Xavier Allonas

Université de Haute-Alsace | UHA · Laboratoire de Photochimie et d'Ingénierie Macromoléculaires (LPIM)

Photobase generators are species that allow the photocatalysis of various reactions, such as thiol‐Michael, thiol‐isocyanate, and ring‐opening polymerization reactions. However, existing compounds have complex syntheses and low quantum yields. To overcome these problems, photobase generators based on the photodecarboxylation reaction were developed...

Photobase generators are species that allow the photocatalysis of various reactions, such as thiol‐Michael, thiol‐isocyanate, and ring‐opening polymerization reactions. However, existing compounds have complex syntheses and low quantum yields. To overcome these problems, photobase generators based on the photodecarboxylation reaction were developed...

3D printed shape memory polymers (SMP) were formed by combining aza-Michael addition and light initiated radical polymerization. Amine consumption and acrylate conversion were monitored by 1H-NMR and Fourier transform infrared spectroscopies. Dynamic mechanical analysis and cyclic thermomechanical tensile tests enabled direct observation of the pol...

The hydrosilylation reaction, describing the addition of Si-H bonds to unsaturated bonds, is performed in the presence of catalysts, usually highly active platinum catalysts. This work focuses on the study of a photoinduced hydrosilylation by the use of benzophenone which promotes the addition reaction of olefin on different hydrosilanes. The react...

A new class of photoinitiators for free radical photopolymerization based on 3-ketoquinolone chromophoric group is presented. Spectroscopic properties, quantum yield in triplet state and efficiency in formation of initiating radicals...

A new, highly reactive photoinitiating system based on a penta-methine cyanine dye and a triarylalkylborate salt for free radical photopolymerization reactions using near infra-red (NIR) light was investigated. The remarkably...

A direct analytical method developed to characterize UV-cured networks based on multi-step pyrolysis-gas chromatography-mass spectroscopy (GC/MS) is presented. Application of the method to characterize (meth)acrylate-based UV-cured networks is discussed. The reversion process of methacrylates is clearly observed during pyrolysis. In contrast, the d...

Fiber-reinforced polymers exhibiting the shape memory effect were created on the basis of a one-pot three-step chemical process. The first step is a Michael addition, which creates linear polymer chains. The second step is free radical photopolymerization, which increases the degree of curing of polymers. The last step is post-consolidation due to...

The effects of molecular weight of PDMS on chemorheology and viscoelastic behavior of siloxane modified waterborne UV-curable polyurethane acrylate dispersions (Si-WUPAs) were assessed via a photo rheometer as a versatile tool for in situ observation of chemical and mechanical characteristics during photopolymerization reaction. The roles of PDMS s...

This study provides a relationship between the photochemical reactivity and the photonic parameters of an acrylate formulation usable in digital light processing (DLP) 3D printing. First the photoreactivity of riboflavin tetrabutyrate (RFT) used as non‐toxic photoinitiator is assessed by laser flash photolysis in the absence and in the presence of...

Three photoinitiating systems (PIS) exhibiting different photoinitiation mechanisms were used for radical photopolymerization of methylmethacrylate (MMA). Namely, a photoactive RAFT agent (N,N benzyl dimethyldithiocarbamate), a type II photoinitiating system (isopropylthioxanthone/amine) and a photocyclic initiating system (isopropylthioxanthone/am...

In free‐radical UV‐curing, the inhibition of the photopolymerization reaction by oxygen leaves in most cases considerable acryl groups on the surface of cured materials. This paper takes advantage of the residual acryl C=C double bonds as reactive site for aza‐Michael addition in order to proceed to surface modification. A formulation composed of b...

Photoinduced thermal frontal cationic polymerization of a diepoxide was found to compete with spontaneous thermal cationic polymerization, due to the unstability of 2,4,6-triphenylpyrylium salt used as coinitiator. In order to...

A new combination of sulfonium salts has been investigated to cure opaque and thick carbon composite materials through photoinduced thermal frontal polymerization reaction. The photopolymerization occurs at the surface of the cycloaliphatic epoxide through the excitation of a triarylsulfonium salt and releases enough heat to decompose an alkyl-base...

In the field of additive manufacturing DLP Vat technologies are promising 3D printing techniques. The need of highly efficient photoiniating systems drives us to the development of photocyclic 3 component initiators. In order to improve the 3D printing sensitivity, we present in this paper the use of synthesized clay to tune up the photochemistry u...

In the field of additive manufacturing DLP Vat technologies are promising 3D printing technics. The need of highly efficient photoiniating systems drives us to the development of photocyclic 3 component initiators. In order to improve the 3D printing sensitivity, we present in this paper the use of synthesized clay to tune up the photochemistry und...

The use of three-component photoinitiating systems (PISs), as a major type of visible light photoinitiating systems, are considerably growing in different industries. However, their low storage and thermal stability could be an obstacle that prevents the fast growth of this type of PIS. In this study, a methylene blue nano-pigment was synthesized,...

Additive manufacturing or 3D printing has attracted the interest of researchers in industry and academia because of its outstanding features. In this study, a new three-component photoinitiating system (PIS) consisting of safranin O (SFH⁺), thiol derivatives and diphenyl iodonium salt was used for the free radical photopolymerization of a diacrylat...

Superhydrophobic surfaces with a water contact angle greater than 150° were prepared by one-step photoinduced crosslinking of a tetraethyl-orthosilicate and a fluorinated organosilane mixture using an efficient photobase catalytic system. Infrared spectroscopy and electron microscopy techniques enabled to investigate the alkoxysilane condensation a...

The Cover Feature represents the photochemical cycle involved in a new three‐component initiating system based on safranine O. Upon green‐light exposure, initiating radicals are produced and start acrylate photopolymerization, making this system suitable for digital light processing (DLP) 3D printing of complex objects (such as an Eiffel Tower). Mo...

The Cover Feature illustrates the application of lanthanide‐doped upconversion nanoparticles in which several photons are involved to emit UV light generated upon near‐IR irradiation. This emission was studied by time‐correlated single photon counting (TCSPC) and applied to cure coatings via photopolymerization with a high‐power line‐shaped laser....

UV-curing technology has been developed and widely used in industry for 6 decades. However, the migration of low-molecular-weight photoproducts is today an important drawback in many application fields such as food packaging materials, leading to unpleasant secondary features such as odor, blooming and contamination. Therefore, many efforts have be...

UCNPs based on NaYF4:Yb3+/Tm3+@NaYF4 generate blue (450 nm, 476 nm) und UV light (345 nm, 362 nm) upon exposure with a laser emitting at 980 nm. Time resolved measurements indicated same origin of the emission monitored at 362 nm and 450 nm by a rise time of 226 μs while their decay occurs with similar time frame of 260 μs. This belongs to an energ...

Vat photopolymerization technologies are promising 3D printing technics in the field of additive manufacturing needing high performance and affordable photoinitiating systems (PIS). In this paper, we introduce a complex PIS based on safranine as photosensitizer and two redox additives. Its photocycling mechanism is explored via laser flash photolys...

The effect of a two‐step free‐radical photopolymerization of an acrylate resin on the polymer properties in the presence of glass fibers is studied. It is found that a first irradiation leading to a partial conversion is effective for the fabrication of a preimpregnated glass‐fiber composite, which can be further processed and fully polymerized thr...

This paper reviews the main principles of cationic photopolymerization. Photoinitiators and monomers reactivity is discussed with special focus paid to iodonium salts as photoinitiators and epoxides, oxetanes, and vinylethers as monomers. The effect of water or alcohol on the structure of the polymer network and the reactivity is depicted. The so‐c...

Silicone-based materials and systems have played a key role over a century. In this work, surface and bulk characteristics of siloxane-modified water-based urethane-acrylate dispersions containing hydrophilic and hydrophobic soft segments with variable molecular weight and also a hard segment were tailored. Feeding and synthesis conditions were cha...

Free‐radical photopolymerization is scarcely used for the manufacturing of fiber‐reinforced polymers. The main issue relies on the penetration depth of light which affects the conversion degree when photopolymerizing thick samples. Consequently, this could lead to inhomogeneous polymer properties. The ability of acylphosphine oxides to photobleach...

A solvent-free process is described for the synthesis of tailor-made molecules from a one-pot, two-step approach combining aza-Michael addition and photoinduced copper(i) catalysed azide-alkyne (photo-CuAAC) reactions. After the first reaction between an amine and an acrylate, cycloaddition between an azide and an alkyne is activated by light irrad...

An investigation into the PET‐RAFT initiation mechanism (photoinduced electron/energy transfer‐reversible addition‐fragmentation chain transfer) for two frequently used photocatalysts with five RAFT agents has been conducted through analysis of electron transfer and triplet energy transfer (electron exchange) pathways. The electronic and redox prop...

This paper focuses on the study of thermomechanical properties of polyester acrylate (PEA) resins based on poly(butylene succinate) (PBS) and isosorbide with incorporation of 1/ diacid chains ranging from succinic acid (C4) to azelaic acid (C9) and 2/ diols with various structures such as butanediol and poly(ethyleneglycol) (PEG) with the aim to af...

In this work, the role of the ketyl radicals produced by the abstraction of a hydrogen from an amine by a thioxanthone-based photoinitiator is considered within the scope of the free radical photopolymerization process. Transient absorption experiments are combined with kinetic modeling of the polymerization reaction. It reveals that thioxanthone-b...

Glass–fiber‐reinforced polymers were manufactured either through a room temperature thermal curing or under ultraviolet (UV) light from a LED. The thermal system yields high performances when a post‐curing process at 65°C is applied. The photochemical curing leads to a composite in a faster timescale, albeit at the extent of the mechanical properti...

UV-curing technology is a powerful technique for a wide range of applications. The advantages of UV-curing, including speed and process controllability, and the wide range of raw materials and solvent-free formulations are well-known. However, some specific end-product issues such as the migration of components in food packaging, the odor in thiol-...

In this work, the inhibition and termination reactions occurring throughout a free radical photopolymerization initiated by a type-I photoinitiator are studied by kinetic modeling. The role of the macroradicals as the main oxygen trapping agents during the inhibition time is identified, and the absence of primary radical consumption by oxygen can b...

Abrasion resistant UV-curable coatings were prepared by mixing an aliphatic urethane diacrylate and different reactive diluents with the aim to bring into light the influence of monomer backbone and functionality on thermomechanical properties and more specifically on abrasion resistance. Therefore, the interdependence between physical damages (abr...

Two hydroxyl derivatives of benzophenone and anthraquinone were chosen as the ligands of zirconium complexes in the substitution of zirconium propoxide to obtain zirconium-based multifunctional photoinitiators (MPIs), Zr–OBP and Zr–OAQ. The MPIs were characterized in terms of molecular structures, UV absorption properties and photoinitiation abilit...

Surface topography and phase-manipulated distribution of hybrid UV curable coatings is performed. Accordingly, phase separation is controlled by changing the inorganic/organic ratio and the photoinitiator content as these are the main thermodynamic and kinetic affecting factors, respectively. Chemical and mechanical evolution of the samples during...

UV-curable systems based on polyethylene glycol diacrylate (PEG-DA) containing various amounts of scattering silicon nitride nanoparticles were studied by real-time Fourier transform infrared (RT FTIR) and real-time UV–visible (RT UV–visible) spectroscopies. Increasing the percentage of nanoparticles into the UV-curable systems caused the photopoly...

A commercial photoinitiator, 2-hydroxy-2-methylpropiophenone (PI-1173), was employed to synthesize a novel multifunctional photoinitiator (MPI) via ligand substitution of zirconium propoxide in the absence of any catalyst. With different feed ratios of the reactant, trifunctional and tetrafunctional zirconium-based photoinitiators were obtained. Th...

The article from this special issue was previously published in Polymers for Advanced Technologies, Volume 28, Issue 4, 2017. For completeness we are including the title page of the article below. The full text of the article can be read in Issue 28:4 on Wiley Online Library: http://onlinelibrary.wiley.com/doi/10.1002/pat.3914/full

Back Cover: The photopolymerization ability of a photoinitiating system for free radical polymerization based on isopropylthioxanthone and a triazine derivative is assessed. The prediction ability of a photopolymerization kinetic model is tested taking into account the main reaction steps from the absorption of photons to the formation of the polym...

Photopolymerization is known to be limited in depth by the light absorption. In addition, oxygen inhibition of acrylate films under air leaves some unreacted double bonds at the surface. Both phenomena account for heterogeneity in the conversion of the cured layer. Therefore, it can be relevant to build thick photopolymers through a multilayering p...

The development of new initiating systems for epoxy resin curing remains a highly interesting topic, especially for composites and coatings applications. Among all the possibilities existing to cure an epoxy resin, recent works have highlighted novel photo-thermal cationic initiators based on pyrylium salts. Interestingly, absorption spectra of tri...

Photopolymerization reaction can be used in self-developing photopolymerizable resin to recording holographic gratings. In this work, the efficiencies of two and three component photoinitiating system for holographic recording are analyzed in term of photopolymerization and grating diffraction yield kinetics. The selected systems are based on a vis...

The interaction of cationic organic dye Astrazon Orange with the synthetic phyllosilicate Laponite® leads to very interesting hybrid materials. Indeed, the Laponite® nanoparticles modify the photophysical properties of Astrazon Orange inducing a stabilization of its excited emissive state by preventing ultrafast isomerisation. The long lived emissi...

Isopropylthioxanthone, a versatile photoinitiator (PI) for free radical photopolymerization (FRP), is combined with a triazine derivative (Tz) in a Type-II photoinitiating system (PIS). Initiation ability of this system for acrylate photopolymerization is assessed using a diacrylate monomer. Involvement of a photoinduced electron transfer mechanism...

In this chapter, a compilation of different systems able to photogenerate active radicals toward polymerization reaction( type I, type II and three component photoinitiating systems) for application in holographic grating recording when associated to monomers is reviewed. In particular, the visible curable system is associated to fluorinated acryla...

In this chapter, a compilation of different systems able to photogenerate active radicals toward polymerization reaction(type I, type II and three component photoinitiating systems) for application in holographic grating recording when associated to monomers is reviewed. In particular, the visible curable system is associated to fluorinated acrylat...

One-pot synthesis of organic – inorganic hybrid materials under light requires specific photoinitiating systems which are able to release several different initiating species after light absorption. In this paper, the reaction mechanism of a photocyclic three-component initiating system based on isopropylthioxanthone as photoinitiator, an iodonium...

Pyrylium salts combined with vinyl ethers are shown to act as new versatile dual-cure initiating systems for both photochemical and thermal initiation of oxirane monomers. The combination of both possibilities allows the curing of thick samples through photoinduced frontal polymerization. On the basis of quantum calculations and photochemical exper...

Synthesis of hybrid materials is an important topic of research for the design of new materials and development of industrial applications. Among the numerous pathways reported in the literature, a concomitant light induced sol-gel process and organic photopolymerization has recently appeared to be a promising alternative. In light of the potential...

For the first time, we report the use of PDMS low-surface-energy blocks to build self-replenishing hydrophobic coatings. As the use of 8-fluorinated-carbon (Teflon-like) end groups (Rf8) has been perceived as a serious concern in industry due to its potential harm for health and environment, alternatives are sought. Poly(dimethyl siloxanes) (PDMS)...

Multi-step curing systems involving photopolymerization are of great interest because they provide easy tunable properties and processes for polymer synthesis. Herein, new perspectives are proposed to form semi-interpenetrated polymer networks through a versatile process involving two orthogonal chemistries. The sequence of reaction has been design...

Inorganic silane oligomer based on tetraethoxysilane was synthesized via sol-gel under acidic condition. UV curable organic-inorganic hybrid coatings were then prepared using the synthesized inorganic oligomers and tetraethylene glycol diacrylate. The effect of organic/inorganic content ratio on gelation and shrinkage of samples was investigated by...

The efficiency of free radical polymerization by photoinitiating systems based on two Astrazon orange cyanine dyes was shown to be directly related to the isomerization process of the dye in the excited states. The impact of resin viscosity on photopolymerization reactions was measured and related to the overall radical quantum yields. The quantum...

A photoinitiating system composed of a sensitizer (isopropylthioxanthone, ITX) and a photobase generator (triazabicyclodecene tetraphenylborate TBD.HBPh4) was successfully applied to the photopolymerization of a thiol-isocyanate-epoxy mixture. The final polymer network was considered in term of the compositional ratio between the thiol-isocyanate a...

A shape memory polymer (SMP) based on diacrylates and primary diamines was designed by ingeniously sequencing double click aza-Michael addition and radical photopolymerization. The chemical approach lies in an additional crosslinking of a 2-step based poly(amino ester)–poly(acrylate)s thus, resulting in enhanced polymer network homogeneity and ther...

Front Cover: Nowaday, pyrylium salts could be considerate to be effective initiators for both photochemical and thermal cationic polymerization of epoxy resin. Triphenylpyrylium salt derivatives are the most efficient structures to photopolymerize the resin. Beside, these compounds also exhibit some thermal reactivity at room temperature in the abs...

The photocatalysis reaction using [RuII(bpy)3]2+ was studied on the example of visible light sensitized Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization. Although both photoinduced electron and energy transfer mechanisms are able to describe this interaction, no definitive experimental proof has been evidenced so far. This pap...

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...

Irradiation of quaternary ammonium salts of phenylglyoxylic acid used as photobase generator activates the release of a strong base in water followed by an important pH jump. This initiates the polymerization of dopamine, leading to an on-demand formation of highly adhesive coating on steel.

The free-radical photopolymerization (FRP) suffers from inhibition by atmospheric oxygen which reacts with excited species and radicals leading to inhibition period, longer irradiation time, incomplete conversion of the coating and heterogeneity in depth conversion with a possibly tacky surface. A study of the influence of several factors that affe...

Pyrylium salts are found to be effective initiators for both photochemical and thermal cationic polymerization of epoxy resin. The photopolymerization results show that triphenylpyrylium salt derivatives are the most efficient structures. These compounds also exhibit some thermal reactivity at room temperature in the absence of light. However in su...

In this paper, the photoinitiated polymerization of thiols with isocyanate is studied by real-time FTIR. Different structures of photobase generators (PBG) based on quaternary ammonium salts of phenylglyoxylic acid were used as catalysts, releasing either weak or strong bases. A fast reaction leading to high conversion was possible only when 1,8-di...

Click reactions involving thiols and acrylates can be performed either through one-step thiol-ene photopolymerization or two-step thiol-Michael addition followed by photopolymerization. It is confirmed that the homopolymerization of acrylates prevents full completion of thiol-ene click addition, therefore leading to high amount of unreacted functio...

Dual-cure initiating systems have emerged as promising alternatives to perform fast and on-demand curing of thick polymers. In this paper, a system based on pyrylium salt/hydroperoxide is reported to be efficient in the polymerization of epoxide resins. The chemical mechanisms involved are studied by ESR, laser flash photolysis and fluorimetry. It...

Interpenetrating Polymer Networks (IPNs) based on a polybutadiene dimethacrylate and a dicyclohexylepoxide mixed at different ratios have been synthesized by photopolymerization. To obtain a complete overview of the formation and phase separation of these IPNs, and to predict the final morphology, miscibility before and after polymerization has bee...

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 mi...

A click chemistry synthetic strategy based on aza-Michael addition and radical photopolymerization is proposed to generate a polymeric network via three time-controlled steps. The selection of primary diamines and diacrylates allows two consecutive aza-Michael reactions to occur. This reaction sequence affords the unique opportunity to interpose a...

Initially developed as an elastomer with an excellent record of barrier and chemical resistance properties, poly(disulfide) has experienced a revival linked to the dynamic nature of the S-S covalent bond. A novel photobase-catalyzed oxidative polymerization of multifunctional thiols to poly(disulfide) network is reported. Based solely on air oxidat...