Structured Latex Particles Research Articles

Morphological study of structured latex particles by Transmission Electron Microscopy

Transmission electron microscopy plays an important role in the study of the influence polymerization conditions have on the morphology of structured latex particles and thus in the understanding of the morphological effect of such particles on the structure-property relationships of polymeric end products.Structured latex particles are prepared by seeded emulsion polymerization, where the first stage is a polymerization of ”the core” poly(n-butyl acrylate) (PBA), followed by a second stage polymerization of ”the shell” poly(benzyl methacrylate/styrene) (P(BM/St)) at various ratios. The changes in polymerization conditions include such variables as the polymerization mode (batch vs. semicontinuous), core/shell ratio, shell thickness, and shell composition. Morphology studies of the structured latex particles are performed by transmission electron microscopy on preferentially stained samples. In a small vial, a few drops of latex sample are combined with a few drops of uranyl acetate (UAc) 2% solution. The uranyl acetate serves as a negative staining to better delineate the particles edges.

Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) core-shell emulsion polymers. Part II: Thermomechanical properties of latex films

Polystyrene(1)/poly(n-butyl acrylate-methacrylic acid)(2) structured latex particles were prepared through a two-stage emulsion polymerization procedure, using a polystyrene (PS) latex seed (118 nm), and differentn-butyl acrylate (BA)/methacrylic acid (MAA) ratios. Polymerization kinetics, particle morphology, and MAA location have already been discussed in the first part of this series. In this second part the thermomechanical behavior of films cast from these latexes was studied. Differential Thermal Analysis and Dynamic Mechanical Analysis (DMA) were employed as characterization techniques for the films. Two polymer phases corresponding to polystyrene and a poly(BA-MAA) copolymer were distinguished. Comparison was made to analogous unfunctionalized PS/PBA systems, as a result of which an effect of MAA upon the phase arrangement in the film was found. Scanning Electron Microscopy of film samples and DMA showed that the evolution of the phase arrangement as a result of annealing was strongly dependent on the type of mechanical and heat treatments being applied to functionalized systems. Finally, the thermomechanical behavior of films was related to the structural features of the corresponding latexes, and computer simulation techniques wer eemployed to establish a mechanistic support for these relationships.

Effects of reaction pathway in emulsion copolymerisation on film mechanical properties

Films obtained from structured latex particles, based on acrylic copolymers produced by a variety of processes, have been characterised by static and dynamic mechanical analysis. Furthermore, the expected heterogeneous structure obtained in staged emulsions, the so called “core-shell” morphology has been reinforced, in some cases, by introduction of a reactive comonomer in the polymerisation recipe. The epoxy function which can be readily analysed, was also chosen for its potential reactivity at high and low temperatures. The obtained results have shown the close correlation between particle microstructure due to peripheral growth and mechanical properties of corresponding latex films.

Latex de particules structurees

A survey of the literature concerning the preparation and the characterization of structured latex particles is presented. The main features of the various processing techniques are discussed; the mechanisms and also the various parameters which shape the polymeric phase arrangement throughout the volume of the particles are emphasized.