Photo-switching and nonlinear optical behaviors of center linked bent-core azobenzene liquid crystalline polymers

Srinivasan, M.; Kannan, P.

doi:10.1007/s10853-011-5423-x

Cited by 39 publications

(14 citation statements)

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“…41 From the aforementioned families of compounds, azobenzenes besides interesting applications in the fields of supramolecular organization, 42,43 manipulation of biological systems using light, 44,45 photoorientation of materials and conversion of light into mechanical energy, 46 have also attracted considerable attention in the field of NLO properties due to the high nonlinear response obtained when adding active end groups to the azobenzene core. 25,[47][48][49][50][51][52][53][54] Strangely enough their efficiency in acting as NLO switches has been the subject of only a few investigations 33,37,38,[55][56][57] and it is the major goal of the present contribution to offer a systematic study of NLO properties for this class of molecules.…”

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confidence: 99%

Designing Efficient Azobenzene and Azothiophene Nonlinear Optical Photochromes

et al. 2014

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International audienceThe present contribution constitutes an extensive density functional theory (DFT) investigation of the nonlinear optical (NLO) properties of a large number of molecules belonging to the azobenzene and azothiophene families of photochromic compounds which can act as NLO switches. Toward the design of systems simultaneously presenting both large total nonlinear response values, beta(tot), and large contrast, beta(ratio), between the cis and trans isomers, we have focused not only on the monomers but also on azobenzene dimers, the latter containing two N=N bonds along the molecular backbone. After it was established that the inclusion of implicit solvation is not important in drawing qualitative conclusions on the NLO switching ability for the investigated systems, gas-phase calculations have shown that for the asymmetric pushpull azobenzene and azothiophene candidates, the combination of strong donating groups such as NPh2, N(Ph-OMe)(2), and N(Ph-NMe2)(2) with the dicyanoethene group CH=C(C=N)(2) as an acceptor delivers large ?trans (150-217 x 10(-30) esu) and non-negligible beta(cis) (18-55 x 10(-30) esu) values as well as substantial contrast, beta(ratio) (3.9-8.7). For the investigated double azobenzenes, it is found that, with a careful choice of donor and acceptor groups, the contrast, beta(ratio), can be significantly increased compared to that of the monomers while maintaining large beta values that facilitate their detection with standard experimental techniques (e.g., electric-field-induced second-harmonic generation). Our results set the stage on which further theoretical and experimental studies can be based in the search for efficient and versatile NLO switches

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confidence: 99%

Designing Efficient Azobenzene and Azothiophene Nonlinear Optical Photochromes

et al. 2014

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“…The photoisomerization studies reveal that the AZMP‐1 shows somewhat faster photoisomerization than other polymers. The time taken for photoisomerization depends on the nature of linking group (electron withdrawing group/donating group) and size of the substituent in the azobenzene moiety 38,43,48,53…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, the Z isomer of AZBP-1 sample were irradiated with 560 nm visible light which causes the cis to trans back isomerization very rapidly compared with that at ambient temperature in dark. 28,38,56 The time required to recover the original state upon illumination with 560 nm visible light are 80 s for AZBP-1 and 90 s for AZBP-2 and 3. The photoisomerization studies reveal that BCLCPs show trans to cis photoisomerization take place at 30, 35, and 35 s whereas reversible processes take place at 80, 90 and 90 s. The bent-core monomers and polymers exhibit very strong photoisomerization phenomena with UV as well as visible light illumination and also thermally reversible.…”

Section: Photo-switching Studies Of Bent-core Monomer and Its Polymermentioning

confidence: 99%

Photo and electrically switchable behavior of azobenzene containing pendant bent‐core liquid crystalline polymers

Srinivasan

Kannan

Roy

2012

J. Polym. Sci. A Polym. Chem.

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New class of photo and electrically switchable azobenzene containing pendant bent‐core liquid crystalline monomers (AZBM 1, 2, and 3) and their polymers (AZBP 1, 2, and 3) are reported. The synthesized precursors, monomers, and polymers were characterized by FT‐IR, 1H, and 13C NMR spectroscopy. Thermal stability of polymers was examined by thermogravimetric analysis and revealed stable up to 260 °C. The mesophase transition of monomers and polymers are observed through polarized optical microscopy (POM) and further confirmed by differential scanning calorimetry (DSC). The electrically switching property of monomers and their polymers were studied by electro‐optical method. Among the three monomers AZBM 1, 2, and 3, AZBM 1 and 2 exhibit antiferroelectric (AF) switching and AZBM 3 exhibits ferroelectric (F) switching behavior. On the other hand, low molecular weight polymers (AZMP 1, 2, and 3) show weak AF and F switching behavior. The photo‐switching properties of bent‐core azo polymers are investigated using UV‐vis spectroscopy, trans to cis isomerization occurs around 25 s for AZBP‐1 and 30 s for AZBP‐2 and 3 in chloroform, whereas reverse processes take place around 80 and 90 s. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

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“…The side-chain bent-core polymers are derived from 1,3-phenylene unit with five aromatic rings, which can be symmetric (Wang et al 2010) as well as asymmetric (Kishore et al 2009), wherein the polymerizable functional groups are generally used, are 1,3-diene (Sentman and Gin 2003), methacrylates or acrylates group (Chen et al 2007a, b) and siloxane group (Keith et al 2005). Interestingly, side-chain bent-core liquid crystalline polymers predominantly demonstrate rich mesomorphism when compared with the main-chain (Saravanan et al 2008), side-chain (Saravanan and Kannan 2010) and dendronized liquid crystalline polymers Percec 2007, 2008;Rosen et al 2009;) are classified as follows: (i) side-chain bent-core liquid crystalline polymer (SBCLCPs), (Chen et al 2007a, b;Srinivasan et al 2013b) (ii) bentcore mesogen-jacketed liquid crystalline polymers (BMJLCPs) ), (iii) central linked bent-core liquid crystalline polymer (CBCLCPs) (Srinivasan and Kannan 2011) and (iv) hydrogen-bonded side chain bent-cores liquid crystalline polymers (HBCLCPs) (Wang et al 2010), were reported based on the polymeric back bone attached to the position of bent-core mesogen pendant. Although BCLCs have been extensively investigated, bent-core side-chain polymers have so far, recorded very limited success with respect to their polar switching properties (Sentman and Gin 2003;Chen et al 2007a, b).…”

Section: Bent-core Side Chain Liquid Crystalline Polymers (Bclcps)mentioning

confidence: 99%

Side Chain Liquid Crystalline Polymers: Advances and Applications

Reddy

Jayaramudu

Ray

et al. 2015

Liquid Crystalline Polymers

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Matters comprise of molecules that exist in three different phases-solids, liquids and gases depending on their arrangement. The arrangement of molecules in a crystalline solid leads to long-range positional and orientational orders. In isotropic liquid, on the other hand, the molecules are arranged randomly and possess no order and flow freely. However, it was observed that a certain class of molecules organise in a different manner in order to exhibit a new phase, popularly known as liquid crystalline phase. Molecules in liquid crystalline phase self-organize, leading to positional/orientation order. Macroscopically, the liquid crystalline phase exhibits flow and appears like an opaque fluid.

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Photo-switching and nonlinear optical behaviors of center linked bent-core azobenzene liquid crystalline polymers

Cited by 39 publications

References 40 publications

Designing Efficient Azobenzene and Azothiophene Nonlinear Optical Photochromes

Designing Efficient Azobenzene and Azothiophene Nonlinear Optical Photochromes

Photo and electrically switchable behavior of azobenzene containing pendant bent‐core liquid crystalline polymers

Side Chain Liquid Crystalline Polymers: Advances and Applications

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