Modern Polymer Spect..

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0 3.14 Case Studies N 0 d - Y N o m orm v I 0 U c- .-- - 0 I I I I ln N 0 m '9 0 0 e Y V 0 L
146 3 Vibratioiiul Sycctm CIS (I Probe of Structural Ordcr 3-25a); (ii) palinitic acid ?-Dz (Figure 3-25b); and (iii) pahnitic acid 3-D2 (Figure 3-25~1. The clear band which appears near 620 cn-' is the gap-niode indicating unquestionably the existence of the local conformation CH?(T)-CD?IT)-CH? both in positions 3 and 4. Identical spectra have been observed along the whole chain, thus confirming the whole lrms structure of palinitic acid in the solid state [107, 110, 1111. 3.14.2 Molecular Mobility and Phase Transitions in Therrnotropic Liquid Crystals from the <strong>Spect</strong>roscopy of Defect Modes The issue is the description of the molecular changes accompanying the phase transitions in systems which show liquid crystalline phases. While much is known on the morphological changes, little is known on what happens to the molecular structure through the various phase transitions. We use defect mode spectroscopy for aiming at the structural changes of prototypical thermotropic liquid crystals such as alkylcyanobiphenyl and polyesters. 3.14.2.1 Case 1: Cyano-alkyl biphenyls Let us first consider dodecyl-cyanobyphenyl which shows two phase transitions at 48 "C (crystalline-semectic A) and at 58.5 "C (smectic A-isotropic). The analysis of the whole spectrum is reported in the original work [112] and we focus here only on the variation with temperature of the conforiiiational structure of the dodecyl side chain which we hope to reveal with the study of the temperature-dependent vibrational spectrum in the 1420-1280 cm-' range where defect modes are expected to occur. Figure 3-26 reports such spectra, together with the difference spectra obtained in the following way. Let s(J + 1) be the spectrum recorded at temperature T(J + 1) and s(j) the spectrum taken at temperature T(j). Then AT = T(J + 1) - T(j) is the temperature gradient in our experiment. From Figure 3-26, while drastic changes are observed from the crystalline to smectic A phase, the spectra do not change much from sniectic A to isotropic. The difference spectra highlight such changes and allow the defect modes GTG', GTG, GG, and end-TG to be identified. The following conclusion can be easily reached: (i) the trans-planar chain exists up to the crystal-smectic A transition; (ii) at the crystal-smectic A transition the trans-planar chain collapses in a conforinationally distorted geometry, as indicated by the appearance of all defect modes listed above; (iii) the observed upward shift of the umbrella deformation mode of the CH3 group from 1376.5 to 1378 cm-l indicates that the environment at the end of the chain is changed; and (iv) no great conformational changes occur from the sniectic A to the isotropic phase; the cyanobiphenyl core must then supervise this phase transition (as also shown by the vibratioiial spectrum). Another case treated is that of 4-cyano, 4'octyloxy biphenyl [113].
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Modern Polymer Spectroscopy Edited
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Modern Polymer Spectroscopy Edited
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Preface For unfortunate reasons the
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However, theory and calculations yi
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Contents 1 Two-Dimensional Infrared
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Con ten t~ xi Index 5.2 Force Field
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Contributors M. Del Zoppo Dipartime
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1 Two-Dimensional Infrared (2D IR)
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1.2 Brick~qrorrnrl 3 . Figure 1-3.
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1.0 , Figure 1-6. The in-phtrse and
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1.2 Bcrckgroinizd 7 where AA (i~) i
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1.2 Background 9 1.2.5 Two-Dimensio
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1.3 Bnsic Properties of 20 IR Corre
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2D IR spectrometer coupled with a d
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1.5 Applirtrtions 15 Unlike a dispe
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\ '\ Melliyleiie 1'7- -3000 Posiliv
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11 Amorphous Crystalline ,...." I F
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1.5 Applications 21 / I 1430 Figure
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1.5 Appliccitioiis 23 Methylene Fig
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1.5 Ajqdicrrtions 25 3024 Figure 1-
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1.5 Applicutions 27 Furthermore. th
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1.7 Coizclirsions 29 derived in a s
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1.9 References 31 [9] Colthup, N. B
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2 Segmental Mobility of Liquid Crys
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SRMPLE/DETECTOR e3 ‘retardation
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2.4 Srvuc me-Dependenr Alignment 37
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2.5 Electric Field-Innductid Orirnt
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2.5 Electric Field-nclticetl Orient
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a -@ COWER SRHPLE ._ 2.5 Elec tric
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2.5 Electric Field-Itzduced Orienta
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2.5 Electric Field-IwrElrced Orient
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2.5 Electric Field-Im/irced Orientu
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2.5 Electric Field-Induced Orientli
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2.5 Electric Field-Induced Orientat
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2.5 Electric Field-Induced Orienfat
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2.5 Elrc tric Field-Iiidircwl Orim
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2500 2008 I s00 WRVtNdMRtR CM-I Fig
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-3.6 Aligmient OJ' Side- Clinin Liy
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~ polyester 2.6 Alignnient qf Side-
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I." 0.9 0.8 Figure 2-34. FTlR 0.7 p
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induced alignment of the investigat
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2.7 Orientation oj Liquid Ci:i,stal
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2.7 Orieritation of Liquid Ciysttrl
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0 8 18 16 1 a W u z a m a 0 Ln m Q
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2.7 Orientation oj Liquid Crystals
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2.7 Orientation of Liquid Crjvtals
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2.7 Orientatioiz of Liquid Crystals
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2.8 Conclusions 81 strain. As A0 is
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3. I0 Refcreiice.r 83 [I 71 Hoffina
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2.10 References 85 [92] Wiesner, U.
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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
Page 110 and 111: 3.4 S11or.f- and Loizg-Rcrizye Vibr
Page 112 and 113: 3.4 Slzort- and Loiig-Range Vibrati
Page 114 and 115: eyularity), e.g., 2. During the pol
Page 116 and 117: 3.5 Towards Lnrger Molecules: From
Page 118 and 119: 3.5 TOIIYW~ Laiyer Molertiles: Fvoi
Page 120 and 121: 3.5 Towmu" Larger Molecules: F~om O
Page 122 and 123: 1700 - CIO --- ca c 22 _- c 12 l l
Page 124 and 125: 3.6 From Dynamics to Vibrational Sp
Page 126 and 127: 3.6 Froin Dynaiiiics to T’ihratio
Page 128 and 129: 3.7 The Case of Isotactic Polypropy
Page 130 and 131: 3.7 The Cuse of Isotactic Polypvop.
Page 132 and 133: 3.8 Density of Vibrational States a
Page 134 and 135: 3.8 Dtvz.sit,v of L’ihrntioizal S
Page 136 and 137: 3.8 Driisity of Vibratioiid StLitrs
Page 138 and 139: 3 9 Mouiiiq ToIvmds Rerrlitv: From
Page 140 and 141: 3.9 Moving Towards Reality: From Or
Page 142 and 143: 3.9 Moving Towards Reality: Froin O
Page 144 and 145: 3.10 Wlmt Do We Learn from Cnlcailc
Page 146 and 147: + 3.11 A Very Siriiple Ccrse: Latti
Page 148 and 149: 3 I1 A Yey) Siiiiple Case: LLittice
Page 150 and 151: 3.11 A Vq> Siiiiplc Crrw: Luttice D
Page 152 and 153: Figure 3-22. Sample eigenvectors in
Page 154 and 155: 3.12 CIS-trans Opening @the Double
Page 156 and 157: 3.13 Defect Modes cis Structtrr.al
Page 158 and 159: 3.13 Defect Mo&s cis Structurcil Pr
Page 162 and 163: 3.14 Case Studies 147 OC 60 58 57.
Page 164 and 165: 3.14 Case Studies 149 GI A V E N U
Page 166 and 167: 3.14 Case Studies 15 1 correspond t
Page 168 and 169: 3.14 Case Studies 153 (I10 + 200) +
Page 170 and 171: 3.14 Case Studies 155 1500 1480 146
Page 172 and 173: 3.14 Case Studies 157 the molecular
Page 174 and 175: 17E (ir 1, R): (iii) z = 4, t = 1,
Page 176 and 177: 3.16 Stnictural Znlioi~zogeneity an
Page 178 and 179: 3.1 7 Fermi Resonancrs 163 stants.
Page 180 and 181: 3.1 7 Femi Resorinnces 165 2 L 1 29
Page 182 and 183: lowing. The CHl-bending mode 6 [cer
Page 184 and 185: 3.17 Ferini Re.sonrriire.s 169 a Fi
Page 186 and 187: 3. I7 Fernii Resoiiances 17 1 terin
Page 188 and 189: 3.18 Band Broadening and Confonnati
Page 190 and 191: 3.18 Bmd Brourleiziriy md Cmforrnat
Page 192 and 193: 3.18 Band Bvoaderiing arid Conjonna
Page 194 and 195: 3.18 Band Broadening and Confornmti
Page 196 and 197: 3.19 A Worked E.utinple 181 pre-mel
Page 198 and 199: 3.19 A Wovh-ecl E.uanzple 183
Page 200 and 201: 3.19 A Worked Example 185 19 5°C 2
Page 202 and 203: 3.19 A Workrd Example 187 Figure 3-
Page 204 and 205: 3.19 A Worked E.rcnniplr 189 LAM I
Page 206 and 207: 3.19 A Worked E.xuniple 191 Figure
Page 208 and 209: 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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