http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

Photoinduced motions in azo-containing polymers.

Over the 100 years since its discovery, liquid crystals have been the intriguing subject for both academia and industries. The textbook of de Gennes The Physics of Liquid Crystals published in 1974 is still the bible for many LC researchers, but new subjects unmentioned in the book have also risen for these years. This chapter describes the story of the recent developments and the future perspectives in physics of liquid crystals, especially focusing on the contributions by Japanese research groups for the last decade.

Physics of Liquid Crystals

Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications, although blue phases are of interest for fast light modulators or tunable photonic crystals, the very narrow temperature range, usually less than a few kelvin, within which blue phases exist has always been a problem. Here we show the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260–326 K). Furthermore, we demonstrate an electro-optical switching with a response time of the order of 10−4 s for the stabilized blue phases at room temperature.

Polymer-stabilized liquid crystal blue phases

http://kbose.weebly.com/uploads/1/0/4/9/10492046/force-distance_curves_by_atomic_force_microscopy_1.pdf

Force-distance curves by atomic force microscopy

Blue phases have two major advantages over commonly used nematic phases:1) the response is much faster, 2) the zero-electric field state is optically isotropic. We demonstrate the sufficiently large electric field-induced birefringence and the micro-second response of the polymer-stabilized blue phases and the induced-isotropic phases without any surface treatment.

62.2: Invited Paper: Fast Electro‐Optical Switching in Polymer‐Stabilized Liquid Crystalline Blue Phases for Display Application

In this paper, we present the phase behavior and electro-optical Kerr effect of the optically isotropic liquid crystal composites, which require no surface treatment for device fabrication. Anomalously large Kerr constant, more than 10−8 mV−2 and fast response, less than sub-milli-second were observed at a room temperature.

39.1: Invited Paper: Optically Isotropic Nano‐Structured Liquid Crystal Composites for Display Applications

Large electro-optic kerr effect in polymer-stabilized liquid-crystalline blue phases

RUBBED polymer films (generally polyimides) are used in flat-panel displays to control the alignment of liquid crystals in contact with the polymer1–8, a phenomenon first discovered by Maugin1 in 1911. Buffing the film with a cloth produces liquid-crystal alignment in the rubbing direction. Several mechanisms have been proposed to explain this effect. The generation of microgrooves or scratches on the polymer surface during rubbing has led to the suggestion that alignment is the result of long-range elastic effects induced by these surface features3–5. Others have suggested that the polymer chains near the surface are aligned during rubbing and that these then serve as templates for liquid-crystal alignment6–13. Other studies 10–l2 have implied that both mechanisms might be operative. Here we present X-ray scattering measurements which show unambiguously that rubbing a polyimide film causes near-surface alignment of the polymer molecules. For a film 200 nm thick, most of the polymer chains within a thin surface region (about 5 nm thick) are aligned in the rubbing direction; for a 6-nm film essentially all of the chains are aligned within 20° of the rubbing direction. This marked orientation of the near-surface chains at temperatures far below the bulk glass transition temperature shows that the mechanical properties of the near-surface region differ significantly from those of the bulk polymer.

Hirotsugu Kikuchi

Papers

Polymer-stabilized liquid crystal blue phases

62.2: Invited Paper: Fast Electro‐Optical Switching in Polymer‐Stabilized Liquid Crystalline Blue Phases for Display Application

39.1: Invited Paper: Optically Isotropic Nano‐Structured Liquid Crystal Composites for Display Applications

Large electro-optic kerr effect in polymer-stabilized liquid-crystalline blue phases

Near-surface alignment of polymers in rubbed films