Ab Rahman, W. Z.

Ahmad, M. B.

Haron, Md. Jelas

Lutfor, Md Rahman

Silong, Sidik

Wan Yunus, Wan Md. Zin

Wan Yusoff, Wan Mohamad Daud

Universiti Putra Malaysia Institutional Repository

Applied Sciences and TechnologiesPreparation and Characterization of New Side Chain Liquid Crystal Polymers5ilong, 5., Lutfor. MR., A" Rahman, WZ., Wan Yunue, WMZ., Haron, MJ., Ahmad, M6., and Wan YU50ff, WMD.Faculty of Science and Environmental StudiesUniversiti Putra Malaysia43400 UPM, Serdang, SelangorMalaysiaE-mail olCorrespondingAuthor:sidik@fsas.upm.edu.myKey words: liquid crystalline polymers; non-linear optical materials, azobenzene mesogenic group, smectic liquidcrystal, discotic liquid crystal.IntroductionLiquid crystalline polymers are beingrecognized for their potential applica-tion in recording and electrooptic de-vices such as digital and holographicstorage, fast optical switches and non-linear optical materials.':". SinceFinkelmann et al. and Ringsdofr' intro-duced the flexible spacer concept, im-mense research efforts have lead to averiety of novel liquid crystal polymersof various mesogenic groups such as• 4 hvri 4 dphtalocymnes, porp ynnes, anperylene.sVarious studies have shown that byvarying the size and geometry of themesogenic core of liquid crystallinemonomers, the properties change dra-matically. Increasing the size of themesogenic core results in enhanced 1t-1toverlap, thus giving rise to larger phasewidths and more stable mesophases.Vast differences for mesoscopic prop-erties are also seen by changing theperiphery, e.g. by changing the sub-stituents on the parimeter of triphenyl-ene disc from pentyloxy to butyloxy,one does not only proceed from a co-lumnar hexagonal packing to the for-mation of so-called plastic discoticphase, but one also increases the mo-bility by an order of magnitude," Thestudy focussed on the role of intercon-necting structural units between theside-chain mesogen and the polymerbackbone. Here we present the reporton the synthesis and characterization ofpolyacrylate-based side-chain liquidcrystalline polymers containing rod-like azobenzene mesogenic groups intheir side chains.Materials and MethodsThe rod-like azobenzene mesogenicmonomer was prepared from 4-aminoacetophenone, which was diazo-ted and coupled with phenol to give 4-(4acetylphenylazo) phenol. Alkylationof this compound with 3-bromopropa-nol and l l-brornoundecanol convertedit into 4-[4-(3-hydroxypropyloxy)phenylazo]acetophenone (L2) and 4-[4-(11-hydroxyundecyloxy) phenylazo]acetophenone (L4). Esterification ofthe hydroxylated compounds withacyloyl chloride in the presence of drytrietyl amine (TEA) using tetrahydrofu-ran as the solvent to afford the polyrn-erisable monomers 4-{[4-(acrolyl-3-oxypropyloxy) phenyl] azo} acetophe-none (L3) and 4-{ [4-(acrolyl-ll-oxyundecyloxy) phenyl]azo} aceto-phenone (L5). The polyacrylates L9 orLIO were prepared from its corre-sponding monomer L3 and L5 respec-tively by free radical polymerization inTHF using 2,2'-azobisisobutyronitrile(AIBN) as an initiator. All new precur-sors and monomers were characterizedby IH, l3CNMR, and UV-Vis spec-troscopy, and GC-MS. Preliminarymesophase characterization of themonomers and polymers is carried outby differential scanning calorimetry(DSC) and polarized light microscopy.Results and DiscussionDifferential scanning calorimetry(DSC) result shows upon cooling fromisotropic state, polymer L-9 shows twoexothermic peaks at 260 and 96°C,corresponding to isotropic-liquid crys-talline and liquid crystalline-crystallinetransitions, respectively. Polymer L9also shows two endothermic peaks at108 and 272 °C under heating cycle.On cooling, the phase transitions ofpolymer LlD were observed at 236 and94°C, corresponding to isotropic-liquid crystalline and liquid crystalline-crystalline transitions, respectively. Onheating two endothermic peaks wereobserved at 107 and 254°C. On cool-ing, the enthalpy changes of isotropic-liquid crystalline transitions are 2.S1and 2.62 Jg.1 corresponding to poly-mers L9 and LlD, respectively. Thesmall enthalpy change indicated thatboth polymers (L9 and LID) exhibitedthe nematic phase. Polymer LII showstwo exothermic peaks on cooling atIDS and 56°C and two endothermicpeaks at 69 and 124°C under heating.The large enthalpy change (11.52 Jg.l)of isotropic-liquid crystalline transitionof LII indicated that polymer exhibitedthe smectic phase. No glass transitiontemperature (Tg) was detected in thegiven temperature range for all mono-mers of the polymers. DSC results forall polymer compounds are summa-rized in Table 1. The melting and thenematic transition temperature formonomers and polymers are dependenton the number of n of CH2'Sin thealkyl segment. Isotropic point (T1)decreased with the increase of thespacer length. The mesophase proper-ties of the polymers (L9, LlD, and LIl)are marked contrast to those of poly-mers, in which the azobenzene unitsubstituted at 4-position by linear al-kyloxy chain containing a variablenumber n of carbon atoms. The lowerhomologues (n=I-3) of the polymerseries exhibited one nematicmesophase, while on further increasingn (n=4,S) an additional smectic phaseformed; polymer became purely srnec-tic for n>6 based on Angeloni et al.8The phase structures of monomer L3and polymer L9 were observed bypolarizing optical microscopy whencooling from the isotropic point to theirliquid crystalline phases. A typicalschlieren texture of monomer L3 andpolymerL9 were observed at 140 and2S9°C, respectively, which are as-signed to nematic phases. The micro-graph of monomer L-5 and corre-sponding LlD in their liquid crystalphases exhibits both typical nematicdroplets upon cooling from isotropicstate are observed at 114 and 234°C.The monomer L8 and correspondingpolymer LII also showed schlierentexture at 56 and 104 "C, respectively,which indicated smectic phases.195UPM R.... rch Repor11997·2000. S«1JOn 2-ExtMd«J Ab~t'lJcts81.~ on lhe mull or DSC and pular-iI-an, upllnl mh;n~opy anltl)"n. ilc:an be cOlII:luded IlIo ..e Iwo me~or munomCl' alkl polymer ~1IC1wnemallc:liquidc:ry.llIlhne behavior. CIne:monomCl' and polymer ~1IC1w0p..cudt,olmeclic phll<IC. Polymer. 1.9 and 1.10po,_ • ,n:ltler propcn~lIy 10 ,ivc rillC:lu lil""lc ltlkl per'mlenl nemalic:me'W,pIiI.<IC. ThUli indic:Aling lhallheplltCcrnenl IIf an Ill! ygcn alorn by ac:arhunyl ,rllup ""I"'Jly cnl1llncc: .. thenemalllgcnM: charac:1CI' IIf the uclhcn-"ne: ,ruup in the "MIc c:haln pulymer.ConclualonaIn c:onc:lu"lon.the liquid c:r)'lillllline:polyrnen ""'llImm, uubcnlCne: mnic-lic" in the "Idc·cham arc prcpared hyU~IQ' c:oovcnllonal 'rcc radIcal pt"IICCU.The mc'W'fIh- bel1llvMII''' 0' the pllly-mer. wcre Invc.o,alCd Willi IIMIlIC:ofIUIlIklJt.u ...mc","nlCr. and il WP lib·IICrvcd lhall U'and I.Ill' e:lIhlhllCdnernatM: phll<IC near iWJ(rupM: p"ml.·fb.... lUdy Will be 'urther cl!lendcd 10the ''PIKat ILaIlt lIOrilJe: malCl'lab.Benefit. 'rom the atudyl'be "udy pt"lIvtdcd 'ir'l hand uperi-e:nc:e: in .ynlhe,i, alkl dwac:leri/inJadvalll:C rnalCl'lid,; ..idc-c:hain liquidc:ry,1lI1 polynlCr •. II Ifalned .."','" inde\IJrllnl. liynlhe,i/inJ and charac:ler-il-InJ "lde'Chaln liqUId cry,,,,1 pllly.mer •• and lhe flIklInJ' of Ihl" "Iudy willIIhcd Inllrc hJhl Inlo Ihi .. area and pave:• wily fill' further "Iudy.Literature cited In the textAn,,,lulII. A.S .• (·iII"'". l>.. ('illllnl. C .•("h",hnl. CL A.... "'II'''. A.• S"W'" R. iItIda.- •.M. I'JII" u.,. c".,...,62~.Finbl-.II. Rln,,,Ju'l, It._, Wend,,' ..1.11. 111711AluA",_,J. C."". 17'1, Z73196Project Publications InRefereed JournalsAoei. K.• 01110. II .• Murakami. J .• Silone.S. iItId Shirakawa. It. I'IW. Side ChainliqUid Cry,llImine PulYlII:elyleneOt-rivallV('1l - Synlhe,io and Pru,,,,nic,·. J.of p"",,,,.,,lvnw, S.·lmc·r unJ T"c·hlK.IIlIt)·.IZ(2b'1): Z74.lullu •• M.R .• Silon, S. Wan Yunu ••W.Ml_. Ab ltahmwl. M.l_. Ahmad. M.iItId IIlInlll. MJ. 201M).Melall"n, Hindlneb)' ('"hellalin, I.i,and. Inll11 New PulymerBeannll Amld .. ,i"", t'ulK:lional Gruup',J. CMm. Rn "2·'53.lulluf. M.R .• SIIOIIII. S. Wan Vunul.W.M.:t~ Ab Ibhman. M.Z .• Ahnwd. M.and lI;aroo. MJ .• 1I1It'1II. M. J.. Ibid .. 5 .•Wan Yunuo. W.M.l •• SIII,nll. S .. Ab.Rahman. M.Z .• Ahmad. M. illtd Suilliman.M. Y.M. 20m. Pr"piII'illiun and('h;arlll:ten.lic "I ....Iy(N·mnhylhydr .. urnic III:ld) Re,in (n,mPt.I)'( Melhyl IKrylalC'·divinyl ""n/..,ne)""ad •. S.·I. In'.ILuh",r).12: '3-".lull"f. M.R .• Silone. 5.. tiM''''. M.J .• AbRahrnIuI. M.l •• Wan Yunu,. W.M.Z .•Ahllllld. M .. ('"he MAn. M.V.H. and Tan.C .... Pr"f'i!l'II"'" and Charlll:teri"liun 01Puly.:rylalC' ('onillinin, AIII""n/.('neM"",I"" in the Side Chain. Alala),Ji#nJ,,.mlCll of """"',ic-al CMmlmy.(.cepeed "II' pubh'lIliun)lUIIIII'. MR .• Silun,. 5..Wlln Vunul.W.Ml .• Ab Rahman. M.Z .• Ahnlllll. M.iItId 1I;ar,,,,.MJ. 2()"I.Synlhe\i. lind,haracteri/allllll ", polylhydn, ... mk acid),helalln. ""in 'fllnl polylnlC'lhyllll:ryhlte)erallC'd "'11' '&an:h. J. "",.1. 1'"/,.,,.. S.·I..7'1: 12~12M.Siklll,. S .• l.ul'"" M.R .• Ab Rahnwn. M.l .•Wan Yunu •• W.M.Z .• 'hu..n. M.J .•Ahmad. M. lind Wlln YU\l.II. W.M.I>.Syn!he'lo and ,h;arlll:lC'rilllli'lII .. I oide·d",in l"Iuld ""y.llIll1ne p"IYM:ryllllC"""'liIlnlnllawhenl"'''' m.. ieue •• 1.1".CryJ'. l.ubtlUllC'd)Sik", •• S .• lullof. M.R .• Wilt! Yunul.W.M.l.. Ah Rahrnan. Ml_.IlIIt,,,,, M.J .•Ahmad. M. iItId Wan VU".". W.M.I>.Synlhc,i, and Cornparioalion 01 UquidCryo .. 1 Pul),,,,,," and Muno,",,"Cunlainin, A/.ubenune Me"".enl,Malu.VJlun Jmmull CIf """/.\·,lc'ulCMmIJ'"" IIK,e""", 'ur pubh'.li'lII)Sirnmcm. J .. Oluten. B .• Paulu •. W ..Kellner. A .. S'huhrnacher .P; A"""I. D..Ellbac:h. K.1t .. Slc"",nl"",),er. K.•Wenda",. UI. lind Illwer.l>. I'I'HI. lul".Ma,n 1I"·HI9.Vlln der Crul. A.M .• WIII'III11I1.J M .•S,hl"hlin ...... Ruhr. U .• Geerh. V. iItIdMullen. K.I'IW. Synt/r. M",. HI1II2):1'~)·lm.Project Publications InConference ProceedingsSuri. M.r.A .. Zain. M.II .• Amill. M.S.M .•Wlln YUM,ff. W.M.!>. lind SII"n •. S.IW7. Synlhe.i.llnd Chlll'lICteri/Jlli,,,, ufSide·Chain I.i'luid ('ryolllillne .... Iy""'f."b.ltruc·u IIIRrJru,,'" Mml"", f'SA.S •U"M.1II9Silun •• 5 .• LUII.. r. M.R .. Wan Yunu ••W.M.l •• Ah Rahnlllrl. M.i'_.lIanlll. M.J ..Mlln!lOl' Ahllllld and Wall Yu>oOff.W.M.D.ZOOO. SynlhC',i. lind Cumplll'i,"li'lII ofl.i'luid Cry> .. 1 Puly"",,, .lId M"numenC''''llIinin. /\wbell/.c:1lC Me",.en ..PfllI:ccdlnl ul IJ" Maluy>ian /\fIlIlyll,a'ChC'nllotty Symp!»iulII. "onl>td.",""Nelleri SembI Ian. 6-7 September ZUlU.7.l1in. M.II .. Itaron. M.J .• Ab Rllhrrum. M.:t~.Win Yunul. W.M.Z. and Sil,,,, •• S. IWM.Synlhc.il lind (,hlll'lII:leri"liun or /\ NewThcm,"ll'11pic Side Chili" Liquid Cry ....Mllno,ner. Simpo.iurn Kimi. Anall.i.Maluy,i. Kc II.ISKAM II). UnivmiliTeknlllllill Mul.yoil. Jllho,. 4·~Nllv.IWII.Graduate ResearchM.. hurnad lIu .. in III)i ;.'.lIin. 21)(1I. Side·(,hain Li'luid Cryolal ""lyrnen(SCLCPo)IM!K:1 Ulliver.ili "uttllMlllay.ia.Muhamad Lull .. r Rnhman. 21)()().PulyrllC'rm..dilkllli .. n (J'hl>( Univer,iti PulnlMIIIII)'III.IIIRellC'.rch funded hy the Inlenlifknlilln III Re,earchIn Prlurlly II""" IIRI'/\)· SIII'IN"l"d by IR .. /\ KM·'(1'J'H,·2()(J()). Cydc IW7. (iranl 1)I)·()2·114·1)()~7.

Preparation and characterization of new side chain liquid crystal polymers

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Preparation and characterization of new side chain liquid crystal polymers

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