Composites of polymers and metal/metalloid oxide nanoparticles and methods for forming these composites

Abstract

Successful dispersion approaches are described for the formation of dispersion of dry powders of inorganic particles. In some embodiments, it is desirable to form the dispersion in two processing steps in which the particles are surface modified in the second processing step. Composites can be formed using the well dispersed particles to form improved inorganic particle-polymer composites. These composites are suitable for optical applications and for forming transparent films, which can have a relatively high index or refraction. In some embodiments, water can be used to alter the surface chemistry of metal oxide particles.

1 . A method for forming a composite of a polymer and metal oxide particles having an average primary particle size of no more than 100 nm, the method comprising:
 gradually blending a portion of a dispersion comprising surface modified metal oxide particles and a dispersant, into polymer solution comprising a polymer and a solvent to form a uniform polymer-inorganic particle composite wherein the dispersant is miscible with the solvent and wherein the blending is performed so that effectively no particles settle from the blend.   
     
     
         2 . The method of  claim 1  wherein the dispersant comprises an organic liquid. 
     
     
         3 . A method for modifying the surface properties of metal oxide particles having an average primary particle size of no more than 50 nm, the method comprising:
 contacting a dry powder of the metal oxide particles with water to increase the (—OH) content of the particle surfaces;   precipitating the particles through the addition of a liquid miscible with water; and   dispersing the particles in an alcohol at a concentration of at least about 1 weight percent with a z-average secondary particle size of no more than about 100 nm.   
     
     
         4 . The method of  claim 3  wherein the contacting with water is performed by mixing the particles with an aqueous solution. 
     
     
         5 . The method of  claim 3  wherein the metal oxide particles are synthesized using laser pyrolysis. 
     
     
         6 . The method of  claim 3  wherein the liquid miscible with water comprises acetone. 
     
     
         7 . A method for producing metal oxide particles in a flow with a surface structure having an enhanced (—OH) contribution, the method comprising:
 exposing a product particle flow with water vapor, wherein the particles are synthesized in the flow from a reactant flow comprising a metal oxide precursor; and 
 collecting the water modified particles. 
 
     
     
         8 . The method of  claim 7  wherein the synthesis of the particles is performed in a reaction chamber and wherein the flow is initiated at a nozzle connected to a reactant delivery system. 
     
     
         9 . The method of  claim 8  wherein the synthesis of the metal oxide particles is driven with an intense light beam intersecting the reactant flow. 
     
     
         10 . The method of  claim 8  wherein the opening of the nozzle is elongated with an aspect ratio of at least about 5 and wherein the laser beam is oriented to propagate along the elongated dimension of the resulting flow so that effectively the entire reactant flow passes through the laser beam. 
     
     
         11 . The method of  claim 8  wherein the water vapor is introduced through vents that are located in a collection channel connected to the reaction chamber where the particles are synthesized.