Golam Mohiuddin

• PhD in Chemistry (Soft Condensed Matter Chemistry-Liquid Crystals)
• Assistant Professor at University of Science and Technology, Meghalaya (USTM)

A new approach accompanied by superstructural frustration is reported by attaching a cholesterol moiety directly to the central bent-core system that displayed exotic BPIII, BPII/I, Ncyb*, TGBA phases including SmAPA, SmA and SmX phases as derived by X-ray scattering results. While higher homologue of the series exhibited spontaneous formation of p...

We have investigated two new series of unsymmetrical four-ring bent-core molecules with methylated azobenzene wings exhibiting nematic mesophase. The difference between the two series was in the relative position of the methyl (-CH3) substituent in respect of the azo (-N=N-) linkage in the molecule. Single crystal X-ray diffraction (SCXRD) analysis...

Recently, an unprecedented observation of polar order, thermochromic behavior, and exotic mesophases in new chiral, bent‐shaped systems with a −CH3 moiety placed at the transverse position of the central core was reported. Herein, a homologous series of compounds with even‐numbered carbon chains from n=4 to 18 were synthesized, in which −Cl was sub...

"de Vries" liquid crystals, defined by a maximum layer shrinkage of ≤1% from the smectic A to C phase transition, are an integral component of ferroelectric liquid crystal (FLC) displays. Bona fide de Vries materials described in the literature are primarily perfluorinated, polysiloxane and polysilane-terminated rod-like (or calamitic) LCs. Herein,...

In this study, we used a new series of highly polar three-ring-based bent-core liquid crystals (BCLCs) to stabilize a wide temperature range of blue phase III (BPIII), including room temperature. A significant finding is the implementation of electro-optical (E-O) switching at room temperature in the current BPIII system. The observed Kerr constant...

In the recent years, a tremendous development has been observed in the field of water-soluble polymers and their applications. The use of water-soluble polymers in the preparation of sustainable, robust, and cost-effective materials over the other polymers is the thrust area of contemporary polymer sciences having several advantages. Water-soluble...

Non-symmetrical cholesterol-based dimers have emerged as crucial materials in the field of liquid crystal research, owing to their remarkable ability to stabilize various exotic mesophases, including the cholesteric nematic (N*)...

Two new homologous series of mesogenic compounds, alkanoic acid 4-{[4-(6-chloro-benzooxazol-2-yl)-phenylimino]-methyl}-3-hydroxy-phenyl ester (3a-c) and alkcanoic acid 4-(6-chloro-benzooxazol-2-yl)-3-hydroxy-phenyl ester (5a-b) incorporating benzoxazole heterocyclic have been prepared and FT-IR, NMR, and MS spectrometry have been used to study the...

A series of isomeric bis-2,6-(monoalkoxyphenyl)pyridine and bis-2,6-(dialkoxyphenyl)pyridine ligands were synthesized and characterized. In order to prepare their chlorogold(III) complexes, intermediate chloromercury(II) complexes were first prepared, but unlike observations from previous studies where they were obtained impure and at best in moder...

A novel nanocomposite system has been prepared by dispersing multiferroic bismuth ferrite nanoparticles (BiFeO$_3$) in a bent-core nematic liquid crystal (8-F-OH) that exhibits cybotactic clusters. Transition temperature, optical textures, order parameter (\emph{S$_{m}$}), and dielectric spectroscopy experiments are performed in the doped system, a...

In liquid crystalline systems, the presence of polar groups at lateral or terminal positions is fundamentally and technologically important. Bent‐core nematics composed of polar molecules with short rigid cores usually exhibit highly disordered mesomorphism with some ordered clusters that favourably nucleate within. Herein, we have systematically d...

The response to applied electric field of a newly synthesized hockey-stick nematic 8-F-OH has been studied. Unusual pattern forming scenarios were found, which show rich variety as a function of frequency, temperature and initial director alignment. The behavior has been compared with those, observed in calamitic and bent-core nematics. Experiments...

Journal of Molecular Structure Available online 9 June 2022, 133496 In Press, Journal Pre-proofWhat are Journal Pre-proof articles? Imine-based highly polar achiral unsymmetrical four-ring bent shaped liquid crystals: Design, Synthesis and Characterization Author links open overlay panelVarshaJainaSantanu KumarPala https://doi.org/10.1016/j.molstru...

Hockey-stick-shaped liquid crystals are interesting due to their unusual physical properties. Nematic phase observed in these materials have shown promising ferroelectric-like switching, ease of alignment in a planar and homeotropic cell, large flexoelectricity, etc. Polar moieties viz. F, Cl, NO2, etc., in their molecular architecture lead to the...

A study on the photoswitching behavior of azobenzene‐based polar hockey‐stick‐shaped liquid crystals (HSLCs) has been presented. Two new series of five phenyl rings based polar HSLCs have been designed and synthesized. Solution state photoisomerization of the synthesized materials was investigated thoroughly via UV‐visible and ¹H NMR spectroscopic...

Many bent-core nematic liquid crystals exhibit unusual physical properties due to the presence of smectic clusters, known as “cybotactic” clusters in the nematic phase. Here, we investigate the effect of these clusters on complex shear modulus (G∗(ω)) of two asymmetric bent-core liquid crystals using microrheology technique. Compound with shorter h...

Many bent-core nematic liquid crystals exhibit unusual physical properties due to the presence of smectic clusters, known as "cybotactic" clusters in the nematic phase. Effect of these clusters on complex shear modulus ($G^*(\omega)$) of such liquid crystals hitherto unexplored. Here, we study flow viscosities and complex shear modulus of two asymm...

Herein, we are reporting a new series of three-ring based polar bent-core molecules with 2-chloro-3-nitrobenzoic acid as the central core, halogen moiety at one terminal and octadecyloxy chain at another terminal. The compounds 10b, 10c, and 10d were shown to exhibit the orthogonal smectic phase during cooling the samples from the isotropic liquid....

We have studied two new series of polar and non-polar four-ring based achiral bent-core molecules containing CN and OCH3 moiety respectively at the tip of the molecular short arm and their molecular self-assembly in crystal and liquid crystal state. Crystal structure analysis revealed the bent molecular geometry of the compounds with bent angle 151...

Herein, we report a new type of azobenzene based unsymmetrical bent-core molecules exhibiting photoswitchability in liquid crystalline state, solid state, solution state and in mixture upon UV irradiation and intense visible light. The compounds exhibited solid state photochromism upon exposure of UV light whereas in liquid crystalline state revers...

We report here the synthesis and thermotropic properties of novel short-core hockey stick-shaped liquid crystalline molecules based on the 1,3,4-thiadiazole core. Polar switching behavior is observed in the cybotactic nematic and smectic mesophases for the bent-core thiadiazole derivatives. The presence of the lateral methoxy moiety in the outer ph...

We report the orientational behavior of nematic liquid crystals (LC) influenced by a cyclic lipopeptide, Polymyxin B (PmB). It was found that PmB can spontaneously self-assemble at aqueous-LC interfaces and induce a homeotropic ordering of the LCs at those interfaces, thus resulting in dark optical appearance of LC under cross polarizers. Density f...

An extensive study of the effect of terminal halogens on the structure-property relationship in three series of polar short-core hockey-stick shaped or L-shaped mesogens has been elucidated. The behaviour of the halogens at the tip of the short arm and the role of end alkyl chain at the long arm on the phase structure of the mesogens have been char...

In this work, hydrogen-bonded liquid crystal exhibiting phase dependent fluorescence has been reported. The H-bonded materials were prepared using pyridenyl benzothiazole and alkoxy benzoic acid as H-bond acceptor and donor respectively. The formation of the target materials was confirmed via different spectroscopic technique and their mesogenic be...

Here, we report the first examples of achiral unsymmetrical three-ring bent-shaped liquid crystals comprising amide and imine linkages with transverse substituents of methyl and chloro moieties on the central phenyl ring in the core, exhibiting polar banana phases. The extensive intra and inter molecular H-bonding induced novel banana mesomorphic p...

Here we report the influence of terminal –F, –Cl and –NO2 substitution on the elastic, dielectric and polar switching behavior of four-ring bent-core liquid crystals (LCs). Elastic constants of nematic liquid crystals are the key parameters in determining the threshold voltage and sensitivity to electro-optical response in a device. The elastic pro...

Liquid Crystals, 2017, Vol: 44, No:14-15,

Bent-core liquid crystals are candidates for promising and interesting new research in the field of liquid crystals (LCs). This class of LCs possess remarkable and unusual characteristic feature in their shape, size, chirality, electrical, optical and transport properties. When subjected to an external electric field, the bent-core LCs often exhibi...

Research on low-temperature polar bent-core nematogens having lower molecular weight has gathered appreciable momentum by virtue of their significance in potential applications. However, the lack of availability and easy-to-perform synthesis processes appears to be the bottleneck towards their fabrication and thereby limiting their possible device...

We report the basic structural understanding of a new class of achiral three-ring bent-core compounds with an imine and ester linkage at the molecular bend, which are shown to exhibit nematic and orthogonal smectic phases at lower temperature. The occurrence of the orthogonal smectic and nematic ordering has been confirmed by optical texture, DSC s...

We report possible biaxiality in the nematic phase of a bent-core liquid crystal compound exhibiting cybotactic clustering in the entire nematic liquid crystal phase using dielectric spectroscopy with promising application in faster switching displays.

We report possible biaxiality in the nematic phase of a bent-core liquid crystal compound exhibiting cybotactic clustering in entire nematic liquid crystal phase using dielectric spectroscopy with promising application in faster switching displays.

Bent-core nematics have attracted growing interest because of the unconventional properties and extraordinary effects exhibited by these liquid crystalline phases. In this report we design, synthesize and characterize four different four-ring achiral bent-core liquid crystals containing a methyl group in the central phenyl ring. The mesomorphic beh...

We report the synthesis and characterization of a new class of achiral three-ring bent-core compounds with an amide and ester linkage at the molecular bend, which are shown to exhibit nematic/phases in wide temperature ranges around room temperature (RT) and undulated SmC phases below RT. In contrast to previous studies, the compounds reported in t...

a Based on the chemical incompatibility between the aromatic mesogenic cores and the flexible end aliphatic (methylene units) chains, which can lead to the formation of polarization modulated layered undulated phases, four-ring bent-core compounds have been designed and synthesized. The designed compounds are thermally and hydrolytically stable due...

Achiral unsymmetrical 2-methyl 3-amino-benzoic acid (2,6-substituted toluene)-derived four-ring bent-core liquid crystals with a polar fluoro or chloro substituent at one end and an alkyloxy group (butyl to dodecyl) at the other end have been synthesised by a simple and straightforward synthetic method. The molecular structure characteri-sation is...

Chiral unsymmetrical dimeric liquid crystals consisting of a cholesterol moiety as chiral entity and a substituted salicylidene imine core (with the substituent being butyl or fluoro or chloro group) interconnected through an even methylene spacer have been synthesised and their mesomorphic properties are characterised. All the dimers exhibit enant...

The synthesis and characterization of stable achiral unsymmetrical four-ring banana-shaped molecules consisting of a laterally chloro substituted 3,4 0 -disubstituted biphenyl unit with an ester linkage between the phenyl rings as the central unit in 4-(N-4 0 -n-tetradecyloxysalicylidene)aminophenyl [2-chloro-5-(N-4 0 -n-tetradecyloxysalicylidene)...

Non-symmetrically substituted four-ring achiral bent-core compounds with polar substituents, i.e.., chloro in the bent or transverse direction in the central core and cyano in the lateral direction at one terminal end of the molecule, are designed and synthesized. These molecules possess an alkoxy chain attached at only one end of the bent-core mol...

A new family of four-ring achiral bent-core compounds derived from 2-methyl 3-amino benzoic acid with the methyl group in the bent direction incorporated into the central core have been designed and synthesised. These compounds possess an alkoxy chain attached at only one end of the bent core molecule, while the other arm con-sists of a biphenyl mo...

a b s t r a c t Achiral unsymmetrical four-ring bent-core liquid crystals with strongly polar cyano and nitro moieties as substituents at one end and alkyloxy group (butyl to dodecyl) at the other end have been synthesized by a simple and straight forward synthetic method. The four phenyl rings are connected through azo, ester and imine linkages re...