Modern Polymer Spect..

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2.5 Electric Field-Innductid Orirntcitioii 39 f 1 P6CN 0 I Figure 2-5. FTIR polarization spectra of the P6CN- and P2CN-system ithe insert schematically shows the aligniiieiit of the mesogens on the anisotropic surface; parallel and perpendicular refers to the polarization of the IR radiation relative to the rubbing direction). can be provided into the relevant mechanisms. In what follows. the application of vibrational spectroscopy to the investigation of different phenomena will be trcated separately. On the one hand we will discuss the electric field-induced changes of nematic LC-systems (low-molecular weight compounds, side-chain licluici-crystallirie
40 2 Segnwital Mobility of Liquid Crystuls aid Liquidcrystalline Polymevs 6CPe 0 C H 3 - ( C H z ) e C - O D C = N 5 44.5°C 48.5OC K - N - I NLCP - 0 2, H -&-O-(CHZ)~$$C O a C - N -. CH2 -n 3S°C 130°C G - N - I Figure 2-6. Sti ucture aiid transition temperatures of the investigated low- aiid highmolecular weight LC systems I6CPB and NLCP). polymers and liquid-crystalline guest-host system) in switch-on/switch-off experiments, and on the other hand we will describe the structural consequences incurred by a ferroelectric side-chain polymer in a poled electric field. Nematic liquid-crystalline molecules, which consist of a rigid inesogenic unit with an attached flexible part (sequence of methylene units, for example) (Figure 2-6), are among the most characteristic thermotropic systems. FTIR spectroscopy has been applied to study the mechanisiii of orientation of the liquid crystals in an electric field; however, at present the experimental data are not always unequivocal, and conclusions obtained are not in complete agreement with each other. T~us, some authors did not detect any differences in orientational rates of the rigid and the flexible part of the LC molecule [16, 51-54], which is in accordance with the commonly accepted mechanism of the orientation of an LC as a cooperative motion of a molecular ensemble [l, 2, 381. Other authors reported, that the motion of the flexible part precedes that of the inesogen in both orientation and relaxation [29, 55-57], and some investigators suggested that the motion of the mesogen precedes the motion of the flexible part [58, 591. With respect to a more detailed exploitation of the spectroscopic data in terms of the synchronization of the segmental motions of different functionalities of the investigated liquid-crystalline systems, 2D-correlation analysis [ 16, 30, 60, 611 has proved an extremely valuable tool. In view of the detailed discussion of this mathematical technique in Chapter 1 of this book; however, this topic will not be treated here, although several results extracted from the presented spectroscopic data are based on the application of the 2Dcorrelation formalism. 2.5.1 Materials To study the addressed phenomena, a commercial sample of p-cyanophenyl p-nhexylbenzoate (hereafter abbreviated as 6CPB) (Figure 2-6) was obtained from Roche (Basel, Switzerland), and used without further purification [53, 541. The transition temperatures of this LC are also presented in Figure 2-6. It should be mentioned, that the nematic phase will be retained during cooling down to 7 "C below the crystal-nematic transition point. To demonstrate the reduction of
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Modern Polymer Spectroscopy Edited
Page 4 and 5: Modern Polymer Spectroscopy Edited
Page 6 and 7: Preface For unfortunate reasons the
Page 8 and 9: However, theory and calculations yi
Page 10 and 11: Contents 1 Two-Dimensional Infrared
Page 12 and 13: Con ten t~ xi Index 5.2 Force Field
Page 14 and 15: Contributors M. Del Zoppo Dipartime
Page 16 and 17: 1 Two-Dimensional Infrared (2D IR)
Page 18 and 19: 1.2 Brick~qrorrnrl 3 . Figure 1-3.
Page 20 and 21: 1.0 , Figure 1-6. The in-phtrse and
Page 22 and 23: 1.2 Bcrckgroinizd 7 where AA (i~) i
Page 24 and 25: 1.2 Background 9 1.2.5 Two-Dimensio
Page 26 and 27: 1.3 Bnsic Properties of 20 IR Corre
Page 28 and 29: 2D IR spectrometer coupled with a d
Page 30 and 31: 1.5 Applirtrtions 15 Unlike a dispe
Page 32 and 33: \ '\ Melliyleiie 1'7- -3000 Posiliv
Page 34 and 35: 11 Amorphous Crystalline ,...." I F
Page 36 and 37: 1.5 Applications 21 / I 1430 Figure
Page 38 and 39: 1.5 Appliccitioiis 23 Methylene Fig
Page 40 and 41: 1.5 Ajqdicrrtions 25 3024 Figure 1-
Page 42 and 43: 1.5 Applicutions 27 Furthermore. th
Page 44 and 45: 1.7 Coizclirsions 29 derived in a s
Page 46 and 47: 1.9 References 31 [9] Colthup, N. B
Page 48 and 49: 2 Segmental Mobility of Liquid Crys
Page 50 and 51: SRMPLE/DETECTOR e3 ‘retardation
Page 52 and 53: 2.4 Srvuc me-Dependenr Alignment 37
Page 56 and 57: 2.5 Electric Field-nclticetl Orient
Page 58 and 59: a -@ COWER SRHPLE ._ 2.5 Elec tric
Page 60 and 61: 2.5 Electric Field-Itzduced Orienta
Page 62 and 63: 2.5 Electric Field-IwrElrced Orient
Page 64 and 65: 2.5 Electric Field-Im/irced Orientu
Page 66 and 67: 2.5 Electric Field-Induced Orientli
Page 68 and 69: 2.5 Electric Field-Induced Orientat
Page 70 and 71: 2.5 Electric Field-Induced Orienfat
Page 72 and 73: 2.5 Elrc tric Field-Iiidircwl Orim
Page 74 and 75: 2500 2008 I s00 WRVtNdMRtR CM-I Fig
Page 76 and 77: -3.6 Aligmient OJ' Side- Clinin Liy
Page 78 and 79: ~ polyester 2.6 Alignnient qf Side-
Page 80 and 81: I." 0.9 0.8 Figure 2-34. FTlR 0.7 p
Page 82 and 83: induced alignment of the investigat
Page 84 and 85: 2.7 Orientation oj Liquid Ci:i,stal
Page 86 and 87: 2.7 Orieritation of Liquid Ciysttrl
Page 88 and 89: 0 8 18 16 1 a W u z a m a 0 Ln m Q
Page 90 and 91: 2.7 Orientation oj Liquid Crystals
Page 92 and 93: 2.7 Orientation of Liquid Crjvtals
Page 94 and 95: 2.7 Orientatioiz of Liquid Crystals
Page 96 and 97: 2.8 Conclusions 81 strain. As A0 is
Page 98 and 99: 3. I0 Refcreiice.r 83 [I 71 Hoffina
Page 100 and 101: 2.10 References 85 [92] Wiesner, U.
Page 102 and 103: t Order/Disorder in Chain Molecules
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onds which hold atoms together thro
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3.2 The Dyriamical Case qf Simll ar
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3.2 The Dyrinniical Case of Sinnll
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3.4 S11or.f- and Loizg-Rcrizye Vibr
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3.4 Slzort- and Loiig-Range Vibrati
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eyularity), e.g., 2. During the pol
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3.5 Towards Lnrger Molecules: From
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3.5 TOIIYW~ Laiyer Molertiles: Fvoi
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3.5 Towmu" Larger Molecules: F~om O
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1700 - CIO --- ca c 22 _- c 12 l l
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3.6 From Dynamics to Vibrational Sp
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3.6 Froin Dynaiiiics to T’ihratio
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3.7 The Case of Isotactic Polypropy
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3.7 The Cuse of Isotactic Polypvop.
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3.8 Density of Vibrational States a
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3.8 Dtvz.sit,v of L’ihrntioizal S
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3.8 Driisity of Vibratioiid StLitrs
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3 9 Mouiiiq ToIvmds Rerrlitv: From
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3.9 Moving Towards Reality: From Or
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3.9 Moving Towards Reality: Froin O
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3.10 Wlmt Do We Learn from Cnlcailc
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+ 3.11 A Very Siriiple Ccrse: Latti
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3 I1 A Yey) Siiiiple Case: LLittice
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3.11 A Vq> Siiiiplc Crrw: Luttice D
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Figure 3-22. Sample eigenvectors in
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3.12 CIS-trans Opening @the Double
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3.13 Defect Modes cis Structtrr.al
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3.13 Defect Mo&s cis Structurcil Pr
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0 3.14 Case Studies N 0 d - Y N o m
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3.14 Case Studies 147 OC 60 58 57.
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3.14 Case Studies 149 GI A V E N U
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3.14 Case Studies 15 1 correspond t
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3.14 Case Studies 153 (I10 + 200) +
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3.14 Case Studies 155 1500 1480 146
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3.14 Case Studies 157 the molecular
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17E (ir 1, R): (iii) z = 4, t = 1,
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3.16 Stnictural Znlioi~zogeneity an
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3.1 7 Fermi Resonancrs 163 stants.
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3.1 7 Femi Resorinnces 165 2 L 1 29
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lowing. The CHl-bending mode 6 [cer
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3.17 Ferini Re.sonrriire.s 169 a Fi
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3. I7 Fernii Resoiiances 17 1 terin
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3.18 Band Broadening and Confonnati
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3.18 Bmd Brourleiziriy md Cmforrnat
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3.18 Band Bvoaderiing arid Conjonna
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3.18 Band Broadening and Confornmti
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3.19 A Worked E.utinple 181 pre-mel
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3.19 A Wovh-ecl E.uanzple 183
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3.19 A Worked Example 185 19 5°C 2
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3.19 A Workrd Example 187 Figure 3-
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3.19 A Worked E.rcnniplr 189 LAM I
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3.19 A Worked E.xuniple 191 Figure
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3.19 A Worked E.vnn~yle 193 Figure
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3.19 A Worked E.vnrqde 195 009.1 00
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3.19 A Worked Example 197 existence
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3.1 9 A Worked Example 199 The soli
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3.20 References 201 very important,
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3.20 References 203 [41] M. Gussoni
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3.20 Refeeveiicrs 205 [I 171 P. Jon
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4 Vibrational Spectroscopy of Intac
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4.3 Georrietvy oj Intuct Po1vniev.r
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1'45 4.4 Geometric Chunges I?zditce
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4.4 Geometric Chmges Iiid~lrcecl bj
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4 5 Mer1iodolog.v of Raiii~11 Studi
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4.7 Poly(p-pheiq.lene) 217 with an
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4.7 Pol)~(p-pheiz~~lene) 219 ENERGY
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is worthwhile pointing out that the
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~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 801 Table 4-3
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4.7 Poly(y-phenylene) 225 Figure 4-
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Table 4-4. Observed Raman frequenci
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4.8 Other Polwieys 229 Table 4-5. T
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under various models. According to
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4. I0 Mechnriism oj Charge. Transpo
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4.12 Reftrences 235 [ 131 Kuzmany,
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4.12 References 237 [98j Matsunuma,
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5 Vibrational Spectroscopy of Polyp
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5.2 FOYCC Fields 241 such calculati
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5.2 Force Fields 243 accounts for o
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5.2 Force Fields 245 centers of the
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5.2 Force Fields 247 ture with conf
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5.3 Amide Modes 249 to the nh initi
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5.3 Ainide Modes 251 Table 5-1. Ami
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Table 5-2. Some amide modes of four
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5.3 Amidc Modes 255 Figure 5-1. Opt
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5.4 Polypeptides 257 nonhydrogen-bo
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5.4 Polvpeptida 259 Figure 5-2. Ant
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I 5.4 Polypeptides 261 )I .- + $ 80
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1226M 1222s (1 1165W 1167s (1 1120V
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135s 9 1 Ms1i 122Wbr 147 NH ob(37)
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5.4 Polypeptides 267 glycine residu
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5.4 Polypeptides 269 Raman bands in
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5.4 Polypeptides 271 Figure 5-7. St
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Frequency (cm-'1 100% b 700 500 300
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5.4 Polypptidt~s 215 Table 5-9. Obs
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~~ ~~ ~~~ ~ ~ ~~ 5.4 Polypeptides 2
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5.4 Poliyeptides 219 Table 5-11. Co
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Table 5-12. Aniide mode frequencies
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1351 Lifson, S., Stern, P. S., J. C
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5.6 Refeverices 285 [130] Tiffany,
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Index Amide modes 249 Amorphous pol
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Step-scan FTIR spectroscopy 14,34 -
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