Hybrid polymer dispersion

Generally, the methods of preparation of aqueous hybrid polymer dispersions may be classified into four groups [17] ... 

In practice, methods (2) and (3) seem to be the most commonly used. Recently, yet another method of preparation of hybrid polymer dispersions, called an active blending has been reported [18]. The components of such active blends or active mixtures remain inactive when in the presence of water, and cross-react during film formation. 

Inorganic organic hybrid polymer dispersed liquid crystalline nanocomposites are reported as suitable candidate for fahricatirHi of photorefractive medium. Winiarz et al. reported one such photorefractive medium which consists of hole transporting polymer composite matrix, electro-opticaUy active nanodroplets of liquid crystal and Cadmium sulphide quantum dots as photosentizers (Winiarz and Prasad 2002). They employed poly(methylmethacrylate) (PMMA) as polymer matrix, N-ethylcarbazole (ECZ) as hole transporting medium and commercial nematic liquid crystal mixture TL 202 for fabrication of the photorefractive medium with Cadmium sulphide as photosentizer. The reported medium exhibits more than 90 % internal diffraction efficiency which is relatively high compared with other PDLC photorefractive medium. 

Most examples discussed so far made use of amorphous inorganic supports or sol-gel processed hybrid polymers. Highly disperse materials have recently become accessible via standard processes and, as a result, materials with various controlled particle size, pore diameter are now available. Micelle-templated synthesis of inorganic materials leads to mesoporous materials such as MCM-41, MCM-48, MSU, and these have been extensively used as solid supports for catalysis [52]. Modifications of the polarity of the material can increase the reactivity of the embedded centre, or can decrease its susceptibility to deactivation. In rare cases, enhanced stereo- or even... 

Preparation of ultrafine monodisperse hybride particles, dispersible in low polar organic solvent, from monodisperse colloidal silica by two-step polymer modification was studied. Bindings of the secondary polymer to monodisperse poly(maleic anhydride-styrene)-modified colloidal silica particles (120 nm) have made the composites in low polar solvent dispersible. The dispersion of the particles in good solvent for the secondary polymer is due to the steric repulsion of solvated polymer chains. The dispersibility of the hybrid particles in poor solvent-rich solution was controlled by delicate balance between nonpolar-nonpolar interaction and electrostatic repusion among the particles. 

Hybrid Systems. Combinations of water-soluble and water-dispersed binders may be used to achieve synergistic effects (e.g., to control the amount of organic solvents or the application behavior). Polymer dispersions or powdered binders may be used as water-dispersible binders [3.43]. The use of polymer dispersions allows the solids content of water-soluble binders to be increased, the level of organic solvents to be reduced, and the physical drying time to be shortened. The use of water-soluble binders provides a broad application spectrum and yields paint films with well-balanced properties. 

Bohm N, Materny A, Kiefer W, Steins El, Muller MM, Schottner G. 1996. Spectroscopic investigation of the thermal cis trans isomerization of disperse red 1 in hybrid polymers. Macromolecule. 29 2599 2604. 

Bon and Kumacheva and coworkers [104] demonstrated that monodisperse solids-stabilized droplets could be generated in a microfluidic flow focusing device, whereby the solid particles were initially present in the dispersed phase. Polymerization of the monomer droplets led to hybrid polymer microspheres. They also showed that non-spherical particles could be obtained by geometric confinement of the droplets in the channel [104,105]. 

Yang J, Hasell T, Wang W, Li J, Brown PD, Poliakoff M, Lester E, Howdle SM (2008) Preparation of hybrid polymer nanocomposite microparticles by a nanoparticle stabilized dispersion polymerization. J Mater Chem 18 998-1001... 

Nanocomposites- hybrid polymer-inorganic nanoconq )osites for dramatic improvement over the properties of traditional polymers without sacrificing density, processability or toughness as in conventional compositeZblend approaches dispersed carbon nanotubes in polymer fiber to provide inqrrovement in tensile and conqiressive prqrerties of Ugh performance polymer fibers. 

Synthesis and Characterisation of Aqueous Hybrid Polyurethane-Urea-Acrylic/Styrene Polymer Dispersions... 

The effect of type of diisocyanate and polyol used in synthesis of hybrid PU/acrylic polymer dispersions was recently reported by authors from Lamberti [32]. 

A recently published patent [33] from Zeneca described in detail the methods of preparation of hybrid polyurethane/vinyl polymer dispersions but neither discussed the effect of various factors on the properties of the hybrid dispersions nor provided any information on their particle morphology. 

Hybrid polyurethane-urea-acrylic/styrene polymer dispersions were prepared according to methods la , lb , 2 and 3 described in Section 6.3.2. Dispersions designated as MDPUR-ASD were made by polymerisation of monomers in DPU according to the methods la, lb and 2 while dispersions designated as MDPUR were made by synthesis of DPUR in ASD according to method 3. In all syntheses the ratio of polyurethane-urea to acrylic/styrene polymer in the hybrid was 2 1. 

In this study, aqueous hybrid polyurethane-urea-acrylic/styrene polymer dispersions were obtained using four different methods. The dispersions are stable and their viscosity, and pH as well as average particle size and particle size distribution are similar to those observed for DPUR. Most of the hybrid dispersions formed transparent films of good mechanical properties, water resistance and organic solvent resistance. 

Table 6.31 Effect of various factors on the properties of hybrid polyurethane-urea-acrylic/styrene polymer dispersions synthesised in this study ... 

Using a mixture of castor oil and hydroxyether of bisphenol-A (HBA) as the polyol and reacting with TDI in the presence of DBTDL catalyst at 35°C, a series of polyurethanes are prepared in an air-circulating oven for 48 h. A series of poly(urethane urea)-vinyl polymer hybrid aqueous dispersions are prepared. Waterborne poly(urethane urea) is synthesised from castor oil and polyoxypropylene polyol M = 1000 g moL ), dimethylol propionic acid and isophorone diisocyanate and then neutralised with tertiary amine. The hybrid aqueous dispersion with high oil content poly(urethane urea) exhibits excellent compressive mechanical strength. Sunflower oil-modified waterborne polyurethane resin may also be prepared. The waterborne resin is synthesised from the monoglyceride of the oU, poly(propylene-ethylene) triol, tartaric acid and toluene diisocyanate, then neutralised with triethyl amine. 

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