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Chemical Analysis of Polymeric Materials Using Infrared Spectroscopy

Chemical Analysis of Polymeric Materials Using Infrared Spectroscopy 56
Chemical Analysis of Polymeric Materials Using Infrared Spectroscopy Charles Yang Department of Textiles The University of Georgia Athens, Athens, GA 30602, USA University of Zagreb, Croatia, November 3, 2011‡‡‡ Outlines Basic Theory of Infrared Specrtrocopy Molecular vibrational energy, infrared spectroscopy and its selection rules Interpretation of Infrared spectra, group frequency and finger print region Dispersive versus Fourier transform infrared spectroscopy The sampling techniques for solids Applications of FT-IR spectroscopy to polymers: qualitative analysis Applications of FT-IR spectroscopy to polymer: quantitative analysisM M 1 2Vibrational Energy of A Diatomic Molecule V - vibrational quantum number, 0, 1, 2… H - Plank constant V - vibrational frequency m µ- reduced mass M M 1 2 M M 12 k- force constant-1 Wavenumber (cm ) of An IR Absortion Peak 5 a. Force constant-10 dynes/cm -24 b. Reduced mass - 1.673 x 10 gAn Absorption Peak in An Vibrational Spectrum CO (gas)An Absorption Peak with Rotational Fine Structure in An Vibrational Spectrum CO (gas)Electric Magnetic RadiationNear-, Mid-, and Far-Infrared Region‡‡ Selection Rules of Infrared Spectroscopy Excitations from V=0 (ground state) to V=1 st (1 excited state (fundamentals) by absorption of IR radiation Absorption can occur only when there is a change in the magnitude and direction of dipole moment of the bondVibrational Modes http://en.wikipedia.org/wiki/Infrared_spectroscopy‡‡‡ Infrared Spectra Interpretation: Group Frequency Start in the group frequency region: -1 4000-1250 cm (-OH, -NH, =C-H, -CH , 2 -CH , CH-, P-H, C=O…) 3 Easy to interpret, little interference Peak assignment Peak position (wavenumbers) Peak height Peak shape ‡‡‡‡ Infrared Spectra Interpretation: Finger Print Region More complex and more difficult to interpret Small structural differences results in significant in spectral differences Complete interpretation impossible Complete identification requires 100% match between sample’s and standard’s spectra in the finger print regionInfrared Spectroscopy: Group Frequency http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/Inf raRed/infrared.htmStretching Vibrations Bending Vibrations -1 -1 Functional Class Range (cm ) Intensity Assignment Range (cm ) Intensity Assignment Alkanes 2850-3000 str CH , CH & CH 1350-1470 med CH & CH 3 2 2 3 2 or 3 bands 1370-1390 med deformation 720-725 wk CH deformation 3 CH rocking 2 Alkenes 3020-3100 med =C-H & =CH (usually sharp) 880-995 str =C-H & =CH 2 2 1630-1680 var C=C (symmetry reduces 780-850 med (out-of-plane intensity) 675-730 med bending) 1900-2000 str cis-RCH=CHR C=C asymmetric stretch Alkynes 3300 str C-H (usually sharp) 600-700 str C-H deformation 2100-2250 var C≡C (symmetry reduces intensity) Arenes 3030 var C-H (may be several bands) 690-900 str-med C-H bending & 1600 & med-wk C=C (in ring) (2 bands) ring puckering 1500 (3 if conjugated)O-H (free), usually 1330- O-H bending (in- 3580-3650 var sharp med Alcohols & 1430 plane) 3200-3550 str O-H (H-bonded), var- 650- O-H bend (out-of- Phenols 970-1250 str usually broad wk 770 plane) C-O 3400-3500 (dil. soln.) wk N-H (1°-amines), 2 1550- med NH scissoring (1°- Amines 2 3300-3400 (dil. soln.) wk bands 1650 -str amines) 1000-1250 med N-H (2°-amines) 660- var NH & N-H 2 C-N 900 wagging (shifts on H- bonding) 2690-2840(2 med C-H (aldehyde C-H) Aldehydes & bands) str C=O (saturated 1350- strα-CH bending 3 Ketones 1720-1740 str aldehyde) 1360 strα-CH bending 2 1710-1720 C=O (saturated 1400- med C-C-C bending str ketone) 1450 1690 str 1100 1675 str aryl ketone 1745 strα, β-unsaturation 1780 cyclopentanone cyclobutanone 2500-3300 (acids) str O-H (very broad) 1395- med C-O-H bending Carboxylic Acids overlap C-H str C=O (H-bonded) 1440 & Derivatives 1705-1720 (acids) med O-C (sometimes 2- 1210-1320 (acids) -str peaks) 1785-1815 ( acyl str C=O halides) str C=O (2-bands) 1750 & 1820 str O-C (anhydrides) str C=O med N-H (1°-amide) II 1040-1100 str O-C (2-bands) 1590- med band 1735-1750 (esters) str C=O (amide I band) 1650 N-H (2°-amide) II 1000-1300 1500- band 1630-1695(amides) 1560 http://orgchem.colorado.edu/hn dbksupport/irtutor/tutorial.htmlPresentation of Infrared Spectra T% = I /I A = -Log T% t 0 10‡‡‡‡‡ Instrumentation of Infrared Spectrometer Source Monochromator (dispersive IR spectrometer) or Interferometer (FT-IR spectrometer) Sample device Detector Data processing, presentation and storage device Dispersive Infrared Spectrometer FT-IR SpectrometerFT-IR Spectrometer‡‡‡‡ Advantages of FT-IR Spectrometry Multiplex advantage, shorter data acquisition time, high S/N ratio by multiple scans High throughput advantage High resolution More accurate frequency/wavelength measurement‡‡ ‡‡ Sampling Techniques for Solids: Transmission Spectra Pressed KBr pellet method Used for all solid samples Water interference Sample/matrix quantity (2-3%, 200 mg KBr) Fully grinding for sample homogeneity for chemically treated fabrics/fibers Cast film For polymeric sample soluble in a volatile organic solvent Choosing the right window materials KBr ZnSeInfrared Spectroscopy Window Materials‡ Sampling Techniques for Solids: Reflectance Methods Diffuse reflectance (DRIFTS) Good for samples which can be ground to fine particles Can be used as a quantitative method High energy throughput and fast data collection Homogeneous particle size, accessory alignment and sample mounting are important experimental parameters ‡‡ Sampling Techniques for Solids: Reflectance Methods F(R ) = c/k’ ∞ Diffuse reflectance (DRIFTS) Quantitative Analysis F(R∞) – maximum peak value c – concentration K’ – related to particle size and molar absorptivity Use of KBr to collect a reference spectra‡ Sampling Techniques for Solids: Reflectance Methods Internal total reflection A thin and flexible film (e.g., elastomer) is placed with pressure against the crystal, good optical contact is necessary. It can be used as a near-surface method (left) Single bounce, small area diamond crystal is developed for a variety of solid samples (right)Sampling Techniques for Solids: Photoacoustic Method FT-IR Photoacoustic Spectroscopy µ – Thermal diffusion length (cm) s 2 -1 α – Thermal diffusivity (cm ·s ) -1 ω – Angular modulation frequency (redians· s ) -1 -1 -1 k – Thermal conductivity (cal·cm ·s ·°C ) -3 ρ –Density (g·cm ) -1 -1 C – Specific heat (cal·g ·°C ) f – modulation frequency (Hz)‡‡‡‡‡ FT-IR Photoacoustic Spectroscopy No sample preparation Near surface analysis Depth profiling Low sensitivity Interferences (water, vibration…)C. Q. Yang, Ind. Eng. Chem. Res., 31, 617- C. Q. Yang, Appl. Spectrosc., 45, 102-108 621 (1992) (1991)‡‡‡ Qualitative Analysis of Polymers and Textiles by FT-IR Spectroscopy: Part 1 Identification of unknown contaminants of rayon fiber UV-induced oxidation of polyethylene nonwoven fabric Identification the functional groups Distribution of the functional groups Thermal oxidation of polyethylene nonwoven fabric Identification the functional groups Distribution of the functional groups‡‡‡‡ The Dyed 2-ply Rayon Yarn with Unknown Contaminations Previously scoured Dyed with a fiber reactive dye Contaminant unknown Spin finish Another contaminant unknown The yarn was extracted Methylene chloride (polar solvent) Hexane (nonpolar solvDRIFTS Spectra of the Dyed 2-ply Rayon YarnsC. Q. Yang, Ind. Eng. Chem. Res., 33,2836-2839 (1994).Photo Oxidation of Polyethylene FilmL. Martin, C. Q. Yang, J. Environ. Polym. Deg., 2, 153-160 (1994).Thermal Oxidation of PE Film L. Martin, C. Q. Yang, J. Appl. Polym. Chem., 51, 389-397 (1994).‡‡‡‡‡ Qualitative Analysis of Polymers and Textiles by FT-IR Spectroscopy: Part 2 Esterification of cellulose by polycarboxylic acids Reactant Product intermediate Mechanism of esterification of cotton by polycarboxylic acids Development of new and more effective DP finishing system In-situ polymerization of unsaturated bifunctional carboxylic acids Catalysis of NaH PO for estertification of 2 2 cellulose by polycarboxylic acidsC. Q. Yang, Textile Res. J., 61, (1991), pp433- 440.Esterification of Cotton by a Polycarboxylic acid O O O C HO C OH C HO H CC CC H H H C OH O Maleic Acid Fumaric Acid (cis-isomer) (trans-isomer) C. Q. Yang, Textile Res. J., 61, (1991), pp433-440.Maleic Acid Succinic AcidC. Q. Yang, J. Polym. Sci. Part I Polym Chem, 31, (1993), pp1187-1193.Cis-Aconitic Acic (CAA) C. Q. Yang, X. Wang, Textile Res. J., 66, (1996), pp595-603.BTCABTCA Bifunctional Acidscis-1,2-cyclo- hexanedicarboxylic acid (cis-1,2-CHA) C. Yang, G. Zhang, Res. Chem. Intermediates, 26, 515-528 (2000).cis-1,2-CHA NaH PO 2 2trans-1,2-cyclo- hexanedicarboxylic acid (trans-1,2-CHA)1,3-hexanedicarboxylic acid (1,3-CHA, mixtures of cis- and trans-isomers)‡‡‡‡ Formation of Cyclic Anhydride of CHA Cis-1,2-CHA forms 5-membered anhydride at temperatures significantly lower than trans-1,2-CHA NaH PO catalyzes the formation of 2 2 anhydride of cis-1,2-CHA 1,3-CHA forms 6-membered cyclic anhydride at much higher temperatures 1,3-CHA forms could not for cyclic anhydrideC. Q. Yang, J. Polym. Sci. Part A Polym Chem, 31, (1993), pp1187-1193.C. Q. Yang, X. Wang, J. Polym. Sci. Part A Polym Chem, 34, (1996), pp1570-1580.trans-aconitic acid (TAA)X. Gu, C. Yang, Re. Chem. Intermediates, 24, 979-997 (1998).‡‡ Formation of the Cyclic Anhydride by Polycarboxylic Acids A polycarboxylic acid, which can form both 5- and 6-membered cyclic anhydride intermediates on cotton, forms 5-membered cyclic anhydride The hydrogen-bonded carboxyl groups in a polycarboxylic acid forms its anhydride at high temperatures than the free carboxyl groups Esterification of Cotton by a Polycarboxylic acid: Reaction Mechanism O O COOH O HOOC HOOC COOH COOH COOH HOOC HOOC O O BTCA OEsterification of Cotton by a Polycarboxylic acid: Reaction Mechanism O O OH O HO O H OOC O O C OOH O OH Cellulo se Or O O OH HO CO O H H OOC H OOC HO O CO OH O O OH H OOC OEsterification of Cotton by a Polycarboxylic acid: Reaction Mechanism O OH O OH HO O O HO O O O OH O O O O OH OH OH HO O HOOC Cellulose COOH O OH HO HO O HO HOOC O O O O HO O OH O O OH OH O OH HO O HO O OHThe Formation of 5-Membered Cyclic Anhydride Intermediate COOH CH CH COOH 2 2 COOH CH CH COOH CH COOH CH 2 2 COOH CH 2 1,2,4-Butanetricarboxylic Acid 1,2,3-Propanetricarboxylic Acid (BTA) (PCA) Scheme 1 Mao Z., Yang, C. Q.,J. Appl. Polym. Sci., 81, (2001), pp2142-2150.200ºC 200ºC 180ºC 180ºC 160ºC 160ºC 150ºC 150ºC 140ºC 120ºC PCA heated 140-200ºC for 2 min. BTA heated 140-200ºC for 2 min.Esterification of Cotton by PCA and BTA 0.45 0.40 0.35 0.30 PCA 0.25 0.20 0.15 BTA 0.10 0.05 150 160 170 180 190 200 o Curing Temperature ( C) Figure 4 Ester carbonyl band intensity of the cotton fabric treated with 6% PCA and that treated with 6.5% BTA versus curing temperature. Ester Carbonyl Band IntensityPCA Forms Two 5-membered Anhydride Intermediates O CH COO-Rcellulose CH CH COOH C 2 2 2 O HO-Rcellulose -H O 2 CH COOH CH C CH COOH O COOH CH CH COOH 2 2 CH COOH 2 PCA COO-Rcellulose CH 2 CH COO-Rcellulose O 2 HO-Rcellulose -H O 2 CH COOH CH C O COO-Rcellulose CH C CH 2 2 O Scheme 2BTA Forms only One 5-membered Anhydride Intermediate O CH C CH COOH CH COO-Rcellulose 2 2 2 O CH C COOH CH CH COOH HO-Rcellulose -H O 2 O CH CH 2 CH 2 2 CH COOH CH 2 COOH CH COOH 2 2 BTA Scheme 3PCA Forms Two 5-membered Anhydride Intermediates O CH COO-Rcellulose CH CH COOH C 2 2 2 O HO-Rcellulose -H O 2 CH COOH CH C CH COOH O COOH CH CH COOH 2 2 CH COOH 2 PCA First Anhydride COO-Rcellulose CH 2 CH COO-Rcellulose O 2 HO-Rcellulose -H O 2 CH COOH CH C O COO-Rcellulose CH C CH 2 2 O Second Anhydride Scheme 2Second Anhydride First Anhydride (A) Cotton/PCA; (B) 180ºC 2min; (D) Cotton/PCA/NaH PO , 150ºC 2min, 2 2 washed, (E) sample above, 180ºC 2min.Esterification Mechanism of Cotton by Polycarboxyic Acids 1. C. Q. Yang, "FT-IR Spectroscopy Study of the Ester Cross-linking Mechanism of Cotton Cellulose," Textile Research Journal, 61, 433-440 (1991). 2. C. Q. Yang, "Infrared Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: I. Identification of the Cyclic Anhydride Intermediate," Journal Polymer Science, Part A: Polymer Chemistry Edition, 33, 1187-1193 (1993). 3. C. Q. Yang, X. Wang, "Infrared Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: II. Comparison of Different Polycarboxylic Acids", Journal Polymer Science, Part A: Polymer Chemistry Edition, 34, 1567-1580 (1996). 4. C. Q. Yang, X. Wang, "Formation of the Cyclic Anhydride Intermediates and Esterification of Cotton Cellulose by Multifunctional Carboxylic Acids: An Infrared Spectroscopy Study", Textile Research Journal, 66, 595- 603(1996). 5. X. Gu, C. Yang, “FT-IR and FT-Raman Spectroscopy Study of the Cyclic Anhydride Intermediates for the Esterification of Cellulose: I. Formation of Anhydride without A Catalyst”, Research on Chemical Intermediates, 24, 979-997 (1998). 6. C. Q. Yang, X. Wang, "The Formation of Five Membered Cyclic Anhydride Intermediates by Polycarboxylic Acids Studied by the Combination of Thermal Analysis and FT-IR Spectroscopy", Journal of Applied Polymer Science, 70, 2711-2718 (1998). 7. C. Yang, X. Gu, “FT-IR and FT-Raman Spectroscopy Study of the Cyclic Anhydride Intermediates for the Esterification of Cellulose: II. Formation of Anhydride with Sodium Hypophophite as a catalyst”, Research on Chemical Intermediates, 25(5), 411-424(1999). 8. X. Gu, C. Yang, “FT-IR Study of the Formation of Cyclic Anhydride Intermediates of Polycarboxylic Acids Catalyzed by Sodium Hypophosphite”, Textile Research Journal, 70, 64-70 (2000). 9. C. Q. Yang, G. Zhang, “FT-IR and FT-Raman Spectroscopy Study of the Cyclic Anhydride Intermediates for the Esterification of Cellulose: III. Cyclic Anhydrides Formed by the Isomers of Cyclohexanedicarboxylic Acid”, Research on Chemical Intermediates, 26, 515-528 (2000). 10.Z. Mao, C. Q. Yang, "IR Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: V. Comparison of 1,2,4-Butanetricarboxylic Acid and 1,2,3-Propanetricarboxylic acid", Journal of Applied Polymer Science, 81, 2142-2150 (2001).The Traditional PMA CH CH CH CH Benzoyl Peroxide H O 2 n n O C C O CH 3 COOH COOH O n = 6‡‡ The BTCA-treated cotton shows lower amount of anhydride intermediate, but higher ester formation and higher WRA The PMA-treated cotton shows higher amount of anhydride intermediate, but lowerer ester formation and lower WRA C. Q. Yang, X. Wang, I. Kang, Textile Res. J., 67, 334-342 (1997).‡‡‡‡‡ Citric Acid (CA) No Toxicity and low Price CH COOH 2 Low DP Performance HOC C OOH Low Laundering Durability CH COOH 2 Fabric Yellowing All are contributed to the – CA OH group ‡‡‡ CA and Poly(maleic Acid) (PMA) PMA form 5-membered anhydride intermediate on cotton, but has low reactivity to esterify cotton due to its large molecular weight (M.W. 1,000-2,000) CA has low reactivity because of the hindrance by its -OH group PMA’s anhydride group esterify CA on cotton under curing conditions ‡‡ The Synergistic Effect of CA and PMA CH COOH 2 CH O C COOH CH COOH 2 CH COOH CH COOH 2 HO C COOH + CH COOH CH COOH CH COOH 2 PMA CA The Reaction of CA and PMA eliminates the hydroxy group of CA, thus increasing its reactivity and reduce yellowing The Reaction of CA and PMA increases the functionality of CATable 1. The WRA of the cotton fabric treated with CA/TPMA with different CA-to-TPMA ratios and cured at 185º for 3 min Tensile Carboxy Mole Ratio WRA (º, w+f) Total Strength -COOH (m) after 10 Retention TPMA CA before wash washes (%, F) 100 0 0.1980 236 237 66 50 50 0.1985 251 61 249 30 70 0.1956 262 249 57 25 75 0.1983 257 251 59 20 80 0.1964 255 246 57 15 85 0.1973 264 252 59 10 90 0.1953 255 57 243 0 100 0.1955 254 231 58 Control 0.00 184 189 100The CA/PMA Nonformaldehyde Durable Press Finishing System: Publication 1. C. Q. Yang, X. Wang, "Infrared Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: III. the Molecular Weight of A Cross linking Agent", Journal of Polymer Science, Part A: Polymer Chemistry Edition, 35, 557- 564(1997). 2. C. Q. Yang, X. Wang, I. Kang, "Ester Cross linking Cotton Fabric by the Polymers of Maleic Acid and Citric Acid", Textile Research Journal, 67, 334- 342 (1997). 3. C. Q. Yang, L. Xu, S. Li, Y. Jiang, "Nonformaldehyde Durable Press Finishing of Cotton Fabrics by Combining Polymers of Maleic Acid with Citric Acid", Textile Research Journal, 68, 457-464(1998). 4. W. Wei, C. Q. Yang, "Polymeric Carboxylic Acid and Citric Acid as A Nonformaldehyde Durable Press Finish", Textile Chemist and Colorist, 32(2), 53-57 (2000). 5. W. Wei, C. Q. Yang, Y. Jiang, "Nonformaldehyde Durable Press Garment Finishing of Cotton Slacks", Textile Chemist and Colorist, 31(1), 34-38 (1999). Yang, C. Q.: Cross linking Agents of Cellulose Fabrics, U.S. Patent 6,165,919, December 26, 2000. ‡‡‡ In-situ Polymerization of MA and ITA on Cotton Choi reported that cotton fabric treated with MA, ITA and a free radical initiator (0.1-0.2% K S O ) underwent “in-situ polymerization” 2 2 8 (H,-M., Coi, Textile Res. J., 62, 1992, 614-618) Choi claimed such treatment imparted wrinkle resistance to cotton without providing laundering durability data. We studied the system using FT-IR spectroscopyC. Q. Yang, Y. Lu,”, Textile Res. J., 70, 359-362 (2000).‡‡‡‡ In-situ Polymerization of MA and ITA on Cotton We found that the treated cotton had no wrinkle resistance durable to multiple laundering We found that the in-situ polymerization takes place only in the presence of K S O 2 2 8 and NaH PO 2 2 Durable wrinkle resistance is achieved only at high K S O (2%) 2 2 8 IR spectra data provide the evidence of polymerization of MA and ITAFree Radical Initiation 2- .- S O 2 8 2SO 4 O O .- . H P + H SO - P H 4 + HSO 4 OM OMChain Propogation and Chain Transfer O O . . x MA H P + H P MA x OM OM O O O O . . H P MA + P H MA H P H H P H + x x OM OM OM OM O O .- H P MA + H SO . - 4 P MA + x H HSO 4 x OM OM O O . P MA H yMA MA + P H H MA y x x OM OMBeer’s Law A = εbc A = log I /I (absorbance) 0 t ε molar absorbability c concentration (m/l) b radiation pass length in sample‡‡‡ FT-IR Spectroscopy Quantitative Analysis Transmission method should be the best sampling technique for quantitative analysis DRIFTS or photoacoustic methods can also be used as long as the particle sizes are homogeneous FT-IR spectroscopy is a secondary quantitative method. Reference samples or internal references are neededC. Q. Yang, G. D. Bakshi, Textile Res. J., 66, 377-384(1996).2 R = 0.982 R = 0.982 R2 = 0.998 2R = 0.984 R = 0.993 2 2O C N HO CH CH OH N 2 2 HO CH CH OH‡‡‡ Conclusions-I FT-IR can be applied as qualitative, semi- quantitative and quantitative methods for analysis of polymers. It is primary used as qualitative or semi- quantitative method. FT-IR detects functional groups of polymers. The peak frequency and intensity provide qualitative and quantitative information. Peak frequency/shape also provide information related to chemical environment of the functional group. FT-IR is a reproducible, fast and relatively inexpensive analytical method for chemical analysis of polymer. The data base for FT-IR were well established in the literatures.‡‡‡‡ Conclusions-II FT-IR can be applied to insoluble and intractable samples. It can be applied to mixture samples without separation. The sampling methods are relatively easy with no or minimum sample preparation. FT-IR is most useful to study the chemical reactions and chemical bonding on solids. FT-IR is a very useful method for identifying organic compounds including polymers. Full identification based solely on FT-IR can be done when a standard sample is available, as discussed here FT-IR can do more for your research if you have thoroughly understanding all aspects of this analytical method.
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