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  • Conference proceedings  (1)
  • molecular aggregates  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Aggregating block copolymers as model systems to study polymer brush dynamics (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 747-755 
    Details
    ISSN: 0392-6737
    Keywords: Neutron scattering techniques (including small-angle scattering) ; Polymers, elastomers, and plastics ; Fluctuation phenomena, random processes and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A-B block copolymers in a selective solvent—good for the B-species and bad for the A-species—form micellar aggregates with a compact A-core with a corona (brush) of B «hairs» reaching into the solvent. Whereas polystyrene(PS)-polyisoprene(PI) in decane forms spherical micelles with a PS core of about 10 nm radius, polyethylene(PE)-polyethylenepropylene(PEP) forms micellar platelets, the shape of which is goverend by the habitus of PE crystallites forming the core. These planar aggregates have large (several hundred nanometers) lateral extension and a core thickness in the range of 10 nm. Both systems are model systems for polymer brushes, either on a spherical surface or planar. Neutron spin-echo experiments allow for the investigation of the dynamics of the brushes which reflects their viscoelastic properties. Results of neutron small-angle and spin-echo investigations are reported. The brush dynamics is explained using a model based on an idea of de Gennes describing the brush properties in terms of scaling relations for osmotic pressure and viscosity of a semi-dilute solution with inhomogeneous density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02456720
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamical aspects of self-organized (macro) molecular systems investigated by neutron spin-echo spectroscopy (1997)
    Springer
    Colloid & polymer science 106 (1997), S. 112-117 
    Details
    ISSN: 1435-1536
    Keywords: Neutron spin-echo ; relaxation dynamics ; molecular aggregates ; microemulsions ; block copolymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Neutron spin-echo (NSE) spectroscopy is a tool to close the gap between light scattering and more conventional neutron spectroscopies. It may also be viewed as an augmentation of small-angle scattering with inelastic, dynamical information. Using a microemulsion system as example for a system of molecular aggregates and a block-copolymer system forming macromolecular aggregates, it is shown what type of dynamics is observable by NSE-spectroscopy. The lamellar phase of a SDS-pentanol-water microemulsion allows for the investigation of different layer modes (undulation, peristaltic mode) the dynamics of which are determined by elastic properties of the interface layers and by the friction due to fluid flow between the layers. Platelet-like aggregates of polyethylene-polyethylenebutylene (PE-PEP) copolymers formed upon cooling a decane solution exhibit a polymeric brush of PEP-hairs on their surface. The fluctuation dynamics of this brush determined by a balance of solvent friction and entropie restoring forces has been observed by NSE spectroscopy. Besides, the direct dynamical information the NSE data allow for the separation of static scattering due to the average structure from the scattering contributions due to mobile fluctuating parts of the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189503
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