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(ν) 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(ν)∝ν2/3, 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(ν)∝ν2-d/2, giving a reliable value of the structural fractal dimension df=2.67 for all the host silica gels.
- Publication:
-
Physical Review Letters
- Pub Date:
- May 2004
- DOI:
- 10.1103/PhysRevLett.92.195504
- Bibcode:
- 2004PhRvL..92s5504L
- Keywords:
-
- 61.43.Hv;
- 61.30.Pq;
- 76.60.Es;
- Fractals;
- macroscopic aggregates;
- Microconfined liquid crystals: droplets cylinders randomly confined liquid crystals polymer dispersed liquid crystals and porous systems;
- Relaxation effects