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  • 1990-1994  (2)
  • 1985-1989  (5)
  • 1940-1944
  • Polymer and Materials Science  (4)
  • mesophases  (2)
  • Adolescents  (1)
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Material
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  • 1990-1994  (2)
  • 1985-1989  (5)
  • 1940-1944
  • 1980-1984  (4)
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Some recent developments in polysilane chemistry (1992)
    Springer
    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 29-45 
    Details
    ISSN: 1572-8870
    Keywords: Polysilenes ; polysilanes ; liquid crystals ; mesophases ; birefringence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract (I) Ordered and disordered polysilane copolymers: Condensation of ClSiMe2Si(n-Hex)2SiMe2Cl with Na/K in toluene at 90°C produced a polymer with a strongly bimodal molecular weight distribution. The high-M w and low-M w portions were separated by fractional precipitation with 2-propanol, and the properties of the two fractions were investigated.29Si-NMR spectra show that the low-M w fraction is fully ordered but the high-M w fraction is randomized. (II) Liquid crystalline polysilanes: Condensation ofn-Bu(n-Hex)SiCl2 with Na in toluene led to a homopolymer which is a rubbery solid at 25°C. The polymer undergoes a second-order transition at −45°C and a first-order (melt) transition at −20°C. X-ray diffraction shows that the polymer has the same structure, a columnar hexagonal lattice, in all three phases; from −20 to 〉200°C, it exists in a columnar liquid crystalline mesophase. Similar hexagonal mesophases were observed at 25°C for the family of copolymers, (n-Hex2Si) n (Alk2Si) m , Alk =n-Pentyl,n-Bu,n-Pr, Et, Me.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696534
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  • 2
    Electronic Resource
    Electronic Resource
    Ethynylene-disilanylene copolymers (1991)
    Springer
    Journal of inorganic and organometallic polymers and materials 1 (1991), S. 545-565 
    Details
    ISSN: 1572-8870
    Keywords: Polysilanes ; sigma-pi conjugation ; mesophases ; polymer crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polymers of structure (SiR2SiR2-C ≡ C-SiR2′SiR2′-C ≡ C) n , in which ethynylene units alternate with disilylene units, have been prepared by two routes: (a) condensation of dichlorodisilanes with dilithium derivatives of 1,2-diethynyldisilanes and (b) ring-opening polymerization of strained cyclic disilanylene-acetylnes, (SiR2SiR2C ≡ C)2. The polymers display UV absorption near 240 nm indicative of σ − π conjugation between the Si2 and the C ≡ C moieties. Polymers with R=R′=n-Bu or R=n-Bu, R′=Ph, undergo solid-state transitions to form liquid crystalline mesophases resembling those observed for many poly(silylenes). Single crystals were obtained for the polymer with R=R′=CH3, by precipitation from dilute cyclohexane solution. The solid-state properties and structures of this family of polymers are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683516
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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
    29Si nuclear magnetic resonance of dimethyl and phenylmethyl containing polysilanes (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 701-712 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 29Si-NMR spectra are reported for poly(methylphenylsilylene), 1, poly(1,1,2-trimethyl-2-phenyldisilene) 2, two samples of poly(dimethylsilylene-co-phenylmethylsilylene), 3a and 3b, and poly(phenylmethylsilylene-co-n-hexylmethylsilylene), 4. The spectra of 3a, 3b, and 4 indicate that these polymers contain blocklike regions with considerable segregation of RMeSi and PhMeSi groups. The spectrum of 2 shows no evidence for stereospecific polymerization. The preparation of 2 from 1,1,2-trimethyl-2-phenyldichlorosilane is also described.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260303
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  • 5
    Electronic Resource
    Electronic Resource
    29Si nuclear magnetic resonance of dialkylpolysilanes (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 713-720 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The silicon-29 nuclear magnetic resonance spectra of a number of dialky- and alkylmethylpoly-silanes are reported. Polysilanes composed of asymmetrically substituted silylenes (i.e., alkylmethylsilylenes) exhibited very broad resonance lines attributed to diastereomeric chemical shifts of stereogenic silylenes alpha and beta to the observed nucles Symmetrically substituted polysilanes showed a single narrow peak. The 29Si chemical shifts for these polysilanes decrease with increasing steric bulk of the substituents, varying inversely with the electronic excitation energy.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260304
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  • 6
    Electronic Resource
    Electronic Resource
    Organosilane high polymers: Oxidation of polycyclohexylmethylsilylene (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 23 (1985), S. 469-473 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.130230904
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  • 7
    Electronic Resource
    Electronic Resource
    Organosilane polymers: Formable copolymers containing diphenylsilylene units (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 23 (1985), S. 479-485 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.130230906
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