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Plugging is probably one of the most challenging issues facing further continuous polymerization process development. Starting with the photopolymerization of n -butyl acrylate miniemulsion in a continuous photoreactor composed by fluoropolymer coiled tubing, we show that three parameters have a critical role on the occurrence of plugging: solids content (⩾30 wt%), surfactant concentration (⩽1 wt%) and tubing diameter (⩽1 mm). In contrast, monomer droplet stability, size and flow rate have a minimal impact. The use of nanodroplets, as individual reactors able to confine the solid products to these droplets, is in no way an efficient strategy to prevent channel clogging. Polymer adsorption occurs locally on macroscopic nucleation sites, where polymer build-up leads gradually to plugging. Based on interfacial tension measurements, we show adhesional wetting as the main trigger of plugging. In this process driven by the high cohesive energy of water, the monomer droplets not originally in contact with the reactor wall makes contact with that surface by displacing water, adhere to it, and polymerize. [ABSTRACT FROM AUTHOR]

Finding eco-efficient and environmentally viable alternatives to chromate coatings represents a fundamental milestone in the aerospace industry. Here, we show a chromate-free approach to protective hybrid coatings on aluminium alloy (AA2024-T3) departing from photoinduced sol–gel and cationic polymerizations. Beginning with a film of n -alkyltrimethoxysilane and diepoxy monomer, we rely on photogenerated superacids to induce the single step formation of two inorganic and organic barrier networks. Such system combines the unique aspects of photopolymerization including fast reactions, temporal control, solvent-free composition and temperature independence. Used without chemical conversion coating or anodizing, some films have passed 2000 h of salt spray testing. [ABSTRACT FROM AUTHOR]

Abstract: An alternative to the Evaporation Induced Self Assembly (EISA) method is described as a fast and simplified approach towards mesoporous silica films. The sol–gel process is photochemically triggered with the aid of photoacid generator (PAG), thereby making mesostructuration independent of film deposition conditions, solvent evaporation and complex chemistry associated with a silica sol. The developed solvent-free synthesis uses non-ionic poly(ethylene oxide)-based surfactants and polydimethoxysiloxane, affording after UV irradiation a film with a wormhole porous framework, and a uniform pore size distribution. The disordered mesostructure was characterized by X-ray diffraction, N2 adsorption, 29Si solid-state NMR and transmission electron microscopy. [Copyright &y& Elsevier]

Abstract: This paper reviews the recent discoveries that were achieved by our group in the field of particle synthesis via ring-opening metathesis polymerization (ROMP). Both polynorbornene and polybutadiene-based particles were prepared by the respective ROMP of norbornene and cyclooctadiene initiated by (PCy3)2Cl2Rug several methods of polymerization in dispersed media, such as dispersion, suspension and miniemulsion. Depending upon the process implemented, particles size was found to range from 300nm to 20μm. [Copyright &y& Elsevier]

An innovative route based on a novel photo-latent ROMP initiator has been explored to synthesize polynorbornene latex particles in miniemulsion. Operation conditions were strongly improved by the use of an annular LED photo-reactor, increasing the uniformity of radiation distribution and enabling to control atmosphere and stirring throughout irradiation. Several parameters (droplet size, irradiance, pre-catalyst structure) were studied in order to improve the monomer conversion profiles, which eventually led to the production of latex with high norbornene conversion (>90%) and 10% solids content. Particular attention was paid to the polymer microstructure, which was found to be highly dependent on the type of initiation mechanism. Image 1 • Synthesis of polynorbornene particles by ROMP in miniemulsion. • Using of efficient photolatent ROMP initiator. • Using of an annular glass photoreactor, allowing both miniemulsion and ROMP under well-controlled inert atmosphere. • High Nb conversions have been reached very quickly (> 90%). • Control of the cis/trans ratio of the polynorbornene thanks to the choice of Ruthenium precatalyst. [ABSTRACT FROM AUTHOR]

• A novel strategy of light-induced crystallization to fabricate hybrid superhydrophobic coatings has been demonstrated. • The hierarchical micro/nano-structure can be precisely controlled. • The cross-linked silsesquioxane hybrid coating possesses good water repellency and high mechanical, chemical stability. Nano/micro structures are crucial for superhydrophobic surfaces, but rare are methods able to generate such dual structuring in a single step using a single precursor. We show that the visible light-controlled self-assembly of bis-silylated alkane precursors can create in one-step organosilica coatings exhibiting two levels of hierarchy: lamellae at nanoscale, and plate-like crystals at microscale. Crystallization rate can be precisely controlled by alkylene bridging group and irradiance. This allowed us to achieve superhydrophobic properties by the creation of a dense and uniform network of nanostructured microcrystals with high surface roughness. The obtained coatings displayed chemical stability, good thermal resistance and high mechanical strength through the cross-linked siloxane structure, which is essential for applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We describe a fast photocalcination process to prepare highly ordered silica mesoporous films through the use of a low-pressure amalgam arc (λ: 185/254 nm). Because radiant power is 2–3 times higher than conventional low-pressure UV lamps, the elimination of the PEO- b -PPO- b -PEO copolymer template in the 2D hexagonal hybrid film has been completed within 50 min, without damage to the mesostructure. The degradation kinetics are impacted by film thickness and irradiance, but hardly copolymer concentration. Compared to thermocalcination, a narrower pore size distribution and lower energy consumption have been found. Photodegradation mostly originates from a photoablation mechanism induced by radiation at 185 nm, while oxidation due to photogenerated reactive oxygen species plays a minor role. Photocalcination has been combined with an initial photoinduced mesostructuration (detailed in Part 1: Microporous Mesoporous Mater., 257 (2017) 42–50), resulting in an unprecedented “all UV” method to mesoporous silica films. The final process relies on dual wavelength photoactivation: UV B to form the hybrid copolymer/silica network, a flash intermediate thermal consolidation, and UV C to decompose the copolymer chains. [ABSTRACT FROM AUTHOR]

In the field of bimodal latex film's formation, finding methods to quantify particle concentration profiles within the film thickness is a challenge. Herein the advantages and limitations of confocal fluorescence microscopy (CFM) and scanning electron microscopy (SEM) are presented. Films are prepared from a bimodal fluorescent acrylic mixture of large non-deformable particles and small deformable particles having high Péclet numbers. A fixed volume fraction of large particles (Φ L) in the dispersion is used with increasing volume fractions of small particles latex (Φ S). At low Φ S , a surface stratification of large particles occurs with thicknesses up to several micrometers, allowing detection by both CFM and SEM. Small particles form a stratified surface layer above a threshold Φ S value. Its thickness of less than 500 nm is evidenced only by SEM due to the resolution limit of the confocal scan. SEM is also able to reveal concentration gradients of large particles below the "small-on-top" stratified layer. [Display omitted] • A low enough vol. fraction in small particles induces a large-on-top stratification. • A critical vol. fraction in small particles induces a small-on-top stratification. • Small-on-top stratified structure is too thin to be resolved by confocal microscopy. • Confocal microscopy evidences large-on-top stratified layer at micrometer-scale. • SEM observations of film cross-sections reveal stratified and gradient structures. [ABSTRACT FROM AUTHOR]

Patterned coatings based on biodegradable crosslinked poly(ester/carbonate) have been prepared by photo-induced ring-opening polymerization of a liquid bifunctional trimethylene carbonate-based monomer using poly(ε-caprolactone) triol as initiator and a guanidine superbase photogenerator activated by irradiation at 385 nm. The influence of various parameters on gel time such as components molar ratios, irradiation time or reaction temperature, has been evaluated by photorheometry. The formulation and experimental conditions offering the shortest gel times were then employed to produce a patterned coating by stereolithography. Sample thickness proves to be independent of irradiation time, but increases with reaction time, thus attesting of a dark polymerization. [Display omitted] • Photo-induced ring-opening polymerization has been employed to prepare coatings. • Liquid formulations containing a bis-cyclic carbonate have been prepared. • Gel times of 1 min were obtained using a PBG releasing TBD under 385 nm. • Patterned coatings have been prepared using a stereolithography apparatus. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fully photodegradable block copolymer nanoparticles containing o -nitrobenzyl group. • Self-immolation mechanism is triggered by a dual photoinduced H-atom abstraction. • Chain scission and o -nitrobenzyl group cleavage take place simultaneously. • The nanoparticles can release a guest molecule in response to irradiation. • The burst release of radicals accompanying degradation can destroy target molecules. When exposed to radiation, photo-responsive block copolymer nanoparticles disassemble to liberate a possible carried guest. However, the particle disruption is rarely accompanied by a polymer chain disintegration into molecular fragments, that would facilitate clearance from the body. We describe herein a novel class of fully photodegradable all-acrylic poly(hydroxyethyl acrylate)- b -poly(o -nitrobenzyl acrylate) (PHEA-PNBA) nanoparticles. Their synthesis proceeds by dispersion polymerization-induced self-assembly (PISA) based on a reversible addition–fragmentation chain transfer mechanism. The self-immolation mechanism is initiated via a dual H-abstraction by the electronically excited o -nitrobenzyl pendant group, first, from the adjacent CH 2 , second, from CH of the polyacrylate chains. The former results in the release of the protecting group, while the latter initiates a cascade of reactions that fragment the whole polymer backbone. Simultaneous chain scission and cleavage of o -nitrobenzyl group combine in turn to induce a fast and complete degradation of the copolymer particles. Synthesis, structural and colloidal characterization of the diblock copolymer nanoparticles, photochemical mechanism governing self-immolation are described. Emphasis is placed on understanding the reaction parameters which are important in controlling degradation rates, in particular nature of continuous phase and degree of polymerization of the PNBA block. UV exposure is exploited to release a model guest (Nile red) from the particles. Additionally, the burst release of free radicals accompanying the chain degradation can serve to decompose a target molecule (methylene blue). [ABSTRACT FROM AUTHOR]