In this communication, we report the successful synthesis of gradient morphology nanoparticles composed of poly(styrene-co-methyl methacrylate) and their characterisation using X-Ray Photoelectron Spectroscopy (XPS).

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The synthesis of composite latex particles possessing core-shell and gradient morphologies, respectively, using seeded starve-fed semibatch emulsion polymerization of styrene (St) and methyl methacrylate (MMA) is presented. The focus is on the effect of the monomer feed order on the particle morphology development. The particle morphology is assessed using a novel approach which entails comparing the experimental surface composition as a function of polymerization time (particle growth) obtained by X-ray photoelectron spectroscopy with the predicted surface composition using a mass balance mathematical model. Both types of composite latexes (core-shell and gradient) feature changes with polymerization time in the oxygen/carbon surface composition which enables one to track the morphology development. Differential scanning calorimetry is also implemented to analyze the extent of phase separation. The monomer feed order is shown to play a crucial role-under the present conditions, gradient and core-shell particles are obtained if the feed order is St/MMA (St fed first), but not if the feed order is reversed. These findings illustrate that thermodynamic factors are important, given that thermodynamically it is more favorable for MMA-rich chains to occupy the oil-water interface to reduce the interfacial tension. Systems where St is the second stage monomer lead to mixed structures rather than the targeted core-shell or gradient morphology with St-rich chains at the particle surface.INTRODUCTION Paints and varnishes are coatings extensively used in daily life to protect and decorate substrates such as metal, wood, plastics, or concrete. Water-based coating systems used in the paint industry are based on resins predominantly synthesized by emulsion polymerization generating particles in the 50-500 nm size range. Depending on the type of nanoparticle morphology, the minimum film formation temperature (MFFT) of paints can be adapted in order to not only enhance coating properties but also lower the volatile organic compounds (VOCs) content-VOCs are usually incorporated to reduce the MFFT. 1-5 Among the common types of composite latexes, two types of morphology have been particularly implemented in industry: core-shell and gradient morphology latexes.

The distribution of unsaturations in the prepolymer of a typical unsaturated polyester (UP) resin (maleic anhydride, phthalic anhydride and 1,2‐propylene glycol) has been shown to influence the kinetics of the cure process with styrene monomer. Segments containing double bonds in close proximity appear to lower the reactivity of the resin due to steric hindrance, as indicated by the fact that the rate of cure and the final degree of cure, measured by differential scanning calorimetry (DSC), increase as the average sequence length (SL) of maleic units decreases. This implies that the reactivity of UP resins may be improved by synthesis of prepolymers with certain reactant sequence‐length distributions. The copolymer formed by the melt condensation process of maleic anhydride, phthalic anhydride and 1,2‐propylene glycol in the absence of a transesterification catalyst has a non‐random structure with a tendency towards blockiness. This was established using 1H NMR analysis in tandem with deterministic and Monte Carlo modelling techniques. Copyright © 2003 Society of Chemical Industry

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