Thermotropic nematic and smectic order in silica glass nanochannels

Optical birefringence measurements on a rodlike liquid crystal, octyloxycyanobiphenyl, imbibed in silica channels (7 nm diameter), are presented and compared to the thermotropic bulk behavior. The orientational and positional order of the confined liquid evolves continuously at the paranematic-to-nematic and sizeably broadened at the nematic-to-smectic order transition, respectively, in contrast to the discontinuous and well-defined second-order character of the bulk transitions. A Landau–de Gennes analysis reveals identical strengths of the nematic and smectic ordering fields (imposed by the walls) and indicates that the smectic order is more affected by quenched disorder (originating in channel tortuosity and roughness) than the nematic transition.

[1]  R. Vink,et al.  Nematics with quenched disorder: violation of self-averaging. , 2010, Physical review letters.

[2]  K. Knorr,et al.  Continuous paranematic-to-nematic ordering transitions of liquid crystals in tubular silica nanochannels. , 2008, Physical review letters.

[3]  Kurt Binder,et al.  Confinement effects on phase behavior of soft matter systems. , 2008, Soft matter.

[4]  K. Knorr,et al.  Rheology of liquids in nanopores: A study on the capillary rise of water, n-Hexadecane and n-Tetracosane in mesoporous silica , 2007 .

[5]  D. Morineau,et al.  Evidence of anisotropic quenched disorder effects on a smectic liquid crystal confined in porous silicon. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.

[6]  S. Žumer,et al.  Influence of finite size and wetting on nematic and smectic phase behavior of liquid crystal confined to controlled-pore matrices. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[7]  S. Žumer,et al.  Calorimetric study of octylcyanobiphenyl liquid crystal confined to a controlled-pore glass. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[8]  S. Žumer,et al.  Effect of dispersed silica particles on the smectic-A-smectic-C* phase transition. , 2002, Physical review. E, Statistical, nonlinear, and soft matter physics.

[9]  N. Clark,et al.  Universality and Scaling in the Disordering of a Smectic Liquid Crystal , 2001, Science.

[10]  R. Blinc,et al.  Birefringence and tilt angle in the antiferroelectric, ferroelectric, and intermediate phases of chiral smectic liquid crystals , 1998 .

[11]  F. Beaubois,et al.  Biaxial nematic and smectic-A boundaries in thin planar samples of 8OCB aligned by rubbed polyimide , 1996 .