title: Universal nuclear spin relaxation and long-range order in nematics strongly confined in mass fractal silica gels.
abstract: We show how the low-frequency dependence of the proton spin-lattice relaxation time T1(nu) of octylcyanobiphenyl liquid crystals confined in high-density silica gels evidences a long-range order nematic phase in spite of the strong confinement and random disorder of the gels. The universal value and frequency dependence observed, T1(nu) proportional, variant nu(2/3), is interpreted within a relaxation model due to director fluctuations in nematic liquid crystals confined to mass fractal porous media. The model provides a relation T1(nu) proportional, variant nu(2-d/2), giving a reliable value of the structural fractal dimension d(f)=2.67 for all the host silica gels.
authors.affiliation: Centro de Física, Instituto Venezolano de Investigaciones Científicas, Apartado 21874, Caracas 1020-A, Venezuela.
authors.forename: N
authors.initials: N
authors.lastname: León
authors.forename: J-P
authors.initials: JP
authors.lastname: Korb
authors.forename: I
authors.initials: I
authors.lastname: Bonalde
authors.forename: P
authors.initials: P
authors.lastname: Levitz