We describe the preparation and characterization of core-shell structured latexes, consisting of different methacrylate cores, covered with a shell of a cross-linked rubber poly(n-butyl acrylate). The structured latexes were prepared via a. two-stage emulsion polymerization process under kinetically controlled conditions by use of reaction calorimetry. Transmission electron microscopy (TEM) confirms the quality of the structural uniformity of the latex particles. The particles maintain their structure during film formation. After drying these structured latexes form nanostructured polymer films. Beside preparation and characterization, first results of investigations of mechanical properties (dynamic mechanical analysis (DMA) and stress-strain experiments) of such nanostructured polymer films are reported.

It is desirable to assess whether the final particle number in heterogeneous polymerizations is predetermined by the number of monomer droplets. If this is really the case nucleation occurs very smoothly via a polymer in monomer solution where the kinetically important step is the initiation reaction inside the droplets. However in the case of emulsion and dispersion polymerizations the nucleation step is a sharp phase transition when the free polymer phase is formed in the continuous phase. This process can be described generally with the classical nucleation theory although it is today not yet possible to give quantitative explanations for some new experimental results. These new experimental results prove the strong influence the kind of the reactor material as well as the stirrer speed has on particle nucleation and final latex properties.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTQuasi-Living Polymerization of N-Isopropylacrylamide onto Poly(ethylene glycol)M. D. C. Topp, I. H. Leunen, P. J. Dijkstra, K. Tauer, C. Schellenberg, and J. FeijenView Author Information Department of Chemical Technology and Institute for Biomedical Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands, and Max-Planck-Institute of Colloids and Interfaces, D-14424 Potsdam, Germany Cite this: Macromolecules 2000, 33, 14, 4986–4988Publication Date (Web):June 14, 2000Publication History Received20 October 1999Published online14 June 2000Published inissue 1 July 2000https://pubs.acs.org/doi/10.1021/ma9917500https://doi.org/10.1021/ma9917500rapid-communicationACS PublicationsCopyright © 2000 American Chemical SocietyRequest reuse permissionsArticle Views562Altmetric-Citations58LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Ions,Micelles,Monomers,Polymerization,Thermal polymerization Get e-Alerts

In this study films of core-shell-structured latex particles are investigated by dynamic scanning force microscopy ‘tapping mode imaging’. Polymer dispersions with cores of the low-viscosity polymer poly(2-ethylhexyl methacrylate) (PEtHMA) and shells of the cross-linked rubber poly(n-butyl acrylate) (PBA) were spread on a flat mica surface to form a monolayer. Topographic as well as phase images were recorded at different amplitudes and damping factors (so-called soft and hard tapping). The topographic images show a continuous matrix formed by the particles, but a clear contrast of individual particles in the phase images could be obtained at high damping factors of the cantilever oscillation. The soft cores embedded in the matrix of the shell polymers caused a perceptible reduction of the phase of oscillation. Consequently, the total particle appeared soft enough because it allowed deformation of the soft cores below. Copyright © 1999 John Wiley & Sons, Ltd.

Comprehensive experimental results are presented for surfactant-free emulsion polymerization of styrene with water-soluble, ionic initiators. Special emphasis is placed on the particle nucleation, the chemical structure of the nucleating species, the change of latex, particle and polymer properties as well as the development of particle morphology with polymerization time. Under special conditions the appearance in transmission electron microscopy pictures of less electron dense anomalous particles is observed. The formation of these structures is discussed and possible formation mechanisms presented. Dialysis of the latexes changed their properties drastically as they became unstable to coagulation. The original latexes did not change their properties over several months.

Two-stage emulsion polymerization controlled with a reaction calorimeter results in core-shell structured latexes with homogeneous size distribution and architecture. We describe the synthesis of so-called "container particles", consisting of a low-viscosity core with a low glass transition temperature (poly(2-ethylhexyl methacrylate), (PEtHMA)), covered with a thin shell of a cross-linked rubber (poly(n-butyl acrylate), (PBA)). Drying of these dispersions results in nanostructured films. A controlled topography and a network superstructure are obtained, which may be adjusted by the size, composition, and architecture of the original particles. Atomic force microscopy (AFM) in the tapping mode is used to study the final latex films. In addition to topographic information, it is possible to display, with a nanometer resolution, the amplitude and phase of response of the cantilever in each pixel, which images the remainder of the former core and shell by their different mechanical loss behavior. The degree of cross-linking of the second stage polymer (PBA) is found to be the major factor influencing the morphology of the polymer films formed. At lower cross-linking densities, even and surface mechanically homogeneous films are obtained. For highly crosslinked shells, it is shown by a combination of AFM modes that the containers collapse and release the low molecular weight liquid core to form a continuous film containing the single, collapsed units.

Drying of emulsions of special polymeric core-shell latexes results in structured films and coatings with advantageous material properties. Here, we focus on so-called "container particles", consisting of a low viscosity core with a low glass transition (poly(2-ethylhexyl methacrylate), PEtHMA), covered by a thin shell of a cross-linked rubber (poly(n-butyl acrylate), PEA). These particles can be regarded as model emulsions of reactive polymeric oils with a very high colloidal stability. The film formation of these latexes was studied by atomic force microscopy (AFM) in the tapping mode as well as by transmission electron microscopy (TEM). It is shown that the films stay nanostructured after the drying process, i. e. they exhibit both a controlled topography as well as a network superstructure originating from the characteristics of the original dispersions.TEM allows to detect the whereabouts of the polar stabilizer. Both continous surfactant films as well as inverted micelles are found. A geometrically induced demixing phenomenon is found which enriches the polar components and might be the molecular reason for the so-called pinhole-effect, the failure of water-born coatings in contact with water.

Reaction calorimetry is a powerful tool for systematic investigations of heterophase polymerizations. The heat flow–time or heat flow–conversion profiles clearly reflect any changes of the recipe components. Results of batch heterophase polymerizations are presented proving the dependence of the reaction rate profiles on the water solubility of the monomers, on the presence of a chain transfer agent, on the type and concentration of the stabilizer and the initiator, respectively, and on the polymerization temperature. A complete mechanistic interpretation of this data collection is nowadays still impossible.

A new class of composite latex particles has been built via two-stage emulsion polymerization. The core-shell container particles with cage properties were synthesized under kinetic controlled conditions by use of reaction calorimetry. Scanning force microscopy (SFM) has been applied to investigate the particle morphology of the poly(2-ethylhexyl methacrylate) /poly(n-butyl acrylate) (PEtHMA/PBA) latexes and the degree of crosslinking of the second stage polymer (PBA) was found to be the major factor influencing the morphology of the polymer films formed.

The regioselectivity of Pd-catalyzed coupling reactions of functionalized benzenes and olefins with respect to the ratio of 1.2-product/1.1-product was monitored by model reactions. The coupling of halobenzenes, benzene triflate, and aryldiazonium salts was studied under various reaction conditions. In order to simulate corresponding polyreactions, special focus was on the coupling of ortho-substituted functionalized benzenes with ethylene or styrene in order to evaluate the input of mono- and disubstituted aryl monomers and the choice of the olefin on the regioselectivity of polyreactions. The results of the model reactions were transferred to the polyreactions. The polymers were characterized by NMR, absorption and photoluminescence spectroscopy as well as electroluminescence.