Photopolymerizable Systems Containing Organophosphorus Compounds as Photoinitiators

p-Methoxybenzoyldialkylphosphonates, terephtaloylbis(dialkylphosphonates), (alkyl=methyl, ethyl), p-methoxybenzoyldiphenylphosphine oxide and terephtaloylbis(diphenylphosphine oxide) were synthesized by Michaelis–Arbuzov reaction. These compounds were used as photoinitiators for radical polymerization of acrylic monomer 1,6-hexandiol diacrylate. The photoinitiating activity was determined by differential photocalorimetry (DPC), in isothermal conditions, using 1,6-hexandiol diacrylate as monomer, in the absence of amines and in the presence of amines as synergist additive. The influence of amine on photoreactivity parameters was studied. The kinetic study of polymerization of 1,6-hexandiol diacrylate sensitized by these radical photoinitiators have been studied by DPC. These compounds performed good photoinitiating activity in comparison with commercial product Lucirin TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide).     

阳离子聚合光引发剂及其阳离子反应机理

综述了阳离子聚合光引发剂的种类、制备和应用，介绍了它们的光分解和由此引发的光引发阳离子聚合反应机理。     

Photopolymerization kinetics of 2-phenylethyl (meth)acrylates studied by photo DSC

The present work deals with the photopolymerization of 2-phenylethyl (meth)acrylates and estimation of their kinetic parameters. Formulations were made by independently homogenizing the monomers with photoinitiators of two different classes. Two different compositions of photoinitiators were used to study the effect of concentration of photoinitiator on cure kinetics. These compositions obtained were tested for photo curing performance using differential photocalorimetry (DPC) or photo DSC under polychromatic radiation. The heat flow against time was recorded for all formulations under isothermal conditions and the rates of polymerization as well as the percentage conversions were estimated. It was observed that due to a longer timescale for reaction diffusion, the methacrylate formulations showed a higher conversion than acrylate formulations. Other parameters such as induction time, maximum rate and conversion attained as well as the time to attain peak maximum were noted. The photopolymerization and kinetic estimations of the formulations including evaluation of kinetic models are discussed.     

Synthesis,photophysical and photochemical studies of benzophenone based novel monomeric and polymeric photoinitiators

Four novel benzophenone-containing photoinitiators (monomers PI-1 and PI-2 and their polymers PPI-1 and PPI-2) were prepared from alkyl α-hydroxymethacrylates. PI-1 was synthesized from reaction of tert-butyl α-bromomethacrylate and 4-hydroxybenzophenone followed by cleavage of tert-butyl groups using trifluoroacetic acid. PI-2 was synthesized from reaction of ethyl α-bromomethacrylate and 3-benzoylbenzoic acid. Thermal polymerization of PI-1 and PI-2 was performed using 2,2′-azobis(isobutyronitrile). PI-1 and PPI-1 show UV absorption (289 and 294 nm) which are red-shifted compared to benzophenone (252 nm), PI-2 (255 nm) and PPI-2 (252 nm). All of the photoinitiators give phosphorescence emissions from their n–π* states. The photopolymerizations of triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate and hexanediol diacrylate initiated by PI-1, PI-2, PPI-1, PPI-2 and benzophenone were studied by photo-differential scanning calorimeter using N,N-dimethyl-p-toluidine as coinitiator. Polymeric photoinitiators were found to have higher efficiencies than benzophenone and monomeric ones. Photopolymerization results are also compared to that of an alkyl α-hydroxymethacrylate-based photoinitiator previously reported by us; and the influence of monomer structure on polymerization efficiency is discussed.     

Photopolymerization kinetics of bis-aromatic based urethane acrylate macromonomers in the presence of reactive diluent

The present work deals with the photopolymerization of bis-aromatic based urethane acrylate macromonomers in the presence of excess end capping agent as reactive diluent and estimation of their kinetic parameters. Formulations were made by independently homogenizing the macromonomers with photoinitiators of three different classes. Three different compositions of photoinitiators were used to study the effect of concentration of photoinitiator on cure kinetics. These compositions obtained were tested for photo curing performance using photo DSC under polychromatic radiation. The heat flows against time were recorded for all formulations under isothermal condition and the rates of polymerization, peak maximum times as well as the percentage conversions were estimated. It was observed that due to a longer timescale for reaction diffusion, formulations with macromonomer containing propoxylated backbone showed higher conversions than the corresponding ethoxylated analogue. The photopolymerization and kinetic estimations of the formulations including evaluation of kinetic model are discussed.     

阳离子光引发剂研究进展

阳离子型光引发剂是一类新型的紫外光固化材料的引发剂。本文介绍了阳离子光引发剂的主要种类及各自的特点 ,讨论了其光引发机理 ,并简述了阳离子光引发剂的的发展概况和主要用途。     

Lichtinduzierte Polymer- und Polymerisationsreaktionen, 47. Photopolymersysteme mit α-sulfonyldesoxybenzoinen als initiatoren

α-Sulfonyl deoxybenzoines are formed by the reaction of desylchloride with sodium arylsulfinates in good preparative yields. The photolysis of these compounds proceeds with quantum yields of about Φ_in = 0.50. Compared to other photoinitiators, α-sulfonyl deoxybenzoines polymerize methylmethacrylate in acetonitrile solution with moderate polymerization quantum yields only. On the contrary, the yellowing of cured polyester resins using these compounds as photoinitiators is much smaller.     

聚氨酯型高分子硫杂蒽酮光引发剂的制备及性能研究

通过三种二异氰酸酯、2-（2,3-二羟基）丙氧基硫杂蒽酮（HPTX）及N-甲基二乙醇胺(MDEA)进行逐步聚合反应,将硫杂蒽酮结构及共引发剂胺结构引入到同一高分子链上,得到侧链含有硫杂蒽酮,主链含有共引发剂胺的聚氨酯型高分子光引发剂。傅立叶红外变换光谱和核磁共振氢谱证实了高分子光引发剂的结构。紫外光谱证实了高分子链的结构对硫杂蒽酮单元的最大紫外吸收几乎没有影响。用光致差示量热计（photo-DSC）研究聚氨酯型高分子光引发剂引发聚氨酯丙烯酸酯树脂（PUA）的光聚合反应,发现PU-IMTX是本文合成的引发剂中引发PUA光聚合最有效的光引发剂。     

鎓盐类阳离子聚合光引发剂的研究进展

碘鎓盐和硫鎓盐是最重要的和应用最广泛的阳离子聚合光引发剂。本文介绍了几种典型的碘鎓盐和硫鎓盐及其引发机理,并就碘鎓盐和硫鎓盐在增加光引发剂的光敏性、增加光引发剂在光引发阳离子聚合体系中的组分相容性以及在阳离子光引发剂中引入自由基等方面的发展状况进行了综述。     

Covalently bound organomodified clay photoinitiators

While organomodified clays are property enhancing additives for composite materials, much of the research thereof has focused on intercalated quaternary ammonium compounds; however, herein the effects of covalently bound organomodified clays (CoBOCs) are explored with particular emphasis on CoBOC photoinitiators. Two commercially available alcoholic photoinitiators (1‐hydroxycyclohexyl phenyl ketone and 2‐hydroxy‐2‐methyl‐1‐phenylpropanone) were reacted with isophorone diisocyanate to form half‐adducts and then reacted with Cloisite 93A, an organophilic montmorillonite clay, to form two CoBOC photoinitiators. The CoBOC photoinitiators were integrated into a standard formulation and subsequently ultraviolet (UV) cured. Property characterization thereof (e.g., adhesion, hardness, and flexibility) yielded unchanged or increased properties with the exception of impact flexibility. Finally, the CoBOC photoinitiators were kinetically characterized via photo‐differential scanning calorimetry (photo‐DSC) within 1,6‐hexanediol diacrylate (HDODA). While increasing concentrations of clay additives generally decrease polymerization rates, increasing concentrations of the CoBOC photoinitiators exhibited increased polymerization rates. Therefore, the CoBOC photoinitiators can enhance the polymerization kinetics and physical properties of UV‐curable coatings. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41883.     

Investigation of the effects of formulation on selected properties of UV curable IPN coatings

Ultraviolet curable coatings based on urethaneacrylic resins were prepared by free radical polymerization. The effects of photoinitiators on the curing reaction and the influence of polyol types and dimethylopropionic acid (DMPA) amounts on the properties of UV curable coatings prepared by free radical polymerization (UVF) were investigated. The effects of polymerization (UVC) and the consequences of postcuring conditions on the properties of UVC were evaluated. The interpenetrating polymer network (IPN) containing UV curable coatings (UVIPN), which were composed of UVF and UVC at different ratios (by weight), were prepared. The properties of UVIPN with varied UVF/UVC ratios were studied. Presented at the 74th Annual Meeting of the Federation of Societies for Coatings Technology, October 24, 1996, Chicago, IL.     

光固化涂料的应用和市场前景

光固化涂料主要由低聚物、单体、光引发剂及助剂组成。UV固化的主要反应历程是由辐射引起光引发剂分解,生成活性自由基引发单体以氐聚物聚合交联。针对光固化涂料的性能特点和光固原理,介绍了光固化涂料的应用领域,阐述了光固化涂料适合多种基材的涂装,研究了光固化涂料在汽车装饰上的应用,指出了光固化涂料的发展前景与潜力。     

Novel 6-bromo-3-ethyl-2-styrylbenzothiazolium <Emphasis Type="Italic">n</Emphasis>-butyl-triphenylborates as photoinitiators of trimethylolopropane triacrylate (TMPTA) polymerization

Summary The series of 6-bromo-3-ethyl-2-styrylbenzothiazolium n-butyltriphenylborates was synthesized and evaluated as photoinitiators of free radical polymerization. The dyes were obtained by the condensation reaction of the 6-bromo-3-ethyl-2-methylbenzothiazolium salts with different alkylaminobenzaldehydes. The resulting styrylbenzothiazole dyes (hemicyanine dyes) paired with n-butyltriphenylborate anion (SBrB2), are shown to be efficient photoinitiators for free radical polymerization of trimethylolpropane triacrylate (TMPTA) induced with the visible emission of an argon-ion laser. The photochemistry of the novel hemicyanine borates was compared to the photochemistry of identical series of the dyes that do not possess the bromo substituent at benzothiazolium residue. The comparison has shown that the introduction of the bromine into benzothiazolium residue causes a small red shift of the electronic absorption maxima, changes the reduction potential of the dye and, finally, increases a photoinitiation ability of the dye.     

Polymeric Michler's ketone photoinitiators: The effect of chain flexibility

Through introducing Michler's ketone (MK) moiety and diglycidyl ether monomers of different molecular chain into the same polymeric chain, polymeric photoinitiators of different chain flexibility, PMKPR, PMKPG and PMKPP were synthesized. These polymeric photoinitiators possess the similar characteristic UV–vis absorption of parent MK, and their photobleaching behavior is similar. The T_g of PMKPR, PMKPG and PMKPP is 58.1 °C, −24.9 °C and −12.5 °C, respectively. Three types of monomer with different functionality, phenoxy ethyleneglycol acrylate (AMP-10G), 2,2-bis[4-(acryloxypolyethoxy) phenyl]propane (A-BPE-10) and trimethylopropane triacrylate (TMPTA), were chosen to be initiated by these photoinitiators. The result indicates the chain structure of photoinitiators has significant influence on the polymerization of monomers. PMKPG is the most efficient polymeric photoinitiator for initiating the polymerization of AMP-10G and A-BPE-10, while PMKPP is the most efficient for TMPTA.     

Mechanisms and relative efficiencies in radical polymerization photoinitiated by benzoin,benzoin methyl ether and benzil

Contrary to widely held views, detailed studies of light absorption characteristics, reaction rates, and molecular weights in radical polymerization of methyl methacrylate photoinitiated by benzoin and benzoin methyl ether indicate that the two photoinitiators have comparable efficiencies; benzil is much less efficient. Mechanisms for initiation, and possible termination processes, for systems involving all three photoinitiators are discussed in the light of results from studies of radical characterization by the spin trapping technique.     

Differential scanning photocalorimetry studies of 1,6‐hexanedioldiacrylate photopolymerization initiated by some organic azides

New types of radical photoinitiators, based on azido and diazido structures, were compared to the reactivity of pure xanthone by using a photocalorimetry technique. Our results show that these photoinitiators are good candidates for radical polymerization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1096–1101, 2003     

Free radical formation in three-component photoinitiating systems

N,N′-diethylthiacarbocyanine iodide (Cy) with two different compounds acting as co-initiators were used in the three-component photoinitiating systems for free radical polymerization of acrylate monomer. The steady state and time-resolved techniques were used to study the fluorescence quenching by co-initiators, as well as laser flash photolysis to investigate an electron transfer process, that occurs in these photoinitiating system (PIS). To investigate the key factors involved with visible-light activated radical polymerizations involving three-component photoinitiators, we used thermodynamic feasibility and kinetic considerations to study photopolymerizations initiated with thiacarbocyanine dye as a photosensitizer. The Rehm–Weller equation was used to verify the thermodynamic feasibility for electron transfer reaction. Experiments show, that the main interaction between the dye and both co-initiators occurs through its excited singlet state. It was concluded, that the key kinetic factors for efficient visible-light activated initiation process are summarized in two ways: (1) to retard back electron transfer and recombination reaction steps and (2) to use a secondary reaction step to consuming dye-based radical and regenerating the original photosensitizer.Basing on the study, it is known that, there are two possible mechanisms of generation of free radicals, which can start polymerization involving photoreducible series mechanism and parallel series mechanism (photoreducible–photooxidizable series mechanism).     

Influence of selected photoinitiators type II on tack,peel adhesion,and shear strength of UV-crosslinked solvent-borne acrylic pressure-sensitive adhesives used for medical applications

This article describes the photoreactive UV-crosslinkable solvent-borne acrylic pressure-sensitive adhesives (PSA) containing unsaturated copolymerizable photoinitiators and their synthesis. The solvent-borne acrylic PSA were synthesized in ethyl acetate as a solvent, and the copolymerizable photoinitiators type II, known as hydrogen abstractors, were incorporated into acrylic polymer chain during conducted radical polymerization process. The synthesized solvent-borne acrylic PSA containing different unsaturated photoinitiators were investigated to evaluate their relevant and significant properties such as tack, peel adhesion, and shear strength after UV exposure.     

The dyes possessing diazine residue as effective photoinitiators of free radicals polymerization

Summary The series of the dyes possessing diazine residue have been investigated as visible-light absorbing photoinitiators of free radical polymerization. The rates of photoinitiation depend on the structure of the dye. Mechanism of the photoinitiation involves the electron transfer process between the dye and the electron donor (co-initiator). The dyes possessing diazine residue in the presence of a suitable electron donor are very effective photoinitiators. This can be attributed to the high quantum yield of their triplet state formation and high rate constant of electron transfer reaction between the dye and electron donor.     

In situ study of photopolymerization by fourier transform infrared spectroscopy

The Fourier transform infrared (FTIR) in situ method was developed for the investigation of photopolymerization. Ultraviolet (UV) cure of a mixture of a cycloaliphatic epoxide, a 2-ethylhexyl acrylate, and photoinitiators, which forms simultaneous interpenetrating polymer network (IPN), was monitored while the sample was irradiated with UV light. Triphenylsulfonium salt and benzoin ether were used as photoinitiators. For the sake of comparison, similar experiments were performed for the epoxide with the triphenylsulfonium salt photoinitiator and the acrylate with the benzoin ether photoinitiator. The epoxy photopolymerization was monitored using an epoxy CH stretching band at 3005 cm^?1 and a ring vibration band at 790 cm^?1. The acrylic photopolymerization was monitored using a C?C stretching band at 1637 cm^?1. The epoxy conversion was less than 60% when the acrylic polymerization was completed in the IPN.