Modern Polymer Spect..

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5.4 Polypeptides 267 glycine residue is achiral, it can adopt the D or L configuration required of alternate chains in the APRS.) This was aided by extensive IR spectra of isotopic derivatives (NH, CD2; and ND, CD2) [97] and by Raman spectra [9S], which were important because macroscopic samples of oriented PGI could not be prepared. The conclusion from vibrational analysis that PGI has an APRS structure was based on a detailed TDC study of the aniide I mode splittings for the APPS as compared with the APRS as a function of the axial shift between adjacent chain [19]. No reasonable shift values for the APPS were in agreement with experiment, whereas the APRS gave excellent agreement for a shift of 0 A, exactly that indicated by the electron diffraction analysis [94]. This structure (Figure 5-3) has a center of inversion and therefore the mutual exclusion rule applies, giving the following symmetry species and activity [ 191: As-21 modes, Raman; A,-20 modes, IR( 11); Bg-21 modes, Rainan; Bu-19 modes, IR(I). The results of the normal mode analysis [96] give an overall rnis error of 6.1 cm-', comparable with that for P-PLA. (The force field for p-PLA was in fact refined from that for PGI [80].) A description of the amide modes of PGI is given in Table 5-7. The splitting of the amide I modes, somewhat smaller than for the APPS structure, is again due to TDC: in its absence the calculated frequencies are 1684 (Ag), 1677 (Au), 1676 (Bg), and 1674 (B,) cm-I. Compared with APPS PLA, CTN d now makes a noticeable contribution to the eigenvector. The amide I1 modes, which are probably at a lower frequency because of the weaker hydrogen bonds, are also split by the TDC interactions: in their absence the calculated modes are at 1534 (Ag), 1535 (A"), 1559 (Bg), and 1559 (B,]) cni-'. The absence of clearly observed high-frequency modes, particularly an IR band near the expected frequency of 1572 cm-I, raises a very important point: it is necessary to be able to predict intensities as well as frequencies. Intensities require knowledge of dipole derivatives (Eq. (5-4)), but since they also depend on correct eigenvectors (Eq. (5-5)) they provide an independent test of the force field. Such an 1R intensity calculation has been done on PGI [20], and the results show that the B, amide I1 mode is indeed predicted to be very weak, in agreement with observation. The amide I11 mode region is quite complex, with mainly NH ib, CN s contributing near 1300 and 1200 ciii-', where only weak bands are observed. In the 'expected' region (1300-1200 cm-'), the strong bands are due to CH? twist (tw)- dominated vibrations. The NH ib contributions now extend to bands about 1400 and below 1200 cm-' . The amide V mode is at a similar frequency to that in ,!I-PLA, even though the PGI hydrogen bond is weaker. This may be because of the large CN t contribution and/or the somewhat different nature of the modes. 5.4.1.3 Parallel-Chain Structures Parallel-Chain Pleated Sheet Although there are no known PPS polypeptides, this general structure is found in proteins [2] and in some tripeptides. in two of which it has been the subject of detailed vibrational analyses [75, 771. The excellent prediction of observed I R and
Table 5-7. Amide mode frequencies (in cm-') of APRS polyglycine I. Observeda Calculated Potential energy distributionb Raman IR A, B" B, B u 1695 CO s(77) CN si15) CTN d(l1) 1685M 1689 CO 475) CN si2Oi C'CN d( 11) 1674s 1677 CO s(74) CNs(211 C"CNd(ll1 1636s 1643 CO s(69) CN si22) C"CN d(ll'1 1602 NH ib(56) CN s(19i C T ~(12) 1572 NH ib(51) C"C s(16) CN s!14! 1517s 1515 NH ibi35) CN s(28i C T s(171 CO ib(14) 1515W 1514 NH ib(35) CN s(271 C'C s(17) CO ibil4) 1410M 1415 CH? w(44) CH? b(3l) NH ib(l4) 1408W 1415 CH? w(40) CH? b(33) NH ib(13) 1304 NH ib(30) CO ib(19) CN si18j C"C sil6) 1295W 1286 NH ibi39) (2°C s(17) CO ib(1hi CN ~(12) 1220w 1213 NC" s(29) NH ib(23) CH2 w(18) CH2 tw(l6) CN s(13j 1214W 1212. NC' s(29) NH ib(23) CH: w(18) CH2 tw(l5j CN ~(13) 1162M 1153 NC" s(50) C"C ~(13) NH ib(l2.) 1152 736 NC' s(50) C'C s(14) NH ib(l2.i CN t(63) NH...O ib(15) NH ob(l1) H...O s(l1) 708s 718 CN t(75) NH...O ib(19) NH ob(16) H...O s(l0) { 718 CN t(791 NH ob(36) NH...O ib(23) H...O s(10) 701 CN t(79) NH ob(29) NH...O ib(25r H...O ~(15) Data taken from [95]. S: strong, M: medium, W: weak. s: stretch, b: bend, ib: in-plane bend, oh: out-of-plane bend, d: deformation, w: wag, tw: twist. t: torsion. Contributions 2 10.
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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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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
Page 232 and 233: 4.7 Poly(p-pheiq.lene) 217 with an
Page 234 and 235: 4.7 Pol)~(p-pheiz~~lene) 219 ENERGY
Page 236 and 237: is worthwhile pointing out that the
Page 238 and 239: ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 801 Table 4-3
Page 240 and 241: 4.7 Poly(y-phenylene) 225 Figure 4-
Page 242 and 243: Table 4-4. Observed Raman frequenci
Page 244 and 245: 4.8 Other Polwieys 229 Table 4-5. T
Page 246 and 247: under various models. According to
Page 248 and 249: 4. I0 Mechnriism oj Charge. Transpo
Page 250 and 251: 4.12 Reftrences 235 [ 131 Kuzmany,
Page 252 and 253: 4.12 References 237 [98j Matsunuma,
Page 254 and 255: 5 Vibrational Spectroscopy of Polyp
Page 256 and 257: 5.2 FOYCC Fields 241 such calculati
Page 258 and 259: 5.2 Force Fields 243 accounts for o
Page 260 and 261: 5.2 Force Fields 245 centers of the
Page 262 and 263: 5.2 Force Fields 247 ture with conf
Page 264 and 265: 5.3 Amide Modes 249 to the nh initi
Page 266 and 267: 5.3 Ainide Modes 251 Table 5-1. Ami
Page 268 and 269: Table 5-2. Some amide modes of four
Page 270 and 271: 5.3 Amidc Modes 255 Figure 5-1. Opt
Page 272 and 273: 5.4 Polypeptides 257 nonhydrogen-bo
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Page 276 and 277: I 5.4 Polypeptides 261 )I .- + $ 80
Page 278 and 279: 1226M 1222s (1 1165W 1167s (1 1120V
Page 280 and 281: 135s 9 1 Ms1i 122Wbr 147 NH ob(37)
Page 284 and 285: 5.4 Polypeptides 269 Raman bands in
Page 286 and 287: 5.4 Polypeptides 271 Figure 5-7. St
Page 288 and 289: Frequency (cm-'1 100% b 700 500 300
Page 290 and 291: 5.4 Polypptidt~s 215 Table 5-9. Obs
Page 292 and 293: ~~ ~~ ~~~ ~ ~ ~~ 5.4 Polypeptides 2
Page 294 and 295: 5.4 Poliyeptides 219 Table 5-11. Co
Page 296 and 297: Table 5-12. Aniide mode frequencies
Page 298 and 299: 1351 Lifson, S., Stern, P. S., J. C
Page 300 and 301: 5.6 Refeverices 285 [130] Tiffany,
Page 302 and 303: Index Amide modes 249 Amorphous pol
Page 304 and 305: Step-scan FTIR spectroscopy 14,34 -
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