Modern Polymer Spect..

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3.14 Case Studies 149 GI A V E N U M BE R 5 Figure 3-27. Liquid crystalline polyester with decamethylene spacers. Temperature-dependent infrared spectrum in the defect modes frequency range (see text). The spectra and shifted one from the other as in a tridimensional plot. three dimensions for the sake of clarity. It becomes apparent that the tvnizs-planar structure (no defect modes in this frequency range) evolves with increasing teniperature with the generation of only the defect mode near 1365 cm-' due to GTG' defects. No absorption due to GG defects (band at 1353 cm-') is observed, i.e., sharp kinks are neither generated in the sinectic nor in the isotropic phases. The
150 3 T’ibratioiinl <strong>Spect</strong>ra L ~S u Probe oj StrzictLir.al Order. intensity of the GTG’ defect inodes increases sharply at the K-S transition, remains on a smooth platem until the S-I transition occurs, and increases steeply in the I phase. It has to be noted that even in the I phase the GG defect mode is still practically not observable. The mechanism on a molecular level which is derived from the vibrational spectra can be suniinarized as follows: at room temperature the sample contains a sizable concentration of ordered material in which the decamethylene spacers are predominantly in the trms-planar structure. When the I(-S transition is approached the main spectroscopic signal observed is that associated to the GTC’ modes. It is known that the GTG’ defect introduces a kink in the chain but does not change the trajectory of the polyniethylene sequence keeping both arms at either side of the defect parallel. The overall effect is that the length of the decaniethylene segment simply shrinks. It follows that in the S phase the spacers shrink because of the introduction of conformational kinks, inducing a sort of shearing motion between the large aromatic mesogenic groups. The lack of any sizable concentration of GG structures even in the I phase leads to the interesting conclusion that the molecular structure in the I phase is not much different from that in the S phase. No indication is found of ‘liquid-like structures’ observed in other polyniethylene systems in the liquid phase. It has been proposed [114] that one way to reconcile the observation of macroscopically isotropic phase with the observation on the molecular level is to envisage that the isotropic phase consists of a collection of microdomains whose directors are randomly oriented. However, inside the microdomains polymer molecules are organized as they are in the S phase. 3.14.2.3 Case 3: Chain Folding in Polyethylene Single Crystals It is known that chain folding occurs in polyethylene crystals; the fold structure, however, has been a subject of interest and controversy [105]. It was obvious for polymer spectroscopists to use vibrational infrared and/or Raman spectra to try to contribute to the understanding of the shape of the fold (i.e., the molecular conformation) within the fold at the surface of polyethylene single crystals. The large amount of spectroscopic work carried out by many authors is sumarized in [115]. Here, we wish to focus specifically on the contribution given by defect mode spectroscopy considering both calculations and experiments. The issue is whether the surface of polyethylene single crystals consists mostly of loosely looped folds or also of a fraction of chains with a tight adjacent re-entry. In the former case, ‘liquid like’ defects such as GG, GTG, GTG’ etc. are expected and can be recognized in the vibrational spectrum. If tight fold re-entry exists defects of the type GGTGG must occur at the surface of the lainellar single crystal. The first question which needed to be answered in a less qualitative way was where to locate the vibrations localized on the GGTGG defect. Calculations have been carried out on a long polymethylene all-tivm host molecule containing evenly spaced GGTGG defects. NET and IIM and the ‘island analysis’ were applied [99]. The most meaningful results are presented below. Two highly localized modes are calculated to lie near 1361 and 1358 cin-’ and
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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
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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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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 160 and 161: 0 3.14 Case Studies N 0 d - Y N o m
Page 162 and 163: 3.14 Case Studies 147 OC 60 58 57.
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
Page 210 and 211: 3.19 A Worked E.vnrqde 195 009.1 00
Page 212 and 213: 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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