Low-frequency Raman-active modes in .alpha.-methyl,.omega.-hydroxyoligo(oxyethylene)s

Abstract

Low-frequency Raman spectra were recorded for a-methy1,w-hydroxyoligo(oxyethylene)s, CIEmOH with m in the range 4-16, Le., 14-50 chain atoms. Longitudinal acoustical mode (LAM) frequencies were identified and compared with those determined previously for a-hydro,whydroxyoligo(oxyethylene)s and a-methy1,o-methoxyoligo(oxyethy1ene)s. On the basis of the linear crystal model of Minoni and Zerbi, the two most prominent bands in the low-frequency spectra were assigned to the LAM-1 and LAM-3 modes of the H-bonded dimer crystallized in a bilayer structure. ' h n t addrm: European Vinyls Corp. ((1) Campbell. C.; Viras. K.; Booth, C. J. Polym. Scl., Polym. Phys. Ed., (2) Viras, K.; Teo, H. H.; Marshall. A.; Domszy, R. C.; King, T. A,; Booth, (3) Viras, K.; King, T. A.; Booth, C. J. Polym. Sei., Polym. Phys. Ed.in press. C.Infrared absorption spectral bandshapes are examined theoretically for the OH stretching vibration in hydrogen-bonded complexes in solution. Two distinct dephasing mechanisms are considered: the indirect mechanism in which the OH vibration is coupled to one or more internal vibrations in the complex, which are in turn coupled to the solvent, and the direct mechanism in which the OH vibration is directly coupled to the solvent. Attention is focused on intramolecularly H-bonded complexes for which extensive spectral data are available for a range of solvent polarity. It is concluded for the complexes considered that the direct mechanism is dominant. In particular, good fits to the experimental data are obtained via this mechanism for spectral width features in a given solvent and as a function of solvent polarity. Some distinctions between intra-and intermolecularly H-bonded complexes are given, and some suggestions for further work are made.

Poly(oxyethylene) Chains and Rings Studied by Raman Spectroscopy and Differential Scanning Calorimetry

“…The primary purpose of this paper is to report the first measurements by low-frequency Raman spectroscopy on new model polymers, cyclic poly(oxyethylene)s. Comparison is made with the vibrational properties of their linear-chain counterparts as a convenient means of connection to the considerable literature on that topic; see, e.g., reports on nonuniform low-molar-mass polymers15,16,18™21 and uniform oligomers. 20,21,32,33 The detailed discussions of the properties of the crystalline chains which can be found in those papers are not repeated here.…”

Preparation and characterization of pure oligo(ethylene glycol)s. 2

“…Characterization of these pure OEG samples has been carried out by various methods: SEC,1-2,4 mass spectroscopy (MS),2a'b NMR,2 IR,2 VPO,2a LS,5 and Raman spectroscopy. 6 However, only a few quantitative measurements to determine their molecular weights M or degree of polymerization x have been performed successfully for low-molecular-weight OEGs. 5 For high-molecularweight OEGs, the values of M or x have been speculated only from chromatographic peak positions in their SEC chromatograms.…”

“…Figure6. Quantitative 100-MHz 13C NMR spectrum of the pure OEG54 sample measured in deuterated chloroform.…”

Chain Folding in Semicrystalline Oxybutylene/Oxyethylene/Oxybutylene Triblock Copolymers Studied by Raman Spectroscopy

“…In principle, the LAM-1 frequency relates to the reciprocal of the length of the vibrating crystal stem. In practice, this ideal relationship is perturbed by several effects, including end-group masses and end and lateral forces. ,,− ,,, The first five entries in Table , which are for copolymers with essentially constant E-block lengths, show directly that the B-block length is a significant variable.…”

“…It is useful first to note the background provided by work on short poly(oxyethylene) chains. In Figure , LAM-1 frequencies (ν 1 , in wavenumbers) obtained ,,,,, for hydroxy- and methyl-ended poly(oxyethylene)s are plotted as the dimensionless product ν 1 l E versus l E . The lines correspond to ν 1 l E = 1.0 × 10 -5 and ν 1 l E = 2.0 × 10 -5 .…”