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  • Polymer and Materials Science  (80)
  • radical complex  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Polymer conformation and NMR chemical shifts, 1. 1H NMR spectrum of alternating methyl methacrylate-styrene copolymer (1980)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 383-397 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: NMR chemical shifts of the methoxyl and α-methyl protons in the alternating methyl methacrylate-styrene copolymer are calculated by taking into account the contributions of the diamagnetic shielding and the magnetic anisotropy effect of the benzene rings in styrene units. The conformational probabilities of the copolymer chain are calculated according to Flory's matrix method. It is deduced from the calculation that NMR should occur at higher field for the methoxyl and at lower field for the α-methyl protons of the methyl methacrylate unit in meso configuration with an adjacent styrene unit (regarding the methoxycarbonyl and phenyl groups) than for the corresponding protons in the unit of racemic configuration. Further, the differences between the chemical shifts for these protons in meso and racemic dyads are nearly equivalent to the differences in chemical shifts between two adjacent peaks of the observed triplet spectra. This result indicates that the spectral assignment based on a theoretical calculation is quite consistent with the one made by a conventional simulation method: from the lower magnetic field, peaks of cosyndiotactic, coheterotactic, and coisotactic triads appear in this order for the methoxyl protons and in the opposite order for the α-methyl protons. Magnetic anisotropy effect contributes to these tacticity-dependent chemical shifts to a far greater extent than diamagnetic shielding. The variation of the chemical shifts due to measuring temperature, probability of isotactic addition, and interactions between groups more than five bonds apart is also discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1980.021810209
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  • 2
    Digitale Medien
    Digitale Medien
    Polymer conformation and NMR chemical shifts, 2Part 1: cf.: 1.. Methoxyl protons NMR spectra of alternating copolymers of methyl (meth)acrylate with (α-methyl)styrene (1980)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 931-940 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: 1H NMR spectra of alternating copolymers of methyl acrylate with styrene, methyl acrylate with α-methylstyrene, and methyl methacrylate with α-methylstyrene show triplet splittings at the methoxyl protons regions, which apparently reflect the cotacticity of triad sequences having a (meth)acrylate unit in the center. The two intervals between two neighboring peaks of the triplet are nearly equivalent for each alternating copolymer, whereas the absolute value of the splitting width is significantly different from one alternating copolymer to another. A theoretical interpretation is given for this observation by calculating the chemical shifts of the methoxyl protons in combination with a conformational analysis of the copolymers. The chemical shift of the protons in meso or racemic type dyad sequence is assigned by averaging the shieldings over all the preferred conformations for the dyad and is accumulated to give the shifts in triad sequences: iso = meso + meso, hetero = meso + racemic, syndio = racemic + racemic. The cotacticity-dependent splittings thus calculated are quantitatively in accordance with the observed spectra and discussed in terms of conformational variation of the copolymers depending on the presence of α-methyl group(s) in neither, either, or both of the monomeric unit(s).
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1980.021810414
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  • 3
    Digitale Medien
    Digitale Medien
    Polymer conformation and NMR chemical shifts, 4Part 3: cf.11.. Contrast of 13C NMR spectra between poly(methyl acrylate-alt-styrene) and poly(methyl methacrylate-alt-styrene) (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 211-221 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The presence of the α-methyl group in the alternating methyl methacrylate-styrene copolymer produces a remarkable difference in its 13C NMR spectra as compared with the spectra of the alternating methyl acrylate-styrene copolymer; cotacticity-dependent splittings occur only in the former spectrum. A theoretical interpretation was attempted for this characteristic spectral variation in terms of the calculated time-averaged chemical shifts for carbons in the dyads constituting the alternating copolymers. Each (meso or racemic) dyad sequence is considered to exist in several conformational states which are mutually exchanging rapidly and the probabilities of which are determined by a statistical mechanical procedure. The calculation of cotacticity-dependent chemical shifts is conducted for the side chain carbonyl, aromatic C1 and methoxyl carbons as well as for some main chain carbons to give good agreement with the observed peak splittings, especially with respect to the side chain carbons. In accordance with the reported assignment, the calculated differences in shielding factors between meso and racemic dyads for the side chain carbons of poly(methyl methacrylate-alt-styrene) are positive, i.e. the meso or isotactic peak appears at higher field than the racemic or syndiotactic peak. Furthermore, the resulting values are relatively large (≈0,63 ppm) in conformity with the experiment. The calculation for the carbons in poly(methyl acrylate-alt-styrene) gives a very small shielding difference (-0,04 to 0,06 ppm) by the dyad cotacticity, being consistent with the observation, i. e. absence of peak splittings.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1982.021830119
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  • 4
    Digitale Medien
    Digitale Medien
    Polymer conformation and NMR chemical shifts, 5Part 4: cf.5. 1H and 13C NMR spectra of poly(methyl methacrylate) (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 223-228 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Tacticity-dependent splittings observed in 1H and 13C NMR spectra of poly(methyl methacrylate) are elucidated by a theoretical procedure which consists of conformational analysis of the polymer chain and shielding calculation. The conformation is analyzed by the statistical mechanical method combined with the force field energy calculation on the dyad sequence models. As significant shielding factors, diamagnetic, anisotropic, and electrostatic terms are taken into account for the chemical shifts of 1H NMR, while paramagnetic, diamagnetic, and anistropic terms are considered for 13C NMR. The calculation is used to assing the α-methyl proton, methoxyl proton, methylene proton, quaternary carbon, methylene carbon, α-methyl carbon, carbonyl carbon, and methoxyl carbon peaks split due to dyad and triad cotacticities. The results are generally consistent with the observed spectra. Especially, the calculated splitting widths are in quantitative agreement with the observed splittings of the methoxyl and α-methyl protons resonances as well as of the carbonyl and α-methyl carbons resonances. Effects of temperature and stereoregularity on the spectra are also discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1982.021830120
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  • 5
    Digitale Medien
    Digitale Medien
    Polymer conformation and NMR chemical shifts, 7Part 6: cf. 10.. Conformational analysis of random copolymers (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 371-381 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A method is developed for the conformational analysis of copolymers with randomly distributed stereo- and comonomer-sequences. The conformational probabilities of dyad sequences constituting a random copolymer chain are calculated as a function of the copolymer composition which is derived from the monomer reactivity ratios and the comonomer feed ratio. The applicability of this method is verified in the conformational analyses of poly(methyl acrylate-co-styrene) and poly(methyl methacrylate-co-styrene). The calculation indicates that the conformational stabilities of dyad sequences are scarcely dependent on the copolymer composition in the former copolymer, whereas they are susceptible to the composition in the latter copolymer. This conformational behavior apparently reflects the geometrical difference between the copolymers: the former is composed of two mono-substituted monomers and the latter of sterically nonequivalent monomers, viz. mono- and di-substituted vinyl compounds. The composition-dependences of 13C NMR chemical shifts of these copolymers are interpreted, based on the conformational calculation by this method.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1983.021840213
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  • 6
    Digitale Medien
    Digitale Medien
    Anionic polymerization of oxiranes and cyclic siloxanes initiated with potassium salt-crown ether systems (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 1383-1392 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Potassium carboxylates and 18-crown-6 form initiator systems for the anionic polymerization of oxiranes to afford polyethers with an acyloxy group at one of the chain ends. Because of the slow initiation as compared to the propagation step, the resulting polymers have wide molecular weight distributions (Mw/Mn ≈ 4,0). The presence of a small amount of water in the catalysts accelerates the initiation to give polymers with narrow molecular weight distributions (Mw/Mn ≤ 1,2). The polymerization of methyloxirane is accompanied by a significant chain-transfer reaction to the monomer, especially at high temperatures. Hexamethylcyclotrisiloxane is also polymerized by the same initiators. Furthermore, potassium salts of carboxylic acids initiate the polymerizations in the presence of a crown ether.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1982.021830603
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  • 7
    Digitale Medien
    Digitale Medien
    Polymer conformation and NMR chemical shifts, 6Part 5: cf.4. Alternating copolymer of α-methylene-γ-butyrolactone with styrene (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 1533-1544 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In view of the structural resemblance of α-methylene-γ-butyrolactone to methyl methacrylate, conformation and NMR chemical shifts of poly(α-methylene-γ-butyrolactone-alt-styrene). are calculated and compared with those of poly(methyl methacrylate-alt-styrene). The conformational energy surfaces for the dyad sequence models of the both copolymers are analogous to each other, as is expected from the similarity in the constituting monomeric units. Agreement of calculation with observation is satisfactory with respect to the cotacticity-dependent splittings in the 13C NMR spectra and is improved by the fixation of a substituent in poly(α-methylene-γ-butyrolactone-alt-styrene). Calculation of 1H chemical shifts gives an alignment of NMR signals which is in accordance with the observation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1982.021830617
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  • 8
    Digitale Medien
    Digitale Medien
    Syntheses of macrocyclic oligoesters from 5-hydroxymethyl-2-furancarboxylic acid (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 2347-2359 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: New macrocyclic oligoesters 3a - d, containing furan rings, were synthesized by condenzation of 5-hydroxymethyl-2-furancarboxylic acid (1) using 2-chloro-1-methylpyridinium iodide (2) as condensing agent. Water-insoluble products were separated by GPC and characterized by IR, NMR, MS, and elemental analysis. The product distribution was found to depend remarkably on the reaction conditions. When the mole ratio of 2 to 1 was 1,65 in pyridine was solvent, the cyclic trimer 3a and the tetramer 3b were obtained, both in more than 30% yield. In addition higher cyclic oligoesters (3c - d), linear oligoesters (5b - e), and the polyester (6) were formed. When a large amount of tributylamine was used as a scavenger of hydrogen halides in toluene as solvent, the polyester was the main product. Condensation in hexane in place of toluene, yielded the linear oligoesters as main products. A mechanism is proposed for the formation of the cyclic oligoesters.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1984.021851112
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  • 9
    Digitale Medien
    Digitale Medien
    Copolymerization of carbon dioxide and oxetane (1977)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 241-246 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1977.021780124
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  • 10
    Digitale Medien
    Digitale Medien
    Polymer effect on fine metal particles and reactive metal complexes (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 14 (1985), S. 55-69 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Colloidal dispersions of various metals in liquid are prepared by reduction of the corresponding metal salts in the presence of protective polymer. The average diameters of the metal particles are controlled in the range 9-150 Å by using appropriate species of protective polymers, reducing reagents and additives. The colloidal rhodium of 9 Å in average diameter has a high catalytic activity for hydrogenation of internal olefins. The colloidal palladium of 18 Å in average diameter exhibits a high catalytic selectivity for hydrogenation of diene to monoene. The protective polymers, e.g., poly-(vinyl alcohol) and poly(N-vinyl-2-pyrrolidone) play an important role in stabilizing the colloidal dispersion as a protective colloid and in increasing the catalytic selectivity through the interaction with the metal particles. A toluene solution of aluminium copper chloride protected by linear polystyrene is prepared as a liquid absorbent of carbon monoxide. Aluminium copper chloride protected by cross-linked polystyrene is prepared as a solid adsorbent of carbon monoxide. The polymer protects the watersensitive metal complex against water contained in the gas. The protecting effect of polymer depends on the species of solvent used in the preparation of solid adsorbent. The polymer effect is discussed on the basis of the interactions of the metal complex with the polymer and with the solvent.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.020141985106
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