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  • Dynamic light scattering  (1)
  • ODT  (1)
  • 1995-1999  (2)
  • 1
    ISSN: 1572-8935
    Keywords: SAXS ; MST ; Correlation function ; ODT ; Polyurethane ; Block copolymer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Three segmented polyurethane block copolymers PU-M, PU-X and PU-T containing different diisocynates, diphenylmethane-4,4'-diisocyanate (MDI), xylene diisocyanate (XDI) and 2,4-toluene diisocyanate (TDI) respectively with the same chain extender 1,4-butanediol (BD) and soft segment polyester-diol were investigated by small-angle X-ray scattering (SAXS). Microphase separation transition (MST) occurred due to the thermodynamic incompatibility between the soft and hard segments. The long domain spacing, interfacial thickness (or transition layer thickness), core zone, and lamellar thickness were determined for these three different polyurethanes from one dimension correlation function after the Fourier transformation of small-angle X-ray scattered intensity curve based on the Strobl and Schneider model. The structural parameters for these three polyurethanes determined from the scattering measurements indicate that the degrees of microphase separation are in the following sequence: PU-M 〉 PU-X 〉 PU-T.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymer research 5 (1998), S. 67-76 
    ISSN: 1572-8935
    Keywords: Poly(vinyl alcohol) ; Borax ; Dynamic light scattering ; Dilute solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Poly(vinyl alcohol)-borate (PVA-borate) complexes in dilute aqueous solutions were investigated by dynamic light scattering (DLS). Two relaxation modes obtained, were scattering vector-q2 dependent and diffusive. The amplitude of slow mode was independent of borax concentration. In the very dilute PVA concentration regime ( [PVA] 〈 5 g/L), the PVA di-diol-borate complexation was dominated by intra-molecular reaction, and the fast mode correlation length ςf which corresponds to the polymer chain dimension increased rapidly with borax concentrations lower than 0.06 M, and reached an asymptote in the higher borax concentration regime. However, for a dilute PVA aqueous solution with higher PVA content (i.e., [PVA] = 9 g/L), both intra-and inter-molecular PVA di-diol-borate complexations might happen. The chain expansion and shrinkage of PVA-borate complex with increasing borax concentration was observed due to the balance between the electrostatic repulsion of the charged diol-borate complexes and the intra-molecular crosslink induced by the intra-molecular di-diol-borate complexation.
    Type of Medium: Electronic Resource
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