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  • Organic Chemistry  (2)
  • Polysilane  (2)
  • Adolescents  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Properties of some polysilane polymers: (n-PrSiMe) n , (i-PrSiMe) n , and (sec-BuSiMe) n (1995)
    Springer
    Journal of inorganic and organometallic polymers and materials 5 (1995), S. 31-42 
    Details
    ISSN: 1572-8870
    Keywords: Polysilane ; nematic mesophase ; liquid crystal ; isotopic phase ; thermochromic transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three polysilane polymers, (n-PrSiMe) n , (i-PrSiMe) n , and (sec-BuSiMe) n , were synthesized and characterized by DSC. UV spectroscopy, wide-angle X-ray diffraction, and optical microscopy, all at variable temperatures. The known thermochromic transition of (n-PrSiMe) n at ∼48 C is associated with a change from an orthorhombic to an isotropic phase. (i-PrSiMe) n was examned as an insoluble and soluble (lowM w) fraction, both existing mainly in an orthohombic lattice at room temperature. (sec-BuSiMe) n has a mesophase structure at 25 C, undergoes a weak endothermic transition to a second (nematic) mesophase near 65 C, and becomes isotropic at ∼160 C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01157521
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of alternating silane copolymers: (Me2Si−R2Si−Me2Si) n (1995)
    Springer
    Journal of inorganic and organometallic polymers and materials 5 (1995), S. 217-236 
    Details
    ISSN: 1572-8870
    Keywords: Polysilane ; NMR ; pyrolysis ; randomization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bimodal molecular weight distributions of alternating copolymers of the type (Me2Si−R2Si−SiMe2) n , where R=hexyl and butyl, were obtained by polymerization of BrSiMe2−R2Si−Me2SiBr, using the Wurtz coupling method. Analysis of the samples by pyrolysis GC MS and solution29Si NMR indicated that some randomization occurred, due to cleavage of the original Si−Si bonds in the monomer. The extent of randomization was significantly greater in the high molecular weight fractions. Based on the nature of the rings from the py MGC/MS traces and the number on nonads found in the29Si spectra, two types of randomization processes have been proposed, involving backbiting followed by (1) ring expulsion or (2) redistribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01057894
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  • 3
    Electronic Resource
    Electronic Resource
    Cigarette withdrawal symptoms in adolescent smokers (1986)
    Springer
    Psychopharmacology 90 (1986), S. 533-536 
    Details
    ISSN: 1432-2072
    Keywords: Cigarette smoking ; Withdrawal ; Adolescents ; Cotinine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract One hundred and sixteen female adolescent smokers were asked about withdrawal symptoms experienced during past attempts to give up smoking for good. Sixty-three percent reported difficulties during abstinence of the kind experienced by adult smokers. Daily smokers were more likely to report withdrawal effects than non-daily smokers (74% versus 47%, P〈0.005). Reported experience of withdrawal symptoms was positively related to self-reports of cigarette consumption and depth of inhalation and nicotine intake as indexed by salivary cotinine concentrations. Reported occurrence of at least one withdrawal effect correlated positively with nicotine intake after controlling for behavioural variables. Our results indicate that teenage smokers are likely to suffer withdrawal symptoms when they try to give up. Behavioural factors and expectations based on observations of adults may have played a part in their experience of withdrawal, but it is also likely that pharmacological factors are implicated even at this early stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174074
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  • 4
    Electronic Resource
    Electronic Resource
    Photoinitiation of vinyl polymerization by polysilanes (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 1 (1987), S. 7-14 
    Details
    ISSN: 0268-2605
    Keywords: Polysilanes ; photoinitiation ; polymerisation ; vinyl monomers ; thin films ; photolysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polysilanes were found to photoinitiate the polymerization of a variety of vinyl monomers including methyl methacrylate, styrene, ethyl acrylate and acrylic acid. Polymerization initiated by polysilane photolysis is rather insensitive to oxygen inhibition, which may make it especially suitable for polymerization of thin films. The initiation efficiency of poly(phenylmethylsilylene) in styrene was determined from dilatometry data to be 1 × 10-3. This rather low efficiency is counterbalanced by the very high extinction coefficient of polysilane polymers, ca. 4-8 × 103 per silicon atom. Possible reasons for the low initiation efficiency and reduced oxygen inhibition of polysilane photoinitiators are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590010103
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  • 5
    Electronic Resource
    Electronic Resource
    Organosilicon polymers with alternating σ- and π-conjugated systems (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 423-430 
    Details
    ISSN: 0268-2605
    Keywords: organosilicon ; polymers ; semiconducting ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of organosilicon polymers containing polysilane and diethynylaryl units along the polymer backbone were synthesized and examined with respect to their optical absorptions. The results indicate that delocalization takes place through the σ-π conjugated system. Lengthening of π-conjugation leads to lower excitation energies while nearly identical UV-vis spectra are observed with increased Si-Si chain length. Introducing a thiophene unit into the π-system instead of a benzene unit leads to a bathochromic shift reflecting greater σ-π delocalization. The polymers undergo photodegradation, probably via cleavage of the Si-Si bonds, and thermal crosslinking by reaction at the C≡C triple bonds. When doped with iodine, these polymers become semiconducting with conductivity of the order of 10-4 S cm-1.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080417
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    Paper (German National Licenses)
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