Waveguide Fabrication In UV-Photocurable Sol–Gel Materials: Influence Of The Photoinitiating System

In this paper we identify and explain the different chemical interactions involved between a sol–gel matrix and photoinitiators used in the fabrication of optical waveguides. A well-established sol–gel matrix composed of 3-methacryloxypropyltrimethoxysilane, zirconium n-propoxide and methacrylic acid was developed, and two different photoinitiators (Irgacure® 819 and 1800) were added to the host matrix. Optical microscopy was used to characterise the structure of the waveguides as a function of the photoinitiator nature and concentration, and aging of the hybrid sol–gel material. It is clearly demonstrated that the width of the waveguides is strongly influenced by the sol aging. Furthermore, it is shown that degradation of photoinitiators occurs during the sol–gel process. Oxidation of the phosphonyl groups by the zirconium complex accounts for this results

Ultraviolet self-generating relief micro-optical elements through crosslinking photopolymerization of liquid resins

The use of a self-processing dry photopolymer layer capable of memorizing optical information as a local change in thickness, is proposed for the fabrication of microlenses, binary holograms and gratings. Relief micro-optical elements are generated by direct imagewise exposure through a mask. A gradient of chemical composition and a gradient of surface free energy cause the transfer of reactive species between dark and illuminated areas. Contrary to conventional lithographic techniques that require wet chemical post-treatment to remove parts of the photoresist material, the fully self-processing character of this technique makes the record available in situ and immediately after exposure

Fabrication of refractive microlens arrays by visible irradiation of acrylic monomers: influence of photonic parameters

The fabrication of refractive microlenses with self-developing photopolymers is reported. A spatially controlled illumination of the photosensitive layer induced an inhomogeneous photopolymerization involving formation of 3-D polymer network, mass-transport process of reactive species and bending of the surface. The process exhibited a completely self-processing character without any chemical post-treatment to reveal the relief. The lens arrays displayed diameters ranging from less than 100 μm to 1 mm and focal lengths from 100 μm to a few millimeters, depending on photonic, optical and physico-chemical parameters. The paper focuses on the importance of photonic parameters in the generation of microlens arrays and discusses the flexibility of this technique in the visible range

Waveguide Fabrication In UV-Photocurable Sol–Gel Materials: Influence Of The Photoinitiating System

In this paper we identify and explain the different chemical interactions involved between a sol–gel matrix and photoinitiators used in the fabrication of optical waveguides. A well-established sol–gel matrix composed of 3-methacryloxypropyltrimethoxysilane, zirconium n-propoxide and methacrylic acid was developed, and two different photoinitiators (Irgacure® 819 and 1800) were added to the host matrix. Optical microscopy was used to characterise the structure of the waveguides as a function of the photoinitiator nature and concentration, and aging of the hybrid sol–gel material. It is clearly demonstrated that the width of the waveguides is strongly influenced by the sol aging. Furthermore, it is shown that degradation of photoinitiators occurs during the sol–gel process. Oxidation of the phosphonyl groups by the zirconium complex accounts for this results

Scaling-up of Mesoporous Silica Films via an Eco-efficient UV Processing Method. Part 2: Photoinduced Calcination

International audienceWe 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

LED-cured self-replenishing hydrophobic coatings based on interpenetrating polymer networks (IPNs)

LED-cured IPN-based coatings bearing hydrophobic functional groups have been developed in order to obtain hydrophobic self-replenishing surfaces with improved mechanical properties. Acrylate/epoxide combinations have been chosen to achieve two different Tgs: a lower one to provide sufficient mobility for self-replenishing behavior and a higher one for sufficient hardness. Detailed characterizations of the mechanical and morphological properties of the IPN coatings, in the absence and presence of covalently bonded fluorinated dangling chains, have been performed. Finally, the self-replenishing behavior of these networks with intrinsic hardness has been investigated. This new approach, which is based on IPN and LED technologies could offer self-replenishing functionality for industrial applications, namely in the automotive or aerospace industry

Scaling-up of Mesoporous Silica Films via an Eco-efficient UV Processing Method. Part 1: Photoinduced Mesostructuration

International audienceDesigning sustainable and industrially viable processing methods to synthesize ordered mesoporous films is a necessary condition to tap their full potential of applications. In order to respond to this challenge, well-established photoacid-catalyzed sol-gel photopolymerization has been harnessed to prepare large (> 100 cm 2) and micrometer-thick porous silica films possessing a 2D hexagonal mesostructure. Our UV irradiation system consists of two inexpensive and low radiant power fluorescent UV tubes (3 mW cm-2 , 280-380 nm) enclosed in a hygrometric chamber. Precise conditions to promote copolymer/silica hybrid film mesostructuration have been determined as regards relative humidity, film thickness and templating agent concentration. The mesostructured films have been analyzed using an extensive range of techniques including electron microscopy, grazing-incidence small-angle X-ray scattering (GISAXS), and N 2 sorption measurements, and solid-state NMR spectroscopy. Mesoporous silica films with a specific surface area up to 314 m 2 g-1 have been achieved with a very low level of microporosity. Coupling of X-ray diffraction (XRD) and FTIR spectroscopy has enabled to shed light into the photoinduced self-assembly mechanism

Influence of actinic wavelength on properties of light-cured interpenetrating polymer networks

Interpenetrating polymer networks (IPNs) composed of different acrylate/epoxide ratios, were synthesized under UV and visible-LED curing conditions. The formation of the IPNs was explored in terms of phase separation, polymerization mechanisms, final mechanical properties and surface morphology. For these purpose, we uniquely combined results of miscibility investigations, confocal Raman microscopy, dynamical mechanical analysis and atomic force microscopy. Transparent films were obtained for all compositions and both irradiation sources. The thermo-mechanical properties of different IPNs were associated to the presence of acrylate- or epoxide-rich phases, as well as, mixed interphases, resulting from the high interpenetration between both networks. Although the final conversions were similar under UV and visible-LED irradiation, we have found evidence that the visible-cured samples provide higher IPN homogeneity and lower Tg, for a higher epoxide content. To explain this trend, the mechanisms and sequence of the acrylate or epoxide networks formation, under UV or LED irradiation, is discussed

Influence of actinic wavelength on properties of light-cured interpenetrating polymer networks

\u3cp\u3eInterpenetrating polymer networks (IPNs) composed of different acrylate/epoxide ratios, were synthesized under UV and visible-LED curing conditions. The formation of the IPNs was explored in terms of phase separation, polymerization mechanisms, final mechanical properties and surface morphology. For these purpose, we uniquely combined results of miscibility investigations, confocal Raman microscopy, dynamical mechanical analysis and atomic force microscopy. Transparent films were obtained for all compositions and both irradiation sources. The thermo-mechanical properties of different IPNs were associated to the presence of acrylate- or epoxide-rich phases, as well as, mixed interphases, resulting from the high interpenetration between both networks. Although the final conversions were similar under UV and visible-LED irradiation, we have found evidence that the visible-cured samples provide higher IPN homogeneity and lower T\u3csub\u3eg\u3c/sub\u3e, for a higher epoxide content. To explain this trend, the mechanisms and sequence of the acrylate or epoxide networks formation, under UV or LED irradiation, is discussed.\u3c/p\u3