In this paper, the preparation of polymer/silica nanocomposite particles in a convenient one‐step process, via in situ miniemulsion polymerization and the sol‐gel technique, is described. The products were characterized using differential scanning calorimetry, transmission electron microscopy, and dynamic light scattering. Moreover, the effects of various reaction parameters, including the content of silica and the concentrations of sodium dodecyl sulfate and potassium persulfate, on the particle size and size distribution were also investigated. It is shown that polymer/silica hybrid nanocomposite particles were successfully synthesized in one step by this novel technique.
Near‐monodisperse, size‐controllable, poly(methyl methacrylate)‐pigment nanoparticle composites were produced using electrohydrodynamic atomization (EHDA). The geometric mean diameters of the composite particles were in the 0.91 to 1.90 µm‐diameter range with geometric standard deviations of approximately 1.05 to 1.12. Increasing the polymer volume fraction and liquid flow‐rate resulted in an increase in the diameter of the composite particles, which agreed well with droplet scaling relations for EHDA. The results here demonstrate that EHDA can be used for polymer‐nanoparticle‐composite production and as an alternative to conventional inkjet printing.
A facile technique is presented to prepare discrete µm‐sized spherulitic particles of BAPC in thin polymer films. Unlike in bulk precipitation or spray crystallization, the present technique offers a method to prepare three‐dimensional semicrystalline particles of narrow particle size distribution that can be readily isolated and collected from the glass substrate as discrete particles. We report the effects of polymer molecular weight, polymer type, and the precursor polymer film thickness on the formation of spherulitic particles and their morphologies. The three‐dimensional spherulitic particles prepared in this study have large specific surface areas, higher crystallinity and melting temperature than the bulk precipitated and crystallized polycarbonate particles.
The solid and thermally instable azoinitiators V‐65 and VR‐110 were embedded within a polymer particle by using the miniemulsion process and afterwards quickly decomposed by thermal treatment below the glass temperature of the polymer. The resulting nitrogen gas overpressure inside the particles leads to a disruption of the polymer particle and a possible sudden release of encapsulated substances. It is shown, by electron microscopic measurements, that the number of burst particles correlates with the applied temperatures as well as the heating time. The surface deformation could be verified by scanning electron microscope analyses.
The synthesis of silver nanoparticles attached on the surface of a hollow cornet‐like polymer matrix which served as a reductant and host matrix is described. This hybrid organic/inorganic macromolecular matrix is exhibiting anion‐exchange properties, porous structure and hollow morphologies, and absorptions in the visible light region. Due to the anion‐exchange property and the 3D orientation of the macromolecular chains the material is defining a new functional organic/inorganic hybrid. For the synthesis of nanoparticles, no other reducing agents were used and silver nanoparticles with a mean diameter of less than 20 nm were attached on the surface of the polymer, thus inheriting the composite with high antibacterial activity tested in bacterial strains and yeasts.
Silica nanoparticles with an average diameter of 12 nm are grafted with PBMA‐b‐PMMA double shells through typical sequential ATRP from bromoisobutyrate initiators anchored at the silica surface using an epoxysilane. A commercially available PMMA homopolymer is used for the preparation of composites with unmodified, silane‐modified and double‐shell‐modified silica particles. Good mechanical properties are obtained for silica double shell containing systems. The silica content in double shell particle systems is varied from 0 to 2.5 wt%. A significant improvement in impact properties is observed. The surface‐modified silica particles are characterized by ATR‐FTIR, NMR, GPC, and thermal analyses. TEM analysis is used to analyze the nature of dispersion of particles in the composites.
1,3,5‐Benzenetrisamide‐based supramolecular nucleating agents for poly(butylene terephthalate) (PBT) are reported. 1,3,5‐Benzenetrisamides combine excellent thermal stability with chemical resistance, basic requirements for the use in high‐melting thermoplastics. To establish structure–property relationships, the central core and peripheral substituents are varied systematically. Dissolution and crystallization behavior of the additives in the PBT melt and the crystallization temperature of PBT are investigated as a function of the additive concentration. Efficient nucleating agents can increase the crystallization temperature of PBT by 10.6 °C to 199.1 °C. A visualization of supramolecular nano‐objects formed in the polymer melt is provided.
The effect of nanosilica addition on the morphology and mechanical properties of blends of isotactic PP and an ethylene/octene copolymer (EOC) is studied. TEM reveals that the well‐dispersed nanoparticles are localized exclusively in the PP phase. In the presence of a maleated PP compatibilizer addition of nanosilica leads to more finely dispersed EOC domains and a finer co‐continuous morphology. The nanoparticles reduce the rate of coalescence of the dispersed phase domains. The mechanical properties depend on the EOC and PP‐g‐MA content. Tensile and flexural properties are significantly enhanced in the presence of the silica nanoparticles, whereas impact properties are not affected. These enhancements are attributed to the favorable microstructure of the blends.
Spherical and tube‐like (TL) silica nanoparticles were melt blended with an isotactic polypropylene (PP) matrix and its effect on the isothermal spherulite growth rate was analyzed by polarized optical microscope. The addition of low amount (≈1 wt.‐%) of either 15 nm spherical or TL particles raises the spherulite growth rate and the nucleation density of spherulites. Samples prepared with silica spheres of 80 nm otherwise do not show any change in the crystallization behavior. By adding a compatibilizer, both the nucleation density and the spherulite growth rate of the pure polymer are increased. Noteworthy, although the nanoparticles do not further increase the nucleation density of the PP/compatibilizer blend, independent of its form and size, they cause a decrease in its spherulite growth rate.
Polymer‐immobilized colloidal crystal films have been fabricated by conventional spray coating and UV curing of silica–acrylic monomer suspensions. Controlling both the viscosity of the suspensions and the wettability of substrates enabled colloidal crystal films with smooth surfaces and brilliant structural colors due to Bragg diffraction. The structural colors could be controlled by particle concentrations in addition to particle diameter. The wettability influenced the thickness of the coated film and it consequently affected the Bragg reflection intensity of the film. Silhouette figures were textured on a substrate having regions with different wettabilities by single spray coating.
A facile and easily industrialized approach for preparing highly dispersed MMT/polymer nanocomposites is developed by combining the latex compounding method and a spray‐drying process. Clay particles are successfully delaminated into layers, and layer re‐stacking is effectively prevented. HR‐TEM and XRD results confirm that MMT layers achieve exfoliated or nearly exfoliated dispersion in both MMT/styrene‐butadiene rubber and MMT/PS nanocomposites. Compared with melt‐blended MMT/SBR composites, MMT/SBR nanocomposites prepared by this new strategy exhibit extremely high dynamic modulus.
Developing co‐continuity in a polymer blend determines a multiphase system with enhanced properties which originate from the synergism of its constituents. Filling a blend with nanoparticles is a promising route to guide its morphology and eventually affect the co‐continuity transition. We add different kinds of nanoparticles to an HDPE/PEO blend to study how they affect the morphology of the blend as function of their surface properties and form factor. We find that PEO drop size is drastically reduced by particles adsorbed at the HDPE/PEO interface. However, we show that a drastic shifting of the co‐continuity threshold may only be achieved when particles affect the rheology of the interface.
This paper demonstrates how the electric‐field‐assisted thermal annealing of octadecylamine‐functionalized SWNT/PMMA films induces an increase in the composite transversal conductivity of several orders of magnitude and a decrease in the lateral conductivity. This difference has been rationalized in terms of the nanotube alignment into the polymer matrix along the electric field direction. This result provides an initial understanding of how electric fields can be used to control the bulk physical properties of such nanocomposites.
Photoresponsive superabsorber particles containing a crosslinked hydrophilic core and a hydrophobic azobenzene‐containing shell were used to prepare photoresponsive polymeric nanomats, thus combining photoresponsivity with high porosity, toughness, and hydrophilicity. The properties of the nanomat composites were highly dependent upon the amount of the superabsorber photochromic particles added. Stable, highly elastic composite nanomats with very high loading (up to ≈50 wt.‐%), good water absorption capacity (4 000%) and relatively good tensile strength (3 MPa) were obtained. The photoresponsive behavior of the composites is demonstrated, which leads to relatively fast water desorption.
A novel method is described to functionalize nanofibers to form a nanocomposite with core/shell particles in order to control protein release. The nanocomposite is produced by electrically neutralizing negatively charged poly(lactic acid) nanofibers with positively charged poly[(lactic acid)‐co‐(glycolic acid)] particles via a one‐step electrohydrodynamic jetting process. The protein‐encapsulated core/shell particles exhibited no significant initial burst release or denaturation. The protein release profile was controlled by porosity and protein/polymer interactions. The method may be promising to engineer intelligent scaffolds that can fulfill the needs of biomimetic materials.
Novel silver/polymer composites based on thiol‐ene chemistry are prepared by an in situ bottom‐up approach. The in situ synthesis of silver particles inside the polymer matrix is achieved in one pot by photoreduction reaction in presence of a silver precursor and the concurrent crosslinking reaction. XPS analysis confirms the formation of silver particles; TEM morphological investigation shows a very good dispersion and distribution of the nanometric silver particles within the thiol‐ene network. Antimicrobial properties of the photocured hybrids are also evaluated.
Crosslinked core/shell PBA/PMMA‐PGMA particles are prepared by emulsion polymerization and dispersed into a UV‐curable cycloaliphatic epoxy resin in the range of 5–15 wt%. The presence of the particles does not significantly affect the UV curing process: a slight decrease of final epoxy group conversion is attributed to an increase in the viscosity when CS‐GMA is added to the photocurable formulation and to an enhanced vitrification effect. The presence of the particles does not modify the Tg of the cured materials, while an enhancement of impact resistance is observed that does not depend on the particle content. FESEM micrographs for epoxy reinforced with core/shell particles indicate a plastic void growth of the epoxy polymer and shear yielding toughening mechanism.
We found that enhanced exfoliation of clay up to 20 wt.‐% in non‐polar polybutadiene (PB) if the PB was blended with a relatively small fraction of hydroxyl‐terminated PB (HTPB). The choice of an intermediate polymer composition to enhance exfoliation was motivated by theoretical predictions of end‐functionalizing effects of Balazs, Farmer, and coworkers. A combination of X‐ray diffraction and rheological measurements were used to optimize HTPB content for enhanced exfoliation. We also observed the competition of the kinetic and thermodynamic processes during the ripening of the exfoliated clay structure.
We demonstrate solution blending of PVDF with PECA obtained by controlled polymerization of ECA. This method circumvents the processing detriments posed by the instant cross‐linking of CAs when encountering aprotic solvents such as DMF, a common PVDF solvent. The slower polymerization of ECA was tracked using NMR spectroscopy. The polymer mixture solutions were spin‐coated to study the film morphology, wettability, and surface energy. The polymer films show strong contribution of basic polar surface energy that can be beneficial in biomedical applications. DSC and TGA were also performed on the blended polymers. The DSC thermograms show clear suppression of PVDF melting point, which provides evidence of two‐polymer miscibility.
CNT based elastomer‐hybrid‐nanocomposites prepared by melt mixing have been investigated showing promising results in technologically relevant electrical, mechanical, and fracture‐mechanical properties. It is demonstrated that the incorporation of CNT in silica‐filled natural rubber results in a good dispersion of the CNT. The materials show an enhanced mechanical stiffness and tensile strength, an increased modulus, and a high electrical conductivity with quite low amounts of CNT, though the tear resistance under dynamical loading is slightly reduced. Using DMA and dielectric spectra, a better understanding of the conduction mechanism, the polymer/tube interaction, and the filler networking in CNT nanocomposites is achieved.
