Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Polymer and Materials Science  (18)
Source
Material
Years
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Cationic polymerization of α-methylstyrene in dichloromethane initiated with system 2,5-dichloro-2,5-dimethylhexene-BCl3. II. Continuous addition of monomer into initiator, quasiliving polymerization (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 2229-2238 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A slow continuous addition of dichloromethana solutions of α-methylstyrene (α-MeSt) into a dichloromethane solution of 2,5-dichloro-2,5-dimethylhexane (DDH) with BCI3 (initiating system II) prepared in advance resulted, in the temperature range between -20 and -40°, in a quasilving polymerization of α-MeSt. At -20°C and a 100% conversion a polymer with a very narrow molecular weight distribution is formed, M̄w/M̄n - 1.1. Quasiliving polymerization of α-MeSt has not been achieved with freshly prepared dischloromethane solutions of DDH with BC3 (initiating sytem I), or with solutions of BCI3 alone (initiating system III). Polarity of the polymerization medium affected molecular weight distribution (MWD) of the polymer, and the polydispersity index decreased with decreasing polarity. MWD of the polymer samples were studied by the GPC method, the structure of poly (α-methylstyrene) (Pα-MeSt) was investigated by the 1H-NMR analysis
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270708
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    High resolution 1H-NMR study of association of polymers in solution. Poly(methyl methacrylate) and poly(vinyl chloride)Presented in part at the 14th IUPAC Microsymposium on Macromolecules, Prague 1974, Abstract D4. (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 3409-3423 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Verfahren zur Bestimmung des Inhalts und der thermischen Stabilität von Assoziaten in Polymerlösungen mittels der anomalen Werte und Änderungen von integrierten Banden-intensitäten in hochaufgelösten 1H-Kernresonanzspektren wird beschrieben. Assoziate in Lösungen von isotaktischem und syndiotaktischem Poly(methylmethacrylat), (PMMA), wurden auf diese Weise gefunden und charakterisiert. Die Assoziatstrukturen in Lösungen von isotaktischem PMMA weisen eine höhere Stabilität auf als Assoziate in Lösungen von syndiotaktischem PMMA. Zwei unterschiedlich stabile Typen von Assoziaten konnten such in Lösungen von ataktischem Poly(vinylchlorid) beobachtet werden.
    Notes: A procedure for the determination of the contents and the thermal stability of associated structures in solutions of polymers is described, making use of the anomalous values and changes of integrated band intensities in high-resolution 1H-NMR spectra. In this way, associated structures in solutions of isotactic and syndiotactic poly(methyl methacrylate), (PMMA), were detected and characterized. The associated structures in solutions of isotactic PMMA are much more stable than the aggregates in solutions of the syndiotactic PMMA. Two types of aggregates differring in stability were also observed in solutions of atactic poly(vinyl chloride).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021761123
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The effect of stereochemical structure on the viscoelastic behaviour of poly(ethyl methacrylate) (1980)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 277-288 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The low-frequency viscoelastic behaviour of three stereoregular samples of poly(ethyl methacrylate) (PEMA) in the main transition region was investigated. The main effect of tacticity in the transition from the syndiotactic sample to the isotactic one consists in a shift of the main transition region (or of the glass transition temperatures, Tg) to lower temperatures by ≈ 70 K. The temperature dependence of the shift factor of all samples could not be adequately described by the single Williams-Landel-Ferry (WLF) equation within the whole range of temperatures; in the range T〉Tg+60K, isotactic PEMA exhibited the largest departures from the WLF equation. In all cases, departures from the WLF equation could be quantitatively described in terms of the temperature dependence of the Andreade coefficient β. The temperature dependence of the Andreade compliance, JA, was also most pronounced for the isotactic sample. Vertical correction of the complex modulus G*, with WLF horizontal shifts preserved, led to the lowest activation energy ΔH for the isotactic sample, which means the highest magnitude of secondary relaxation mechanism in this sample. The birefringence measurement showed that the molecular nature of the deformational birefringence is independent of the tacticity of the sample and does not vary in the range Tg+25K〈T〈Tg+100K. In all the characteristics mentioned here, parameters of a conventional sample obtained by radical polymerization approached those of the syndiotactic sample.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1980.021810125
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    An investigation of the self-aggregation process of syndiotactic poly(methyl methacrylate) in solution by using infrared spectra (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 2099-2105 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The time dependence of self-aggregation of syndiotactic (s) poly(methyl methacrylate) (PMMA) in dilute toluene or CCl4 solutions was investigated using infrared (IR) spectra measurements. The IR spectra were also recorded in s-PMMA solutions where no self-aggregation takes place (benzene, acetonitrile). It was found that the helix conformation with a large number of units per turn (near-tt) in aggregated s-PMMA is formed in parallel with intermolecular interactions of ester groups of s-sequences. The connection between the fraction of s-sequences in the helix conformation determined for unaggregated s-PMMA in various solvents using IR spectra and the ability of s-PMMA to form self-aggregates (double helix) in a certain solvent is discussed. Intersegmental contacts which occur in s-PMMA in CCl4, i.e. in a thermodynamically poor solvent, lead to a decrease in the equilibrium aggregated fraction, to the slowing-down of the aggregation process and to the decomposition of the majority of aggregated structures during evaporation of the solvent; their effect is similar to that of chemical crosslinking.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890912
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Infrared spectra and crystallinity of isotactic poly(methyl methacrylate) and of its deuterated analogues (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 2705-2711 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of partially crystalline and amorphous samples of isotactic poly(methyl methacrylate) (i-PMMA), poly[methyl (α,α,α-2H3)methacrylate] (i-PMMA-α-CD3), poly-[(2H3)methyl methacrylate] (i-PMMA-OCD3), and poly[(2H3)methyl (α,α,α,2,2-2H5)methacrylate] (i-PMMA-D8) were measured. Infrared spectra of the pure crystalline forms of these substances were obtained by digital separation. It was found that in acetonitrile, CDCl3, and toluene solutions, i-PMMA has the same conformational structure as in the amorphous state; conformational structures of crystalline i-PMMA are not present in the solutions in measurable amounts.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021881121
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    HR-NMR study of formation and structure of the stereocomplex of poly(methyl methacrylate) in solution (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 2939-2956 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aus hochaufgelösten Kernresonanzspektren wurde der Gehalt p an assoziiertem Stereokomplex in Lösungen von isotaktischem und syndiotaktischem Poly(methyl methacrylat) bestimmt. Mit Hilfe der p-Werte wurde festgestellt, daß in aromatischen Lösungsmitteln die minimale Länge der assoziierten syndiotaktischen Sequenzen ca. 10 Monomereinheiten beträgt, in CCl4 und CD3CN ist die minimale Länge ca. 3 Monomereinheiten. Im assoziierten Stereokomplex ist das Verhältnis der Monomereinheiten von isotaktischen und syndiotaktischen Sequenzen (iso:syndio) = 1:1,5; die Dissoziation des Stereokomplexes erinnert bei Erhöhung der Temperatur an das Schmelzen von Mikrokristallen. Der Schmelzpunkt der assoziierten Segmente steigt in einem gegebenen Lösungsmittel mit der Länge der assoziierten Sequenzen.
    Notes: From high-resolution NMR spectra of mixtures of solutions of isotactic and syndiotactic poly(methyl methacrylate), the content p of the associated stereocomplex was determined. From the values of p, the minimum length of associated syndiotactic sequences was found to be ca. 10 monomeric units in aromatic solvents and ca. 3 such units in CCl4 and CD3CN. In the associated stereocomplex the ratio of monomeric units in isotactic and syndiotactic sequences is (iso/syndio) = 1:1,5; the process of dissociation of the stereocomplex with increasing temperature is reminiscent of the melting of microcrystallites. The melting point of associated segments in a given solvent increases with the length of the associated sequences.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021751014
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Characterization of the structure of the stereocomplex of poly(methyl methacrylate) in solution from NMR relaxation data (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 729-743 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Mit dem Impulsspektrometer bestimmte Relaxationszeiten T2, sowie Linienformen in Hochauflösungs- und Breitband-Kernresonanzspektren (HR- und BL-NMR) haben gezeigt. daß im assoziierten Stereokomplex von isotaktischem (it-) und syndiotaktischem (st-) Poly(methylmethacrylat) (PMMA) zwei Protonentypen vorkommen, die sich durch + Beweglichkeit unterscheiden. Aus der Analyse der unter dem magischen Winkel aufgenommenen Kernresonanzspektren (MAR-NMR) wurde gezeigt, daß die Beweglichkeit von Estergruppen im Stereokomplex weitgehend behindert ist. Aus der Temperaturabhängigkeit der HR-NMR Spektren der gemischten Lösungen von it- und st-PMMA in Benzol können die assoziierten Stereokomplexsegmente als Vernetzungspunkte eines Gerüstes von nichtassoziierten Sequenzen charakterisiert werden.
    Notes: From the values of relaxation times T2 determined on a pulse spectrometer, and from the shape of bands in high resolution (HR-) and broad line (BL-) NMR spectra, two types of protons, different in mobility, were found to exist in the associated stereocomplex of isotactic (it-) and syndiotactic (st-) poly(methyl methacrylate) (PMMA). From the analysis of NMR spectra, measured at magic angle rotation (MAR-NMR), the mobility of the ester groups in the stereocomplex is shown to be greatly hindered. Temperature changes of HR-NMR spectra of mixed solutions of it- and st-PMMA in benzene indicate that the associated segments of the stereocomplex can be characterized as junctions of a network of nonassociated sequences.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760315
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    High resolution 1H-NMR study of association of polymers in solution. Poly(methyl methacrylate) and poly(vinyl chloride) (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 957-957 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770334
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    NMR study of aggregation of heterotactic-like poly(methyl methacrylate) in solution (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 861-870 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aggregation of heterotactic-like poly(methyl methacrylate) (PMMA) in some solutions was proved by NMR spectroscopy. It was found that the fraction of aggregated units depends on solvent, solution concentration and temperature; the aggregates are completely decomposed at 45°C. Aggregation occurs by intermolecular interactions of m-diads with rrr-tetrads, i. e. by interactions of the stereocomplex type. The formation of a stable aggregated structure is probably a consequence of the microstructure of the heterotactic-like PMMA chain, with relatively long sequences of regularly repeating mrrr pentads or mrrr hexads. The aggregation in mixtures of heterotactic-like PMMA solutions with isotactic or syndiotactic PMMA solutions was also studied.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021880420
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    1H and 13C nuclear magnetic relaxation and molecular motion in solid poly(L-alanine) (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1451-1461 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nuclear magnetic relaxation data both for proton and for carbon-13 nuclei in solid-powder poly(L-alanine) are analyzed together, in order to obtain information on the molecular motions in polypeptides. For this analysis the “model-free” approach is used. Three types of internal motions are determined in the α-helix conformation of the investigated polymer. An inhomogeneous distribution of correlation times is shown to be inherent in each type of motion. The first type is the methyl group rotation around the symmetry axis with correlation times of about one hundred picoseconds at room temperature. The second type are the small-amplitude (≈10°) individual oscillations of backbone groups as well as of the axis of the methyl group, with correlation times from ten to one hundred nanoseconds at room temperature. The last type is the α-helix backbone motion with correlation times of a few microseconds at room temperature and with amplitudes of 20° or more, which possibly represents the cooperative motion of several neighbouring groups in the main chain.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930621
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...