Computational and experimental determinations of the UV adsorption of polyvinylsilsesquioxane-silica and titanium dioxide hybrids
Issue title: Frontiers in Biomedical Engineering and Biotechnology – Proceedings of the 2nd International Conference on Biomedical Engineering and Biotechnology, 11–13 October 2013, Wuhan, China
Affiliations: School of Science, Harbin Institute of Technology, Harbin, 150001, China | Key Laboratory of Bio-based Material Science and Technology, Northeast Forestry University, Harbin 150040, China | School of Chemical Engineering, Harbin Institute of Technology, Harbin, 150001, China | Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721, USA
Abstract: Sunscreens that absorb UV light without photodegradation could reduce skin cancer. Polyvinyl silsesquioxanes are known to have greater thermal and photochemical stability than organic compounds, such as those in sunscreens. This paper evaluates the UV transparency of vinyl silsesquioxanes (VS) and its hybrids with SiO2(VSTE) and TiO2(VSTT) experimentally and computationally. Based on films of VS prepared by sol-gel polymerization, using benzoyl peroxide as an initiator, vinyltrimethoxysilane (VMS) formulated oligomer through thermal curing. Similarly, VSTE films were prepared from VMS and 5–25 wt-% tetraethoxysilane (TEOS) and VSTT films were prepared from VMS and 5–25 wt-% titanium tetrabutoxide (TTB). Experimental average transparencies of the modified films were found to be about 9–14% between 280–320 nm, 67–73% between 320–350nm, and 86–89% between 350–400nm. Computation of the band gap was absorption edges for the hybrids in excellent agreement with experimental data. VS, VSTE and VSTT showed good absorption in UV-C and UV-B range, but absorbed virtually no UV-A. Addition of SiO2 or TiO2 does not improve UV-B absorption, but on the opposite increases transparency of thin films to UV. This increase was validated with molecular simulations. Results show computational design can predict better sunscreens and reduce the effort of creating sunscreens that are capable of absorbing more UV-B and UV-A.
Keywords: Silsesquioxane, silica, titanium dioxide, hybrid films, ultraviolet region, sunscreen, computation of band gap
