α-Tocopherol release from active polymer films loaded with functionalized SBA-15 mesoporous silica

Abstract

The aim of the present work is the study of the migration from active LDPE polymer films of α-tocopherol adsorbed onto purely siliceous and amino-functionalized SBA-15 mesoporous silica. In particular, the effect of the pore size and the chemical functionality of the internal walls of the mesophase was thoroughly investigated.Co-condensation of tetraethylorthosilicate and aminopropyltriethoxysilane was exploited to bind amino groups on the pore surface of SBA-15. The synthesized mesoporous powders were characterized by means of X-ray diffraction and N2 adsorption/desorption at 77K. Powders loaded with tocopherol were characterized by infrared spectroscopy and thermogravimetric analysis. Results show that the maximum of the pore size distribution reduces from 90Å for purely siliceous SBA-15 to 73Å for amino-functionalized SBA-15. Infrared analysis shows that tocopherol interacts with the amino groups of functionalized SBA-15.Migration tests were performed at 25°C, using 96% v/v ethanol as fatty food simulant, on both polymer films containing about 1% wt/wt of free tocopherol and about 3% wt/wt of tocopherol loaded onto purely siliceous and amino-functionalized SBA-15. The tocopherol diffusivity of films containing functionalized mesoporous silica decreased of about 60% with respect to films containing free tocopherol. This is due to the decrease in the pore size and to the increase in diffusion resistance caused by the functionalization of the internal pore walls with the amino groups. Moreover, the oxygen radical absorbing capacity assay of the produced active polymer films proved the antioxidant effectiveness of tocopherol released from samples after manufacturing process.