Effect of particle morphology on film morphology and properties (original) (raw)
Related papers
Polymer, 2012
Films cast from multiphase polymer particles have the potential to combine the properties of their components synergistically. The properties of the film depend on the hybrid polymer architecture and the film morphology. However, how the polymer microstructure and particle morphology are transformed during film formation to determine the film morphology is not well understood. Here, using waterborne alkyd-acrylic nanocomposite particles in a case study, it was found that phase migration leading to the formation of aggregates occurred during film formation. A coarse-grained Monte Carlo model was developed to account for the effects of polymer microstructure and particle morphology on the morphology of the film. The model was validated by comparing its predictions with the observed effects, and then used to explore combinations of polymer microstructure and particle morphology not attainable with the system used as a case study. Significantly, the morphology of the particles was found to have a greater influence than the compatibility of the phases in determining the film structure.
Nanostructured hybrid materials from aqueous polymer dispersions
Advances in Colloid and Interface Science, 2004
Organic-inorganic (O-I) hybrids with well-defined morphology and structure controlled at the nanometric scale represent a very interesting class of materials both for their use as biomimetic composites and because of their potential use in a wide range of technologically advanced as well as more conventional application fields. Their unique features can be exploited or their role envisaged as components of electronic and optoelectronic devices, in controlled release and bioencapsulation, as active substrates for chromatographic separation and catalysis, as nanofillers for composite films in packaging and coating, in nanowriting and nanolithography, etc. A synergistic combination or totally new properties with respect to the two components of the hybrid can arise from nanostructuration, achieved by surface modification of nanostructures, self-assembling or simply heterophase dispersion. In fact, owing to the extremely large total surface area associated with the resulting morphologies, the interfacial interactions can deeply modify the bulk properties of each component. A wide range of starting materials and of production processes have been studied in recent years for the controlled synthesis and characterization of hybrid nanostructures, from nanoparticle or lamellar dispersions to mesoporous materials obtained from templating nanoparticle dispersions in a continuous, e.g. ceramic precursor, matrix. This review is aimed at giving some basic definitions of what is intended as a hybrid (O-I) material and what are the main synthetic routes available. The various methods for preparing hybrid nanostructures and, among them, inorganic-organic or O-I core-shell nanoparticles, are critically analyzed and classified based on the reaction medium (aqueous, non-aqueous), and on the role it plays in directing the final morphology. Particular attention is devoted to aqueous systems and water-borne dispersions which, in addition to being environmentally more acceptable or even a mandatory choice for any future development of large output applications (e.g. in paint, ink and coating industry), can provide the thermodynamic drive for self-assembling of amphiphilics, adsorption onto colloidal particles or partitioning of the hybrid's precursors between dispersed nanosized reaction loci, as in emulsion or miniemulsion free-radical polymerization. While nanoencapsulation and self-assembling processes are already exploited as commercially viable fabrication methods, a newly developed technique based on two-stage sol-gel and freeradical emulsion polymerization is described, which can grant a versatile synthetic approach to hybrid O-I nanoparticles with tailor-made composition of both the organic core and the silica or organosilica shell, and good control on morphology, size and heterophase structure in the 50-500 nm range. Styrene or acrylate homo-and copolymer core latex particles need to be modified with a reactive comonomer, such as trimethoxysilylpropyl methacrylate, to achieve efficient interfacial coupling with the inorganic shell. Accurate control over pH and process conditions is required to avoid latex coagulation or, in case of organic particles with uniform composition, incipient intraparticle crosslinking. ᮊ
Progress in Organic Coatings, 2019
Two phase latex particles offer a potential route to obtain homogeneous, transparent and mechanically strong films with low minimum film formation temperature (MFFT) without the addition of any kind of volatile organic compound (VOC). In this work, we have studied how the morphology of hybrid latex particles influences the morphology and the mechanical strength of polymer films cast from latex dispersions. Hybrid particles containing a hard, high T g seed (Styrene(S)/Acrylamide(AM), T g = 101°C) and a low T g (Methyl Methacrylate (MMA)/Butyl Acrylate(BA)/Styrene(S), T g = 13°C) second phase polymer were synthesized. Different particle morphologies were obtained by slight variation of the amount of AM in the seed and S in the second-stage polymer. Film morphologies and properties for films cast at 60°C were compared in order to find a link between particle morphology and film properties. Moreover, the effect of annealing temperature on film morphology was investigated. Through careful control of particle microstructure during the latex synthesis it is shown that good control over the final properties of the polymer film can be obtained, even for nominally similar polymer mixtures.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2001
Particles with a soft (s) core of poly (n-butyl acrylate)/poly (methyl methacrylate) (PBA/PMMA) copolymer and a hard (h) shell of PMMA were synthesized via a two-stage polymerization process. Two synthesis parameters were investigated: (i) the phase ratio of the core and the shell; and (ii) the compatibility of the two phases. The s/h phase ratio was varied from 100:0 to 0:100. The compatibility between the two phases was changed by (i) using acrylic acid (AA); (ii) by using pure PBA as core material; and (iii) by cross-linking the shell. Particle morphology was characterized by atomic force microscopy (AFM) on freeze-dried and on tempered single particles. The degree of coverage was found to depend on the shell content and the phase compatibility. The results are in good agreement with findings from transmission electron microscopy and solid state NMR given in Acta Polymerica [50 (1999) 347]. The experimental results are compared to predictions from simulation work on the particle morphology based on thermodynamic and kinetic considerations. The second part of the paper focuses on the phase distribution and the film morphology of films formed by the structured particles. Phase distribution at the surfaces, degree of film formation and the phase distribution in the bulk are characterized by AFM, cross-correlated and compared to the findings regarding particle structure in the first part of the paper. This approach is to our knowledge unique regarding its completeness and new in its methodology. The microscopic results concerning the bulk, the single particle and the surface properties are correlated to macroscopic properties like the minimum film forming temperature, pendulum hardness and gloss. : S 0 9 2 7 -7 7 5 7 ( 0 1 ) 0 0 4 9 9 -X
Silicone–polyacrylate composite latex particles. Particles formation and film properties
Polymer, 2005
Composite latex particles with a polydimethylsiloxane PDMS core and a poly(methyl methacrylate-con -butyl acrylate) P(MMA-BA) copolymer shell were synthesized by seeded emulsion polymerization using the PDMS latex as the seed. The compatibility between the two polymer phases was changed by introducing vinyl groups in the latex core. Monomer conversions and particle size evolution were monitored to see the influence of the nature of the core functionality on the polymerization kinetics and on the extent of secondary nucleation. Particle morphology was characterized by cryo-transmission electron microscopy. The P(MMA-BA) copolymer formed a regular shell around the PDMS seed, whereas nonuniform coatings were formed when vinyl functionalities were introduced into the seed. Films were produced from the latexes, and their surface property was analyzed by X-ray photoelectron spectroscopy and contact angle measurements. It was shown that the PDMS component segregated to the polymer/air interface and that the extent of segregation depended on the original particles structure. Because PDMS has a very low glass transition temperature, it can easily diffuse throughout the film material. However, protected by an acrylic shell, polymer diffusion is significantly hindered and the film then displays all the characteristic properties of the acrylic copolymer. The surface composition of the films formed by the structured particles which PDMS core was not totally covered by the polyacrylate, was found to be intermediate between the composition of the films issued from the core-shell latexes and that of the films produced from blends of pure polyacrylate and PDMS latexes.
Encapsulation of Inorganic Particles by Dispersion Polymerization in Polar Media
Journal of Colloid and Interface Science, 1998
rounded by a polymer shell (1-3). The technique of poly-Polymer encapsulation of small silica particles, using dispermer encapsulation is becoming more and more popular since sion polymerization of styrene in aqueous ethanol medium with polymer-encapsulated particles offer very interesting actual poly(N-vinyl pyrrolidone) (PVP) as stabilizer, is described. Siland potential applications. Encapsulated pigments are inica particles, directly synthesized by the Stö ber process in an volved in the manufacture of cosmetics, inks, and paints to aqueous ethanol medium, are either unreacted (hydrophilic improve the compatibility between the filler and the binder. character) or coated with 3-(trimethoxysilyl) propyl methacry-The process of encapsulation is of particular interest in agrilate (MPS) (hydrophobic character) , which is grafted at the culture and pharmaceutical industries to produce controlledsilica particle surface. When the bare silica particles are used release products such as encapsulated pesticides and drugs as the seed, there is a strong tendency of the silica beads to cover the surface of the polystyrene particles and obviously en-(4). Encapsulation technologies have developed to reduce capsulation does not occur. On the contrary, when the silica toxicity, to mask taste and odor, to facilitate storage or transsurface is made hydrophobic by coating, the inorganic particles port, and to improve the stability of the encapsulated product. are entirely contained in the polystyrene particles as evidenced Polymer-encapsulated inorganic particles may also have inby microscopy techniques (TEM, SEM, AFM). It is shown that teresting properties in areas such as adhesives, textiles, opsome polystyrene chains are then chemically bonded to the silica tics, and electronics (5). particles, through the coupling agent MPS, and that only a small Most methods of encapsulation employ, so far, mechaniamount of bonded polystyrene, compared to the total polystycal processes. Recently, a new encapsulation technology has rene synthesized, is sufficient to obtain encapsulation of the been developed which consists in the coating of fine inorsilica particles with the entire amount of polystyrene syntheganic powders (submicrometer in size) in aqueous system sized during the polymerization. Under our experimental condiby emulsion polymerization. This new polymer-encapsulations, each polystyrene latex particle contains, on average, 4 to 23 silica beads depending, in particular, on the size of the silica. tion process is of particular interest in the paint industry We believe that it is possible to control the composite particle where a uniform distribution of the pigment in the matrix size and morphology by a convenient choice of the composition is required. Latex-encapsulated pigments offer many advanof the system. Moreover, this new polymer-encapsulation protages. The encapsulation of titanium dioxyde with poly cess could be used to synthesize other organic-inorganic com-(methyl methacrylate) has been extensively studied by Caris posite particles, using, for example, other monomers or mineret al. (6-9), who used titanate coupling agents to improve als.
Langmuir, 2007
Water-based copolymer dispersions were prepared using methyl methacrylate (MMA), ethyl acrylate (EA) (MMA/EA = 1:2), and a series of nonionic polymerizable surfactants, i.e., "surfmers" based on poly(ethylene glycol)-(meth)acrylates. The latexes were compared with the behavior of a conventionally stabilized (nonionic nonylphenol ethoxylate, NP100 with 84 ethylene oxide units) dispersion with the same MMA-EA composition (PMMAEA). A number of techniques were employed in order to characterize structure, dynamics, and film formation properties: solution/solid-state NMR, dynamic/static light scattering (DLS/SLS), differential scanning calorimetry (DSC), tensile/shear mode dynamic mechanical thermal analysis (DMTA), and atomic force microscopy (AFM). The surfmers were found to be miscible with the MMA-EA copolymer at room temperature, with 46-85 mol % of the reacted surfmer detected at the particle surfaces, and the remaining part buried in the particle bulk. In contrast, the NP100 surfactant formed a separate interphase between the copolymer particles with no mixing detected at room temperature or at 90 degrees C. For a 4.0% dry weight concentration, NP100 phase separated and further crystallized at room temperature over a period of several months. Composition fluctuations related to a limited blockiness on a length scale above approximately 2 nm were detected for PMMAEA particles, whereas the surfmer particles were found to be homogeneous also below this limit. On a particle-particle level, the dispersions tended to form colloidal crystals unless hindered by a broadened particle size distribution or, in the case of PMMAEA, by the action of NP100. Finally, a surface roughness (Rq) master plot was constructed for data above the glass transition temperature (Tg) from Tg + 11 degrees C to Tg + 57 degrees C and compared with the complex shear modulus over 11 frequency decades. Shift factors from the 2 methods obeyed the same Williams-Landel-Ferry (WLF) temperature dependence, thus connecting the long-time surface flattening process to the rheological behavior of the copolymer.
High PVC film-forming composite latex particles via miniemulsification, part 1: Preparation
Journal of Applied Polymer Science, 2006
Miniemulsification technology was used to encapsulate TiO 2 particles inside a styrene/n-butyl acrylate copolymer with high loading levels (11 to 70% PVC (pigment volume concentration)). In this approach, a St/BA copolymer dissolved in toluene in the presence of a costabilizer (hexadecane) was mixed with a dispersion of TiO 2 particles in toluene and sonified, and then emulsified in an aqueous surfactant solution by sonification. The effect of sonification time on both the dispersibility of the TiO 2 particles in the presence of the copolymer and hexadecane and on the encapsulated particle size was investigated. Particle size analysis by dynamic light scattering showed that these composite latexes are quite stable. It was also found that as the TiO 2 loading increased from 11 to 43% PVC, the particle size of the TiO 2 dispersion decreased while the polymerencapsulated TiO 2 particle size increased. The effect of sur-factant concentration (sodium lauryl sulfate, SLS) on the encapsulated particle size was investigated using four different SLS concentrations in the 11% PVC system. The results showed that as the SLS concentration increased the particle size decreased, as expected. Also it was found that the minimum surfactant concentration that gives stable encapsulated TiO 2 particles is above 10 mM SLS. The role of HD in the recipe was studied for an artificial latex containing no TiO 2 and one prepared at 11% PVC, in terms of particle size before and after solvent stripping, and its effect on the T g .