Zero-VOC technologies combining ecological and economic efficiency are destined to occupy a growing place in the polymer economy. Today, Polymerization in dispersed systems and Photopolymerization are the two major key players. The hybrid technology based on photopolymerization in dispersed systems has emerged as the next technological frontier, not only to make processes even more efficient and eco-friendly, but also to expand the range of polymer products and properties. This review summarizes the current knowledge in research relevant to this field in an exhaustive way. Firstly, fundamentals of photoinitiated polymerization in dispersed systems are given to show the favourable context for developing this emerging technology, its specific features as well as the distinctive equipment and materials necessary for its implementation. Secondly, a state-of-the-art and critical review is provided according to the seven main processing methods in dispersed systems: emulsion, microemulsion, miniemulsion, dispersion, precipitation, suspension, and aerosol.
Electrically conductive polymer/rGO (reduced graphene oxide) films based on styrene and n-butyl acrylate are prepared by a variety of aqueous latex based routes involving ambient temperature film formation. Techniques based on miniemulsion polymerization using GO as surfactant and "physical mixing" approaches (i.e., mixing an aqueous polymer latex with an aqueous GO dispersion) are employed, followed by heat treatment of the films to convert GO to rGO. The distribution of GO sheets and the electrical conductivity depend strongly on the preparation method, with electrical conductivities in the range 9 × 10 −4 to 3.4 × 10 2 S/m. Higher electrical conductivities are obtained using physical mixing compared to miniemulsion polymerization, which is attributed to the former providing a higher level of self-alignment of rGO into larger linear domains. The present results illustrate how the distribution of GO sheets within these hybrid materials can to some extent be controlled by judicious choice of preparation method, thereby providing an attractive means of nanoengineering for specific potential applications.
Historically,
the synthesis of aqueous polymer dispersions has
focused on radical chain-growth polymerization of low-cost acrylate
or styrene emulsions. Herein, we demonstrate the potential of UV-initiated
thiol–ene
step-growth radical polymerization, departing from a nontransparent
difunctional monomer miniemulsion based on ethylene glycol dithiol
and diallyl adipate. Performed without solvent and at ambient conditions,
the photopolymerization process is energy-effective, environmentally
friendly, and ultrafast, leading to full monomer consumption in 2
s,
upon irradiating a miniemulsion contained in a 1 mm thick quartz
cell microreactor. The resultant linear poly(thioether ester) particles
have an average
diameter of 130 nm. After water evaporation, they yield a clear elastomeric
film combining chemical resistance and high degree of crystallinity
(55%).
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