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  • 1985-1989  (4)
  • 1965-1969
  • Polymer and Materials Science  (3)
  • Ditylum brightwellii  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Characterizing the silica deposition vesicle of diatoms (1989)
    Springer
    Protoplasma 151 (1989), S. 158-163 
    Details
    ISSN: 1615-6102
    Keywords: Lectins ; Mannose ; Silica deposition vesicles ; Ditylum brightwellii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The present study on a centric diatom,Ditylum brightwellii, includes two parts: detection of sugars in the silica deposition vesicle (SDV) with lectins and labeling the developing siliceous cell wall in the SDV with rhodamine 123. Cells with developing valves are treated with SDS to remove all the cytoplasmic contents, then either stained with fluorescein labeled lectins or thin-sectioned and stained with colloidal gold labeled lectins. The results show that mannose is part of the organic matrix in the SDV. Rhodamine 123, a non-toxic fluorescent laser dye, enters the cell immediately and is trapped in the SDV probably by the high reducing potential of the SDV. Silica is co-deposited with rhodamine 123 in the SDV, and the resulting valves and girdle bands become fluorescent. Implications of this study for the mechanism of silicification are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403453
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  • 2
    Electronic Resource
    Electronic Resource
    Properties of ultraviolet cured polydimethylsiloxane-urea acrylates (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 2115-2135 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of polydimethylsiloxane-urea acrylate prepolymers was synthesized by reacting aminopropyl-terminated polydimethylsiloxane (ATPS) with isocyanatoethyl methacrylate (IEM). The oligomers were cured using ultraviolet radiation in the presence of different reactive diluents. Three systems were prepared with varying ATPS soft segment molecular weight. All of the samples were transparent. However, microphase separation was indicated by the observation of two glass transition temperatures attributed to separate ATPS and IEM/reactive diluent phases. Increasing ATPS molecular weight led to a lower rubbery phase transition temperature and a smaller rigid phase volume fraction. These effects were reflected in lower modulus and tensile strength at room temperature, and higher elongation at break. An increase in the reactive diluent content resulted in an increase in Young's modulus and the ultimate tensile strength of these materials. Increasing reactive diluent content caused the rubbery phase transition peak to decrease in magnitude without changing its position and shifted the hard segment transition to higher temperature. The tensile strengths and moduli of these materials were higher than those reported in the literature for other polydimethylsiloxane and urethane acrylate materials.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300527
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and properties of polycyanoethylmethylsiloxane polyurea urethane elastomers: A study of segmental compatibility (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 315-337 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of polyurea urethane block polymers based on either aminopropyl-terminated polycyanoethylmethylsiloxane (PCEMS) soft segments or soft segment blends of PCEMS and polytetramethylene oxide (PTMO) were synthesized. The hard segments consisted of 4,4′-methylenediphenylene diisocyanate (MDI) chain-extended with 1,4-butanediol. The hard segment content varied from 11 to 36%, whereas the PTMO weight fraction in the soft segment blends varied from 0.1 to 0.9. The cyanoethyl side group concentration was also varied during the synthesis of the PCEMS oligomer. The morphology and properties of these polymers were studied by differential scanning calorimetry, infrared spectroscopy, dynamic mechanical and tensile testing, and small-angle x-ray scattering. These materials exhibited microphase separation of the hard and soft segments; however, attaching polar cyanoethyl side groups along the apolar siloxane chains promoted phase mixing in comparison with polydimethylsiloxane-based polyurethanes. The increased phase mixing is postulated to lead to improved interfacial adhesion and thus can account for the observed improvement in ultimate tensile properties compared with polydimethylsiloxane-based polyurethanes. Both hard segment content and cyanoethyl concentration are important factors governing the morphological and tensile properties of these polymers.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260209
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Poly(chloropropylmethyl-dimethylsiloxane)-polyurethane elastomers: Synthesis and properties of segmented copolymers and related zwitterionomers (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 2681-2702 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of polyurethane block copolymers based on hydroxybutyl terminated poly(chloropropylmethyl-dimethylsiloxane) and poly(tetramethylene oxide) soft segments of molecular weights 2100 and 2000, respectively, were synthesized. The hard segments consisted of 4,4′-methylenediphenylene diisocyanate (MDI) that was chain extended with either 1,4-butanediol (BD) or N-methyldiethanolamine (MDEA). The materials chain extended with MDEA were ionized using 1,3-propane sultone. The weight fraction of the hard segments was in the range 0.30-0.45. The effect of mixed soft segments, chain extenders, and zwitterionization on the extent of phase separation and physical properties was studied by utilizing differential scanning calorimetry and dynamic mechanical, stress-strain, and Fourier Transform Infrared spectroscopy experiments. All of these short segment block copolymers showed nearly complete phase separation. The zwitterionomer materials exhibited ionic aggregation within the hard domains. Although hard segment crystallinity or ionic aggregation did not affect the morphology, hard domain cohesion was important in determining the tensile and viscoelastic properties of these elastomers.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1986.090241207
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    Paper (German National Licenses)
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