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  • Polymer and Materials Science  (80)
  • molecular orbital method  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Polymerization of coordinated monomers. XXII. Ab initio molecular orbital study on the binary radical complexes of 2-methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride as a model of growing radical end (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 763-768 
    Details
    ISSN: 0887-624X
    Schlagwort(e): alternating copolymerization ; ab initio molecular orbital method ; boron trichloride ; growing radical end ; radical complex ; methyl methacrylate ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The geometrical and electronic structures of the binary radical complexes of 2-methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride were determined by using an ab initio molecular orbital method. The 2-methoxycarbonyl propyl radical complex was a model of the growing radical end in the copolymerization of methyl methacrylate in the presence of boron halides. The most stable structure of the binary radical complex composed of 2-methoxycarbonyl propyl radical with boron trichloride was a twisted form in which the dihedral angle between the vinyl group and the ester group was 32°, while that of the binary radical complex composed of methyl methacrylate radical with boron trifluoride was a planar form as the free radical. The frontier orbital energy of 2-methoxycarbonyl propyl radical was lowered by 0.06 au by the coordination of boron trichloride, while that was lowered only by 0.02 au by the coordination of boron trifluoride. The polymerization mechanism was elucidated on the basis of these predictions. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1993.080310322
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  • 2
    Digitale Medien
    Digitale Medien
    Kinetic study on the photo-induced alternating copolymerization of methacrylate and styrene using boron trichloride (1987)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 25 (1987), S. 181-185 
    Details
    ISSN: 0887-6258
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1987.140250406
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  • 3
    Digitale Medien
    Digitale Medien
    Polymerization of coordinated monomers. XX. Ab initio molecular orbital study on the binary molecular complex composed of methyl methacrylate and boron trichloride (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1507-1514 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stereo and the electronic structures of methyl methacrylate and the binary molecular complex composed of methyl methacrylate and boron trichloride are determined by quantum chemical calculations based on ab initio molecular orbital methods with the STO-3G basis set. The Stable structures of methyl methacrylate in the free state are a transoid from and a cisoid form. The transoid form is slightly (0.5 kcal/mol) more stable than the cisoid form. The total energy change accompanying binary molecular complex formation is calculated to be -43 kcal/mol. The most stable structure of the binary molecular complex composed of methyl methacrylate and boron trichloride is a twisted form in which the dihedral angle between the vinyl group and the ester group is 19.7°. A large amount of electron transfer from methyl methacrylate to boron trichloride is calculated to occur on binary molecular complex formation. Mulliken's population analysis shows the electron transfer to be the origin of the twist of the binary molecular complex. The energy level of the lowest unoccupied molecular orbital is substantially lowered by the coordination of boron trichloride.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1991.080291015
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  • 4
    Digitale Medien
    Digitale Medien
    Polymerization of coordinated monomers. XXI. Ab initio molecular orbital study on the binary molecular complex composed of methyl methacrylate and boron trifluoride (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2011-2015 
    Details
    ISSN: 0887-624X
    Schlagwort(e): molecular orbital method ; methyl methacrylate ; boron trifluoride ; alternating copolymerization ; molecular complex ; ab initio ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stereo- and electronic structures of the binary molecular complex composed of methyl methacrylate and boron trifluoride are obtained by using an ab initio molecular orbital method with an STO-3G basis set. The total energy change on the binary molecular complex formation is -1.3 X 10-2 Hartree (-8.2 kcal/mol). The electron transfer from methyl methacrylate to boron trifluoride and the change in the energy level of the lowest unoccupied molecular orbital of methyl methacrylate on the complex formation with boron trifluoride are much smaller than those on the complex formation with boron trichloride. A twisted form in which the dihedral angle between the vinyl plane and the ester plane is 16.9° is the most stable structure of the binary molecular complex composed of methyl methacrylate and boron trifluoride. A strong bonding overlap population between a β-hydrogen of methyl methacrylate and a fluorine of boron trifluoride is found in this conformation. © 1992 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1992.080300926
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  • 5
    Digitale Medien
    Digitale Medien
    Polymer conformation and NMR chemical shifts, 3Part 2: cf.:8.. Calculation of conformational energies on alternating acrylate-styrene copolymers (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 3237-3256 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Conformational energies of meso and racemic dyads of four alternating copolymers composed of methyl methacrylate or methyl acrylate with styrene or α-methylstyrene are computed by an empirical force field method as a function of the rotational angles about the skeletal bond pair within each of the dyads. The patterns of the energy contour surfaces of poly(methylacrylate-alt-styrene) and poly(methyl methacrylate-alt-α-methylstyrene) resemble respectively those of the corresponding homopolymers, i.e. poly(styrene) or poly(methyl acrylate) and poly(α-methylstyrene) or poly(methyl methacrylate). On the other hand the energy maps of poly(methyl methacrylate-alt-styrene) and poly(methyl acrylate-alt-α-methylstyrene) containing an α-methyl group in either of the monomeric units, greatly differ from those of the homopolymers of the component monomers. For all the alternating copolymers, the ḡ state is more than 5 kcal/mol higher in energy than the lowest energy state, as it was for the homopolymers. The cutoff distance, employed as a tentative measure of the solvent effect in the calculation of nonbonded interaction, gives a significant effect on the conformational energy, especially of the meso-tt state. Bond interaction parameters for various pairs of substitutents in the copolymers are evaluated from the calculation and they are compared with those determined from the conformational analysis of the homopolymers to check whether or not they are generally applicable to conformational analysis of polymers. Furthermore, conformational probabilities are calculated by the matrix method using the data of the energy calculation.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1981.021821129
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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    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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