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Synthetic Metals 159 (2009) 576–582

Contents lists available at ScienceDirect

Synthetic Metals

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ynthesis and properties of liquid crystalline conjugated disubstitutedolyacetylene containing cyanoterphenyl mesogenic pendant

ie Chen, Yiwang Chen ∗, Weihua Zhou, Xiaohui Henstitute of Polymers/Institute for Advanced Study, Nanchang University, Xuefu Road 999, Nanchang 330031, People’s Republic of China

r t i c l e i n f o

rticle history:eceived 13 October 2008eceived in revised form 7 November 2008ccepted 27 November 2008vailable online 14 January 2009

eywords:iquid crystallinity

a b s t r a c t

Novel acetylene monomers containing cyanoterphenyl groups, namely, 4-[(4′-cyano-4-terphenylyl)oxy]-1-butyl-1-butyne M(1) and 3-[(4′-cyano-4-terphen-ylyl)oxy]-1-phenyl-1-proyne M(2) are synthesized.M(1) was polymerized with WCl6–PhSn4 catalyst successfully to give the liquid crystalline conju-gated disubstituted polyacetylene containing cyanoterphenyl mesogenic pendant P(1). Polymerizationof monomer M(2) was carried out in a series of different solution, but did not obtain any product. Theresults indicate that the stereoeffect of the bulky cyanoterphenyl group and phenyl seems to inhibitthe reaction. The structures and properties of the disubstituted polyacetylene P(1) and monomers

olyacetylenehotoluminescenceyanoterphenyl

were characterized and evaluated with nuclear magnetic resonance, infrared spectroscopy, thermo-gravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet spectroscopy,and photoluminescence. The monomers show enantiotropic smectic phases in the heating and coolingprocesses, while the polymer P(1) exhibits a nematic phase when observed with a polarizing opti-cal microscope. The existence of the chromophoric cyanoterphenyl core endows the monomers withhigh photoluminescence, and the polymer P(1) prepared from M(1) can emit a strong UV light of411 nm.

. Introduction

Conjugated polymers have been extensively studied for theirotential application in light-emitting diode (LED), organic lasers,hin film transistors and solar cells [1–7]. Introducing the orientable

esogenic moieties onto a conjugated polymer backbone mightncrease the conjugation in the main chain and yield polymers withermanent coupling between electro-active properties and order.hus liquid crystalline conjugated polymers (LCCP) are currentlyrawing interest from the viewpoint of multifunctional electricalnd optical materials [8–10].

Polyacetylene is an archetypal conjugated macromolecule andts functionalization has attracted much synthetic effort over theast decades [11–14]. Compared to the instability and intractabilityf polyacetylene, substituted polyacetylenes show thermal stabil-ty, good solubility, excellent luminescence and photoconductivityy introducing different mesogens [15]. If the substituent is a liq-

id crystalline group, the polymer is not only soluble in organicolvents, but also easily aligned by spontaneous orientation ofhe liquid crystalline group. Besides, it could be macroscopicallyligned by an external perturbation, such as shear stress, electric

∗ Corresponding author. Tel.: +86 791 3969562; fax: +86 791 3969561.E-mail address: ywchen@ncu.edu.cn (Y. Chen).

379-6779/$ – see front matter © 2008 Elsevier B.V. All rights reserved.oi:10.1016/j.synthmet.2008.11.028

© 2008 Elsevier B.V. All rights reserved.

or magnetic force field. A large number of monosubstituted poly-acetylenes bearing various pendant groups have been designedand synthesized, which can be endowed with such functionalproperties as mesomorphism, luminescence, photoconductivity,gas permeability, chain helicity [16–27]. However, monosubsti-tuted polyacetylenes still suffer from the instability problem: manyof them degrade during storage, especially in the solution stateexposed to air [27]. In contrast, disubstituted polyacetylenes oftenenjoys such advantages as being thermally more stable, betterfilm forming, and mechanically much stronger [28,29]. Disubsti-tuted polyacetylenes are generally more luminescent than theirmonosubstituted counterparts, due to the reduction in interchaininteractions caused by the better chain separation in the disubsti-tuted polymer system [30–32].

The terphenyl core has a calamitic structure that is com-patible with mesomorphic ordering and is well known to giveliquid crystals that have high birefringence [33,34]. Cyanoterphenylderivatives have been used in the preparation of a wide range ofnematic mixtures and, in general, these have high thermal stabilityas well as chemical and photochemical stability [35]. It also has been

reported that cyanoterphenyls bearing alkoxy substituents showhigh photoluminescence efficiency [36].

In this article, the cyanoterphenyl group as the chromophoricmesogenic pendant was introduced onto the polyacetylenes mainchain to synthesize a novel of disubstituted polyacetylene, and

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he properties of the polymer and monomers were also investi-ated.

. Experimental

.1. Materials

n-Butyllithium, trimethyl borate, 4-(4-bromophenyl)phenol, 3-henyl-2-proyn-1-ol, tetrakis(triphenylphosphine)palladium(0),-octyn-1-ol and diethyl azodicarboxylate (DEAD), 40% in tolueneere purchased from Alfa Aesar and used as received without any

urther purification. Tetrahydrofuran (THF), toluene and dioxaneere dried over sodium. Other chemicals were obtained from

hanghai Reagent Co., Ltd., and used as received.

.2. Techniques

The infrared (IR) spectra were measured on a ShimadzuRPrestige-21 Fourier transform infrared (FTIR) spectrophotome-er with the KBr method. The proton nuclear magnetic resonance1H NMR) spectra were recorded on a Bruker ARX 400 NMRpectrometer with deuterated chloroform or THF as the sol-ent and tetramethylsilane (ı = 0) as the internal reference. Theltraviolet–visible (UV) spectra of the samples were obtained withHitachi UV-2300 spectrophotometer. The photoluminescence

PL) of the polymers was measured on a Shimadzu RF-5301PCpectrofluorophotometer. Thermogravimetry (TG) was performednder nitrogen with a PerkinElmer TGA 7 at a heating rate of0 ◦C/min and with a sample size of 8–10 mg. Phase-transitionemperatures were determined with a PerkinElmer DSC 7 differ-ntial scanning calorimeter with a constant heating/cooling rate of0 ◦C/min. Texture observations were made with a Nikon E600POLolarizing optical microscope equipped with an Instec HS 400 heat-

ng and cooling stage. The X-ray diffraction (XRD) study of theamples was carried out on a Bruker D8 Focus X-ray diffractometerperating at 30 kV and 20 mA with a copper target (� = 1.54 Å) andt a scanning rate of 1◦/min.

.3. Synthesis of the monomers

The synthesis and structures of the monomers are outlined incheme 1. All the reactions and manipulations were carried outnder a nitrogen atmosphere.

Scheme 1. Illustration of procedures

ls 159 (2009) 576–582 577

2.4. 4-Cyanobenzeneboronic acid (compound 1)

A solution of n-butyllithium (30 ml, 2.87 M in hexane, 0.086 mol)was added dropwise to a stirred, cooled (−110 ◦C) solution of 4-bromobenzonitrile (15 g, 0.082 mol) in dry THF (180 ml) under drynitrogen. The solution was stirred at below −100 ◦C for 1 h and asolution of trimethyl borate 20.8 ml in dry THF (60 ml) was added atbelow −100 ◦C. The solution was allowed to warm to room temper-ature overnight. 10% hydrochloric acid was added and the solutionwas stirred for 1 h at room temperature. The product was extractedinto ether and the organic layer was washed with water and driedwith MgSO4. The solvent was removed in vacuo and the crude prod-uct dissolved in THF and precipitated with n-hexane to give a yellowsolid with yield of 70%.

2.5. 4-Hydroxy-4′-cyanoterphenyl (compound 2)

Under a dry nitrogen atmosphere a solution of 2.00 g of4-cyanobenzeneboronic acid (13.6 mmol) in 10 ml of ethanolwas added to a solution of 2.75 g of 4-(4-bromophenyl)-phenol (97%, 11.02 mmol) and 0.42 g of tetrakis(triphenyl-phosphine)palladium(0) (99%, 0.36 mmol) in 20 ml of benzene and20 ml of aqueous Na2CO3 (2 M). The reaction was conducted underreflux overnight. The reaction mixture was then shaken with ethylacetate and the insoluble parts were filtered off. The organic layerwas dried with anhydrous MgSO4, and the solvent was removedby evaporation in vacuo. The crude product was recrystallized fromacetone to provide a yellow powder, 65% yield. IR (KBr, cm−1): �2215 (C N), 3351 (–OH). 1H NMR (ppm, CDCl3): 7.73–7.65 (fourd, aromatic, 8H), 7.53 (d, aromatic, 2H ortho to cyano), 6.93 (d,aromatic, 2H ortho to hydroxyl), 4.91 (s, 1H, –OH).

2.6. 4-[(4′-Cyano-4-terphenylyl)oxy]-1-butyl-1-butyne M(1)

The 3-octyn-1-ol (0.48 g, 3.80 mmol), 4-hydroxy-4′-cyanoter-phenyl (1.0 g, 3.70 mmol), PPh3 (1.16 g, 4.41 mmol), and DEAD(40 wt% in toluene, 1.96 g, 4.41 mmol) were dissolved in 60 ml ofanhydrous THF. The mixture was stirred at room temperature for

12 h. After the formed solid was filtered out, the solution was con-centrated with a rotary evaporator. The residue was purified witha silica gel column with dichloromethane/n-hexane (v/v = 4/1) asthe eluent to give a white solid in a 70% yield. IR (KBr, �, cm−1):2233 (C N, C C). 1H NMR (400 MHz, CDCl3, ı, ppm): 7.93–7.66 (m,

for synthesis of the monomers.

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romatic, 8H), 7.56, 7.59 (d, aromatic, 2H ortho to cyano), 7.02, 7.00d, aromatic, 2H ortho to –O–), 4.13–4.09 (t, 2H, –OCH2–), 2.68 (t, 2H,OCH2CH2C ), 2.17 (t, 2H, CCH2), 1.48–1.25 (m, 4H, –CH2CH2–),.93–0.89 (t, 3H, –CH3).

.7. 3-[(4′-Cyano-4-terphenylyl)oxy]-1-phenyl-1-proyne M(2)

The 3-phenyl-2-proyn-1-ol (0.41 g, 3.1 mmol), 4-hydroxy-4′-yanoterphenyl (0.81 g, 3.0 mmol), PPh3 (0.944 g, 3.6 mmol), andEAD (40 wt% in toluene, 1.6 g, 3.6 mmol) were dissolved in 50 mlf anhydrous THF. The mixture was stirred at room temperatureor 24 h. After the reaction finished, the solution was concentratedith a rotary evaporator. The residue was purified with a silica gel

olumn with dichloromethane/n-hexane (v/v = 4/1) as the eluento give a white solid in a 63% yield. IR (KBr, �, cm−1): 2230 (C N,

C). 1H NMR (400 MHz, CDCl3, ı, ppm): 7.73–7.64 (m, aromatic,H), 7.61, 7.59 (d, aromatic, 2H ortho to cyano), 7.46, 7.45 (d, aro-atic, 2H, ortho to C C), 7.32–7.29 (m, aromatic, 3H), 7.15, 7.13 (d,

romatic, 2H ortho to –O–), 4.98 (s, 2H, –OCH2–).

.8. Polymerization

All the polymerization reactions and manipulations were car-ied out under nitrogen using Schlenk techniques in a vacuum lineystem or in an inert-atmosphere glovebox (Vacuum Atmospheres),xcept for the purification of the polymers, which was done in anpen atmosphere. A typical experimental procedure for the poly-erization of P(1) is given below.Into a baked 20 ml Schlenk tube with a stopcock in the sidearm

as added 369.0 mg (1.0 mmol) of M(1). The tube was evacuatednder vacuum and then flushed with dry nitrogen three timeshrough the sidearm. Freshly distilled toluene (2 ml) was injectednto the tube to dissolve the monomer. The catalyst solution wasrepared in another tube by dissolving 20.0 mg of WCl6 and 22.0 mgf Ph4Sn in 2 ml of toluene. The two tubes were aged at 60 ◦C for5 min, and the monomer solution was transferred to the catalystolution using a hypodermic syringe. The polymerization mixtureas stirred at 60 ◦C under nitrogen for 24 h. The solution was then

ooled to room temperature, diluted with 5 ml of chloroform, anddded dropwise to 500 ml of acetone through a cotton filter undertirring. The precipitate was allowed to stand overnight, which washen filtered with a Gooch crucible. The polymer was washed withcetone and dried in a vacuum oven to a constant weight.

P(1), brown powder: IR (KBr, �, cm−1): 2221 (C N). 1H NMR400 MHz, CDCl3, ı, ppm): 7.63–7.42 (m, aromatic, 10H), 6.89,.83 (m, aromatic, 2H ortho to –O–), 4.01–3.98 (m, 2H, –OCH2–),.55–2.38 (m, 4H, –CH2C CCH2), 1.45–1.18(m, 4H, –CH2CH2–),.85–0.83 (m, 3H, –CH3).

. Results and discussion

.1. Synthesis of the monomers

The synthetic routes of the monomers are shown in Scheme 1.he 4-hydroxy-4-cyanoterphenyl was synthesized throughuzuki reaction between 4-cyanobenzeneboronic acid and 4-(4-romophenyl) phenol using tetrakis(triphenylphosphine)palla-ium(0) as the catalyst. Monomer M(1) and monomer M(2) wererepared by 4-hydroxy-4-cyanoterphenyl with 3-octyn-1-ol and-phenyl-2-proyn-1-ol via etherification in the presence of theEAD/PPh3, respectively. The monomers were isolated in 63–70%

ields and characterized by spectroscopic methods (see the Sec-ion 2). The monomers showed a weak band at about 2230 cm−1

ssociated with the C C stretch which is merged to the absorptionand of C N at 2233 cm−1 (Fig. 1). The 1H NMR spectra shown inig. 2 confirmed that the monomers are the expected products.

Fig. 1. FT-IR spectra of the monomer M(1), M(2) and polymer P(1).

3.2. Synthesis of the polymers

Transition-metal catalysts are the most commonly used cat-alysts for acetylene polymerizations. Syntheses of disubstitutedpolyacetylenes have, however, been difficult. It is even more chal-lenging to polymerize disubstituted acetylenes containing polarfunctional groups. Transition-metal compounds such as TaCl5and NbCl5 are the best-known catalysts for the polymerizationof nonpolar disubstituted acetylenes [37]. These transition-metalcatalysts are often found to be incapable of initiating the poly-merizations of acetylenes monomers containing polar functionalgroups, such as ester and ether units. The polar cyano functionalgroup is known to be “toxic” to the classical metathesis cata-lysts for acetylene polymerizations [38]. Thus, polymerizations ofmonomers M(1) and M(2) may be difficult because they contain thepolar ether and cyano units.

However, WCl6–Ph4Sn has been known to be effective cata-lyst for polymerizations of disubstituted polyacetylenes with polarfunctional groups, such as cyano unit [38]. We first attempted topolymerize monomer M(1) in toluene, using WCl6–Ph4Sn as cat-alyst at 60 ◦C for 24 h, delightly, gives a high molecular weightpolymer in a moderate yield. So monomer M(2) was polymerizedunder similar conditions: stirring a toluene solution of monomerM(2) under nitrogen in the presence of the W mixture at 60 ◦C for24 h, however, in sharp contrast to the fact that the polymerizationof monomer M(1), gives no polymeric product. Raising the temper-ature to 80 ◦C did not yield any product. The reaction carried out indioxane with the same W mixture at 60 ◦C and 80 ◦C temperature,but did not obtain any polymer yet. Changing the solvent to THF,the same sad results were received. The bulky phenyl in monomerM(2) replacing the alkyl chain in monomer M(1), especially withthe existence of the bulky and rigid cyanoterphenyl group, seemsto inhibit the reaction and demolish the expectation.

3.3. Structural characterization

The monomers and the polymeric product were characterizedby spectroscopic methods and all the products gave satisfactorydata corresponding to their expected molecular structures (see Sec-tion 2 for details). The monomer M(1) and M(2) showed a weak

−1

band at about 2230 cm associated with the C C stretch whichis merged to the absorption band of C N at 2233 cm−1. Due tothe absorption band merged to the absorption band of C N, thedisappearance of the C C stretch in the polymer P(1) is difficultto be observed, but the absorption band C N at 2233 cm−1 in

L. Chen et al. / Synthetic Meta

Fig. 2. 1H NMR spectra of monomer M(1), M(2) and polymer P(1) (symbol (*) rep-resents the peaks of deuterated-THF).

ls 159 (2009) 576–582 579

the monomer shifted to the low frequency at 2221 cm−1 in thepolymeric product (Fig. 1), which means that the monomer M(1)was polymerized with the W complex catalyst successfully. In the1H NMR (400 MHz) spectra, the 1H NMR spectra of polymer andmonomers are shown in Fig. 2. The resonance peaks in the 1H NMRspectrum of polymer P(1) are broader than that of M(1) and the pro-tons of polymer P(1) are upfield-shifted after the monomer M(1).This shows that the monomer M(1) is polymerized successfully.Except the peaks of solvent and water remained in the spectrum,no unexpected signals are observed in the spectrum of the polymerand all the resonance peaks can be assigned to appropriate protonsas marked in Fig. 2. The 1H NMR spectra as well as the IR analy-ses confirmed that the acetylene triple bond has been consumedby the polymerization reaction and that the molecular structure ofthe polymeric product P(1) is indeed polymer.

3.4. Thermal stability and liquid crystallinity

Since the formation of mesophases of a thermotropic liquid crys-talline polymer is realized by the application of heat, the thermalstability of the polymer is thus of primary importance. Probably dueto the protective “jacket effect” of the thermally stable mesogenicpendants [39,40], the introduction of the mesogenic units into themacromolecular structures has dramatically enhanced the resis-tance of the polymers to thermolysis. The mesogenic polyacetylenealmost do not lose any weights at a temperature as high as above300 ◦C (shown in Fig. 3). The thermal stability of the polymer isfurther substantiated by the DSC analysis: no irreversible peaks sus-piciously associated with polymer degradation are observed at thehigh temperatures during the cycles of repeated heating–coolingscans.

Acetylene monomers M(1) and M(2) and polymer P(1) exhibitedoptical anisotropy when heated or cooled; this suggests that theacetylene monomers and P(1) were liquid crystalline. Fig. 4 showsmicrophotographs of the mesomorphic textures of M(1), M(2), andP(1) taken under a polarized optical microscope. M(1) and M(2)formed anisotropic melts with a birefringent texture, which indi-cated thermotropic liquid crystalline behavior of these monomers.The focal-conic fan texture indicated that the mesophasic natureof M(2) was a SmA phase. The dynamic process of the texture for-

mation revealed that many batonnet-like structures emerged fromthe dark background and grew to bigger domains when M(2) wascooled from its isotropic melt. Different from the M(2), M(1) pos-sesses two different masophase. It formed a nematic phase withtypical threaded texture first before the emergence of the SmA

Fig. 3. TG thermograms of polymer P(1) under nitrogen at a heating rate of20 ◦C/min.

580 L. Chen et al. / Synthetic Metals 159 (2009) 576–582

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ig. 4. Mesomorphic textures of the melting state for M(1) at (a) 143 ◦C, (b) 161 ◦C, (he isotropic states at a cooling rate of 1 ◦C/min.

hase. The polymer P(1) readily formed a nematic phase cooledrom its isotropic melt. With the aid of XRD measurements, the

esomorphic textures of monomers and polymer were identifieddiscussed later).

To learn more about the thermal transitions of the monomersnd polymer, we measured their thermograms under nitrogenn a differential scanning calorimeter. Fig. 5 shows the DSChermograms of the monomers and polymer. M(2) enters the smec-ic A (SmA) mesophase from its isotropic state at 182.1 ◦C. The

esophase is stable in a temperature range over 77.2 ◦C before M(2)nally solidifies at 108.5 ◦C. The associated k–SmA and SmA–i tran-ition profiles of M(2) can be observed at 113.5 and 209.4 ◦C. The

SC thermogram of M(1) shows three transition peaks at 103.9,43.1, and 168.2 ◦C in the first cooling cycle. The mesophase inhis temperature range (168.2–143.1 ◦C) is identified to be nematichase because threaded texture is observed when M(1) is cooledo 143.1 ◦C. Then the typical focal-conic fan texture running across

◦C, and (d) 173 ◦C, (e) M(2) at 179 ◦C, and (f) P(1) at 210 ◦C observed on cooling from

the backs of threaded textures, however, disappear upon fur-ther cooling to 103.9 ◦C. Reheating M(1) regenerates the SmA andnematic phase textures in sequence; that is, the mesomorphism isenantiotropic. In the first cooling cycle of P(1), exothermic peaksassociated with its i–N transition and N–g transition are observedat 218.1 and 200.1 ◦C, respectively. Its corresponding N–i transitionis detected as a broad endothermic bump peaked at 211.2 ◦C duringthe second heating scan. The nematic phase is thus enantiotropic.

We carried out powder XRD experiments (shown in Fig. 6) togain more information concerning the molecular arrangements,modes of packing, and types of order in the mesophases of thepolyacetylene liquid crystals. The XRD patterns were obtained from

the mesogenic polyacetylene quenched with liquid nitrogen fromits liquid crystalline states, whereas the mesophases in the liq-uid crystalline states at the given temperature were frozen bythe rapid quenching with liquid nitrogen. The diffractogram ofM(2) showed a sharp reflection and a broad halo at 2� = 4.74◦

L. Chen et al. / Synthetic Metals 159 (2009) 576–582 581

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ig. 5. DSC thermograms of the monomers and polymer recorded under nitrogenuring the (a) first cooling and (b) second heating scans at a scan rate of 10 ◦C/min.

nd 2� = 21.85◦, respectively, from which d-spacings of 18.49 and

.06 Å were derived. The d-spacing derived from the low-angle peakas close to the calculated molecule length of M(2) at its most

xtended conformation (19.56 Å), thus providing a smectic A (SmA)esophase in a monolayer arrangement. The XRD diffractogram

ig. 6. X-ray diffraction patterns of the monomers and polymer quenched from theiriquid crystalline states.

Fig. 7. UV spectra of THF solution of the monomers and polymer with the concen-tration of 0.125 mM.

of M(1) also displays Bragg reflections at low and high angles.The sharp reflection at the low-angle (2� = 4.72◦) corresponds toa layer spacing of 19.03 Å, which is in considerable is close to themolecular length (21.76 Å). This confirms the SmA nature of themesophase and suggests that the mesogens are packed in a mono-layer structure. Interestingly, when the M(1) was polymerized usingWCl6–Ph4Sn as catalyst, the low-angle peak is disappeared and onlya broad halo in high angle region (2� = 21.85◦) remained. This indi-cates that the existence of less order in the polymer than in themonomer by polymerized and P(1) forms nematic phase.

3.5. Electronic absorption and PL

The ultraviolet–visible (UV) and PL spectra of M(1), M(2) andP(1) in THF are given in Figs. 7 and 8, respectively. The monomersand polymer did not absorb photons at wavelengths longer than300 nm. The absorptions of the monomers and polymer wereassignable to the �–�* bands of the cyanoterphenyl mesogenicpendant because the monomers and polymer had similar absorp-tion wavelengths. Besides, the absorptions of the polymer arestronger than that of its corresponding monomer. The polyacety-

lene backbone absorptions of the polymer were, however, too weakto be observed. The low absorptivity of the polymer main chain mayhave been due to the reduction of the effective conjugation lengthsalong the polyacetylene backbone by the bulky pendant groups.

Fig. 8. Photoluminescence spectra of THF solutions of the monomers and polymerwith the concentration of 0.125 mM (excitation wavelength: 320 nm).

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A polymer with both liquid crystalline and light-emitting prop-rties may find unique technological applications [41], and mostonjugated polymers emit intensely in solution but become weakmitters when fabricated into films [42,43]. We thus investigatedhe fluorescence properties of the polymer and monomers in diluteHF solutions. When the monomer M(2) were photoexcited at20 nm, the monomer emits a strong UV light of about 390 nm inHF, and M(1) emits a strong UV light of 400 nm. Polymer P(1) emitsV light slight red-shifting to 411 nm, whose intensity is muchigher than that from M(1). It indicates that the emitting center isoth the mesogenic cyanoterphenyl pendant and the backbone. Onhe other hand, energy transfer from the pendant to the backboneavors stronger emission in the photoluminescence of polyactylene.

. Conclusions

In this work, we designed and synthesized a group of disubsti-uted polyacetylenes monomers and polymer, and introduce thehromophoric cyanoterphenyl mesogenic pendant onto the poly-cetylenes main chain. The effects of the structural variations onhe chemical and physical properties of the monomers and polymerere investigated. WCl6–Ph4Sn is a effective catalyst for M(1) toroduce polymer with expected structure, but inactive for polymer-

zing the monomer M(2). The monomers and polymer are all liquidrystalline and exhibit enantiotropic mesophases when heatedr cooled. M(2) shows an SmA mesophase, whereas M(1) showsematic and SmA mesophases, and P(1) show a nematic phaseith less order than its corresponding monomer. The existence of

he chromophoric cyanoterphenyl core endows the monomers withigh photoluminescence, and the polymer P(1) prepared from M(1)an emit a strong UV light of 411 nm.

cknowledgements

Financial support for this work was provided by the Nationalatural Science Foundation of China (50773029), the Natural Sci-nce Foundation of Jiangxi Province (520044 and 2007GZC1727),iangxi Provincial Department of Education, and Program forhangjiang Scholars and Innovative Research Team in UniversityIRT0730).

eferences

[1] J.H. Burroughes, D.D.C. Bradley, A.R. Brown, R.N. Marks, K. Mackay, R.H. Friend,P.L. Burns, A.B. Holmes, Nature 347 (1990) 539.

[2] G. Gustafsson, Y. Gao, G.M. Treacy, F. Klavetter, N. Colaneri, A.J. Hegger, Nature357 (1992) 477.

[3] A.G. MacDiarmid, Synth. Met. 125 (1) (2001) 11.

[

[

[

ls 159 (2009) 576–582

[4] S.R. Marder, B. Kippelen, A.K.-Y. Jen, N. Peyghambrian, Nature 388 (1997) 845.[5] D. Bowman, B.R. Mattes, Synth. Met. 154 (2005) 29.[6] A.J. Heeger, J. Phys. Chem. B 105 (36) (2001) 8475.[7] K. Lee, S. Cho, S.H. Park, A.J. Heeger, C.-W. Lee, S.-H. Lee, Nature 441 (4) (2006)

65.[8] H. Shirakawa, Y. Kadokura, H. Goto, S.-Y. Oh, K. Akagi, Mol. Cryst. Liq. Cryst. 255

(1994) 213.[9] J.W.Y. Lam, X. Kong, B.Z. Tang, Polym. Mater. Sci. Eng. 80 (1999) 159.

[10] H. Kuroda, H. Goto, K. Akagi, A. Kawaguchi, Macromolecules 35 (2002) 1307.[11] Heeger, MacDiarmid, Shirakawa won the Nobel Prize in Chemistry in 2000 for

their pioneer work in the area.12] H. Shirakawa, Angew. Chem. Int. Ed. 40 (2001) 2575.

[13] E. Yashima, K. Maeda, T. Nishimura, Chem. Eur. J. 10 (2004) 43.[14] J.W.Y. Lam, B.Z. Tang, Acc. Chem. Res. 38 (2005) 745.[15] C.C.W. Law, J.W.Y. Lam, A. Qin, Y. Dong, H.S. Kwok, B.Z. Tang, Polymer 47 (2006)

6642.[16] W.Z. Yuan, J.Z. Sun, Y. Dong, M. Haüssler, F. Yang, H.P. Xu, A. Qin, J.W.Y. Lam, Q.

Zheng, B.Z. Tang, Macromolecules 39 (2006) 8011.[17] K. Okoshi, K. Sakajiri, J. Kumaki, E. Yashima, Macromolecules 38 (2005) 4061.[18] K. Akagi, S. Guo, T. Mori, M. Goh, G. Piao, M. Kyotani, J. Am. Chem. Soc. 127 (2005)

14647.[19] F. Sanda, T. Kawaguchi, T. Masuda, N. Kobayashi, Macromolecules 36 (2003)

2224.20] C. Xing, J.W.Y. Lam, K. Zhao, B.Z. Tang, J. Polym. Sci.: Part A: Polym. Chem. 346

(2008) 2960.21] P. Mastrorilli, C.F. Nobile, R. Grisorio, A. Rizzuti, G.P. Suranna, D. Acierno, E.

Amendola, P. Iannelli, Macromolecules 37 (2004) 4488.22] 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. 44 (2006) 4532.23] F. Sanda, H. Araki, T. Masuda, Macromolecules 37 (2004) 8510.24] L.M. Lai, J.W.Y. Lam, A. Qin, Y. Dong, B.Z. Tang, J. Phys. Chem. B 110 (2006) 11128.25] B.S. Li, S.Z. Kang, K.K.L. Cheuk, L. Wan, L. Ling, C. Bai, B.Z. Tang, Langmuir 20

(2004) 7598.26] W.Z. Yuan, Y. Mao, H. Zhao, J.Z. Sun, H.P. Xu, J.K. Jin, Q. Zheng, B.Z. Tang, Macro-

molecules 41 (2008) 701.27] W.Z. Yuan, A. Qin, J.W.Y. Lam, J.Z. Sun, Y. Dong, M. Ha1ussler, J. Liu, H.P. Xu, Q.

Zheng, B.Z. Tang, Macromolecules 40 (2007) 3159.28] J.W.Y. Lam, B.Z. Tang, J. Polym. Sci., Part A: Polym. Chem. 41 (2003) 2607.29] J.W.Y. Lam, Y. Dong, C.C.W. Law, Y. Dong, K.K.L. Cheuk, L.M. Lai, Z. Li, J. Sun, H.

Chen, Q. Zheng, H.S. Kwok, M. Wang, X. Feng, J. Shen, B.Z. Tang, Macromolecules38 (2005) 3290.

30] J. Hua, J.W.Y. Lam, X. Yu, L. Wu, H.S. Kwok, K.S. Wong, B.Z. Tang, J. Polym. Sci.:Part A: Polym. Chem. 46 (2008 2025).

31] R.G. Sun, Y.Z. Wang, D.K. Wang, Q.B. Zheng, A.J. Epstein, Synth. Met. 111 (2000)403.

32] R.G. Sun, T. Masuda, T. Kobayashi, Synth. Met. 91 (1997) 301.33] M. Hird, K.J. Toyne, G.W. Gray, S.E. Day, D.G. McDonnell, Liq. Cryst. 15 (1993)

122.34] M. Goulding, S. Green, O. Parri, D. Coates, Mol. Cryst. Liq. Cryst. 265 (1995) 27.35] L. Oriol, M. Pinol, J.L. Serrano, C. Martinez, R. Alcala, R. Cases, C. Sanchez, Polymer

42 (2001) 2737.36] B.M. Conger, J.C.L. Mastrangelo, S.H. Chen, Macromolecules 30 (1997) 4049.37] M. Teraguchi, T. Masuda, Macromolecules 35 (2002) 1149.38] X. Kong, B.Z. Tang, Chem. Mater. 10 (1998) 3352.39] Y.L. Mi, B.Z. Tang, Polym. News 26 (2001) 170.

40] J.W.Y. Lam, X. Kong, Y.P. Dong, K.K.L. Cheuk, K. Xu, B.Z. Tang, Macromolecules

33 (2000) 5027.[41] M. ONeill, S.M. Kelly, Adv. Mater. 15 (2003) 1135.42] M. Grell, D.D.C. Bradley, G. Ungar, J.S. Hill, K.S. Whitehead, Macromolecules 32

(1999) 5810.43] Y. Li, G. Vamvounis, S. Holdcroft, Macromolecules 14 (2004) 6900.