The effect of position of octadecyloxy tail on the formation of liquid crystal with chalconyl-ester and chalconyl-vinyl ester series: Comparison with corresponding linkage group

Article abstract of DOI:10.1080/15421406.2016.1272222

Two series of chalconyl-based liquid crystals which differ from each other in the position of the first linking group have been synthesized and characterized by elemental analyses and spectroscopic techniques such as Fourier transform infrared and proton magnetic resonance magnetic resonance [¹H NMR] spectroscopy. The mesomorphic properties of these compounds were observed by optical polarized light microscopy (POM) and differential scanning calorimetry (DSC). We have synthesized two homologous series viz. 3-(3-(4-(Octadecyloxy) phenyl) acrylonyl) phenyl 3-(4-n-alkoxyphenyl) acrylate (series-1) and 3-(3-(4-(Octadecyloxy) phenyl) acryloyl) phenyl 4-n-alkoxy benzoate (series-2). Series-1 has chalconyl-ester central linkage group while in series-2 chalconyl-vinyl ester group is present and tail octadecyloxy side chain is common in both homologous series. All the homologous in present series display LC property in enantiotropical manner except first three homologous in both series.

Full text of DOI:10.1080/15421406.2016.1272222

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
The effect of position of octadecyloxy tail on the
formation of liquid crystal with chalconyl-ester
and chalconyl-vinyl ester series: Comparison with
corresponding linkage group
R. B. Solanki, Vinay. S. Sharma & R. B. Patel
To cite this article: R. B. Solanki, Vinay. S. Sharma & R. B. Patel (2017) The effect of position of
octadecyloxy tail on the formation of liquid crystal with chalconyl-ester and chalconyl-vinyl ester
series: Comparison with corresponding linkage group, Molecular Crystals and Liquid Crystals,
643:1, 216-232, DOI: 10.1080/15421406.2016.1272222
To link to this article: http://dx.doi.org/10.1080/15421406.2016.1272222
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Date: 23 February 2017, At: 21:43

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –
http://dx.doi.org/./..
The effect of position of octadecyloxy tail on the formation of
liquid crystal with chalconyl-ester and chalconyl-vinyl ester
series: Comparison with corresponding linkage group
R. B. Solanki, Vinay. S. Sharma, and R. B. Patel
Chemistry Department, K. K. Shah Jarodwala Maninagar Science College, Gujarat University, Ahmedabad,
Gujarat, India
ABSTRACT
KEYWORDS
Liquid crystal; chalcone;
smectic; nematic;
enantiotropy
Two series of chalconyl-based liquid crystals which differ from each
other in the position of the first linking group have been synthesized
and characterized by elemental analyses and spectroscopic techniques
such as Fourier transform infrared and proton magnetic resonance
magnetic resonance [1H NMR] spectroscopy. The mesomorphic prop-
erties of these compounds were observed by optical polarized light
microscopy (POM) and differential scanning calorimetry (DSC). We
have synthesized two homologous series viz. 3-(3-(4-(Octadecyloxy)
phenyl) acrylonyl) phenyl 3-(4-n-alkoxyphenyl) acrylate (series-1) and
3-(3-(4-(Octadecyloxy) phenyl) acryloyl) phenyl 4-n-alkoxy benzoate
(series-2). Series-1 has chalconyl-ester central linkage group while in
series-2 chalconyl-vinyl ester group is present and tail octadecyloxy
side chain is common in both homologous series. All the homologous
in present series display LC property in enantiotropical manner except
first three homologous in both series.
GRAPHICAL ABSTRACT
CONTACT R. B. Solanki
ravindrasolanki@gmail.com; Vinay S. Sharma
Department, K. K. Shah Jarodwala Maninagar Science College, Gujarat University, Ahmedabad , Gujarat, India.
vinaysharm@gmail.com
Chemistry
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

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
217
1. Introduction
Liquid crystals are matter in a state that has properties between those of conventional liquid
and solid crystals. For instance, a liquid crystal may flow like a liquid, but its molecules
may orient in a crystal like way [1–4]. 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. Presently, we have
focus on thermotropic liquid crystals in which, phase transition into liquid crystal phase as
temperature changed [5–10]. Liquid crystals in the nematic group are most commonly used
in the production of liquid crystal displays (LCD) due to their unique physical properties
and wide temperature range [10–14]. In the nematic phase, liquid crystal molecules are
oriented on average along a particular direction. By applying an electric or magnetic field,
the orientation of the molecules can be derived in a probable approach [15–18]. Yelamaggad
et al. reported the bent-core unsymmetrical dimers in which cholesteryl ester and chalconyl
moiety are present, which enhances the biaxiality and chirality of the system [19].
A number of chalcone having reported to exhibit a broad spectrum of anti-bacterial, anti-
fungal, antiulcer, antimalarial, antitumor, anticancer, anti-inflammatory, antitubercular. The
–
=
–
–
presence of α, β-unsaturated functional group in chalcone ( CH CH CO ) is responsi-
ble for anti-microbial activity, which can be altered depending upon the type of substituent
present on the aromatic rings [20–24]. Thus, the objective of the work is to synthesize and
study the effect of chalconyl-ester linkage group and geometrical shape on mesomorphism.
Vorlander and Dtsch reported bent-core liquid crystals and reported their mesogenic prop-
erties [25]. Matsunaga and Miyamoto reported first time on a series of bent-core molecule,
as 1,3-phenylene bis[4-(4-n-octyloxyphenyliminomethyl) benzoate] derivatives [26]. In 1996,
Niori et al. reported on ferro electricity in a smectic phase formed by bent-shaped Schiff base
derivatives in an achiral mesogens [27]. Gorecka et al. reported that chiral nonlinear optic
effect shown in achiral bent-core molecules is due to interaction between polarity and chiral-
ity [28]. Ros et al. studied that the banana-shaped mesophase synthesization is based on the
appropriate combination between rigid bent-core units with terminal side chain [29]. Subala
et al. reported that the same homologous series with the same core and increasing number
of chain length is responsible in the contribution of the phase sequence B6-B1-B2 [30]. Many
series of liquid crystalline compounds containing heterocyclic groups have been synthesized
due to their usefulness in wide application electrical, optical, biological, and medical field
[31,32]. Gopalakrishnan et al. reported chalcone-based single crystals, growth, and compar-
ison of two new enone shifted chalcones and their NLO behavior [33]. Tandel et al. studied
the chain chalconyl polymers compound to exhibiting threaded-type nematic phases [34].
Vinyl esters linkage group have been well known for last decades of years, Vora et al. [35]
reported that binary mixtures of cinnamate esters exhibit a wide range of smectic and nematic
mesophase. Doshi et al. reported homologous series based on chalconyl vinyl ester linkage
group [36–40]. Sadashiva et al. [41] reported the synthesis and mesomorphic properties of
some ester of trans-4-n-alkoxy cinnamic acid and trans-4-n-alkoxy-α-methyl cinnamic acid
with branched chain alkyl tails exhibiting ferroelectric and anti-ferroelectric phases. Prajapati
et al. studied [42,43] some homologous series consisted of cinnamate linkage group and show
its effect on mesomorphic properties of liquid crystalline compounds. The ethylene unit is
connecting one part of rigid core with another in calamatic mesogenic molecules.
In this present article, an attempt has been made to synthesize two nonlinear homologous
=
–
–
=
–
series-1 and series-2. Series-1 has –CH CH COO and –CO CH CH linkage group and
–
–
=
–
–
series-2 has –COO and –CO CH CH linkage group. However, the terminal ( OC18H37)

218
R. B. SOLANKI ET AL.
group is same in both the present homologous series. Here, in the present study, we compare
the effect of linkage group on LC behavior, thermal stability, mesophase length, and com-
mencement of mesophase in present article. Recently, our group reported isomeric and non-
isomeric chalconyl ester linking group-based homologous series [44–46]. Group efficiency
order and structure relation with mesomorphism will be derived.
2. Experimental
2.1. General
For the synthesis of target chalconyl-ester homologous series, the following materials were
used: 4-hydroxy benzoic acid, 4-hydroxy benzaldehyde, Alkyl halides (Lancaster, England),
Anhydrous K2CO3, 3-hydroxy acetophenone was purchased from (SRL, India), DCC (Dicy-
clohexyl carbodimide) was purchased from Fluka Chemie (Switzerland), Dimethyl amino
pyridine DMAP (4,4ꢀ-dimethylamino pyridine) was obtained from Finar chemicals (India),
Dichloro methane, Ethanol, Acetone required for synthesis were used as received except sol-
vents that were dried and distilled prior to use. The molecular structures of the target prod-
ucts and the intermediates were confirmed by spectroscopic analysis and elemental analysis.
Representative homologous series were characterized by elemental analysis, Infrared spec-
troscopy, 1H NMR spectra. IR spectra were recorded by Perkin-Elmer spectrum GX, 1HNMR
spectra were recorded on Bruker using CDCl3 as solvent. Microanalysis was performed on
Perkin-Elmer PE 2400 CHN analyzer. Texture image of some homologous for nematic phase
was determined by miscibility method. Transition temperature and LC properties (Textures)
were determined using an optical polarizing microscopy equipped with heating stage and
digital camera. Decomposition temperatures were determined by using Shimadzu (DSC)
differential Scanning Calorimeter with a heating rate of 5°C to 10.0°C min−1. Thermody-
namic quantities enthalpy (ꢀH) and entropy (ꢀS = ꢀH/T) are qualitatively discussed. The
mesophase and transition temperatures and enthalpies for all chalconyl-ester-based liquid
crystals were determined by differential scanning calorimetry (DSC) and polarizing optical
microscopy (POM).
2.2. Synthesis of series-1 and series-2 compounds
... Synthesis of -n-alkoxy benzoic acid (C) and -n-alkoxy cinnamic acid (A)
4-n-alkoxy benzoic acid and 4-n-alkoxy cinnamic acid were prepared by method reported by
Dave and Vora [47].
... Synthesis of -n-alkoxy benzaldehyde
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 [48].
... Synthesis of -(-hydroxyphenyl)--(-(octadecyloxy)phenyl)prop--en--one (B)
Chalcone (B) was prepared by usual established method [49]. (Yield: 72%, m.p. 86°C, IR
(KBr): vmax/ cm−1 3390 (-OH str.-bonded), 3079–3120 ( CH str. aliphatic alkyl group), 1660
–
– =
– = –
–
( C O, group), 1580–1620 ( C C ) aromatic, 1205–1280 ( OCH2- ether linkage), 960
(Trans alkene), 750–780 (-meta substituted phenyl ring).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
219
... General procedure for the synthesis of α--(ꢀ-n-alkoxy-cinnamoyloxy)
benzoyl-β-ꢀꢀ-octadecyloxy phenyl ethylene (series-)
The chalconyl ester based compound which had been prepared by the esterification of
the appropriate 4-n-alkoxy cinnamic acid (A) (2.02 mmol) and chalcone (C) (0.246 g,
2.02 mmol), dicyclohexyl carbodiimide (DCC) (0.457 g, 2.22 mmol), and dimethylaminopy-
ridine (DMAP) in catalytic amount (0.002 g, 0.2 mmol) in dry CH2Cl2 (DCM) (30 mL) was
stirred at room temperature for 48 hr. The white precipitate of DCU was obtained, which
was isolated by filtration and discarded, while the filtrate was evaporated to dryness. The
resultant crude residue was purified by column chromatography on silica gel eluting with
dichloromethane, recrystallization from methanol: chloroform as eluent (2:3) until constant
transition temperatures were observed [50].
C5 (Series-1): IR (KBr): vmax/cm−1 740 Polymethylene group of ( CH2-)n of −OC5H11,
–
–
–
– – –
648 Polymethylene group of ( CH2-)n of OC18H37, 810( C H def. m di-substituted), 972
– – –
– – –
– –
– =
( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1230, 1157 ( C O str in −(CH2)n
– – –
– = –
chain, 1381 and 1442 ( C H def. in CH2), 1504 ( C C )str, 1658 ( C O group), 1724
–
–
– –
–
=
–
( COO ester group), 2854 and 2924( C H str in CH3), 972 (trans, CH CH ) group,
1H NMR (CDCl3): 0.88–0.90 (t, J = 7.2 Hz, 6H, CH3 of –OC5H11 and –OC18H37),
–
–
–
1.26 (m, n-poly methylene groups of OC18H37), 1.31 (q, 8H, CH2 of –OC5H11 and
–OC18H37), 1.29 (P, J = 8.1 Hz, 10 H of −OC5H11 and –OC18H37 group), 1.75 (m, n-
–
–
–
poly methylene groups of –OC5H11), 3.5–3.6 (s, OCH2 CH2-of OC18H37), 4.06 (t, J =
– –
–
–
6.1 Hz, 6H, O CH2 CH2- of –OC5H11 and OC18H37), 7.54–7.56 (d, J = 15.6 Hz, 1H,
–
–
=
–
–
–
=
–
CO CH CH ), 8.30–8.32 (d, J = 15.6 Hz, 1H, CO CH CH ), 7.62–7.64 (d, J =
–
=
–
–
–
=
–
–
15.2 Hz, 1H, CH CH COO ), 6.30 (d, J = 15.2 Hz, 1H, CH CH COO ), 6.94–6.91
and 7.60–7.62 (d, J = 8.2 Hz, 4H, left side phenyl ring), 7.71 and 8.56, 8.41 (d, J = 7.8 Hz, 4H,
central phenyl ring), 7.61 and 6.95–6.92 (d, J = 8.4 Hz, 4H, terminal phenyl ring), elemental
analysis: calculated for C47H62O5: C, 79.88; H, 8.78; O, 11.33; found: 79.82; H, 8.70; O,
11.24%.
C7 (Series-1): IR (KBr): vmax/cm−1 740 Polymethylene group of ( CH2-)n of –OC7H15,
–
–
–
– – –
648 Polymethylene group of ( CH2-)n of OC18H37, 810( C H def. m di-substituted),
– – – – – – – –
972 ( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1230, 1157 ( C O str in
– – –
– = –
– =
–(CH2)n chain, 1381 and 1442 ( C H def. in CH2),1504 ( C C )str, 1658 ( C O group),
–
–
– –
–
=
–
1724 ( COO ester group), 2854 and 2924( C H str in CH3), 972 (trans, CH CH )
1
–
group, H NMR (CDCl3): 0.88–0.90 (t, J = 7.2 Hz, 6H, CH3 of –OC7H15 and –OC18H37),
–
–
1.26 (m, n-poly methylene groups of OC18H37), 1.31 (q, 8H, CH2 of –OC7H15 and
–OC18H37), 1.29 (P, J = 8.1 Hz, 10 H of –OC7H15 and –OC18H37 group), 1.75 (m, n-
–
–
–
poly methylene groups of –OC7H15), 3.5–3.6 (s, OCH2 CH2- of OC18H37), 4.06 (t, J =
– –
–
–
7.6 Hz, 6H, O CH2 CH2- of –OC7H15 and OC18H37), 7.54–7.56 (d, J = 15.6 Hz, 1H,
–
–
–
=
–
–
–
–
=
–
CO CH CH ), 8.30–8.32 (d, J = 15.6 Hz, 1H, CO CH CH ), 7.62–7.64 (d, J = 15.2 Hz,
=
–
–
=
–
–
1H, CH CH COO ), 6.30 (d, J = 15.2 Hz, 1H, CH CH COO ), 6.94–6.91 and 7.60–
7.62 (d, J = 8.2 Hz, 4H, left side phenyl ring), 7.71 and 8.56, 8.42 (d, J = 7.6 Hz, 4H, central
phenyl ring), 7.60–7.61 and 6.95–6.92 (d, J = 8.4 Hz, 4H, terminal phenyl ring), elemental
analysis: calculated for C44H58O5: C, 79.89; H, 9.23; O, 10.86; found: 79.12; H, 9.10; O,
10.80%.
C1 (Series-1): IR (KBr): vmax/cm−1 740 Polymethylene group of ( CH2-)n of –OCH3,
–
–
–
– – –
648 Polymethylene group of ( CH2-)n of OC18H37, 810( C H def. m di-substituted), 972
– – – – – – – –
( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1230, 1157 ( C O str in –(CH2)n
– – – – =
– = –
chain, 1381 and 1442 ( C H def. in CH2), 1504–1560 ( C C )str, 1658 ( C O group),

220
R. B. SOLANKI ET AL.
–
–
– –
–
=
–
1730 ( COO ester group), 2854 and 2990 ( C H str in CH3), 932 (trans, CH CH )
1
–
group, H NMR (CDCl3): 0.88–0.90 (t, J = 7.2 Hz, 6H, CH3 of –OCH3 and –OC18H37), 1.26
–
–
(m, n-poly methylene groups of OC18H37), 1.31 (q, 8H, CH2 of –OC5H11 and –OC18H37),
1.29 (P, J = 8.1 Hz, 10 H of –OCH3 and –OC18H37 group), 1.75 (m, n-poly methylene groups
–
–
–
– –
–
of –OCH3), 3.5–3.6 (s, OCH2 CH2- of OC18H37), 4.06 (t, J = 7.6 Hz, 6H, O CH2 CH2-
–
–
–
=
–
of –OCH3 and OC18H37), 7.54–7.56 (d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.32 (d,
–
–
=
–
–
=
–
–
J = 15.6 Hz, 1H, CO CH CH ), 7.62–7.64 (d, J = 15.2 Hz, 1H, CH CH COO ), 6.30
–
=
–
–
(d, J = 15.2 Hz, 1H, CH CH COO ), 6.94–6.91 and 7.60–7.62 (d, J = 8.2 Hz, 4H, left side
phenyl ring), 7.71 and 8.56, 8.41 (d, J = 7.6 Hz, 4H, central phenyl ring), 7.61 and 6.95–6.92
(d, J = 8.4 Hz, 4H, terminal phenyl ring), elemental analysis: calculated for C43H56O5: C,
79.14; H, 8.58; O, 12.26; found: 79.04; H, 8.51; O, 12.20%.
C2 (Series-1): IR (KBr): vmax/cm−1 740 Polymethylene group of ( CH2-)n of –OC2H5,
–
–
–
– – –
648 Polymethylene group of ( CH2-)n of OC18H37, 810( C H def. m di-substituted), 972
– – – – – – – –
( C H def. hydrocarbon), 1044 ( C O ) str, 1381 and 1234, 1158 ( C O str in –(CH2)n
– – –
– = –
– =
chain, 1381 and 1450 ( C H def. in CH2), 1510 ( C C )str, 1658 ( C O group), 1740
1
–
–
– –
–
=
–
( COO ester group), 2854 and 2991( C H str in CH3), 962 (trans, CH CH ) group, H
–
NMR (CDCl3): 0.88–0.90 (t, J = 7.1 Hz, 6H, CH3 of –OC2H5 and –OC18H37), 1.26 (m,
–
–
n-poly methylene groups of OC18H37), 1.31 (q, 8H, CH2 of –OC2H5 and –OC18H37), 1.29
(P, J = 8.1 Hz, 10 H of –OC2H5 and –OC18H37 group), 1.75 (m, n-poly methylene groups of
–
–
–
– –
–
–OC18H37), 3.5–3.6 (s, OCH2 CH2- of OC18H37), 4.06 (t, J = 7.6 Hz, 6H, O CH2 CH2-
–
–
–
=
–
of –OC2H5 and OC18H37), 7.54–7.56 (d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.32 (d,
–
–
=
–
–
=
–
–
J = 15.6 Hz, 1H, CO CH CH ), 7.62–7.64 (d, J = 15.2 Hz, 1H, CH CH COO ), 6.30
–
=
–
–
(d, J = 15.2 Hz, 1H, CH CH COO ), 6.94–6.90 and 7.60–7.62 (d, J = 8.2 Hz, 4H, left side
phenyl ring), 7.71 and 8.56, 8.42 (d, J = 7.6 Hz, 4H, central phenyl ring), 7.61 and 6.95–6.92
(d, J = 8.4 Hz, 4H, terminal phenyl ring), elemental analysis: calculated for C44H58O5: C,
79.27; H, 8.70; O, 12.01; found: 79.21; H, 8.62; O, 11.90%.
C12 (Series-1): IR (KBr): vmax/cm−1 740 Polymethylene group of ( CH2-)n of –OC12H25,
–
–
–
– – –
648 Polymethylene group of ( CH2-)n of OC18H37, 810( C H def. m di-substituted), 972
– – – – – – – –
( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1230, 1157 ( C O str in –(CH2)n
– – –
– = –
– =
chain, 1381 and 1442 ( C H def. in CH2), 1504 ( C C )str, 1658 ( C O group), 1724
1
–
–
– –
–
=
–
( COO ester group), 2854 and 2924 ( C H str in CH3), 972 (trans, CH CH ) group, H
–
NMR (CDCl3): 0.88–0.90 (t, J = 6.2 Hz, 6H, CH3 of –OC12H25 and –OC18H37), 1.26 (m,
–
–
n-poly methylene groups of OC18H37), 1.31 (q, 8H, CH2 of –OC12H25 and –OC18H37), 1.29
(P, J = 8.1 Hz, 10 H of –OC12H25 and –OC18H37 group), 1.75 (m, n-poly methylene groups of
–
–
–
– –
–
–OC12H25), 3.5–3.6 (s, OCH2 CH2- of OC18H37), 4.06 (t, J = 7.6 Hz, 6H, O CH2 CH2-
–
–
–
=
–
of –OC5H11 and OC18H37), 7.54–7.56 (d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.31 (d,
–
–
=
–
–
=
–
–
J = 15.4 Hz, 1H, CO CH CH ), 7.62–7.64 (d, J = 15.2 Hz, 1H, CH CH COO ), 6.30
–
=
–
–
(d, J = 15.2 Hz, 1H, CH CH COO ), 6.94–6.91 and 7.60–7.62 (d, J = 8.2 Hz, 4H, left side
phenyl ring), 7.71 and 8.56, 8.41 (d, J = 7.6 Hz, 4H, central phenyl ring), 7.61 and 6.95–6.92
(d, J = 8.4 Hz, 4H, terminal phenyl ring), elemental analysis: calculated for C54H78O5: C,
80.39; H, 9.67; O, 9.67; found: 80.30; H, 9.58; O, 9.62%.
C14 (Series-1): IR (KBr): vmax/cm−1 740 Polymethylene group of ( CH2-)n of –OC14H29,
–
–
–
– – –
648 Polymethylene group of ( CH2-)n of OC18H37, 812 ( C H def. m di-substituted), 972
– – – – – – – –
( C H def. hydrocarbon), 1064 ( C O ) str, 1281 and 1230, 1159 ( C O str in –(CH2)n
– – –
– = –
– =
chain, 1381 and 1440 ( C H def. in CH2), 1534 ( C C )str, 1650 ( C O group), 1734
–
–
– –
–
=
–
( COO ester group), 2854 and 2921 ( C H str in CH3), 962 (trans, CH CH ) group,
1
–
H NMR (CDCl3): 0.88–0.90 (t, J = 7.2 Hz, 6H, CH3 of –OC5H11 and –OC18H37), 1.26
–
–
(m, n-poly methylene groups of OC18H37), 1.31 (q, 8H, CH2 of –OC5H11 and –OC18H33),

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
221
1.29 (P, J = 8.1 Hz, 10 H of –OC14H11 and –OC18H37 group), 1.75 (m, n-poly methylene groups
– –
–
–
–
–
of –OC5H11), 3.5–3.6 (s, OCH2 CH2- of OC16H33), 4.06 (t, J = 7.6 Hz, 6H, O CH2 CH2-
–
–
–
=
–
of –OC14H29 and OC18H37), 7.54–7.56 (d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.32 (d,
–
–
=
–
–
=
–
–
J = 15.6 Hz, 1H, CO CH CH ), 7.62–7.64 (d, J = 15.2 Hz, 1H, CH CH COO ), 6.32
–
=
–
–
(d, J = 15.1 Hz, 1H, CH CH COO ), 6.94–6.91 and 7.60–7.62 (d, J = 8.2 Hz, 4H, left side
phenyl ring), 7.71 and 8.56, 8.41 (d, J = 7.4 Hz, 4H, central phenyl ring), 7.60–7.61 and 6.95–
6.92 (d, J = 8.4 Hz, 4H, terminal phenyl ring), elemental analysis: calculated for C56H82O5: C,
80.57; H, 9.83; O, 9.59; found: 80.12; H, 9.78; O, 9.50%.
... General procedure for the synthesis of α--(ꢀ-n-alkoxy benzoyloxy)
benzoyl-β-ꢀꢀ-octadecyloxy phenyl ethylene (series-)
The chalconyl ester based compound which had been prepared by the esterification of the
appropriate 4-n-alkoxy benzoic acid (A) (2.02 mmol) and chalcone (C) (0.246 g, 2.02 mmol),
dicyclohexylcarbodiimide (DCC) (0.457 g, 2.22 mmol) and dimethylaminopyridine (DMAP)
in catalytic amount (0.002 g, 0.2 mmol) in dry CH2Cl2 (DCM) (30 mL) was stirred at room
temperature for 48 hr. The white precipitate of DCU is obtained, which was isolated by
filtration and discarded, while the filtrate was evaporated to dryness. The resultant crude
residue was purified by column chromatography on silica gel eluting with dichloromethane,
recrystallization from methanol: chloroform (2:3) until constant transition temperatures were
observed [50].
C5 (Series-2): IR (KBr): vmax/cm−1 731 Polymethylene group of ( CH2-)n of –OC5H11,
– – –
–
–
–
648 Polymethylene group of ( CH2-)n of OC18H37, 810( C H def. m di-substituted), 970
– – – – – – – –
( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1230, 1157 ( C O str in –(CH2-)n
– – –
– = –
– =
chain, 1381 and 1442 ( C H def. in CH2), 1504–1510 ( C C )str, 1650 ( C O group),
1730 ( COO ester group), 2854 and 2924 ( C H str in CH3), 940 (trans, CH CH ) group,
–
–
– –
–
=
–
1
–
H NMR (CDCl3): 0.88–0.90 (t, J = 7.8 Hz, 6H, CH3 of –OC5H11 and –OC18H37), 1.26–1.29
–
(m, 28H, CH2 of –OC5H11 and –OC18H37), 1.76 (m, n-poly methylene groups of –OC5H11
–
–
and OC18H37), 1.43 (t, J = 7.1 Hz, 3H, OC18H37), 1.31 (q, J = 7.6 Hz, 4H, –OC5H11 and
–
– –
–
–
–
OC18H37), 4.06 (t, J = 7.6 Hz, 6H, O CH2 CH2- of –OC5H11 and OC18H37), 7.54–7.56
–
–
=
–
–
=
–
(d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.32 (d, J = 15.6 Hz, 1H, CO CH CH ),
7.14–8.12 (d, J = 8.4 Hz, 4H, left side phenyl ring), 7.67–7.82, 8.01 (d, J = 8.2 Hz, 4H,
central phenyl ring), 6.95–7.64 (d, J = 7.8 Hz, 4H, terminal phenyl ring), elemental analysis:
calculated for C45H62O5: C, 79.17; H, 9.99; O, 11.73; found: C, 79.12; H, 8.90; O, 11.72%.
C8 (Series-2): IR (KBr): vmax/cm−1 728 Polymethylene group of ( CH2-)n of –OC8H17,
–
–
–
– – –
647 Polymethylene group of ( CH2-)n of OC18H37, 812 ( C H def. m di-substituted),
– – – – – – – –
971 ( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1230, 1157 ( C O str in
– – –
– = –
–(CH2-)n chain, 1381 and 1442 ( C H def. in CH2), 1508–1510 ( C C )str, 1650
– =
–
–
– –
( C O group), 1730 ( COO ester group), 2850 and 2990 ( C H str in CH3), 960
1
–
=
–
–
(trans, CH CH ) group, H NMR (CDCl3): 0.88–0.90 (t, J = 7.8 Hz, 6H, CH3 of
–
–OC8H17 and –OC18H37), 1.26–1.29 (m, 32H, CH2 of –OC8H17 and –OC18H37), 1.76
–
(m, 4H, n-poly methylene groups of –OC8H17 and OC18H37), 1.43 (t, J = 7.1 Hz, 3H,
–
– –
–
–
OC18H37), 4.06 (t, J = 7.6 Hz, 6H, O CH2 CH2- of –OC8H17 and OC18H37), 7.54–7.56
–
–
=
–
–
–
=
–
(d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.32 (d, J = 15.6 Hz, 1H, CO CH CH ),
7.14–8.12 (d, J = 8.4 Hz, 4H, left side phenyl ring), 7.67–7.82, 8.01 (d, J = 8.2 Hz, 4H,
central phenyl ring), 6.94–7.64 (d, J = 7.8 Hz, 4H, terminal phenyl ring), elemental anal-
ysis: calculated for C48H68O5: C, 79.55; H, 9.39; O, 11.04; found: C, 79.48; H, 9.34; O,
10.94%.

222
R. B. SOLANKI ET AL.
C10 (Series-2): IR (KBr): vmax/cm−1 718 Polymethylene group of ( CH2-)n of –OC10H21,
–
–
–
– – –
646 Polymethylene group of ( CH2-)n of OC18H37, 810( C H def. m di-substituted),
– – – – – – – –
971 ( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1230, 1157 ( C O str in
– – –
– = –
– =
–(CH2-)n chain, 1381 and 1442 ( C H def. in CH2), 1510 ( C C )str, 1630 ( C O
–
–
– –
group), 1730 ( COO of ester group), 2834 and 2984 ( C H str in CH3), 960 (trans,
1
–
=
–
–
CH CH ) group, H NMR (CDCl3): 0.88–0.90 (t, J = 7.8 Hz, 6H, CH3 of –OC10H21
–
and –OC18H37), 1.26–1.29 (m, 36H, CH2 of –OC10H21 and –OC18H37), 1.76 (m, 4H,
–
–
n-poly methylene groups of –OC10H21 and OC18H37), 1.43 (t, J = 7.2 Hz, 6H, OC18H37),
– –
–
–
4.06–4.10 (t, J = 7.6 Hz, 6H, O CH2 CH2- of –OC10H21 and OC18H37), 7.54–7.56
–
–
=
–
–
–
=
–
(d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.32 (d, J = 15.6 Hz, 1H, CO CH CH ),
7.14–8.12 (d, J = 8.4 Hz, 4H, left side phenyl ring), 7.66–7.82, 8.01 (d, J = 8.2 Hz, 4H,
central phenyl ring), 6.95–7.64 (d, J = 7.8 Hz, 4H, terminal phenyl ring), elemental anal-
ysis: calculated for C50H72O5: C, 79.78; H, 9.57; O, 10.25; found: C, 79.72; H, 9.48; O,
10.18%.
C12 (Series-2): IR (KBr): vmax/cm−1 722 Polymethylene group of ( CH2-)n of –OC12H25,
–
–
–
– – –
648 Polymethylene group of ( CH2-)n of OC18H37, 812 ( C H def. m di-substituted), 970
– – – – – – – –
( C H def. hydrocarbon), 1064 ( C O ) str, 1381 and 1281, 1157 ( C O str in –(CH2-)n
– – –
– = –
– =
chain, 1381 and 1442 ( C H def. in CH2), 1504–1510 ( C C )str, 1630 ( C O group),
1740 ( COO , of ester group), 2854 and 2924 ( C H str in CH3), 940 (trans, CH CH )
–
–
– –
–
=
–
1
–
group, H NMR (CDCl3): 0.88–0.90 (t, J = 7.8 Hz, 6H, CH3 of –OC12H25 and –OC18H37),
–
1.26–1.29 (m, 40H, CH2 of –OC12H25 and –OC18H37), 1.76 (m, 4H, n-poly methylene
–
–
–
groups of –OC12H25 and OC18H37), 1.42 (t, J = 7.2 Hz, 6H, OC12H25 and OC18H37), 1.31
–
– –
–
(q, J = 7.6 Hz, 4H, –OC12H25 and OC18H37), 4.06–4.10 (t, J = 7.6 Hz, 6H, O CH2 CH2-
–
–
–
=
–
of –OC5H11 and OC18H37), 7.54–7.56 (d, J = 15.6 Hz, 1H, CO CH CH ), 8.30–8.32
–
–
=
–
(d, J = 15.6 Hz, 1H, CO CH CH ), 7.14–8.12 (d, J = 8.4 Hz, 4H, left side phenyl ring),
7.67–7.82, 8.02 (d, J = 8.2 Hz, 4H, central phenyl ring), 6.96–7.64 (d, J = 7.8 Hz, 4H, terminal
phenyl ring), elemental analysis: calculated for C52H76O5: C, 80.00; H, 9.75; O, 10.25; found:
C, 79.92; H, 9.60; O, 10.14%.
C18 (Series-2): IR (KBr): vmax/cm−1 648–680 Polymethylene group of ( CH2-)n of
–
–
– – –
– – –
OC18H37, 812 ( C H def. m di-substituted), 960 ( C H def. hydrocarbon), 1064
– – – – – – – –
( C O ) str, 1381 and 1230, 1157 ( C O str in –(CH2-)n chain, 1381 and 1442 ( C H def.
– = –
– =
–
–
in CH2), 1504–1560 ( C C )str, 1630 ( C O group), 1760 ( COO ester group), 2854 and
1
– –
–
=
–
2990 ( C H str in CH3), 930 (trans, CH CH ) group, H NMR (CDCl3): 0.88–0.90 (t, J =
–
–
7.8 Hz, 6H, CH3 of –OC18H37), 1.26–1.29 (m, 52H, CH2 of –OC18H37), 1.76 (m, 4H, n-poly
–
–
methylene groups of OC18H37), 1.43 (t, J = 7.1 Hz, 6H, OC18H37), 1.31 (q, J = 7.6 Hz, 4H,
–
– –
–
–
OC18H37), 4.06–4.10 (t, J = 7.8 Hz, 6H, O CH2 CH2- of OC18H37), 7.54–7.56 (d, J =
–
–
=
–
–
–
=
–
15.6 Hz, 1H, CO CH CH ), 8.30–8.31 (d, J = 15.6 Hz, 1H, CO CH CH ), 7.14–8.12
(d, J = 8.4 Hz, 4H, left side phenyl ring), 7.67–7.82, 8.02 (d, J = 8.2 Hz, 4H, central phenyl
ring), 6.96–7.64 (d, J = 7.8 Hz, 4H, terminal phenyl ring), elemental analysis: calculated for
C58H88O5: C, 80.55; H, 10.18; O, 9.25; found: C, 79.92; H, 10.12; O, 9.14%.
3. Result and discussion
3.1. POM investigation
In order to investigate the influence of the central linkage and terminal substituted octadecy-
–
loxy ( OC18H37) tail group on the mesophase behavior of liquid crystalline compounds, we

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
223
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
·
·
·
·
·
·
·
·
·
·
·
·
·
–
—
—
—
—
—
—
—
.
.
.
.
.
—
—
—
—
—
·
—
—
—
—
—
—
.
.
.
.
.
.
.
.
.
.
·
·
·
·
·
·
·
·
·
·
·
·
·
.
.
.
.
.
.
.
.
.
.
—
·
·
·
·
·
·
·
·
·
·
·
·
.
.
.
·
·
·
·
have synthesized and studied the effect of linking group as well as the effect of alkyl aliphatic
chain length with rigid core such as benzene ring present in two homologous series. In the
present article, we have prepared 13 homologous (C1 to C8, C12, C14, C16, C18) in both series.
In series-1, compounds C4 to C8 show only an enantiotropic nematic mesophase, while in
higher homologous C10, C12, C14, C16, C18 show smectic as well as nematic mesophase enan-
tiotropical manner. Odd–even effect has been observed in Sm-N, N-I transition temperature
at C6 to C7 homolog in series-1. In series-2, mesophase commences from C4 to C18 in which
C4 to C18 show nematic phase while C5 to C10 exhibit enantiotropic smectic as well as nematic
mesophase. The transition temperatures of series-1, -2 are shown in Tables 1 and 2.
C1 to C3 homologous in both series-1 and series-2 does not show LC phase due to the high
crystallinity of compounds. The nonmesomorphicity of C1, C2, C3 homolog is attributed to
the low magnitudes of intermolecular dispersion forces and low magnitudes of dipole–dipole
interactions leading to high crystallizing tendency, which causes abrupt breaking of crystal
lattices due to unsuitable and unfavorable magnitudes of anisotropic forces of intermolecular
attractions. Thus, irregular breaking of crystal lattices suddenly takes place at relatively higher
temperature. Thus, crystalline solid state is directly converted into isotropic phase without
showing any LC properties.
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
·
·
·
·
·
·
·
·
·
·
·
·
·
—
—
—
—
—
—
—
—
·
—
—
—
—
—
—
·
·
·
·
·
·
·
·
·
·
·
·
·
.
.
.
.
.
.
.
.
.
.
.
.
—
.
.
.
.
.
.
.
.
.
.
—
·
.
.
.
.
.
—
—
—
—
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·

224
R. B. SOLANKI ET AL.
Figure . Phase diagram of series-.
Transition curves Cr-I/M, Sm-N, and N-I are plotted against the number of carbon atoms
present in n-alkyl chain versus transition temperatures by linking like or related transition
points; as depicted in a phase diagrams shown in Figures 1 and 2. In Figure 1, Cr-I/M transi-
tion curve initially falls up to C4 and rises at C5 and falling to C6 and then rises to C7 homolog
and then continued to falling at C10 and rising at C14 and continued to descend up to C18
homolog with overall descending tendency. In Cr-I/M curve, odd–even effect is present at
C5 and C7 homolog. Sm-N transition curve decreases at C12 homolog and increases at C16
homolog, respectively. N-I transition curve starts falling and rises at C7 homolog due to odd–
even effect and then gradually decreasing with increasing alkyl chain in alkoxy group.
In Figure 2, Cr-I/M transition curve initially falls at C6 homolog then gradually increases
due to exhibition of odd–even effect at C7 and then continued to falling up to last C18 homolog.
Sm-N transition curves descend initially up to C6 homolog and rise at C7 homolog because
Figure . Phase diagram of series-.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
225
Figure . Texturesofcompoundsofseries-observedbetweencrosspolarizers:(a)SmCphaseofC at°C;
(b) Sm C phase of C at °C; (c) nematic phase of C at °C; (d) Blue phase of C at °C.
of exhibition of odd–even parity and falling at C10 homolog then continued to rising up to
C12 homolog with slight decrease in magnitudes and reaching maxima at C18 homolog due to
its abnormality. N-I transition curves descend at C6 homolog and then ascend to C7 homolog
and continued decreasing at C10 homolog and increase up to C18 homolog.
The exhibition of smectic mesophase in C5 homolog indicates the presence of lamellar
packing of molecules in the crystal lattices of rigid crystals, which maintains sliding layered
molecular arrangement in floating condition under the influence of exposed thermal vibra-
tions, which causes the formation of smectogenic mesophase in enantiotropic manner.
The crystalline compounds sandwiched between the glass slide and coverslip were heated
to the isotropic state, and heating and cooling rate (2°C min−1), respectively, and observing
mesophase texture images are shown in Figures 3 and 4. Textures of the compounds of
series-1 are shown in Figure 3. Compound C10 formed the SmC phase observed at 68°C on
heating condition, which was further confirmed by DSC analysis. Compound C14 exhibited
a texture of SmC mesophase at 78°C upon cooling condition. Compound C16 displayed
nematic mesophase image at 84°C on heating condition. Compound C18 formed a blue phase
texture image at 80°C during heating and cooling conditions and it was confirmed by DSC
measurement upon heating and cooling trace.
Textures of the compounds of series-2 are shown in Figure 4. Compound C5 formed the
SmC phase observed at 66°C on heating condition and cooling temperature, and by rising
the temperature up to 80°C nematic phase is appeared, which was further confirmed by

226
R. B. SOLANKI ET AL.
Figure . TexturesofcompoundsofSeries-observedbetweencrosspolarizers:(a)SmCphaseofC at°C;
(b) Sm C phase of C at °C; (c) Sm C phase of C at °C; (d) schlieren texture of C at °C.
DSC analysis. Compound C6 exhibited a broken fan type texture of SmC mesophase at 57°C
upon heating condition. Compound C10 formed texture image of SmC mesophase at 62°C
on heating condition. Compound C16 exhibited schlieren type texture image at 80°C during
heating and cooling conditions and it was confirmed by DSC measurement. In addition, we
conclude that the mesophase appeared in series-1 and series-2 during heating and cooling
condition, respectively.
Table 3 shows the comparison of the Sm-N and N-I thermal stabilities and mesophase
length of series-1, -2. Commencement of smectic phase in series-2 is from C5 homolog while
it late commences in C10 homolog in series-1. The smectic mesophase range of compounds
in series-2 is 5°C lower than the compounds in series-1. While the nematic mesophase range
of compounds in series-1 is 3°C lower than the compounds in series-2. Gray explained that
increase in the breadth of the molecules reduces both the nematic and smectic thermal
stabilities [51]. Series-1 and series-2 were synthesized by various route shown in Schemes 1
and 2, structure-wise both the series differ at first linking group and second linking group
while terminal hexadecyloxy chain is same in both series. We have studied comprehensively
Table . Thermal stability comparison of Sm-N and N-I in series-, −.
Series
Series-
Series-
Sm-I or Sm-N or N-Sm commencement
of smectic phase
N-I or I-N commencement of nematic
phase
Total mesophase length
. (C - C) C
. (C — C) C
.°C to .°C C C
. (C — C/C) C
. (C- C) C
.°C to .°C C C

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
227
Scheme . Synthetic route of A, B, and C intermediate.
the effect of linking group as well as alkyl aliphatic chain present in left alkoxy side chain and
flexibility due to terminal side chain to form mesogens. It has been proven that length altering
of the alkyl chain affects LC property. Hence, we have observed the presence of vinyl carboxy
–
=
–
–
( CH CH COO ) linkage group in series-1. Thus, the resultant non-coplanarity, due to
twist received on account of the bumping of the oxygen and hydrogen atoms into the non-
–
–
bonded hydrogen atoms of the adjacent benzene rings. While in absence of COO group
in series-2 in place of –CH CH COO central bridge effectively contributes to molecular
=
–
–
=
–
rigidity and flexibility due to decrease in length by the absence of –CH CH group and
increases suitable magnitudes of intermolecular end to end attractions and closeness. Thus,
the thermal stability of nematic phase is highest as compared to series-1. The late commence-
ment of smectic phase in series-1 may be due to weakening of the lateral attractions because of
the disproportionate length to breadth ratio. Comparatively, the commencements of smectic
phase early in series-2 either lateral to terminal attractions maintain the propionate molecular
force or the lateral attractions predominate over the terminal attractions. Thermal stability of
smectic phase in series-1 is little higher than series-2, due to involving conjugated double bond
–
=
–
–
( Ch CH ), which increases molecular rigidity more than –COO central bridge. Therefore,

228
R. B. SOLANKI ET AL.
Scheme . Synthetic route of target compounds of series- and series-.
the stabilization of the smectic phase for series-1 is little more than series-2, due to molecular
length, and long chain can obviously be attributed to extent of molecular non-coplanarity
maintained favorably to facilitate and weakening of the terminal intermolecular interactions.
Figure . DSC curve of the compound. (a) C homolog (Series-), (b) C homolog (series-), (c) C homolog
(series-), and (d) C homolog (series-).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
229
Table . Transition temperature (°C) and enthalpy (J g−) and entropy change (J g− k−) by DSC measure-
ment (series-).
Homologous
or Comp.
Heating
scan (°C)
Cooling
scan (°C)
ꢀH
ꢀH
ꢀS
ꢀS
Transition
(-Jg−
)
(J g−
)
(J g− k−
)
(J g− k−
)
C10
Cr-SmC
SmC-N
N-I
Cr-N
N-I
Cr-N
N-I
Cr-SmC
SmC-N
N-I
.
.
>.
.
>.
.
>.
.
.
>.
.
.
—
.
—
.
—
.
.
—
.
.
.
.
.
.
.
.
.
.
.
.
—
.
—
.
—
.
.
—
.
.
.
.
.
.
.
.
.
.
.
.
—
.
—
.
—
.
.
—
C7
C4
C18
3.2. DSC study
DSC is a valuable method for detecting phase transitions. The thermal behavior of novel
homologous series-1, -2 was confirmed by using DSC measurement shown in Figure 5.
Thermogram is traces in both heating and cooling condition. The first endothermic peak of
compound C10 (series-1), at heating condition is observed at 60.01°C, this indicates the pres-
ence of SmC phase. DSC analysis confirmed the phase observed by POM study. While second
endothermic peak observed at 79.28°C, which indicates the presence of nematic phase, on
cooled condition again two endothermic peaks were traced at 62.92°C and 87.21°C. For
compound C7 (series-1), only one significant peak is observed at 95.78°C, while on cooling
stage it was traced at 100.01°C. For compound C12 (series-2), one endothermic peak which
is observed at 82.15°C confirmed the presence of nematic phase, which was confirmed by
POM study, while on cooled condition endothermic peak was traced at nearly 85.01°C. For
compound C6 (series-2), it was observed that Sm C phase and blue phase are present by
POM analysis, which was further confirmed by DSC measurement. On heating condition,
first endothermic peak is observed at 50.67°C and second endothermic peak is observed at
73.92°C and further cooling condition first endothermic peak traces at 53.98°C and second
endothermic peak observed at 75.38°C, respectively. Furthermore, compound C4 (series-1)
in Figure S1 (ESI) exhibited one endothermic peak at 81.56°C on heating condition, and one
endothermic peak at 84.28°C on cooling condition. Compound C18 (series-1) in Figure S1
(ESI) exhibited two endothermic peaks at 50.28°C and 78.30°C on heating condition, and
two endothermic peaks at 49.82°C and 79.20°C on cooling condition. For compound C18
Table . Transition temperature (°C) and enthalpy (J g−) and entropy change (J g− k−) by DSC measure-
ment (series-).
Heating
scan
(°C)
Homologous
or Comp.
Cooling
scan (°C)
ꢀH (-J
g−
ꢀH
ꢀS
ꢀS
Transition
)
(J g−
)
(J g− k−
)
(J g− k−
)
C6
Cr-SmC
SmC-N
N-I
Cr-N
N-I
Cr-N
N-I
Cr-N
N-I
.
.
>.
.
>.
.
>.
.
>.
.
.
—
.
—
.
—
.
—
.
.
.
.
.
.
.
.
.
—
.
—
.
—
.
.
.
.
.
.
.
.
.
.
.
—
.
—
.
—
.
—
C12
C14
C18
.
.
.
—

230
R. B. SOLANKI ET AL.
Figure . Space filling diagram of series- and -.
(Series-2) in Figure S1 (ESI), endothermic peak is observed at 82.38°C on heating condition,
and again endothermic peak traces at 89.92°C on cooling condition.
Thus, chalconyl-ester-based nonlinear compound displays lower melting type mesomor-
phism. In addition, present homologous series-1, -2 show mesomorphic behavior at lower
temperature. Transition temperature obtained by DSC analysis at heating and cooling con-
dition and the value of enthalpy and entropy are mentioned in Tables 4 and 5. Molecules of
every homolog are randomly oriented in all possible directions with high order of disorder
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 high temperature at observed during heating condition. The
mesophases obtained in enantiotropical manner in present series-1, -2 are smectogenic and
nematogenic, respectively.
The geometrical shapes of series-1, -2 are nonlinear bent type without any lateral group
substitution which is shown in Figure 6. Both the series-1, -2 are differing with each other due
–
=
–
to linearity and aromaticity, the presence of ethylene ( CH CH ) linkage group in series-1
increases the linearity of molecules.
Figure . Proposed molecular packing of the Sm C phase in present both series.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
231
The proposed molecular packing of the SmC phase is given in Figure 7. The arrangement
of molecule is non-isomeric bent type shape. This is due to the molecular packing of the alkyl
chains with linking groups oriented in tilted way directions in smectic layers structure and
effect of flexibility to induce smectic mesomorphism.
4. Conclusions
In this article, we have described the synthesis and thermotropic properties of two novel non-
linear homologous series having chalconyl-ester and chalconyl-vinyl ester as central linking
group with terminal octadecyloxy tail group. C1 to C3 do not exhibit LC behavior due to high
crystallizing tendency, while rest of homologs show lower melting type mesomorphism. In
addition, the length of alkoxy tail has been varied from homolog to homolog in the same
series-1, -2 to induce mesomorphism. In series-1, compounds C4–C8 show only an enan-
tiotropic nematic mesophase, while in higher homologs C10, C12, C14, C16, C18 show smectic
as well as nematic mesophase in enantiotropical manner. In series-2, mesophase commences
from C4 to C18 in which C4 to C18 show nematic phase while C5 to C10 exhibit enantiotropic
smectic as well as nematic mesophase. The group efficiency order derived on the basis of ther-
mal stability, early commencement of mesophase, and upper and lower mesophase length. The
mesomorphism was confirmed by POM, DSC.
Acknowledgments
Authors acknowledge thanks to Dr. R.R. Shah, principal of K. K. Shah Jarodwala Maninagar Science
College, Ahmedabad. Authors also thank to Centre of Excellence, NFDD centre, Rajkot for the analyt-
ical and spectral services.
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