Silicone–polyacrylate composite latex particles. Particles formation and film properties

Designing Multicomponent Polymer Colloids for Self-Stratifying Films

Aqueous polymer colloids known as latexes are widely used in coating applications. Multicomponent latexes comprised of two incompatible polymeric species organized into a core-shell particle morphology are a promising system for self-stratifying coatings that spontaneously partition into multiple layers, thereby yielding complex structured coatings requiring only a single application step. Developing new materials for self-stratifying coatings requires a clear understanding of the thermodynamic and kinetic properties governing phase separation and polymeric species transport. In this work, we study phase separation and self-stratification in polymer films based on multicomponent acrylic (shell) and acrylic-silicone (core) latex particles. Our results show that the molecular weight of the shell polymer and heat aging conditions of the film critically determine the underlying transport phenomena, which ultimately controls phase separation in the film. Unentangled shell polymers result in efficient phase separation within hours with heat aging at reasonable temperatures, whereas entangled shell polymers effectively inhibit phase separation even under extensive heat aging conditions over a period of months due to kinetic limitations. Transmission electron microscopy is used to track morphological changes as a function of thermal aging. Interestingly, our results show that the rheological properties of the latex films are highly sensitive to morphology, and linear shear rheology is used to understand morphological changes. Overall, these results highlight the importance of bulk rheology as a simple and effective tool for understanding changes in morphology in multicomponent latex films.

The morphology of poly(terminal vinyl dimethicone-co-methyl methacrylate-co-n-butyl acrylate)/pigment composite film and its application in pigment printing of polyester fabric

In this study, a series of poly(terminal vinyl dimethicone-co-methyl methacrylate-co-n-butyl acrylate)/pigment composite particles (P(DMS-Acr)/PB CPs) were successfully prepared via miniemulsion polymerization and their latex film microstructures on were examined carefully using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and so on. Significant phase separation was observed after film formation, and the copper phthalocyanine blue (PB) particles tend to distribute in the polysiloxane island phase. After baking at 120 °C, the protrusions were generated. With increasing amount of vinyl terminated polydimethylsiloxane (ViPDMS) or baking time, the number of the protrusions became more and the appearance of the protrusions tends to be sharp. When the P(DMS-Acr)/PB CPs were applied in fabric printing, a continuous film was formed on the surface of the fabric at room temperature and therefore the gaps between yarns were blocked. However, the gaps in the fabric reappeared after baking at 120 °C, which could be attributed to the rapid flow of the polymer component. Finally, the fiber was coated with a layer of latex film containing a large number of mastoid structures, and the printed fabric could still retain the majority of the gaps between yarns and between fibers. Therefore, the printed fabric exhibited excellent performances such as good air permeability, softness, and rubbing fastness.

Poly(terminal vinyl dimethicone-co-methyl methacrylate-co-n-butyl acrylate)/pigment composite latexes were prepared by miniemulsion polymerization and the morphology of the composite film on the surface of polyester fabric and substrate was studied.

Morphology control of silicone/poly(methyl methacrylate) (elastic/glassy) composite particles

Composite particles consisting of elastic silicone and glassy poly(methyl methacrylate) were prepared. The morphology of the particles could be alternated between sea-island and core–shell structures by controlling the annealing temperature.

Studies on Synthesis and Characterization of Aqueous Hybrid Silicone-Acrylic and Acrylic-Silicone Dispersions and Coatings. Part I

The objective of the study was to investigate the effect of the method of synthesis on properties of aqueous hybrid silicone-acrylic (SIL-ACR) and acrylic-silicone (ACR-SIL) dispersions. SIL-ACR dispersions were obtained by emulsion polymerization of mixtures of acrylic and styrene monomers (butyl acrylate, styrene, acrylic acid and methacrylamide) of two different compositions in aqueous dispersions of silicone resins synthesized from mixtures of silicone monomers (octamethylcyclotetrasiloxane, vinyltriethoxysilane and methyltriethoxysilane) of two different compositions. ACR-SIL dispersions were obtained by emulsion polymerization of mixtures of the same silicone monomers in aqueous dispersions of acrylic/styrene copolymers synthesized from the same mixtures of acrylic and styrene monomers, so the compositions of ACR and SIL parts in corresponding ACR-SIL and SIL-ACR hybrid dispersions were the same. Examination of the properties of hybrid dispersions (particle size, particle structure, minimum film forming temperature, Tg of dispersion solids) as well as of corresponding coatings (contact angle, water resistance, water vapour permeability, impact resistance, elasticity) and films (tensile strength, elongation at break, % swell in toluene), revealed that they depended on the method of dispersion synthesis that led to different dispersion particle structures and on composition of ACR and SIL part. Generally, coatings produced from hybrid dispersions showed much better properties than coatings made from starting acrylic/styrene copolymer dispersions.

Silicone-containing aqueous polymer dispersions with hybrid particle structure

In this paper the synthesis, characterization and application of silicone-containing aqueous polymer dispersions (APD) with hybrid particle structure are reviewed based on available literature data. Advantages of synthesis of dispersions with hybrid particle structure over blending of individual dispersions are pointed out. Three main processes leading to silicone-containing hybrid APD are identified and described in detail: (1) emulsion polymerization of organic unsaturated monomers in aqueous dispersions of silicone polymers or copolymers, (2) emulsion copolymerization of unsaturated organic monomers with alkoxysilanes or polysiloxanes with unsaturated functionality and (3) emulsion polymerization of alkoxysilanes (in particular with unsaturated functionality) and/or cyclic siloxanes in organic polymer dispersions. The effect of various factors on the properties of such hybrid APD and films as well as on hybrid particles composition and morphology is presented. It is shown that core-shell morphology where silicones constitute either the core or the shell is predominant in hybrid particles. Main applications of silicone-containing hybrid APD and related hybrid particles are reviewed including (1) coatings which show specific surface properties such as enhanced water repellency or antisoiling or antigraffiti properties due to migration of silicone to the surface, and (2) impact modifiers for thermoplastics and thermosets. Other processes in which silicone-containing particles with hybrid structure can be obtained (miniemulsion polymerization, polymerization in non-aqueous media, hybridization of organic polymer and polysiloxane, emulsion polymerization of silicone monomers in silicone polymer dispersions and physical methods) are also discussed. Prospects for further developments in the area of silicone-containing hybrid APD and related hybrid particles are presented.

Synthesis and characterization of UV-curable acrylate films modified by functional methacrylate terminated polysiloxane hybrid oligomers

Methacrylate terminated polysiloxane segments migrated to the top surface of the composite UV-curable polyacrylate film.

Synthesis and Characterization of Encapsulated Nanosilica Particles with an Acrylic Copolymer by in Situ Emulsion Polymerization Using Thermoresponsive Nonionic Surfactant

Nanocomposites of encapsulated silica nanoparticles were prepared by in situ emulsion polymerization of acrylate monomers. The synthesized material showed good uniformity and dispersion of the inorganic components in the base polymer, which enhances the properties of the nanocomposite material. A nonionic surfactant with lower critical solution temperature (LCST) was used to encapsulate the silica nanoparticles in the acrylic copolymer matrix. This in situ method combined the surface modification and the encapsulation in a single pot, which greatly simplified the process compared with other conventional methods requiring separate processing steps. The morphology of the encapsulated nanosilica particles was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM), which confirmed the uniform distribution of the nanoparticles without any agglomerations. A neat copolymer was also prepared as a control sample. Both the neat copolymer and the prepared nanocomposite were characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analyses (TGA), dynamic mechanical thermal analysis (DMTA) and the flame resistance test. Due to the uniform dispersion of the non-agglomerated nanoparticles in the matrix of the polymer, TGA and flame resistance test results showed remarkably improved thermal stability. Furthermore, DMTA results demonstrated an enhanced storage modulus of the nanocomposite samples compared with that of the neat copolymer, indicating its superior mechanical properties.

Synthesis of polystyrene/polysilsesquioxane core/shell composite particles via emulsion polymerization in the existence of poly(γ-methacryloxypropyl trimethoxysilane) sol

Here, we synthesized the polystyrene/polysilsesquioxane (PS/PSQ) core/shell latex particles via emulsion polymerization, which behave as an amusing morphology. First, the nanosized PSQ particles were prepared by the hydrolysis-condensation reaction of γ-methacryloxypropyl trimethoxysilane (MPTS) in ethanol medium. Subsequently, the as-obtained methacryloxypropylene functionalized PSQ (PMPTS) sol was directly added into the emulsion system of styrene (St) monomer, and PS/PSQ composite particles with core/shell structure were obtained through emulsion polymerization. We found that the structure of the composite particles can be affected by the synthesis parameters such as reaction time, content of PMPTS added in the reaction, amount of coemulsifier, and the pH value of emulsion system, which were systemically explored by transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and thermogravimetric analysis (TGA) in this work. These results indicate that the PMPTS particles in the size of about 5 nm could first absorb onto the surface of PS latex particles so as to assemble in a strawberry-like morphology. The further coalescence among the PMPTS particles would result in a continuous PMPTS shell around the PS core. Moreover, the hollow PSQ capsules were prepared after extraction of the PS core by organic solvent, further confirming the core/shell structure of the as-synthesized PS/PMPTS particles. Meanwhile, we also explored the application of the PS/PSQ core/shell particles as a new kind of Pickering emulsifier in the emulsion polymerization of St, and composite particles with complex patchy morphologies have been obtained finally under different ratios of styrene monomer to PS/PMPTS colloidal emulsifier.

Silica encapsulation by miniemulsion polymerization: distribution and localization of the silica particles in droplets and latex particles

The impact of including hydrophobically modified silica on the morphology of miniemulsified monomer mixtures and that of the resulting polymer particles was investigated, with emphasis placed on the distribution and localization of the inorganic phase. Silica nanoparticles with diameters of 20 and 78 nm were first modified with γ-methacryloxypropyl trimethoxysilane (γ-MPS) to favor their dispersion in methyl methacrylate (MMA)/n-butyl acrylate (BuA) and mixtures of varying MMA to BuA weight ratios. The monomer-silica dispersions were then emulsified by ultrasonication, and the resulting silica-loaded droplets were examined using cryo-transmission electron microscopy (cryo-TEM). This represents the first time such silica-loaded nanodroplets were examined in this way. The results of the cryo-TEM show that whereas the silica particles could easily be dispersed in MMA or a mixture of MMA and BuA to produce stable dispersions, the emulsification step promotes the (re)localization of the silica at the oil-water interfaces. It was also shown that not all droplets are equal; some droplets and particles contain no silica whereas others contain many silica particles. After the subsequent polymerization step, the silica was buried inside the latex particles.

Soft Core–Hard Shell Silicone Hybrid Nanoparticles Synthesized by Miniemulsion Polymerization: Effect of Silicone Content and Crosslinking on Latex Film Properties

Composite nanoparticles consisting of ‘soft’ silicone oil and ‘hard’ polyacrylate with core–shell morphology were obtained by a one-step synthesis via the miniemulsion process. Various parameters, i.e. the viscosity and amount of the silicone, the surfactant content, the (co)monomers affecting the particle size and morphology were studied. With an optimum hydrophilicity of the polymer shell, composite particles possessing a well-defined core–shell morphology were obtained as determined by transmission electron microscopy. The fully encapsulated silicone oil (40 wt-%) in a slightly crosslinked polyacrylate shell showed good film formation as revealed by atomic force microscopy. The ability to highly confine silicone oil in the composite film could clearly be evaluated from contact angle measurements. By finely changing the crosslink concentration in the polymeric shell, tunable hydrophobic properties of films cast from silicone core–polyacrylate shell latexes could be achieved. In addition, the high thermal resistance and excellent water-resistant properties of the film were shown by thermal gravimetric analysis and water swelling determination. These composite latexes are presented as new alternatives for practical utility in waterborne coatings.