Effect of confinement to porous glass on structure and optical properties of alkylcyanobiphenyls

The 4-n-alkyl-4'-cyanobiphenyls (nCB, n is the number of carbon atoms in al kyl radical, n = 5, 8) confined to porous glasses with four different mean pore sizes (2, 4 54 and 90 nm) have been studied. Using FT MIR and NIR spec troscopy methods we have investigated the interaction of nCB molecules with pore surface. It has been shown that the interaction is accompanied by the formation of hydrogen bonds between SiOH group on the glass pore surface a nd cyano-group of nCB monomer. This is demonstrated by the change in the po sition and shape of CN stretching and Q(C equivalent to N) + Q(C = C) combi nation bonds in the vibrational spectra of confined nCB depending on pore s ize and the length of alkyl tail. To the contrary, in the case of benzophen one confined to PG, weak pi...OHSi hydrogen bonds are formed.