Synthesis and phase behaviors of side-chain liquid-crystalline polymers containing azobenzene mesogen with the different length alkyl tail

Article abstract of DOI:10.1002/pola.26683

A series of side-chain liquid-crystal polymers, poly[6-[4-(4′-n-alkyl benzoateazo)phenoxy]-hexylmethacrylate]s (PMAzoCOOR_m, m = 1, 2, 3, 4, 5, 6, 8, 10, 14, and 18) have been prepared by two synthetic methods. The chemical structure of the monomers was confirmed by ¹H NMR and mass spectrometry. The molecular characterizations of the polymers were performed with ¹H NMR and gel permeation chromatograph. The phase behaviors of polymers were investigated by the combination of techniques including differential scanning calorimetry, polarized optical microscopy, and small-angle X-ray scattering. For m = 1, 2, 3, 4, 5, and 6, the polymers exhibited a monosmectic A phase in which the smectic layer period was almost identical to the side-chain length. In addition, for m = 2, 3, 4, and 5, they presented the monosmectic C phase in low temperature; moreover, the tilt angle increased from 23.3 to 40.5°. For m = 8, 10, 14, and 18, the polymers showed a bilayer smectic A phase in which the layer spacing was larger than a fully extended side chain but less than two extended chains. On the other hand, for the clearing point, with the increasing of m, it first decreased, and then increased. All of these indicated that the length of alkyl tails played an important role in the phase behaviors of these polymers.

Full text of DOI:10.1002/pola.26683

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Synthesis and Phase Behaviors of Side-Chain Liquid-Crystalline Polymers
Containing Azobenzene Mesogen with the Different Length Alkyl Tail
Sheng Chen, Aihua Ling, Hai-Liang Zhang
Key Laboratory of Polymeric Materials and Application Technology of Hunan Province, Key Laboratory of Advanced Functional
Polymer Materials of Colleges, Universities of Hunan Province, College of Chemistry, Xiangtan University, Xiangtan 411105,
Hunan Province, China
Correspondence to: H.-L. Zhang ( E-mail: hailiangzhang1965@yahoo.com.cn)
Received 27 January 2013; accepted 13 March 2013; published online 00 Month 2013
DOI: 10.1002/pola.26683
ABSTRACT: A series of side-chain liquid-crystal polymers,
poly[6-[4-(40-n-alkyl benzoateazo)phenoxy]-hexylmethacrylate]s
(PMAzoCOORm, m 5 1, 2, 3, 4, 5, 6, 8, 10, 14, and 18) have
been prepared by two synthetic methods. The chemical struc-
ture of the monomers was confirmed by 1H NMR and mass
spectrometry. The molecular characterizations of the polymers
were performed with 1H NMR and gel permeation chromato-
graph. The phase behaviors of polymers were investigated by
the combination of techniques including differential scanning
calorimetry, polarized optical microscopy, and small-angle X-
ray scattering. For m 5 1, 2, 3, 4, 5, and 6, the polymers exhib-
ited a monosmectic A phase in which the smectic layer period
was almost identical to the side-chain length. In addition, for
m 5 2, 3, 4, and 5, they presented the monosmectic C phase in
low temperature; moreover, the tilt angle increased from 23.3
to 40.5ꢀ. For m 5 8, 10, 14, and 18, the polymers showed a
bilayer smectic A phase in which the layer spacing was larger
than a fully extended side chain but less than two extended
chains. On the other hand, for the clearing point, with the
increasing of m, it first decreased, and then increased. All of
these indicated that the length of alkyl tails played an impor-
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tant role in the phase behaviors of these polymers.
2013
Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.
2013, 00, 000–000
KEYWORDS: azobenzene mesogen; liquid crystalline polymers;
phase behavior; side-chain liquid crystalline polymers;
structure-property relations
decouples the opposing tendencies of the liquid-crystal
groups to self-assemble from those of the polymer back-
bones to adopt random coil conformations. Systematic stud-
ies on the structure–property relationship of the azo-
containing side-chain LCPs have also revealed that phase
INTRODUCTION In recent years, azobenzene (azo)-containing
side-chain liquid-crystalline polymers (azo-SCLCPs) have
attracted considerable attention on account of their wide
range of potential applications such as optical data storage,
holographic imaging, photo-switches, nonlinear optics, polar-
ization holography, and soft actuators as artificial muscles.1–13
The performance of the functional azo-SCLCPs is based on
the photoinduced fast and reversible isomerization between
the trans and the cis isomers of azobenzene upon exposure
to UV or visible light, which triggers significant changes in
the physicochemical properties of polymer materials which
is usually related to their LC properties. Therefore, it is nec-
essary to investigate the structure–property relationship of
azo-SCLCPs to understand the principles of structure forma-
tion and structure manipulation.14–22
transition behaviors are strongly dependent on them.33–39
16
ꢀ
For example, Garcıa et al. have studied the phase behaviors
of liquid-crystalline polymers bearing phenylene(azoben-
zene) moieties substituted with an electron-donor or elec-
tron-acceptor lateral group. The results showed that these
polymers exhibited smectic-type mesophases that extend
over broad temperature ranges. Monolayer and bilayer smec-
tic arrangements were observed depending on the length of
the spacer and tail, as well as on the nature of the lateral
substituent. In polymers bearing CN groups, the interdigi-
tated structures may arise from dipolar interactions between
cyano groups. Polymers bearing OCH3 groups displayed pref-
erentially tilted mesophases. Cook et al.14 have systematically
researched the influence of flexible spacer length from 3
to 11 on the self-organization of the poly[x-(4-methoxyazo-
benzene-40-oxy)alkyl methacrylate]s. Authors pointed out
that the propyl and butyl members showed exclusively
For SCLCPs, the phase behaviors of them are largely deter-
mined by the polymer backbone, the flexible spacer, the mo-
lecular structure of the mesogens, and the terminal
substitutent.23–32 Usually, the anisotropic interactions
between the mesogenic groups give rise to the observation
of liquid-crystalline behavior, whereas the flexible spacer
Additional Supporting Information may be found in the online version of this article.
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nematic behavior; the pentyl, hexyl, octyl, and decyl mem-
bers formed a nematic and a smectic A phase, whereas the
heptyl, nonyl, and undecyl homologues exhibited only a
smectic A phase. Li et al.18 have reported the synthesis of a
series of new side-chain liquid-crystalline polymethacrylates
with amide group-substituted azo mesogens and different
lengths of flexible spacers and terminal alkyl chains. In this
context, hydrogen-bonding interactions among the amide
groups proved to play a decisive role in forming and stabiliz-
ing the smectic C phase. In addition, the length of the flexible
spacers and the terminal tails also showed great influence
on the phase transition behavior of the azo polymers in
terms of their glass transition temperatures (Tg) and phase
transition temperatures, where the increase in the tail length
led to a broader range of liquid-crystalline phase for the azo
polymers.
SCHEME 2 The first synthetic route of the MAzoCOORm
(m 5 1, 2, 3, 4, 5, and 6).
water before being dried with anhydrous calcium chloride
and then distilled. All the other reagents were commercially
available and used as received.
In this study, we intend to describe a detail study of the LC
behavior of a series of side-chain liquid-crystalline polymers
bearing azobenzene mesogen with different tail lengths,
poly[6-[4-(40-alkyl benzoateazo)phenoxy]-hexylmethacrylate]s
(PMAzoCOORm, m is the length of alkyl tails). The molecular
structure of polymers is shown in Scheme 1. Compared to
the flexible spacer, side-chain tails have gained less attention
in the research of azo-SCLCPs. In many cases, it is found that
no significant tail length effect was found on the phase struc-
tures of azo-SCLCPs. However, varying the side-chain tail
length, molecular packing behaviors of PMAzoCOORm can be
changed. On the other hand, although the phase behavior of
PMAzoCOOR6 has been studied by some groups,18 no report
focuses on the influence of alkyl tail length on the liquid-
crystalline behavior of the polymers (m 5 1–18). Moreover,
such a study of the phase behavior of the complete homolo-
gous series would allow for the rational design of new poly-
mers having tailored phase behavior.
Measurements
1NMR measurements were performed on a Bruker ARX400
MHz spectrometer using with CDCl3 as solvent and tetrame-
thylsilane as the internal standard at room temperature.
The apparent number-average molecular weight (Mn) and
polydispersity index (PDI 5 Mw/Mn) were measured on a gel
permeation chromatography (GPC) (WATERS 1515) instru-
ment with a set of HT3, HT4, and HT5. The m-styragel col-
umns usedꢀTHF as an eluent and the flow rate was 1.0 mL/
min at 38 C. All the GPC data were calibrated with polysty-
rene standards.
TGA was performed on a TA-SDT 2960 instrument at a heat-
ꢀ
ing rate of 20 C/min in nitrogen atmosphere.
Differential scanning calorimetry (DSC) traces of all the poly-
mers were obtained using a TA-Q10 DSC instrument. The
temperature and heat flow were calibrated using standard
materials (indium and zinc) at a cooling and heating rates of
10 C/min. Samples with a typical mass of about 5 mg were
encapsulated in sealed aluminum pans.
EXPERIMENTAL
Materials
ꢀ
Anhydrous tetrahydrofuran (THF) was distilled from sodium
benzophenone ketyl under argon and used immediately. Trie-
thylamine (Et3N) was refluxed with potassium hydroxide
and distilled. N,N-dimethyl formamide (DMF) was dried with
anhydrous magnesium sulfate and then with potassium hy-
droxide, finally distilled under vacuum. 2,2-Azobisisobutyro-
nitrile (AIBN) was freshly recrystallized from methanol.
Chlorobenzene (Acros, 99%) was purified by washing with
concentrated sulfuric acid to remove residual thiophenes, fol-
lowed by two times of washing with distilled water, once
with 5% sodium carbonate solution, and again with distilled
LC texture of the polymers was examined under polarized
optical microscopy (POM) (Leica DM-LM-P) equipped with a
Mettler-Toledo hot stage (FP82HT).
Small-angle X-ray scattering (SAXS) experiments were per-
formed using a high-flux SAXS instrument (SAXSess, Anton
Paar) equipped with Kratky block-collimation system and a
Philips PW3830 sealed-tube X-ray generator (Cu KR). The
wavelength was 0.1542 nm. A highly sensitive SAXS imaging
plate which was 264.5 mm away from the sample was used
to collect the signal in vacuum. Samples were placed in
between aluminum foils which were folded and sandwiched
in a steel sample holder. After background subtraction, des-
mearing was performed according to the Lake’s method. A
temperature control unit (Anton Paar TCS300) in conjunc-
tion with the SAXSess was utilized to study the structure at
various temperatures.
SCHEME
1
Chemical structures
of
the polymers
(PMAzoCOORm).
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(48.39 g, 0.2 mol) were dissolved in 200 mL of acetone. Af-
ter the reaction was refluxed for one night, the mixture was
hot filtered to remove inorganic salts. Much of acetone was
removed by rotating evaporation, and then the reaction mix-
ture was precipitated into a large amount of methanol, and
was filtered. The resulting solid was dried at 40 ꢀC under
vacuum for 48 h to constant weight.
6-[4-(40-Methyl benzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR1)
Methacrylic acid, KHCO3, and 4-[40-(6-bromohexyloxy)pheny-
lazo]methybenzoate were dissolved in DMF. After the reac-
tion has taken place for one night at 100 ꢀC, the mixture
was precipitated into large amount of water and was filtered,
SCHEME 3 The second synthetic route of the MAzoCOORm
(m 5 8, 10, 14, and 18).
ꢀ
then dried 40 C under vacuum for 48 h to constant weight.
1H NMR (400 MHz, CDCl3, ppm): d 5 1.43–1.87 (m, 8H,
C@CACOOACACH2ACH2ACH2ACH2A), d 5 1.95 (s, 3H,
AC@CACH3), 3.96 (m, 3H, ACOOACH3), 4.05–4.08 (m, 2H,
ACH2AOA), 4.16–4.19 (m, 2H, AC@CACOOACH2A), 5.56,
6.10 (s, 2H, CH2@CA), 7.00–7.02 (d, 2H, ArAH), 7.90–7.95 (q,
4H, ArAH), 8.17–8.19 (d, 2H, ArAH). Mass spectrometry (MS)
(m/z) [M] Calcd for C24H28N2O5, 424.49; found, 424.993.
Synthesis of the Monomers
For convenience, the 6-[4-(40-n-alkyl benzoateazo)phenoxy]-
hexylmethacrylate monomers were named MAzoCOORm and
the corresponding polymers were named PMAzoCOORm (m is
the number of the carbons of alkyl tails). In this study, two
synthetic routes were designed to prepare the monomers
(Schemes 2 and 3). With the former one, the monomers with
short alkyl tail were easily prepared; however, the monomer
with long alkyl tail was hard to synthesize because it was dif-
ficult to dissolve in the H2O or H2O/acetone for the long-n-
alkyl 4-amino benzoate. With the latter one, although the syn-
thetic route was complicated, it could overcome such defect.
6-[4-(40-Ethyl benzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR2)
1H NMR (400 MHz, CDCl3, ppm): d 5 1.26 (m, 3H, ACACH3),
1.43–1.85 (m, 8H, C@CACOOACACH2ACH2ACH2ACH2A),
1.95 (s, 3H, AC@CACH3), 4.06 (m, 2H, ACH2AOA), 4.17 (m,
2H, AC@CACOOACH2A), 4.40–4.42 (m, 2H, ACOOACH2A),
5.56, 6.11 (s, 2H, CH2@CA), 7.00–7.02 (d, 2H, ArAH), 7.90–
7.95 (q, 4H, ArAH), 8.17–8.19 (d, 2H, ArAH). MS (m/z) [M]
Calcd for C25H30N2O5, 438.52; found, 438.809.
MAzoCOORm (m 5 1, 2, 3, 4, 5, and 6) were synthesized by
the first route (Scheme 2). Here, we reported the synthetic
details of monomer MAzoCOOR1 as representative.
Methyl 4-Amino Benzoate
6-[4-(40-Propylbenzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR3)
4-Aminobenzoic acid (10 g, 0.073 mol), anhydrous methanol
(125 mL), and concentrated sulfuric acid (7.5 mL) were
added into a three-neck round-bottom flask. After the mix-
ture was refluxed for 5 h by stirring, the excessive methanol
was removed by air distillation. Then, the mixture was pre-
cipitated into a large amount of water and some saturated
sodium carbonate solution was added. Then, the mixture
was filtered and the resulting solid was collected and dried
at 40 ꢀC under vacuum for 48 h to constant weight. White
sheet-shape crystal was obtained.
1H NMR (400 MHz, CDCl3, ppm): d 5 1.04–1.08 (t, 3H,
ACACH3), 1.48–1.87 (m, 10H, C@CACOOACACH2A
CH2ACH2ACH2A,
ACOOACACH2A),
1.95
(s,
3H,
AC@CACH3), 4.05–4.08 (t, 2H, ACH2AOA), 4.13–4.16 (m,
2H, AC@CACOOACH2A), 4.30–4.33 (m, 2H, ACOOACH2A),
5.56, 6.10 (s, 2H, CH2@CA), 7.00–7.02 (d, 2H, ArAH), 7.90–
7.96 (q, 4H, ArAH), 8.17–8.19 (d, 2H, ArAH). MS (m/z) [M]
Calcd for C26H32N2O5, 452.23.; found, 452.859.
6-[4-(40-Butylbenzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR4)
4-[(40-Hydroxy)phenylazo]methylbenzoate
Methyl 4-amino benzoate (9 g, 0.055 mol) was dissolved in a
mixture of distilled H2O (50 mL) and concentrated HCl (20
mL). Under ice-water bath, a solution of NaNO2 (4.2 g, 0.06
mol) and hydrochloric acid (40 mL) was added. Then, the
resulting mixture was dropped into a solution of phenol (5
g, 0.055 mol) and sodium hydroxide (100 mL). After that,
the reaction proceeded for 2 h. Finally, the pH of the solution
was adjusteꢀd to about 3 and the slurries were filtered and
dried at 40 C under vacuum for 48 h to constant weight.
1H NMR (400 MHz, CDCl3, ppm): d 5 1.04 (m, 3H, ACACH3), 1.48–
1.87
(m,
12H,
C@CACOOACACH2ACH2ACH2ACH2A,
ACOOACACH2ACH2A), 1.95 (s, 3H, AC@CACH3), d 5 4.05–4.08
(t, 2H, ACH2AOA), 4.13–4.15 (m, 2H, AC@CACOOACH2A), 4.17–
4.19 (m, 2H, ACOOACH2A), 5.56, 6.11 (s, 2H, CH2@CA), 7.00–7.02
(d, 2H, ArAH), 7.90–7.96 (q, 4H, ArAH), 8.17–8.19 (d, 2H, ArAH).
MS (m/z) [M] Calcd for C27H34N2O5, 466.57; found, 466.789.
6-[4-(40-Pentylbenzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR5)
4-[40-(6-Bromohexyloxy)phenylazo]methybenzoate
4-[(40-hydroxy)phenyalazo]methylbenzoate (5.12 g, 0.02
mol), K2CO3 (2.76 g, 0.02 mol), and 1,6-dibromohexane
1H NMR (400 MHz, CDCl3, ppm): d 5 0.93–0.96 (t, 3H,
ACACH3),
1.43–1.85
(m,
14H,
C@CACOOACA
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CH2ACH2ACH2ACH2A, ACOOACACH2ACH2ACH2A), 1.95
(s, 3H, AC@CACH3), 4.05–4.08 (t, 2H, ACH2AOA), 4.16–
4.19 (t, 2H, AC@CACOOvCH2A), 4.33–4.36 (m, 2H,
ACOOACH2A), 5.56, 6.11 (s, 2H, CH2@CA), 7.00–7.02 (d,
2H, ArAH), 7.90–7.96 (q, 4H, ArAH), 8.17–8.18 (d, 2H,
ArAH). MS (m/z) [M] Calcd for C28H36N2O5, 480.6; found,
480.908.
6-[4-(40-Hexylbenzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR6)
SCHEME
4
The synthetic route of the polymers
1H NMR (400 MHz, CDCl3, ppm): d 5 0.92 (m, 3H, ACACH3),
1.36–1.86 (m, 16H, C@CACOOACACH2ACH2ACH2ACH2A,
ACOOACACH2ACH2ACH2ACH2A), 1.95 (s, 3H, AC@CA
CH3), 4.07 (m, 2H, ACH2AOA), 4.16–4.17 (m, 2H,
AC@CACOOACH2A), 4.35 (m, 2H, ACOOACH2A), 5.56, 6.11
(s, 2H, CH2@CA), 7.00–7.27 (d, 2H, ArAH), 7.90–7.96 (q, 4H,
ArAH), 8.17–8.19 (d, 2H, ArAH). MS (m/z) [M] Calcd for
(PMAzoCOORm).
4H, ArAH), 8.16–8.18 (d, 2H, ArAH). MS (m/z) [M] Calcd for
C33H46N2O5, 550.73; found, 551.452.
6-[4-(40-Tetradecylbenzoateazo) phenoxy]-
hexylmethacrylate (MAzoCOOR14
)
1H NMR (400 MHz, CDCl3, ppm): d 5 0.90 (m, 3H, ACACH3),
1.28–1.87 (m, 32H, C@CACOOACACH2ACH2ACH2ACH2A,
ACOOACACH2ACH2ACH2ACH2ACH2ACH2ACH2ACH2ACH2
ACH2ACH2ACH2A), 1.97 (s, 3H, AC@CACH3), 4.08 (m, 2H,
ACH2AOA), 4.18–4.21 (m, 2H, AC@CACOOACH2A), 4.36
(m, 2H, ACOOACH2A), 5.58, 6.13 (s, 2H, CH2@CA), 7.02–
7.04 (d, 2H, ArAH), 7.90–7.96 (q, 4H, ArAH), 8.16–8.18 (d,
2H, ArAH). MS (m/z) [M] Calcd for C37H54N2O5, 606.84;
found, 607.222.
C
29H38N2O5, 494.62; found, 495.457.
MAzoCOORm (m 5 8, 10, 14, and 18) were synthesized by
the second route (Scheme 3).
6-[4-(40-Benzoic acidazo) phenoxy]-hexylmethacrylate
This chemical intermediate was prepared by the method
described in the previously published literature.40
1H NMR (400 MHz, DMSO-d6, ppm): d 5 1.45–1.82 (m, 8H,
ACH2ACH2ACH2ACH2A), 1.91 (m, ACH3), 4.14 (m, 4H,
AOACH2A, ACH2AOA), 6.05, 5.70 (s, 2H, CH2@C), 7.16–
7.19 (d, 2H, aromatic protons), 7.93–7.97 (q, 4H, aromatic
protons), 8.14–8.16 (d, 2H, aromatic protons).
6-[4-(40-Octadecylbenzoateazo) phenoxy]-
hexylmethacrylate (MAzoCOOR18
)
1H NMR (400 MHz, CDCl3, ppm): d 5 0.90 (m, 3H, ACACH3),
1.28–1.87 (m, 40H, C@CACOOACACH2ACH2ACH2ACH2A,
ACOOACACH2ACH2ACH2ACH2ACH2ACH2ACH2ACH2ACH2
ACH2ACH2ACH2ACH2ACH2ACH2ACH2A), 1.97 (s, 3H,
AC@CACH3), 4.08 (m, 2H, ACH2AOA), 4.19 (m, 2H,
AC@CACOOACH2A), 4.36 (m, 2H, ACOOACH2A), 5.58, 6.13
(s, 2H, CH2@CA), 7.02–7.04 (d, 2H, ArAH), 7.92–7.98 (q, 4H,
ArAH), 8.18–8.20 (d, 2H, ArAH). MS (m/z) [M] Calcd for
6-[4-(40-Octylbenzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR8)
6-[4-(40-Benzoic acidazo) phenoxy]-hexylmethacrylate (1.0 g,
0.0019 mol), KHCO3 (0.38 g, 0.0038 mol), and 1-bromooc-
tane (0.37 g, 0.0019 mol) were dissolved in 15 mL of DMF.
After the reaction has taken place for one night at 100 ꢀC,
the reaction mixture was precipitated into large amount of
water, and then filtered. The resulting solid was dried at 40
ꢀC under vacuum for 48 h to constant weight.
C41H62N2O5, 662.94; found, 663.597.
Synthesis of the Polymers
The polymers were obtained by conventional solution radical
polymerization (Scheme 4), typically carried out as described
in the following example.
1H NMR (400 MHz, CDCl3, ppm): d 5 0.91 (m, 3H, ACACH3),
1.28–1.87 (m, 20H, C@CACOOACACH2ACH2ACH2ACH2A,
ACOOACACH2ACH2ACH2ACH2ACH2ACH2A), 1.97 (s, 3H,
C@CACH3), 4.07–4.10 (t, 2H, ACH2AOA), 4.18–4.21 (t, 2H,
AC@CACOOACH2A), 4.35–4.38 (t, 2H, ACOOACH2A), 5.58, 6.13
(s, 2H, CH2@CA), 7.02–7.04 (d, 2H, aromatic protons), 7.92–7.98
(q, 4H, aromatic protons), 8.18–8.20 (d, 2H, aromatic protons). MS
(m/z) [M] Calcd for C31H42N2O5, 522.68; found, 523.214.
The monomer, AIBN, and chlorobenzene were added into a
dried reaction tube containing a magnetic stirrer bar. The
molar ratio was set with Nmonomer:NAIBN 5 200:1, and the
monomer mass concentration was 25%. After three freeze–
pump–thaw cycles, the tube was sealed under vacuum. Poly-
ꢀ
merization was carried out at 65 C for more than 24 h. The
sample except PMAzoCOOR18 was purified by similarly rep-
recipitating three times from THF into methanol. PMAzo-
COOR18 was purified by petroleum ether.
6-[4-(40-Decylbenzoateazo) phenoxy]-hexylmethacrylate
(MAzoCOOR10
)
1H NMR (400 MHz, CDCl3, ppm): d 5 0.88 (m, 3H, ACACH3),
1.28–1.85 (m, 24H, C@CACOOACACH2ACH2ACH2ACH2A,
ACOOACACH2ACH2ACH2ACH2ACH2ACH2ACH2ACH2A), 1.95
(s, 3H, AC@CACH3), 4.06 (m, 2H, ACH2AOA), 4.17 (m, 2H,
AC@CACOOACH2A), d 5 4.34 (m, 2H, ACOOACH2A), 5.56,
6.10 (s, 2H, CH2@CA), 7.00–7.02 (d, 2H, ArAH), 7.90–7.96 (q,
RESULTS AND DISCUSSION
Synthesis and Characterization of Monomers
A series of new methacrylate azo monomers with the differ-
ent lengths of alkyl tail (m 5 1, 2, 3, 4, 5, 6, 8, 10, 14, and
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18) were synthesized according to the synthetic route shown
in Schemes 2 and 3. When alkyl tail was short, 4-[(40-hydrox-
y)phenylazo]-n-alkyl benzoate was easily synthesized via the
first synthetic route. However, n-long alkyl 4-amino benzoate
was difficult to dissolve in the H2O or H2O/acetone, indicat-
ing that 4-[(40-hydroxy)phenylazo]-n-long-alkyl benzoate was
hard to prepare. Therefore, two synthetic routes were
employed to synthesize our objective monomers. The 1H
NMR and MS spectrums of two representative azo monomers
(MAzoCOOR1 and MAzoCOOR18) are shown in Supporting In-
formation Figure S1. The characteristic resonances of the
vinyl group at 5.55 and 6.10 ppm can be seen clearly. In
addition, the chemical shifts and peak integrations of all the
protons in the monomer are in excellent agreement with its
expected structure. MS spectrums further confirmed the mo-
lecular structure.
Mesomorphic Properties of the Monomers
The thermal behavior of the monomers was examined by a
combination of DSC and POM. Figure 1(a,b) shows the first
cooling and the second heating DSC curves of MAzoꢀCOORm
(m 5 1, 2, 3, 4, 5, 6, 8, 10, 14, and 18) at a rate of 10 C/min
under nitrogen atmosphere after eliminating the thermal his-
tory. Table 1 lists the transition temperatures and enthalpies.
The heating DSC curves of MAzoCOORm (m 5 3, 5, and 8)
displayed a single endothermic melting peak. Above the
melting point, the samples were isotropic. In the cooling
runs, two exothermic peaks were observed for each com-
pound. The typical smectic textures were observed only
upon cooling from isotropic melt, indicating the formation of
the monotropic smectic phase [Fig. 2(a)]. Further cooling,
crystalline texture was formed [Fig. 2(b)]. For the MAzo-
COOR1 and MAzoCOOR10, they also formed the monotropic
smectic phase. In the case of MAzoCOORm (m 5 2, 6, 14, and
18), there were two transitions on both heating and cooling
thermographs, responding to the crystalline melting and the
transition from a smectic mesophase to an isotropic liquid
FIGURE 1 DSC curves of MAZoCOORm during the first cooling
scan (a) and the second heating scan (b) at a rate of 10 ꢀC/min
under nitrogen atmosphere.
TABLE 1 Liquid-Crystallinities of the Monomers
Phase Transition Temperature (ꢀC) and Enthalpy Changes (J/g)
Samples
Second Heating
First Cooling
MAzoCOOR1
MAzoCOOR2
MAzoCOOR3
MAzoCOOR4
MAzoCOOR5
MAzoCOOR6
MAzoCOOR8
MAzoCOOR10
MAzoCOOR14
MAzoCOOR18
C1 93.18(112.1)C2 99.87(18.17) I
C 62.87(91.57) S 77.46(15.54) I
C 68.9(114.5) I
I 99.68(19.72) S 63.03(26.67) C2 61.10(6.189)C1
I 77.31(16.07) S 32.69(70) C
I 70.44(13.74) S 49.47(88.87)C
I 61.81(80.19)C
C 80.58(68.92) I
C 55.79(102.5) I
I 55.63(11.29) S 35.43(85.13) C
I 43.35(1.654) S 38.44(35.73) C
I 49.12(6.218) S 44.04(46.57) C
I 50.49(10.62) S1 39.81(8.337) S2 36.25(6.522) C
I 51.32(6.926) S 31.20(31.47) C
I 52.69(13.57) S 50.91(23.56)C
C 40.76(2.638) S 45.55(10.95) I
C 53.6(64.8) I
C 53.2(59.28) I
C 31.19(27.52) S 50.09(10.27) I
C 50.53(14.52) S 63.16(140.3) I
C, crystal; S, smectic; I, isotropic state.
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that is, the temperatures at 5% weight loss of the samples
ꢀ
under nitrogen was about 320 C measured by TGA at a rate
of 10 ꢀC/min (Table 2). Figure 3(a) shows the first cooling
and the second heating DSC curves of PMAzoCꢀOORm (m 5 1,
2, 3, 4, 5, 6, 8, 10, 14, and 18) at a rate of 10 C/min under
nitrogen atmosphere after eliminating the thermal history.
Based on the transitional phenomenon of the polymers, the
curves shown in Figure 3(a,b) could be divided into three
types. The first one was PMAzoCOOR1 and PMAzoCOOR6.
The DSC traces showed that they contained a weak second-
order transition assigned as a glass transition and a single
endothermic peak. When the polymers were cooled from
the isotropic phase, PMAzoCOOR1 formed a smectic needle-
like texture and PMAzoCOOR6 presented a granular texture.
The POM results of them are shown in Figure 5(a,d). This
assignment is supported by the entropy change associated
with the transition and which is comparable to that seen for
other types of side-chain liquid-crystal polymers.41
FIGURE 2 Smectic texture of MAzoCOOR3 at 67 ꢀC (a) and
crystal texture of MAzoCOOR3 at 45 ꢀC (b) (magnification:
5003).
or from an isotropic liquid to a smectic mesophase, showing
the formation of the enantiotropic smectic phase. In the case
of MAzoCOOR4, it exhibited only crystal phase.
Synthesis and Characterization of Polymers
The free-radical polymerization of MAzoCOORm initiated by
AIBN in chlorobenzene gave the corresponding polymers
(PMAzoCOORm), with moderately high molecular weights in
good excellent yields. The polymerization results are sum-
marized in Table 2. The conversion of monomer to polymer
The second one was PMAzoCOORm (m 5 2, 3, 4, and 5). The
DSC traces contain two endothermic peaks and a weak
second-order transition regardless of heating or cooling. The
latter has been assigned as a glass transition. For PMAzo-
COOR5, careful examination also reveals that a broad and rel-
atively weak transition exists left before the major one as
shown in Figure 4. On cooling, those two peaks become
more obvious [Fig. 3(a)]. On cooling the isotropic phase of
each polymer, a smectic needle-like texture (smectic A
phase) was found first [Fig. 5(b)] and this assignment is sup-
ported by the big entropy change in the Figure 3(a). On fur-
ther cooling, smectic schlieren texture developed, indicating
the smectic C phase [Fig. 5(c)]. This transition process is
supported by the small entropy change in the Figure 3(b).
1
was confirmed by H NMR. As a representative example, the
1H NMR spectra of monomer MAzoCOOR2 and polymer PMA-
zoCOOR2 are shown in Supporting Information Figure S2.
MAzoCOOR2 showed characteristic resonances of the vinyl
group at 5.55 and 6.10 ppm. After polymerization, the sig-
nals disappeared completely. The adsorption peaks of PMA-
zoCOOR2 were quite broad and consistent with the expected
polymer structure.
Phase Transitions and Phase Structures of the Polymers
The thermal stabilities of the polymers were investigated
with TGA in nitrogen atmosphere (Supporting Information
Fig. S3). All the polymers have very good thermal stability,
The third one was PMAzoCOORm (m 5 8, 10, 14, and 18). All
polymers had a rather broad endothermic peak in high tem-
perature when heating or cooling. In addition, the
TABLE 2 GPC, DSC, and TGA Results and Liquid Crystallinity of PMAzoCOORm
Mn (3104)
Mw/Mn
Phase Transitions (ꢀC) and Enthalpy Changes (J/g)b
a
a
c
Td (ꢀC)
Sample
Yield (%)
PMAzoCOOR1
PMAzoCOOR2
PMAzoCOOR3
PMAzoCOOR4
PMAzoCOOR5
PMAzoCOOR6
PMAzoCOOR8
PMAzoCOOR10
PMAzoCOOR14
PMAzoCOOR18
80
82
80
81
79
86
75
76
83
87
7.69
2.22
1.97
2.12
2.18
2.07
2.16
1.95
1.99
2.18
1.81
g85.7 SmA198.4(13.9)I
358
350
354
315
334
330
365
364
320
363
10.06
7.00
g77.9SmC131.6(0.58) SmA167.6 (13.6)I
g54.9SmC118.0(2.05) SmA135.2 (11.1)I
g68.1SmC117.3(3.28) SmA121.6 (7.3)I
g47.1SmC108.9(0.22) SmA114.1 (8.6)I
g17.2 SA77.7(9.3)I
8.37
7.44
8.81
10.72
10.77
12.40
11.16
SA107.8(15.9)I
SA111.9(14.3)I
Cr-10.6(6.1) SA122.3(16.1)I
Cr38.4(30.3) SA130.1(14.8)I
a
The molecular weights (Mn) and polydispersity (Mw/Mn) were deter-
monolayer Smetic
C
phase; SmA, monolayer Smetic
A
phase; SA,
mined by GPC in THF on the basis of standard polystyrene calibration.
bilayer Smetic A phase; Cr, crystal of long-chain alkane.
The temperature at which 5% weight loss of the sample was reached
from TGA under nitrogen atmosphere.
b
c
Phase transitions and corresponding enthalpy changes were evaluated
by DSC at
a
rate of 10 ꢀC/min under the second heating. SmC,
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diffraction peaks (d001, d002, and d003) at a periodicity of
001 5 2.77 nm (d001 5 2p/q*). The layer spacing of d001 is
d
little longer than the length of the fully extended monomer
molecular length (L 5 2.61 nm), thus suggesting the mono-
ꢀ
layer SmA phase [Fig. 7(b)]. On heating to 220 C, no diffrac-
tion pattern is seen, indicating that the polymers enter into
isotropic phase, which is consistent with the DSC result. For
PMAzoCOOR6, the thermal 1D SAXS experiments showed
their structural evolution similar to that of PMAzoCOOR1.
In comparison, one strong scattering peak with q* 5 2.5
nm21 and one weak scattering peak with 2q* 5 5.01 nm21
from 20 to 115 ꢀC can be observed for PMAzoCOOR3 [Fig.
6(b)], indicating that it is more difficult for PMAzoCOOR3 to
form the liquid-crystalline mesophase with a long-range-or-
dered lamellar structure than PMAzoCOOR1. The scattering
peak of PMAzoCOOR3 corresponds to a d-spacing of 2.51 nm,
which is shorter than the calculated extended length of one
unit of PMAzoCOOR3 (L 5 2.86 nm). Combined with the
result of POM, it suggested a tilted monosmectic layer (SmC)
of the side group with a tilted angle of 30ꢀ to the layer nor-
mal [Fig. 7(a)]. On heating to 135 ꢀC, the layer spacing d100
changed to 2.89 nm, revealing the existence of a nearly
100% interdigitated smectic A structure (SmA). The phase
behavior of PMAzoCOOR2, PMAzoCOOR4, and PMAzoCOOR5
is similar to the PMAzoCOOR3 and the results are summar-
ized in Table 3. Furthermore, it is worth noting that the tilt
angle increased from 23.3 to 40.5ꢀ.
As shown in Figure 6(c), a first-order sharp peak is centered
at q* 5 1.08 nm21 and a higher-order diffraction peak
appear at 2q* 5 2.19 nm21. The ratio of the scattering vec-
tors of the two peaks q*:2q* was 1:2, suggesting the pres-
ence of a long-range-ordered lamellar structure with a layer
spacing d 5 6.28nm. The obtained d-values proved to be
greater than the calculated molecular length (L 5 3.68 nm)
for the fully extended side-chain liquid-crystalline unit of
FIGURE 3 DSC curves of PMAzoCOORm during the first cooling
scan (a) and the second heating scan (b) at a rate of 10 ꢀC/min
under nitrogen atmosphere.
PMAzoCOOR14 and PMAzoCOOR18 exhibited the crystalline
melting peaks of the long alkoxy tails in low temperature.
On cooling the isotropic phase, a granular texture was
formed [Fig. 5(e,f)]. This transition process is supported by
the big entropy change in the DSC in the high temperature.
To further study the phase transitions and the phase struc-
tures of PMAzoCOORms at different temperatures, 1D SAXS
experiments were performed. Before the SAXS experiment,
the samples were subjected to 6 h of annealing at a certain
temperature and then cooled to the room temperature.
Meantime, to elucidate the packing of mesogens in the meso-
phase, the experimental interlayer distance (or smectic pe-
riod) d001 was compared to the lamellar spacing L calculated
using molecular modeling software from Material Studios
3.0. L is the distance between a C-atom of the end-methyl
group of the mesogen (full extended) and the carbon atom
of the polymer chain. Figure 6(a–c) shows the temperature-
variable SAXS profiles of PMAzoCOOR1, PMAzoCOOR3, and
PMAzoCOOR10, respectively. Figure 6(a) shows the typical
temperature-dependent 1D SAXS patterns of PMAzoCOOR1.
At 30 ꢀC, the diffraction pattern is constituted by three
FIGURE 4 DSC curves of PMAzoCOOR5 during the second
heating scan at a rate of 10 ꢀC/min under nitrogen atmosphere.
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FIGURE 5 Representative POM images of the texture of PMAzoCOOR1 at 190 ꢀC (a), PMAzoCOOR3 at 130 ꢀC (b) and 113 ꢀC (c),
PMAzoCOOR6 at 60 ꢀC (d), PMAzoCOOR10 at 107 ꢀC (e), and PMAzoCOOR18 at 125 ꢀC (f) (magnification: 5003).
PMAzoCOOR10, but slightly smaller than 2L, suggesting a
bilayer lamellar structure, as schematically shown in Figure
behaviors although there was only minute difference in
structure between P6/n and PMAzoCOORm. First, the Tgs of
the polymers from PMAzoCOOR1 to PMAzoCOOR6 basically
7(c). For PMAzoCOOR8, PMAzoCOOR14, and PMAzoCOOR18
,
ꢀ
they have similar results to the PMAzoCOOR10
.
decrease on increasing tail length from 85.7 to 17.2 C. This
behavior is attributed to the plasticization of the backbone
Influence of the Alkyl-Tail Lengths on the Phase
Behaviors
by the side chains. However, no Tg was detected after n > 6.
ꢀ
For P6/n, the Tg decreased from 141 to 117 C (4 ꢁ n ꢁ 18).
Based on the results of DSC, POM, and 1D SAXS experiments,
the dependence of the transition temperatures on the length
of alkyl tail, m, for the PMAzoCOORm series is shown in Fig-
ure 8. Compared with the phase behavior of the amide
group-substituted azo polymers P6/n (n 5 4, 6, 8, 12, and
18),18 the PMAzoCOORm exhibits the different phase
Second, the clearing temperature shows a significant
decrease from PMAzoCOOR1 to PMAzoCOOR6, and then
increase from PMAzoCOOR6 to PMAzoCOOR18. This variation
originates from the changes of phase structures. The mono-
layer SmA phase was formed when m ꢁ 6, whereas the
bilayer SA phase was formed when m > 6. For P6/n, the
FIGURE 6 SAXS profiles of PMAzoCOOR1 (a), PMAzoCOOR3 (b), and PMAzoCOOR10 (c) recorded during the heating process with
intensity in log scale.
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FIGURE 7 Possible liquid-crystalline mesophase structures of PMAzoCOORm
.
clearing temperature increased markedly when the number
of carbon in the terminal alkyl chain increased from 4 to 12,
but they leveled off when n was further increased. Third, for
P6/n, the polymers just formed bilayer Sc. For PMAzoCOORm
(2 ꢁ m ꢁ 5), they could form the SmC phase and SmA phase.
investigated by the combined technology of DSC, POM, and
SAXS. The results of the experiment indicated that the length
of alkyl tails played an important role in the phase behaviors
of these polymers. For short tail lengths (from 1 to 6), a
monosmectic A phase was observed in which the mesogens
are fully interleaved. Moreover, a monosmectic C was seen
when m 5 2, 3, 4, and 5. Further increasing alkyl length, a
bilayer smectic A phase emerged in which alkyl tails over-
lapped. Meantime, the changes of phase structures lead to
CONCLUSIONS
We have successfully synthesized a series of new methacry-
late azo monomers (MAzoCOORm, m 5 1, 2, 3, 4, 5, 6, 8, 10,
14, and 18) via two ways. Upon using conventional radical
polymerization, we further obtained the corresponding azo-
benzene homopolymers. The chemical structures of the
monomers and polymers were confirmed by various charac-
terization techniques. For the first time, the phase structures
and transitions of these polymers were extensively
TABLE 3 Structure Parameters for the PMAzoCOORm (m 5 1–6)
determined from SAXS
a
T (ꢀC)
d
001(A)
d
001/L Tilt Angleb
˚
˚
Sample
L (A)
PMAzoCOOR1 26.1
PMAzoCOOR2 27.3
PMAzoCOOR3 28.6
PMAzoCOOR4 29.8
PMAzoCOOR5 31.1
PMAzoCOOR6 32.3
30
30
30
30
30
30
27.7
25.5
25.1
24.3
25.0
33.5
1.06
0.93
0.88
0.82
0.80
1.04
0
23.3
31.8
39.3
40.5
0
FIGURE 8 The dependence of the transition temperatures on
the number of methylene units, m, in the alkyl tails for the
PMAzoCOORm series.
a
Measured from molecular modeling using Material Studios 3.0.
Calculated from h 5 cos21(d001/L).
b
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18 X. Li, L. Fang, L. Hou, L. Zhu, Y. Zhang, B. Zhang, H. Zhang,
Soft Matter. 2012, 8, 5532–5542.
the decrease of the clearing point, and then the increase of
the clearing point. The driving force for the formation of dif-
ferent smectic phase is believed to be the optimization of the
packing efficiency of the side chains, whereas the backbones
are confined to lie between the smectic layers.
19 X. Li, R. Wen, Y. Zhang, L. Zhu, B. Zhang, H. Zhang, J.
Mater. Chem. 2009, 19, 236–245.
20 Y. Tian, K. Watanabe, X. Kong, J. Abe, T. Iyoda, Macromole-
cules 2002, 35, 3739–3747.
21 Z. Zheng, J. Xu, Y. Sun, J. Zhou, B. Chen, Q. Zhang, K.
Wang, J. Polym. Sci. Part A: Polym. Chem. 2006, 44, 3210–
3219.
ACKNOWLEDGMENT
22 X. Q. Zhu, J. H. Liu, Y. X. Liu, E. Q. Chen, Polymer 2008, 49,
3103–3110.
This research was financially supported by the Innovation Plat-
form Open Foundation of University of Hunan Province
(10k067) and the National Nature Science Foundation of China
(51073131, 21174117).
23 V. Percec, D. Tomazos, Adv. Mater. 1992, 4, 548–561.
24 J.G. Rudick, V. Percec, Acc. Chem. Res. 2008, 41, 1641–1652.
25 J.G. Rudick, V. Percec, N J. Chem. 2007, 31, 1083–1096.
26 B.M. Rosen, C. J. Wilson, D. A. Wilson, M. Peterca, M. R.
Imam, V. Percec, Chem. Rev. 2009, 109, 6275–6540.
27 V. Percec, C. H. Ahn, G. Ungar, D. J. P. Yeardley, M. Moller,
S. S. Sheiko, Nature 1998, 391, 161–164.
REFERENCES AND NOTES
1 A. Bobrovsky, V. Shibaev, Polymer 2006, 47, 4310–4317.
28 V. Percec, D. Schlueter, Y. K. Kwon, J. Blackwell, M. Moller,
P. Slangen, J. Macromol. 1995, 28, 8807–8818.
2 M. Han, S. Y. Morino, K. Ichimura, Macromolecules 2000, 33,
6360–6371.
29 J. M. Rodriguez-Parada, V. Percec, J. Polym. Sci. Part A:
Polym. Chem. 1986, 24, 1363–1378.
3 K. Ichimura, Chem. Rev. 2000, 100, 1847–1874.
4 T. Ikeda, J. Mater. Chem. 2003, 13, 2037–2057.
30 V. Percec, M. Lee, H. Jonsson, J. Polym. Sci. Part A: Polym.
Chem. 1991, 29, 327–337.
5 T. Ikeda, J.-i. Mamiya, Y. Yu, Angew. Chem. Int. Ed. 2007, 46,
506–528.
31 V. Percec, M. Lee, J. Heck, H. E. Blackwell, G. Ungar, A.
Alvarez-Castillo, J. Mater. Chem. 1992, 2, 931–938.
6 T. W. Lee, Y. Byun, B. W. Koo, I. N. Kang, Y. Y. Lyu, C. H.
Lee, L. Pu, S. Y. Lee, Adv. Mater. 2005, 17, 2180–2184.
32 V. Percec, B. Hahn, Macromolecules 1989, 22, 1588–1599.
33 A. A. Craig, C. T. Imrie, J. Mater. Chem. 1994, 4, 1705–1714.
7 W. Li, S. Nagano, T. Seki, N J. Chem. 2009, 33, 1343–1348.
8 A. Natansohn, P. Rochon, Chem. Rev. 2002, 102, 4139–4176.
34 J. L. Zhou, X. F. Chen, X. H. Fan, C. P. Chai, C. X. Lu, X. D.
Zhao, Q. W. Pan, H. Y. Tang, L. C. Gao, Q. F. Zhou, J. Polym.
Sci. Part A: Polym. Chem. 2006, 44, 4532–4545.
9 J. M. Schumers, C. A. Fustin, J. F. Gohy, Macromol. Rapid
Commun. 2010, 31, 1588–1607.
10 T. Ubukata, M. Hara, K. Ichimura, T. Seki, Adv. Mater. 2004,
16, 220–223.
35 A. A. Craig, C. T. Imrie, Macromolecules 1995, 28, 3617–
3624.
11 E. Uchida, N. Kawatsuki, Polymer 2006, 47, 2322–2329.
12 P. Xie, R. Zhang, J. Mater. Chem. 2005, 15, 2529–2550.
13 Y. Yu, T. Ikeda, Angew. Chem. Int. Ed. 2006, 45, 5416–5418.
36 C. Cojocariu, P. Rochon, Macromolecules 2005, 38, 9526–
9538.
37 S. Yin, H. Xu, X. Su, Y. Gao, Y. Song, J. W. Y. Lam, B. Z.
Tang, W. Shi, Polymer 2005, 46, 10592–10600.
14 A. G. Cook, R. T. Inkster, A. Martinez-Felipe, A. Ribes-Greus,
I. W. Hamley, C. T. Imrie, Eur. Polym. J. 2012, 48, 821–829.
38 A. A. Craig, I. Winchester, P. C. Madden, P. Larcey, I. W.
Hamley, C. T. Imrie, Polymer 1998, 39, 1197–1205.
ꢀ
15 S. Freiberg, F. Lagugne-Labarthet, P. Rochon, A. Natansohn,
Macromolecules 2003, 36, 2680–2688.
39 C. T. Imrie, F. E. Karasz, G. S. Attard, Macromolecules 1992,
25, 1278–1283.
ꢀ
ꢀ
ꢀ
ꢀ
16 T. Garcıa, L. Larios-Lopez, R. J. Rodrıguez-Gonzalez, G.
ꢀ
ꢀ
Martınez-Ponce, C. Solano, D. Navarro-Rodrıguez, Polymer
40 H. J. Haitjema, R. Buruma, G. O. R. A. Van Ekenstein, Y. Y.
Tan, G. Challa, Eur. Polym. J. 1996, 32, 1437–1445.
2012, 53, 2049–2061.
17 J. Isayama, S. Nagano, T. Seki, Macromolecules 2010, 43,
4105–4112.
41 C. T. Imrie, F. E. Karasz, G. S. Attard, Macromolecules 1993,
26, 3803–3810.
10
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