the vicinity of the benzene ring. C=O double chemical bonds are perp endicular with regard to the central chain. We have calculated a relat ively large value of the HOMO-LUMO energy gap on one hand and, on the other hand, we have estimated a substantially smaller experimental ene rgy gap based on our spectroscopic measurements. An essential influenc e of the benzene rings on the non-linear optical properties has also b een suggested. To check the above semi-empirical results, ab initio ca lculations have been performed for the molecule fragments as well as f or the full MDF-2 structure. An enlarged structure (a tetramer) has al so been investigated using the UHF method with a PM3 parametrization. (C) 1998 Elsevier Science S.A. All rights reserved.