Synthetic pathway for a new calamitic series of liquid crystal: Comparison with corresponding linkage group

Article abstract of DOI:10.1080/15421406.2017.1370957

Reduction-responsive cystamine-incorporated gelatin microspheres were prepared by an emulsification method. On SEM micrograph, the microsphere, prepared at pH 9.0 and at the carboxyl/amino group molar ratio of 1:1, was sphere-like and its diameter was a few to 100 μm. The gelatin to cystamine ratio of the microsphere was about 1:0.2 (w/w), determined by energy dispersive X-ray spectroscopy. Two endothermic peaks were observed around 92°C and 126°C, which were thought to be the melting point of gelatin-rich phase and that of cystamine-rich phase, respectively. The microsphere released its payload (FITC-dextran) in dithiothreitol (a reducing agent) concentration-dependent manner.

Full text of DOI:10.1080/15421406.2017.1370957

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
Synthetic pathway for a new calamitic series of
liquid crystal: Comparison with corresponding
linkage group
Vinay S. Sharma, Rajesh H. Vekariya, Anuj S. Sharma & R. B. Patel
To cite this article: Vinay S. Sharma, Rajesh H. Vekariya, Anuj S. Sharma & R. B. Patel
(2017) Synthetic pathway for a new calamitic series of liquid crystal: Comparison with
corresponding linkage group, Molecular Crystals and Liquid Crystals, 652:1, 143-157, DOI:
10.1080/15421406.2017.1370957
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Date: 24 October 2017, At: 01:16

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –
https://doi.org/./..
Synthetic pathway for a new calamitic series of liquid crystal:
Comparison with corresponding linkage group
Vinay S. Sharmaa, Rajesh H. Vekariyab, Anuj S. Sharmab, and R. B. Patela
aChemistry Department, K. K. Shah Jarodwala Maninagar Science College, Gujarat University, Ahmedabad,
Gujarat, India; bDepartment of Chemistry, School of Science, Gujarat University, Ahmedabad, Gujarat, India
ABSTRACT
KEYWORDS
Calamitic; liquid crystals;
nematic; rod type; smectic
Two homologous series based on three linking groups have been syn-
thesized and characterized by elemental analyses and spectroscopic
techniques such as Fourier transform infrared [FT-IR] and protonmag-
netic resonance magnetic resonance [1H-NMR] spectroscopy. The meso-
morphic properties of these compounds were observed by optical
polarized light microscopy (POM) and differential scanning calorimetry
(DSC). In this present investigation, we have synthesized two homolo-
gous series viz. 4-(3-oxo-3-(4-((-3-phenylallylidene)amino) phenyl) prop-
1-en-1-yl) phenyl 4-n-alkoxy benzoate) (series-1) and 4-(3-oxo-3-(4-((-3-
phenylallylidene) amino) phenyl) prop-1-en-1-yl) phenyl 3-(4-n-alkoxy
phenyl) acrylate (series-2). Both of the series are differing with respect
to the first linking group. All the homologous in the following series
exhibitsLCphaseonheatingaswellascoolingconditionexceptfirsttwo
homologue(C1, C2)inseries-1andthreehomologue(C1, C2, C3)inseries-2.
GRAPHICAL ABSTRACT
1. Introduction
The arrangement of molecules in liquid crystals (LCs) takes place in a number of ways lead-
ing to various phases of different order and symmetry between crystalline solid and isotropic
liquid [1–4]. Study on LC state is planned with a view to understand and establish the effect
CONTACT Vinay S. Sharma
vinaysharma@gmail.com
Science College, Gujarat University, Ahmedabad, , Gujarat, India.
Chemistry Department, K.K. Shah Jarodwala Maninagar
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
©  Taylor & Francis Group, LLC

144
V. S. SHARMA ET AL.
of molecular structure on LC properties [5] as a consequence of molecular rigidity and flex-
ibility [6–8]. In order to avail novel LC materials to the various groups of researchers work-
ing with different aims, objects, and views with different angles to continue and extend their
research. Liquid crystals can be divided into thermotropic, lyotropic and metallotropic phases.
Thermotropic and lyotropic liquid crystals consist mostly of organic molecules although few
minerals are also known [9–10]. Liquid crystals in the nematic group are most widely used in
production of liquid crystal displays (LCD) mainly due to their unique physical property such
as a wide temperature range. In addition, the nematic phase in which liquid crystal molecules
are oriented on average along to a particular direction. By applying an electric or magnetic
field, the orientation of the molecules can be derived in a probable approach [11–12]. Litera-
ture studies revealed that the schiff base has been widely employed as a linking group for the
synthesis of different forms of liquid crystals [13–15].
Different chalcone derivatives have exhibited broad spectrum of anti-bacterial, antifungal,
antiulcer, antimalarial, antitumor, anticancer, anti-inflammatory and antituberculor activity
[16–20]. It is believed that the presence of α, β-unsaturated functional group in chalcone
–
=
–
–
( CH CH CO ) is responsible for the anti-microbial activity, which can be altered depend-
ing upon the type of substituent present on the aromatic rings [21–22]. To the best of our
knowledge, liquid crystalline materials based on chalconyl central linking group are rarely
–
–
=
–
reported in the literature. It has been observed that CO CH CH linkage is less conducive
to mesomorphism as compared to CH N , COO , N N , CH CH COO linkages
group because of the presence of non-linearity and angle strain arising from the presence of
–
= – –
– – = – –
=
–
–
– =
–
–
=
–
keto ( C O) group [23]. Surprisingly, when CO CH CH linkage is linked with another
linking group and it becomes conductive to exhibits mesophase. In the literature studies,
there are several reports of mesogenic compounds having chalcone linkage. Vora et al. [24]
reported a homologous series of polymers containing a chalcone linkage. Soon afterword
Chudghar and his co-workers reported a homologous series containing on ester-chalcone
linkages [25]. Yeap et al. have also synthesized mesomorphic compounds containing on
ester-chalcone linkage [26]. Guan et al. reported phloroglucinol based star shaped sym-
metrical trimeric liquid crystalline compounds containing three rod like schiff base arms
[27]. The mesomorphic properties of aromatic Schiff base esters arising from substituents
varying in their polarities have been reported by Ha et al. [28]. Many mesogenic homologous
series contain two central linkages, one of which may be ester and the other azomethine
[29–33]. In 2007, Yellamaggad et al. have developed salicylaldimine based banana-shaped
mesogens derived from laterally substituted resorcinol [34]. Recently, Doshi et al. have
reported chalconyl ester and chalconyl vinyl ester linkage group inbuilt between three phenyl
rings and studied the effect on mesomorphism by substituted groups at terminal and lateral
side [35–39].
Thus, the main object of this present work to synthesized and studied the effect of
chalconyl-ester and allylidene amino linkage group on mesomorphism. Many series of liquid
crystalline compounds containing heterocyclic groups have been synthesized due to their
usefulness in wide application such as electrical, optical, biological and medical field [40].
In our recent reports, we have developed some homologous series based on Cis and Trans
cinnamate and benzoate linkage group [41–45]. Our research group also reported some
linear and nonlinear homologous series which consisted three phenyl rings bonded through
–
=
–
–
–
–
vinyl ester ( CH CH COO ) and ester ( COO ) linkage group connected with chalconyl
central group having alkoxy terminal group at left end and different terminal group or
lateral substitution on right side [46–48]. We have also reported the single chalconyl linkage
group between two phenyl rings exhibited monotropy or enantiotropy mesophase with low

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
145
thermal stability [49–51]. In continuation of our efforts to synthesized newly liquid crystalline
–
–
materials, we have introduce some new calamitic liquid crystal based on ester ( COO )
–
=
–
–
–
=
–
–
or vinyl ester ( CH CH COO ) with chalcone ( CH CH CO ) and allylidene amino
( N CH CH CH ) group. We have compared the thermal stability and mesophase proper-
– =
–
=
–
–
=
–
ties of series-1 and series-2 as well as studied the effect of extra part of ethylene ( CH CH )
on mesomorphism in series-2.
2. Experimental
2.1. General
For the synthesis of target compounds in homologous series-1 and -2, the following mate-
rials were used: 4-hydroxy benzoic acid, 4-hydroxy benzaldehyde, Alkyl halides (Lancaster,
England), Anhydrous K2CO3, KOH, Malonic acid, 4-amino acetophenone, cinnamaldehyde
were purchased from (SRL, Mumbai, India), DCC (Dicyclohexyl carbodimide) was purchased
from Fluka Chemie (Switzerland), Dimethyl amino pyridine DMAP (4,4ꢀ-dimethylamino
pyridine) was purchased from Finar chemicals (India), Dichloro methane, Ethanol, Pyridine,
Acetone required for synthesis were used as received except solvents which were dried and
distilled prior to use. The molecular structures of the target products and the intermediates
were confirmed by spectroscopic analysis and elemental analysis. Representative homolo-
1
gous series were characterised by elemental analysis, Infrared spectroscopy, H NMR spec-
tra. IR spectra were recorded by Perkin-Elmer spectrum GX, 1HNMR spectra were recorded
on Bruker (400 MHz) using CDCl3 as a solvent. Microanalysis was performed on Perkin-
Elmer PE 2400 CHN analyser. Texture image of nematic phase were determined by using
miscibility method. Transition temperature and LC properties (Textures) were determined
using an optical polarising microscopy (POM) equipped with heating stage attached to the
camera. Decomposition temperatures were determined using of Shimadzu (DSC) differential
Scanning Calorimeter with a heating rate of 5°C to 10°C min−1. Thermodynamic quantities
=
enthalpy (ꢀH) and entropy (ꢀS ꢀH/T) are mentioned in Table–4.
2.2. Synthesis of Series-1 and Series-2 compounds
... Synthesis of -n-alkoxy benzoic acid (a) and Trans -n-alkoxy cinnamic acid (b)
4-n-alkoxy benzoic acid and 4-n-alkoxy cinnamic acid were prepared by method reported by
Dave and Vora [52].
... Synthesis of -n-alkoxy benzaldehyde (a)
4-n-Alkoxybenzaldehydes were synthesized by refluxing 4-hydroxybenzaldehyde (1 equiv.)
with corresponding n-alkyl bromides (1 equiv.) in the presence of anhydrous K2CO3 (1 equiv.)
and dry acetone as a solvent [53].
... Synthesis of -(-((-phenyl allylidene) amino) phenyl) ethanone (a)
Schiff base of 4-amino acetophenone and cinnamaldehyde was prepared by reported method
[54]. (Brown colour, Yield: 74%), IR (KBr): vmax/cm−1 3077 (C H str.), 1597 (CH N), 961
–
=
=
–
=
(CH CH ), 1650 (C O str.). elemental analysis: calculated for C17H15ON: C, 81.92%; H,
6.02%; O, 6.42%; N, 5.62%; found: C, 81.18%; H, 5.94%; O, 6.37%; N, 5.58%.

146
V. S. SHARMA ET AL.
... Synthesis of -(-hydroxy phenyl)---((-phenyl allylidene) amino) phenyl)
prop--en--one (a)
Chalcone (4a) was prepared by usual reported method [55]. (brownish yellow, Yield: 67%),
IR (KBr): vmax/cm−1 3460 ( OH str.-bonded), 3079–3020 ( C H str. aliphatic alkyl group),
–
– –
– = –
=
– =
– – –
2932, 1598 (CH N), 1667 ( C O, group), 1584–1610 ( C C ) aromatic, 1280 ( O CH2
ether linkage), 962 (Trans alkene). elemental analysis: calculated for C24H19O2N: C, 81.58%;
H, 5.38%; O, 9.06%; N, 3.96%; found: C, 81.48%; H, 5.28%; O, 8.77%; N, 3.89%.
... General procedure for the synthesis of (Series-)
The compound has been prepared by esterification of the appropriate 4-n-alkoxy ben-
zoic acid (1a) (2.02 mmol) and chalcone (4a) (0.246g, 2.02 mmol), dicyclohexyl carbodi-
imide (DCC) (0.457g, 2.22 mmol) and dimethylaminopyridine (DMAP) in catalytic amount
(0.002g, 0.2 mmol) in dry CH2Cl2 (DCM) (30 mL) was stirred at room temperature for 48h.
The slightly white precipitate of DCU is obtained which was isolated by filtration and remove,
while the filtrate was evaporated to dryness. The resultant crude residue was purified by col-
umn chromatography on silica gel eluting with methanol: chloroform as eluent (1:4) [56]. The
synthesis route of derivatives for series-1 and series-2 were mention in scheme –1 and –2.
C1 (series-1): IR (KBr): vmax/cm−1 2966 (C H str. of alkane), 1650 (C O str. of car-
–
=
=
–
–
bonyl carbon of chalconyl group), 1601 (C C str. of alkene in chalcone), 1730 ( COO
–
–
–
group), 992 (C H bending of alkene), 1170 (C O str. of ether linkage), 1231 (C O str. of
1
–
=
–
–
=
–
–
carbonyl (>CO) group, 960 (trans, CH CH of CH CH CO ) group. H-NMR: 3.81
–
– =
–
–
=
–
–
(t, 3H, CH3 of polymethylene OCH3), 7.81 & 7.52 (d, 2H, CH CH CO ), 7.44 (d,
–
= –
– =
–
=
–
1H, N CH CH C ), 6.83 & 7.20 (d, 2H, N CH CH CH ), 8.07 & 7.10 (4H, first
phenyl ring), 7.32 & 7.72 (4H, second phenyl ring), 7.87 & 7.38 (4H, third phenyl ring), 7.61,
7.40, 7.31 (5H, fourth phenyl ring). Elemental analysis: calculated for C32H25O4N: C, 78.85%;
H, 5.13%; O, 13.14%; N, 2.87%; found: C, 78.45%; H, 5.01%; O, 13.07%; N, 2.81%.
C2 (series-1): IR (KBr): vmax/cm−1 2960 (C H str. of alkane), 1660 (C O str. of carbonyl
–
=
=
–
–
carbon of chalconyl group), 1608 (C C str. of alkene in chalcone), 1760 ( COO group), 992
(C H bending of alkene), 1180 (C O str. of ether linkage), 1241 (C O str. of carbonyl (>CO)
group, 960 (trans, CH CH of CH CH CO ) group. H-NMR: 1.32 (t, 3H, CH3
of polymethylene OC2H5), 4.06 (t, 2H, OCH2 CH2 of OC2H5), 7.82 & 7.52 (d, 2H,
–
–
–
1
–
–
=
–
–
=
–
–
–
–
–
–
–
–
=
–
–
– =
–
= –
– =
–
=
–
CH CH CO ), 7.46 (d, 1H, N CH CH C ), 6.83 & 7.21 (d, 2H, N CH CH CH ),
8.07 & 7.10 (4H, first phenyl ring), 7.32 & 7.71 (4H, second phenyl ring), 7.87 & 7.38 (4H,
third phenyl ring), 7.61, 7.40, 7.32 (5H, fourth phenyl ring). Elemental analysis: calculated
for C33H27O4N: C, 79.04%; H, 5.38%; O, 12.77%; N, 2.79%; found: C, 78.88%; H, 5.31%; O,
12.71%; N, 2.72%.
C4 (series-1): IR (KBr): vmax/cm−1 2930 (C H str. of alkane), 2820 (C H str. of (CH2 )n
–
–
–
–
–
=
group of OC4H9 alkyl chain, 1660 (C O str. of carbonyl carbon of chalconyl group),
1612 (C C str. of alkene in chalcone), 1750 ( COO group), 1520 ( C C str. of aromatic
=
–
–
– =
–
–
–
ring), 984 (C H bending of alkene), 1188 (C O str. of ether linkage), 1240 (C O str. of car-
–
=
–
–
–
=
–
–
bonyl (>CO) group, 962 (trans, CH CH of CH CH CO ) group, 781 polymethylene
1
–
–
–
–
( CH2 ) of OC4H9. H-NMR: 0.92 (t, 3H, CH3 of polymethylene OC4H9), 1.42–1.76 (m,
4H, OC4H9), 4.06 (t, 2H, OCH2 CH2 of OC4H9), 7.87 & 7.51 (d, 2H, CH CH CO ),
7.48 (d, 1H, N CH CH C ), 6.84 & 7.22 (d, 2H, N CH CH CH ), 8.06 & 7.12 (4H,
first phenyl ring), 7.30 & 7.72 (4H, second phenyl ring), 7.86 & 7.38 (4H, third phenyl ring),
7.61, 7.40, 7.31 (5H, fourth phenyl ring). Elemental analysis: calculated for C35H31O4N: C,
79.39%; H, 5.86%; O, 12.09%; N, 2.64%; found: C, 79.31%; H, 5.78%; O, 11.97%; N, 2.58%.
–
–
= –
–
–
–
–
=
–
–
– =
–
– =
–
=
–

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
147
Scheme . Synthetic route of derivatives.
C5 (series-1): IR (KBr): vmax/cm−1 2940 (C H str. of alkane), 2830 (C H str. of (CH2 )n
–
–
–
–
–
=
=
group of OC5H11 alkyl chain, 1610 (C O str. of carbonyl carbon of chalconyl group),
1602 (C C str. of alkene in chalcone), 1730 ( COO group), 1540 ( C C str. of aro-
matic ring), 994 (C H bending of alkene), 1188 (C O str. of ether linkage), 1246 (C O
str. of carbonyl (>CO) group, 960 (trans, CH CH of CH CH CO ) group, 789 poly-
methylene ( CH2 ) of OC5H11. H-NMR: 0.90 (t, 3H, CH3 of polymethylene OC5H11),
1.31–1.76 (m, 6H, OC5H11), 4.06 (t, 2H, OCH2 CH2 of OC5H11), 7.88 & 7.52 (d, 2H,
–
–
– =
–
–
–
–
–
=
–
=
–
–
1
–
–
–
–
–
–
–
–
–
–
–
=
–
–
– =
–
= –
– =
–
=
–
CH CH CO ), 7.48 (d, 1H, N CH CH C ), 6.84 & 7.22 (d, 2H, N CH CH CH ),
8.08 & 7.10 (4H, first phenyl ring), 7.31 & 7.74 (4H, second phenyl ring), 7.87 & 7.38 (4H,
third phenyl ring), 7.61, 7.40, 7.32 (5H, fourth phenyl ring). Elemental analysis: calculated
for C36H33O4N: C, 79.55%; H, 6.07%; O, 11.78%; N, 2.57%; found: C, 79.49%; H, 5.91%; O,
11.73%; N, 2.49%.

148
V. S. SHARMA ET AL.
Scheme . Synthetic route of series- and series-.
... General procedure for the synthesis of (Series-)
The compound has been prepared by esterification of the appropriate Trans 4-n-alkoxy cin-
namic acid (A) (2.02 mmol) and chalcone (C) (0.246g, 2.02 mmol), dicyclohexylcarbodi-
imide (DCC) (0.457g, 2.22 mmol) and dimethylaminopyridine (DMAP) in catalytic amount
(0.002g, 0.2 mmol) in dry CH2Cl2 (DCM) (30 mL) was stirred at room temperature for 48h.
The slightly white precipitate of DCU is obtained which was isolated by filtration and dis-
carded, while the filtrate was evaporated to dryness. The resultant crude residue was purified
by column chromatography on silica gel eluting methanol: chloroform (1:4) [56].
C1 (series-2): IR (KBr): vmax/cm−1 2956 (C H str. of alkane), 1660 (C O str. of carbonyl
–
=
=
–
–
carbon of chalconyl group), 1608 (C C str. of alkene in chalcone), 1740 ( COO group),
=
–
–
1510, 1543 (C C str. of aromatic ring), 996 (C H bending of alkene), 1178 (C O str. of ether
1
–
–
=
–
linkage), 1288, 1246 (C O str. of carbonyl (>CO) group, 971 (trans, CH CH ) group. H-
NMR: 3.83 (t, 3H, CH3 of polymethylene OCH3), 7.62 & 6.32 (d, 2H, CH CH COO ),
–
–
–
=
–
–
– =
–
= –
– =
–
=
–
7.46 (d, 1H, N CH CH C ), 6.82 & 7.21 (d, 2H, N CH CH CH ), 6.86 & 7.61 (4H,
first phenyl ring), 7.20 & 7.71 (4H, second phenyl ring), 7.87 & 7.39 (4H, third phenyl ring),
7.57, 7.32, 7.31 (5H, fourth phenyl ring). Elemental analysis: calculated for C34H27O4N: C,
79.53%; H, 5.26%; O, 12.47%; N, 2.72%; found: C, 79.48%; H, 5.21%; O, 12.37%; N, 2.68%.
C2 (series-2): IR (KBr): vmax/cm−1 2952 (C H str. of alkane), 1660 (C O str. of carbonyl
–
=
=
–
–
carbon of chalconyl group), 1604 (C C str. of alkene in chalcone), 1750 ( COO group),
=
–
–
1510, 1541 (C C str. of aromatic ring), 997 (C H bending of alkene), 1172 (C O str. of ether
1
–
–
=
–
linkage), 1286, 1243 (C O str. of carbonyl (>CO) group, 972 (trans, CH CH ) group. H-
NMR: 1.32 (t, 3H, CH3 of polymethylene OC2H5), 4.06 (t, 2H, OCH2 CH2 of OC2H5),
–
–
–
–
–
–

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
149
–
=
–
–
– =
–
= –
7.61 & 6.31 (d, 2H, CH CH COO ), 7.47 (d, 1H, N CH CH C ), 6.83 & 7.20 (d, 2H,
– =
–
=
–
N CH CH CH ), 6.85 & 7.61 (4H, first phenyl ring), 7.21 & 7.70 (4H, second phenyl
ring), 7.86 & 7.39 (4H, third phenyl ring), 7.57, 7.32, 7.31 (5H, fourth phenyl ring). Elemental
analysis: calculated for C35H29O4N: C, 79.69%; H, 5.50%; O, 12.14%; N, 2.65%; found: C,
79.61%; H, 5.42%; O, 12.07%; N, 2.59%.
C4 (series-2): IR (KBr): vmax/cm−1 2951 (C H str. of alkane), 1650 (C O str. of carbonyl
–
=
=
–
–
carbon of chalconyl group), 1608 (C C str. of alkene in chalcone), 1760 ( COO group),
1510, 1543 ( C C str. of aromatic ring), 996 (C H bending of alkene), 1178 (C O str.
of ether linkage), 1288, 1246 (C O str. of carbonyl (>CO) group, 972 (trans, CH CH )
group, 770 polymethylene ( CH2 ) of OC4H9. H-NMR: 0.90 (t, 3H, CH3 of polymethy-
– =
–
–
=
–
–
–
–
1
–
–
–
–
–
–
–
–
= –
–
–
lene OC4H9), 1.45–1.76 (m, 4H, OC4H9), 4.06 (t, 2H, OCH2 CH2 of OC4H9), 7.61
–
=
–
–
– =
& 6.31 (d, 2H, CH CH COO ), 7.48 (d, 1H, N CH CH C ), 6.84 & 7.21 (d, 2H,
– =
–
=
–
N CH CH CH ), 6.85 & 7.61 (4H, first phenyl ring), 7.20 & 7.70 (4H, second phenyl
ring), 7.86 & 7.39 (4H, third phenyl ring), 7.56, 7.32, 7.31 (5H, fourth phenyl ring). Elemen-
tal analysis: calculated for C37H33O4N: C, 80.0%; H, 5.94%; O, 11.53%; N, 2.52%; found: C,
79.92%; H, 5.89%; O, 11.49%; N, 2.47%.
C12 (series-2): IR (KBr): vmax/cm−1 2954 (C H str. of alkane), 2842 (C H str. of (CH2 )n
–
–
–
–
–
=
=
group of OC12H25 alkyl chain, 1640 (C O str. of carbonyl carbon of chalconyl group),
–
–
=
1604 (C C str. of alkene in chalcone), 1730 ( COO group), 1510, 1543 (C C str. of aro-
–
–
–
matic ring), 996 (C H bending of alkene), 1178 (C O str. of ether linkage), 1288, 1246 (C O
–
=
–
–
–
str. of carbonyl (>CO) group, 972 (trans, CH CH ) group, 770 polymethylene ( CH2 )
of OC12H25. H-NMR: 0.90 (t, 3H, CH3 of polymethylene OC12H25), 1.29–1.76 (m, 20H,
OC12H25), 4.06 (t, 2H, OCH2 CH2 of OC12H25), 7.63 & 6.31 (d, 2H, CH CH COO ),
7.48 (d, 1H, N CH CH C ), 6.84 & 7.21 (d, 2H, N CH CH CH ), 6.86 & 7.61
(4H, first phenyl ring), 7.21 & 7.70 (4H, second phenyl ring), 7.87 & 7.39 (4H, third
phenyl ring), 7.57, 7.32, 7.31 (5H, fourth phenyl ring). Elemental analysis: calculated for
C45H49O4N: C, 80.95%; H, 7.34%; O, 9.59%; N, 2.09%; found: C, 80.89%; H, 7.18%; O, 9.47%;
N, 2.01%.
1
–
–
–
–
–
–
–
= –
–
–
=
–
–
– =
–
– =
–
=
–
3. Result and discussion
In the present study, we have synthesized 13 homologues of two series such as 4-(3-oxo-3-
(4-((3-phenylallylidene) amino) phenyl) prop-1-en-1-yl) phenyl 4-alkoxy benzoate (series-1)
and 4-(3-oxo-3-(4-((3-phenylallylidene) amino) phenyl) prop-1-en-1-yl) phenyl-3-(4-alkoxy
phenyl) acrylate (series-2) and their mesomorphic properties were studied by using differen-
tial scanning calorimetry (DSC) and polarizing optical microscopy (POM).
3.1. POM investigation
We have synthesized and studied the effect of a linking group as well as the effect of vary-
–
–
ing aliphatic alkyl chain length from small spacer ( OCH3) to the high spacer ( OC18H37)
with presence of four benzene rings as a central rigid core in present homologous series-
1 and series-2. In the present investigation, we have synthesized thirteen homologous (C1
to C8, C12, C14, C16, C18) in both series. All the compounds of both the series exhibit only
nematic mesophase on heating as well as cooling condition. In series-1, mesophase com-
mences from C3 homologue while in series-2, it commences from C4 homologue respectively.
Texture images of nematic phase were determined by using miscibility method (Table–1). The
transition temperature of series-1 and series-2 are shown in Table–2 and Table–3.

150
V. S. SHARMA ET AL.
Table . Texture of nematic phase of C, C, C, C by miscibility method.
Sr. No.
Homologue
Texture (Series-)
Texture (Series-)

C
C
C
C
Threaded
Rod-like
Rod-like
Schlieren
Threaded
Schlieren
Threaded
Schlieren



Table . Transition temperature in°C by POM (Series-).
Transition temperatures in°C
Sr. No.
R = n-alkyl group
Cr
Smectic
Nematic
Isotropic













C
C
C
C
C
C
C
C
C
C
C
C
C
·
·
·
·
·
·
·
·
·
·
·
·
·
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
·
—
—
—
—
—
.
.
.
.
.
.
.
.
.
.
.
.
.
·
·
·
·
·
·
·
·
·
·
·
·
·
.
.
.
.
.
.
.
.
.
.
.
—
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Table . Transition temperature in°C by POM (Series-).
Transition temperatures in°C
Sr. No.
R = n-alkyl group
Cr
Smectic
Nematic
Isotropic













C
C
C
C
C
C
C
C
C
C
C
C
C
·
·
·
·
·
·
·
·
·
·
·
·
·
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
·
—
—
—
—
—
—
—
.
.
.
.
.
.
.
.
.
.
.
.
.
·
·
·
·
·
·
·
·
·
·
·
·
·
.
.
.
.
.
.
.
.
.
.
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Homologous C1 and C2 from series-1 and C1 to C3 from series-2 directly passing through
isotropic condition without display mesophase due to the presence of short alkyl spacer on
left side chain causes high crystallinity tendency. The nonmesomorphicity of C1 to C2 from
Table . Relative thermal stability in°C.
Series
Series-
Series-
N-I
.°C
C
. to .
.°C
C
. to .
Commencement of nematic phase
Total temperature range of mesophase
C
C
C
C

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
151
Figure . Phase diagram of series-.
series-1 and C1 to C3 from series-2 is mainly attributed to the low magnitudes of intermolec-
ular dispersion forces and low magnitudes of dipole-dipole interactions leading to its high
crystallising tendency which causes abrupt breaking of crystal lattices due to unsuitable and
unfavourable magnitudes of anisotropic forces of intermolecular attractions. Thus, an irregu-
lar breaking of crystal lattices and suddenly takes place at relatively higher temperature. There-
fore, the crystalline solid state directly converted into isotropic phase without showing LC
phase. The phase diagram of both the series are given in Figure–1 and Figure–2.
–
–
A phase diagram (Figure–1) of a newly series-1 consisted of Cr N/I and N I transition
–
curves indicating the phase behaviours of series-1. The Cr N/I transition curve initially
falling up to C5 homologue and then continued with overall descending tendency up to last
C18 homologue. The Odd-even effect is present only in C5 to C7 homologues of series-1. It
–
can be noted that the Cr N/I transition curve decrease with increment of alkoxy group in
Figure . Phase diagram of series-.

152
V. S. SHARMA ET AL.
Figure . Photomicrograph of optical texture obtained for the nematic image of C8 at °C (series-); (b)
Photomicrograph of optical texture obtained for the nematic image of C10 at °C (series-).
–
the side chain except C6 homologue. Whereas in N I transition curve start decrease at C5
homologue and then rises at C7 homologue due to the presence of odd-even effect and then
continued decrease up to last C18 homologue of series-1. The plot of transition temperature
against the number of carbon atoms in the alkoxy group (Figure–2) shows a smooth falling
–
–
tendency for Cr N/I and N I transition curve throughout the series. No odd-even effect is
–
–
observed in Cr N/I and N I transition curve. It has observed that sematic mesophase is not
found in both the series. The exhibition of nematic phase in C3 to C18 (series-1) and C4 to C18
(series-2) is attributed to the suitable magnitudes of end to end intermolecular anisotropic
forces of attractions and closeness as a consequence of favourable molecular rigidity, linear-
ity due to the presence linking group and flexibility caused by the presence of left side chain
generate permanent dipole moment across the long molecular axis, suitable magnitudes of
dispersion forces and dipole-dipole interactions, molecular polarizability and polarity which
facilitate the molecules under microscopic study to float on the surface with statically parallel
orientational order within certain range of temperature as nematic phase [57].
The solid samples held between an untreated glass slide and a coverslip, which were heated
to their isotropic phase and cooled slowly. As shown in Figure 3a, a schlieren type nematic
texture pattern of compound C8 (series-1) seen at 136°C, while in compound C10 (series-2)
schlieren type nematic pattern seen at 138°C on cooling condition.
The changing trend in mesomorphic behaviours of series-1 is compared with structurally
similar analogous series-2, as mention in Figure–4. Both the series are identical with respect
to two linking group and four phenyl ring. The first linkage group in both the series are dif-
–
=
–
–
ferent. Presence of vinyl ester ( CH CH COO ) group in series-2 increases the molecular
–
–
length as compare to ester ( COO ) group of series-1. Thus, changing in molecular length,
permanent dipole moment across the long molecular axis, molecular rigidity or flexibility
due to presence of side alkoxy tail group, which may vary from changing to lower member
Figure . Structurally similar analogous series.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
153
Figure . Space filling diagram of (a) series-; (b) series-.
to higher member altering the magnitudes of mesomorphism. The presence of ester linkage
group between two phenyl rings plays a major role in the emergence of nematic mesophase.
It can be noted that the ester group increases the mobility and flexibility of particular parts of
liquid crystal molecule and hence affects the type of mesophase and its mesophase length. It
–
=
–
–
is observed that the presence of vinyl ester ( CH CH COO ) part of series-2 increases the
–
–
mesophase thermal stability as compare to ester ( COO ) part of series-1.
The space-filling diagram is mention in Figure 5, which indicate energy minimise in both
series-1 and series-2 respectively. The molecular length of series-2 is higher than series-1 due
–
=
–
to the presence of ethylene ( CH CH ) group in cinnamate linkage. Therefore they differ
with respect to each other with combined effects of molecular rigidity and flexibility, including
intermolecular distance and molecular polarizability, which operates LC behaviours of series.
–
=
–
Addition of double bond ( CH CH ) in the system increases the polarizability and length
of the molecule which was disclosed by the Gray et al. [58].
3.2. Thermal stability and temperature range of mesophase
Table 4 represents some thermometric data of series-1 and series-2 in a comparative manner.
Thermal stability of series-1 is lesser than series-2, while nematic mesophase commences early
in series-1 as compare to series-2. Temperature range of mesophase is in increasing order of
lower to a higher homologue of series-1 and series-2. The early or late commencement of
mesophase depends upon the extent of molecular non-co-planarity caused by central linkage
group and their magnitudes of polarity as well as polarizability.
3.3. Propose mechanism
Figure–6 indicates the proposed mechanism of arrangement of molecules to display nematic
phase in both the series-1 and series-2, which contains three linkage group and left side alkoxy
tail group. Thus, on heating condition, the molecules are randomly oriented in all possible
directions with the high order of disorder or high entropy in a reversible manner.
3.4. DSC analysis
The thermal behaviour of newly synthesized homologues of series-1 and series-2 were exam-
ined by using DSC measurement. In Figure–7, homologue C7 shows one endothermic peak at

154
V. S. SHARMA ET AL.
Figure . Propose model of molecular arrangement of nematic phase.
146.2°C in the heating cycle, which indicates the presence of nematic phase. That was further
confirmed by POM analysis. While on cooling condition, the exothermic peak observed at
142.1°C. Compound C18 shows first endothermic peak at 101.2°C during the heating cycle,
while in cooling cycle, it appears at 108.2°C, which was further confirmed by POM analysis
which indicates the nematic mesophase appeared in an enantiotropically manner. Compound
C12 exhibits an endothermic peak at 126.1°C on heating cycle which reveals with POM study.
On the cooling cycle, exothermic peak observed at 125.2°C. Compound C6 shows endother-
mic peak at 156.2°C that indicates the presence of crystal to the nematic phase transition,
Figure . DSC thermograms of compound (a) C (series-); (b) C (series-); (c) C (series-); (d) C (series-).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
155
Table . Transition temperature (°C) and enthalpy (J g−) and entropy change (J g−k−) by DSC
measurement.
Homologues
or Comp.
Heating
scan(°C)
Cooling
scan(°C)
Transition
ꢀH (-Jg−
)
ꢀH (Jg−
)
ꢀS(J g−k−
)
ꢀS(J g−k−
)
–
C7
Cr N
.
>
.
>
.
>
.
>
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
.
—
–
N I
(series-2)
C18
–
Cr N
–
(series-1)
C12
(series-1)
C6
(series-2)
N I
–
Cr N
–
N I
–
Cr N
–
N I
it traces again on cooling condition, and the single peak was traced at 154.3°C, which was
further confirmed by POM analysis.
The phase transition temperatures and the value of enthalpy and entropy were measured by
carrying out DSC thermal analysis. The phase transition temperatures, enthalpy and entropy
values for the present synthesized series-1 and series-2 are summarized in Table–5. Molecules
of every homologue randomly oriented in all possible directions with a high order of disor-
=
der or entropy (ꢀS ꢀH/T) beyond isotropic temperature and the enthalpy value (ꢀH). But,
at cooled condition, the same from and below isotropic temperature, the mesophase is per-
sisted to appear reversibly at the lower temperature at observed during heating condition. The
mesophase obtained in this present series is enantiotropically nematogenic.
4. Conclusion
A two new homologous series of ester (series-1) and vinyl ester (series-2) containing chalcone
and allylidene amino derivatives having terminal left alkoxy chains (n = 1 to 8, 10, 12, 14, 16,
18) has been synthesized. The lower member C1 to C2 (series-1) and C1 to C3 (series-2) shows
nonmesomorphic behavior while higher members of both the series exhibited enantiotropic
nematic mesophase transition with good thermal stabilities.
Acknowledgement
Authors acknowledge thanks to Dr. R. R. Shah, principal and management of K. K. Shah Jarodwala Man-
inagar Science College, Ahmedabad. Authors are also thankful to NFDD Centre for providing analytical
and spectral services.
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