Preparation Of Waterborne TiO₂/PU Nanocomposite Via RAFT Polymerization Process

Polyurethane (PU) is one of the fastest growing polymer materials in modern industry since PU can have a variety of characteristics such as wear-resistance, oil-resistance, chemical corrosion-resistance, and rigidity, it's widely used in area of coating industry, leather finishing and adhesives Industry.Storage-stable TiO2/polyurethane (PU) nanocomposite (TiO2/PU) emulsions were prepared via in situ RAFT emulsion polymerization of 2-hydroxyethyl acrylate (HEA)-capped PU macromonomer, using azobisisobutyronitrile (AIBN) and 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid (BCSPA) anchored onto TiO2 nanoparticles (TiO2-BCSPA), as a radical initiator and reversible addition-fragmentation chain transfer (RAFT) agent, respectively. When the molar ratio of AIBN to TiO2-BCSPA increased from 1:3 to 1:10, the polydispersity index (PDI) of PUs in the nanocomposites decreased to 1.06, due to more effective RAFT polymerization in the emulsions. The tensile strengths of the nanocomposite films were significantly enhanced, due to the coordination bonds between the TiO2 nanoparticles and the-COOH end groups of the PUs. The nano-composite films significantly enhanced tensile strength, as with titanium dioxide and polyurethane chain of chemical bonding, TiO2/PU emulsion stability and storage of 3 months without significant precipitation, and particle size distribution changed little.The new point in the research is that modified TiO2 agent first was used in the RAFT polymerization as a RAFT agent; that result to the inorganic nano-particles to form chemical bonds in the end of polymer chain. A stable waterborne inorganic nano-particles/polyurethane emulsions were synthesized successfully which may be model for synthesis of inorganic nano-particles/organic polymer composites.