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Synthesis and electro-optical properties of fluorene containing blue luminescent rod-coil homopolymers with pendant pyridine

Sahu D., Chakroborty S.

Materials Science Poland

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2017

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Vol. 35, No. 1

217--224

EN

Two well defined, blue luminescent homopolymers containing 9,9-diethylfluorene core with electron withdrawing pendant pyridine, Suzuki-coupled with the corresponding borolane of decoxy phenyl (PFPA) and naphthalene (PFNA) have been designed and synthesized efficiently. The obtained rod-coil polymers have the average molecular weight of 15212 (PFPA) and 15130 (PFNA) with polydispersity indices (PDIs) 1.07 and 1.3, respectively. The polymers have good solubility and high thermal stability with the decomposition temperature of 362 °C (PFPA) and 367 °C (PFNA) correspondingly. Furthermore the optical and electrochemical properties of the polymers have been investigated. The polymers exhibited photoluminescence (PL) maxima at 410 nm (PFPA) and 414 nm (PFNA) excited at 340 nm, as stable blue luminescence polymers at low concentration of 10−6 M with a quantum yield of 0.64 and 0.62, respectively. In addition the annealed (150 °C) polymer films showed better stability of its photoluminescence spectra. Absorbance and fluorescence emission spectra of PFPA and PFNA were compared in order to evaluate the effects of substituent, phenyl and naphthalene in pyridine pendant fluorene moieties.

2

Synthesis and properties of high tilted antiferroelectric esters with partially fluorinated alkoxyalkoxy terminal chains

Żurowska M., Dąbrowski R., Dziaduszek J., Czupryński K., Skrzypek K., Filipowicz M., Bennis N., Otón J. M.

Opto-Electronics Review

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2008

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Vol. 16, No. 3

251-256

EN

Novel chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described. Their phase transition temperatures, enthalpies, and electrooptical properties are reported. A helical pitch in pure compounds and their mixtures based on selective reflection of light is also characterized.

3

Tunable topographical cellulose for electro-optical liquid crystal cells

Costa I., Almeida P. L., Filip D., Figueirinhas J. L., Godinho M. H.

Opto-Electronics Review

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2006

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Vol. 14, No. 4

299-303

EN

In this work we have used acetoxypropylcellulose (APC) to produce free standing solid films (~60 µm) that were used for assembling electro-optical devices. Thin films were obtained from concentrated lyotropic solutions of cellulose derivatives. Induced by the cast and shearing preparation conditions wrinkles and band textures can be observed in their free-surface plane. In order to eliminate and control these textures we used a process similar to that introduced in literature [1] which consists of storing the films in the same solvent-vapour atmosphere as the solution system. Lyotropic APC liquid crystalline solutions in dymethylacetamide (DMA) with crosslinker were prepared, thin films were obtained by using a shear/casting technique and stored in the solvent-vapour atmosphere until a planar structure was achieved. The dried crosslinked films were analyzed by optical polarised microscopy (POM) and scanning electron microscopy (SEM). The films with different topographies were used to produce optical cells composed by the cellulose derivative film covered on both free surfaces by a layer of the nematic liquid crystal E7 and placed between two transparent conducting substrates. The electro-optical properties of these cells were obtained.

4

Effect of polymer-dispersed liquid crystal morphology on its optical performance

Kłosowicz S. J., Aleksander M.

Opto-Electronics Review

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2004

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Vol. 12, No. 3

305-312

EN

The effect of the preparation method and its parameters and system composition on the polymer-dispersed liquid crystal morphology are described including size, shape, and concentration of liquid crystal droplets. Three different methods of polymer-dispersed liquid crystal preparation – encapsulation, solvent-induced phase separation, and photopolymerization- induced phase separation have been studied. It has been confirmed that the mean size of liquid crystal droplets is proportional to the liquid crystal concentration and approximately inversely proportional to the solidification rate. Depending on the preparation parameters it is possible to obtain, from the same components, a composite in which liquid crystal droplets’ size differs by four orders of magnitude. The driving voltage decreases while switching time increases with a size of liquid crystal droplets. The composites containing elongated liquid crystal droplets exhibit different electrooptical properties than those containing spherical droplets. Generally, changing composite morphology one can adjust electrooptical performance of polymer-dispersed liquid crystal.

5

Investigation of electrooptical properties of supertwisted nematic efect for multibottle liquid crystal mixture system

Parka J., Żmija J., Dąbrowski R.

Journal of Technical Physics

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1998

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Vol. 39, no 2

205-211

EN

Electrooptical properties of supertwised nematic effect depend on material constants of liquid crystal technical parameters of display construction. Optimisation of these parameters for isothiocyanate and esters liquid crystals mixtures has been carried out. Some experimental results have been presented.