Alex Lubnin - Nanostructured and Hollow Polyurethane Dispersions

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  Publication Details (including relevant citation   information):

  Surface Coatings International, Part B: Coatings Transactions,   Vol. 89, No. 3, pp. 201-208 (2006)


  Due to their   superior properties, ease of use and ‘green’ nature, water-borne   polyurethane dispersions (PUDs) are often

  materials of   choice for a wide spectrum of applications. Common processes for   making these dispersions do not offer easy ways of controlling   particle morphology/architecture. This puts PUDs in a position   inferior to structured acrylic emulsions. The latter are most   readily produced by the sequential or staged addition of   monomers, which is widely used in the engineering of structured   acrylic and vinyl emulsion polymers. Because PU oligomers do not   diffuse through the aqueous phase, this route is closed for PUDs.   How can this fundamental obstacle be overcome? In this paper, a   new

  method is   described that enables the preparation of nanostructured PU   particles with a wide variety of morphologies. The method is   comprised of the preparation of two prepolymers with different   hydrophilicities, which are mixed together

  before the   dispersion step. Surprisingly, the mixture ‘remembers’ that it is   made of two different prepolymers, and as soon

  as the   prepolymer is dispersed in water, diffusion within the particles   sets in. The origin of this unexpected memory is

  examined in   detail. The interplay of diffusion, phase separation and chain   extension determines the morphological outcome. Various   previously inaccessible PU particle morphologies, including   core-shell, ‘ice-cream cone’, lobed and hollow particles, have   been prepared. This novel patent-pending technology opens up new   horizons for PUD chemistry.

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