Search results for " Crystal"

Structural variations of liquid crystalline polymers with phasmidic-type mesogens

1989

Abstract The fixation of phasmidic-type mesogens through spacer groups to polysiloxane backbones provided a method of obtaining liquid crystalline polymers with phasmidic mesogens as side groups. The polymer 6b showed a bilayer structure in the mesophase range. The tendency to form liquid-crystalline phase depends on the number and the length of alkoxy substituents.

Synthesis, structure and properties of liquid crystalline polymers

1981

The following is an extended abstract of a paper presented at the conference on Liquid Crystalline Polymers in Leeds, 1980, summarising the principles of the synthesis of thermotropic liquid crystalline polymers, their structure dependant phase behaviour and their orientation in electric and magnetic fields.

Combined main chain/side chain polymers. A new class of liquid crystalline polymers with unusual structural, thermodynamic and dynamic properties

1990

Abstract Combined main chain/side chain polymers carry rigid rod-like mesogenic units both in the side chain and along the chain backbone. The properties of such combined systems are expected to be controlled by the competition of the interactions between the mesogenic units in the side and main chains as well as the tendency of the chain backbones to maximize their entropy. The thermodynamic, structural and dynamic properties of such combined main chain/side chain liquid-crystalline polymers were investigated for various chain architectures. The combined systems were found to display properties corresponding in many cases to a favourable superposition of properties characteristic of both m…

Elastic Properties of Liquid Crystal Elastomer Balloons

2001

We introduce a method to measure elastic properties of smectic liquid crystalline elastomers. Freely suspended smectic polymer films containing photoreactive groups are inflated to spherical bubbles and crosslinked by UV light irradiation. After crosslinking, the balloon volume is varied and elastic properties of the material are determined from the relation between radius and inner excess pressure. The influence of the network topology on the elastic behaviour is discussed.

Photo-crosslinking in freely-suspended films of ferroelectric lc-polymers

1995

X-ray topographic study of solid-state polymerized poly-[1,2-bis-(p tolylsulphonyloxymethylene)-1-butene-3-inylene]

1976

Local extinction contrast effects have been observed in macroscopic polymer crystals, using Berg-Barrett X-ray topography. Results from as-polymerized crystals indicate that the crystals are perfect enough for defect regions to be imaged. As-polymerized crystals exhibited apparent defects lying along [021]. [010] slip traces in the (100) surface of a crystal were imaged; the slip system here appears to be consistent with (h01) [¯10h], forh, l ≠ 0 and [010] the chain direction.

Structure and Chemical Bonds in Black Ti(C, N, O) Thin Films

2010

Dye-containing S∗cside-on/end-on copolymers

1995

Abstract Mesomorphic copolysiloxanes, which combine ‘normal’ end-on linked chiral mesogenic units inducing S∗c phases and side-on fixed chromophores were prepared. The interplay of the different orientational tendencies of these moieties, which are perpendicular (end-on linked mesogenic groups) or parallel (side-on fixed chromophores) to the polymer chain, lead to a strong destabilization of the S∗c phase. However, copolymers with up to about 10 mol % of chromophores still show a smectic C∗ phase. FTIR measurements show that both moieties orient parallel to each other and perpendicular to the polymer chains. These copolymers are interesting to consider as coloured guest-host S∗c materials f…

X-ray investigation of combined main-chain/side-chain liquid-crystalline polymers

1990

Abstract Structural investigations on six combined liquid-crystalline polymers using the X-ray technique are described. The measurements have allowed a characterization of the liquid-crystalline phases and have led to our first ideas about the phase structures. All mesogenic groups are arranged parallel to each other, the shortest segment in the main-chain or in the side-chain determines the smectic layer spacing. A modified designation for liquid-crystalline phases of high polymers is proposed.

Study of smectic elastomer films under uniaxial stress

2004

We study the mechanical properties of free-standing films of smectic liquid crystalline elastomers. Macroscopically ordered elastomer films of submicrometer thickness are prepared from freely suspended smectic A polymer films by photo crosslinking. The deformation characteristics depend criticically on the sample composition, in particular on the density of mesogenic side chains at the siloxane backbone. In materials where the siloxane backbone is only partially substituted (dilute systems), a uniaxial stretching of the films in the layer plane is accompanied by a shrinkage of the smectic layers. This layer shrinkage is to only a minor extent achieved by the induction of a molecular tilt. W…