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Home Azerbaijan Technologies Development of Novel Colloid-Liquid Crystal Composites Displaying Network Formation

Development of Novel Colloid-Liquid Crystal Composites Displaying Network Formation

Description

The method of phase separation was used for development of novel small particles-liquid crystalline composites displaying network formation. Composites have been created by variation of type and concentration of liquid crystal (LC) and polymer, and also regime of mixing and cooling. The following materials are used for development of liquid crystalline composites:
liquid crystals 4-pentylcyano-4'-biphenyl (5CB);
liquid crystal 4-methoxybenzilidene - 4' – butylaniline (MBBA);
liquid crystal 4-ethoxybenzilidene-4'-butylaniline (EBBA);
the mixture of MBBA and EBBA with molar ratio of 1:1 ( H-37) and 2:1 (H-8);
polymer poly(2-methyl-5-vinylprydine)(PMVP);
polymer poly(ethyleneglycol) (PEG);
polymer poly(vinylalcohol (PVA);
the stabilizer heptixybenzoic acid (HOBA).

The kinetics of network formation has been investigated by the methods of polarized microscopy and small-angle scattering of laser radiation through obtained composites 5CB + PEG + HOBA and H-37+PVMP + HOBA in which the matrix of the first composite has positive optical anisotropy and the matrix of the second one – negative.

Threshold voltages of homeotropic-planar transition and the elctrohydrodynamic instability, times of switching on and switching off for these effects, and also volt-contrast characteristics of these composites have been determined.

It is shown that the network is formed at some critical concentration: it equals to 7% for the H-37+PVMP + HOBA system while for the 5CB + PEG + HOBA composite – 9%. At that case, temperature of isotropic-nematic transition is shifted to low temperatures for the H-37+PVMP + HOBA composite while it remains constant for the 5CB + PEG + HOBA composite. The threshold voltages of homeotropicnematic transition and the electrohydrodynamic instability increase, contrast ratios are worsen, the rise time remains constant while the decay time decreases in the H- 37+PVMP + HOBA composite. The threshold voltages of the homeotropic-nematic transition increases, the electrohidrodynamic instability does not change, contrast ratios are worsen, the rise and decay times decreases in the 5CB + PEG + HOBA composite.

Innovative Aspect and Main Advantages

Novel type of self-assembly systems which are formed at preliminary heating of the mixture of polymer and LC above melting temperature Tm of polymer and temperature Tin of isotropic-nematic transition of LC has been developed. At intermixing process the drops of polymer are formed in the isotropic phase of LC. These drops are transformed to the solid balls at slow cooling of the mixture lower Tm, and then form network in liquid crystal phase at further cooling. At that case, the ball sizes depend on cooling rate. The 2D and 3D periodic structures may be formed in these composites. The parameters of these structures are operated by applied electric field.

Areas of Application

The components of photonic devices operated by electric field: displays, photonic crystals, gratings.


Fig. 1 Network formation at slow cooling of colloid-liquid crystalline
composite H-37 + PMVP + HOBA (87%+12%+1%) from the
isotropic phase of LC.

Stage of Development

Development of technology of creating of periodic structures on the base of obtained composites. The Eurasian patent application has been considered.

Contact Details

Institute of Physics
Contact person: Ibragimov Tahir Djumshud oglu
Address: 33, H. Javid Avenue, AZ1143, Baku, Azerbaijan
Tel: (99 412) 4310992;
Fax: (99 412) 4310992
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Baku State University
Contact person: Bayramov Gazanfar Muzaffar oglu
Address: 23, Khalilov Street, AZ1148, Baku, Azerbaijan
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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