Porous films by backfilling with reactive compounds

Abstract

The invention provides methods for modifying one or more properties of porous thin films. In such methods, a formulation comprising a reactive species is applied to the porous thin film and allowed to crosslink. In some embodiments, the crosslinked network thus formed imparts increased mechanical strength and wear resistance to the porous thin films.

What is claimed is: 
     
         1 . A filled film comprising:
 a porous thin layer-by-layer (LbL) film less than 10 um thick, disposed on a substrate, and comprising an inorganic material in the form of charged nanoparticles, a polymer polyelectrolyte, and an interconnected network of open pores; and   a crosslinked reactive species disposed within a first portion of the interconnected network of open pores.   
     
     
         2 . The film of  claim 1 , wherein the inorganic material is a metal oxide selected from titanium dioxide, silicon dioxide, cerium dioxide, tin oxide and zirconium oxide. 
     
     
         3 . The film of  claim 1 , wherein the polyelectrolyte is selected from poly(diallyldimethylammonium chloride) (PDAC), poly(allylamine hydrochloride (PAH), poly(sulfonated styrene) (PSS), poly(acrylic acid) (PAA), poly(ethylene imine), poly(vinyl alcohol), poly(ethylene oxide), polythiophenes, and copolymers thereof. 
     
     
         4 . The film of  claim 1  wherein the polyelectrolyte is a biologically derived polyelectrolyte selected from chitosan, carboxymethylcellulose, polysaccharides, hyaluronic acid, and copolymers thereof. 
     
     
         5 . The film of  claim 1 , wherein the reactive species is an orthosilicate selected from tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), and tetrapropyl orthosilicate. 
     
     
         6 . The film of  claim 1  wherein the reactive species is a crosslinkable acrylate selected from 2-hydroxyethyl acrylate (HEA), pentaerythritol triacrylate (PETA), 2-hydroxyethyl methacrylate (HEMA), trimethylolpropane triacrylate (TMPTA), and 1,6-hexandiol diacrylate (HDDA). 
     
     
         7 . The film of  claim 1  wherein the inorganic material is silicon dioxide or titanium dioxide, the polyelectrolyte is poly(diallyldimethylammonium chloride) (PDAC), and the reactive species is tetraethyl orthosilicate (TEOS). 
     
     
         8 . The film of  claim 1  wherein the substrate is glass or plastic. 
     
     
         9 . The film of  claim 1  wherein a second portion of the interconnected network of open pores is filled with an ambient gas. 
     
     
         10 . The film of  claim 1  wherein the crosslinked reactive species completely fills the interconnected network of open pores. 
     
     
         11 . The film of  claim 1  wherein the LbL film has a porosity between 0.05 and 0.5. 
     
     
         12 . The film of  claim 1  wherein the LbL film has a porosity less than 0.1. 
     
     
         13 . The film of  claim 1  wherein the LbL film comprises pores that have an average diameter of less than 1 μm. 
     
     
         14 . The film of  claim 1  wherein the nanoparticles are formed from a material selected from oxides, sulfides, nitrides, and zero-valent metals. 
     
     
         15 . The film of  claim 1  wherein the nanoparticles and polymer polyelectrolyte are arranged into bilayers, and wherein the LbL film comprises 7 or more bilayers. 
     
     
         16 . The film of  claim 1  wherein the crosslinked reactive species is present within at least 30% of the volume of pores in the LbL film. 
     
     
         17 . The film of  claim 1  wherein the crosslinked reactive species comprises silicon, titanium, or aluminum, or an organic material selected from acrylate monomers, methacrylate monomers, epoxy monomers, and vinyl monomers. 
     
     
         18 . The film of  claim 1  comprising:
 a plurality of first monolayers of the charged nanoparticles; and 
 a plurality of second monolayers of opposite charged nanoparticles comprising the polymer polyelectrolyte, 
 wherein the film comprises the first monolayers alternating with the second monolayers.