Benzophenone-di-1,3-dioxane as a novel initiator for free radical photopolymerization

Benzophenone-di-1,3-dioxane (BP-DDO), a novel photoinitiator for free radical polymerization, was synthesized and characterized. The photopolymerization kinetics of BP-DDO was studied by real-time infrared spectroscopy (FT-IR). When this photointiator was used to efficiently initiate polymerization of acrylates and methacrylates, there was an optimum cure rate with the increase in BP-DDO concentration. Both the polymerization rate and final conversion increased with the increase in light intensity. The kinetics study of photopolymerization of TMPTA showed that BP-DDO was a more effective photoinitiator than benzophenone and benzophenone/ethyl-4-dimethylaminobenzoate (EDAB).     

Synthesis and photopolymerization characterization of a novel difunctional photoinitiator

A novel difunctional photoinitiator HBP‐TDI‐HBP based on 4‐hydroxybenzophenone (HBP) and toluene‐2,4‐diisocyanate (TDI) was synthesized and characterized by ¹H NMR and UV–Vis absorption spectroscopy. The kinetics of photopolymerization was studied by real‐time infrared spectroscopy. It showed that HBP‐TDI‐HBP was a more effective photoinitiator than benzophenone. When this photointiator and amine were used to efficiently initiate polymerization of acrylates and methacrylates, both rate of polymerization and final conversion increased with increase of HBP‐TDI‐HBP concentration, light intensity, and amine concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Visible light curing of bisphenol-A epoxides and acrylates photoinitiated by (η6-benzophenone)(η5-cyclopentadienyl) iron hexafluorophosphate

Visible light curing of diglycidyl ether of bisphenol-A (DGEBA) epoxy oligomer and acrylate monomers photoinitiated by (η⁶-benzophenone)(η⁵-cyclopentadienyl) iron hexafluorophosphate (Fc-BP) under a halogen lamp were studied by near infrared spectroscopy. Fc-BP exhibited high efficiency in the radical photopolymerization of acrylate monomers, even without the presence of tertiary amines. Under the same light source, however, benzophenone did not show any photoinitiating ability. Fc-BP could also be used to photoinitiate the cationic polymerization of DGEBA. There was an obvious increase in the photopolymerization rate of DGEBA and a decrease in the induction period when benzoyl peroxide was used as a photosensitizer. The induction period at the beginning of DGEBA cationic polymerization was eliminated by introducing a certain amount of cycloaliphatic epoxy monomer ERL4221 as an active diluent. However, the final epoxy conversion was decreased when ERL4221 was used.     

1,3-dioxane methylcoumarin as a novel photoinitiator for free radical polymerization

1,3-Dioxane methylcoumarin (DOMC), a novel photoinitiator (PI) for free radical polymerization, was synthesized and characterized. UV–vis absorption spectroscopy was used to investigate its photochemical behavior during the photophysical process. The photopolymerization kinetics of DOMC was studied by real-time infrared spectroscopy (FTIR). There was an optimum curing rate with the increase in DOMC concentration. Both the polymerization rate and final conversion increased with the increase in light intensity. DOMC was the most efficient PI for tripropylene glycol diacrylate (TPGDA) in different acrylate monomers. The kinetics study of TPGDA photopolymerization showed that DOMC was a more effective PI than benzophenone/ethyl-4-dimethylaminobenzoate. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of 4,4′-diacryloyloxybenzophenone

A copolymerizable type II photoinitiator 4,4′-diacryloyloxybenzophenone (DABP) based on 4,4′-dihydroxybenzophenone (DHBP) and acryloyl chloride was synthesized, and its structure was confirmed by ¹H NMR and real-time infrared spectroscopy. UV–vis absorption spectroscopy of DABP exhibited red-shifted maximal absorption as compared with benzophenone (BP). The kinetics of photopolymerization was studied by real-time infrared spectroscopy. It showed that DABP was a more effective photoinitiator than benzophenone. When this photointiator and amine was used to efficiently initiate polymerization of acrylates and methacrylates, both rate of polymerization and final conversion increased and the induction period was shortened with increase of amine concentration, DABP concentration and light intensity.     

Photoinduced redox initiation for fast polymerization of acrylaytes based on latent superbase and peroxides

The article presents a highly effective strategy for photopolymerization of acrylates via photolatent redox-accelerated reaction based on the synergistic photoinitiating systems containing photolatent superbase and readily available peroxides. Polymerization of acrylates could be instantly initiated with the effective interaction between the photogenerated amine and peroxides. Due to the persistent interaction of produced longeval amine with peroxides, remarkable post conversion after irradiation, which is significant for radiation crosslinking of photo-screened materials, was thus initially achieved in photoinitiated free radical polymerization. To explore the synergistic interactions of the photoinitiating systems, the effect of peroxide structures and QA-DBU:BPO ratios had been examined by RTIR, showing that all peroxides are applicable as the final conversion rate of acrylates is concerned. Further, BPO and CHP significantly accelerated the photopolymerization rate in air atmosphere. The synergistic efficiency of QA-DBU and BPO as a photopolymerization initiatiation system was close to that of the conventional D-1173 photoinitiator.     

Acrylic resins resisting oxygen inhibition during free‐radical photocuring. I. Formulation attributes

A resin system was found to be resistant to the formation of an oxygen‐inhibited layer when cured in air via conventional free‐radical photopolymerization. The resins, containing multifunctional acrylates and a high concentration of a photoinitiator, were applied as thin film coatings and photocured with either visible light (400–500 nm) or UV light (254 nm). Fourier transform infrared spectroscopy with an attenuated total reflection attachment and pencil hardness were used to assess the surface double‐bond conversion and the surface hardness of the coatings cured in air and without air, respectively. The surfaces of many tested resins could produce similar conversions under both curing conditions. Optimally formulated resins had a high conversion and hardness even when the irradiance was as low as 50 mW/cm² for the visible light and 4 mW/cm² for the UV light. The requirements for possessing such a unique curing property are presented. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and photopolymerization of 4‐(1‐propenyl)oxybutyl acrylate

Hybrid monomer, 4‐(1‐propenyl)oxybutyl acrylate, with cationic and free radical polymerizable group was synthesized. Real‐time Fourier transform infrared spectroscopy (FTIR) was used to monitor the photopolymerization kinetics of the monomer. Photopolymerization processing conditions, such as light intensity, photoinitiator concentrations have been evaluated. It was found that hybrid monomer showed higher efficiency of photopolymerization in comparison with the blend system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Kinetics studies of hybrid structure formation by controlled photopolymerization

Real-time FT-NIR spectroscopy was used to monitor the individual monomer photopolymerization kinetics within the hybrid methacrylate/vinyl ether system composed of 2-phenoxyethyl methacrylate and tri(ethylene glycol) methyl vinyl ether. Photopolymerization processing conditions, such as light intensity, photoinitiator type (both free radical and cationic) and initiator ratios and concentrations, that provide preferential direction of polymer formation based on individual monomer photopolymerization kinetics and overall conversion have been evaluated. Single source UV-light irradiation was employed to produce either single or dual-stage hybrid polymerization, validating the potential of one-step, one-pot methodology for initiating stage-curable polymerizations.     

可聚合型光引发剂4-丙烯酰氧基二苯甲酮的光聚合性能研究

以实时红外光谱（RT-IR）法研究了合成的4-丙烯酰氧基二苯甲酮（4-ABP）的光聚合动力学性质，考察了不同单体、不同引发剂和助引发剂浓度、不同光强对聚合性能的影响．以萃取法对比研究了4-ABP和二苯甲酮（BP）在固化膜中的的残留量．结果表明，4-ABP是一种非常有效的光引发剂．随着引发剂浓度和光强的增大，单体转化率、最大反应速率都增大，诱导期缩短．萃取实验表明4-ABP在固化膜中的残留量远低于BP．     

Novel sulfur—containing benzophenone derivative as radical photoinitiator for photopolymerization

A novel, highly efficient, polymerizable sulfur‐containing photoinitiator for free radical polymerization, benzophenone thio‐acetic acid (BP‐S‐CH₂‐COOH) was synthesized, characterized, and compared to photoinitiator parameters of the benzophenone (BP) and benzophenone/(phenylthio)acetic acid couple. The photoinitiator possesses a greatly redshifted UV maximal absorption in comparison to BP. Laser flash photolysis studies suggest that photoinitiator radicals are generated by photocleavage of C? S bond. Photopolymerization of 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate (TMPTA) demonstrated that one‐component system BP? S? CH₂? COOH is more efficient for polymerization than two‐component system. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Visible light sensitive photoinitiating systems: Recent progress in cationic and radical photopolymerization reactions under soft conditions

Although there have been many reports on photoinitiating systems adapted to visible lights for radical photopolymerization, the challenge for the design and development of photoinitiating systems for cationic photopolymerization or concomitant radical/cationic photopolymerization (for interpenetrating polymer network IPN synthesis) with visible lights still remains open. Particularly, the recent development of cheap and easily accessible LEDs operating upon soft visible light irradiations has opened new fields for polymer synthesis. Since 2011, many novel photoinitiating systems based on organic and organometallic compounds with excellent visible light absorption have emerged and exhibited outstanding photoinitiating abilities especially for cationic photopolymerization. In this review, recent progress (mainly from 2011 to early 2014) in applications of photoinitiators and sensitive photoinitiating systems under visible lights are reported. In addition, their relative efficiencies in the photopolymerization of different monomers are exemplified and discussed.     

Surface modification of a UV curable acrylate coating: In situ introduction of hydrophobic properties

Two polyfunctional silanes polymethyl-hydrosiloxane (I) and octakis(dimethylsiloxy)-T8-silsequioxane (II) are proposed as new co-initiators for radical acrylate photopolymerization reactions. In the presence of a type II photoinitiator such as benzophenone, isopropylthioxanthone or camphorquinone, these compounds are found reactive. The influence of oxygen is also examined. Incorporating only 1% (w/w) of I into an epoxy acrylate matrix allows the formation, under air, of a coating exhibiting a hydrophobic surface. In free radical promoted cationic polymerization, the addition of I to a BP/Φ₂I⁺ system significantly enhances, under air, both the polymerization rate and the final conversion. The autoxidation reaction of I in the presence of BP under air generates a hydrophobic polymer surface. The reaction mechanisms are discussed on the basis of laser flash photolysis experiments.     

Ultraviolet photopolymerization induced by a triazine derivative

2‐(3,4‐Methdioxyphenyl)‐4,6‐bis(trichloromethyl)‐ 1,3,5‐triazine (MBTTR) was used as a photoinitiator for the polymerization of acrylate monomer. Ultraviolet–visible absorption spectroscopy was used to investigate the photochemical behavior during the photophysical process. The photopolymerization kinetics were monitored by real‐time Fourier transform infrared spectroscopy. The polymerization rates of the acrylates were significantly higher than those of the methacrylates. When MBTTR induced the polymerization of trimethylolpropane triacrylate, there was an optimum polymerization rate and the final conversion was obtained at 0.1 wt % MBTTR. MBTTR was an inefficient photoinitiator for ethyl vinyl. The final conversions of tripropylene glycol diacrylate induced by MBTTR and triazine/1,3‐benzodioxole were similar. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photopolymerization kinetics of cycloaliphatic epoxide–acrylate hybrid monomer

An epoxide–acrylate hybrid monomer was synthesized by the controlled reaction of a cycloaliphatic epoxide and acrylic acid. The photopolymerization kinetics was investigated using a real‐time infrared spectroscopy technique. The influences of photoinitiator concentration, free radical initiator and polymerization atmosphere on the polymerization were studied. The hybrid monomer showed unique photopolymerization kinetics in the photopolymerization process and the final conversions of epoxy groups and acrylate double bonds were improved synchronously. Dynamic mechanical analysis results demonstrated that the hybrid monomer cured film formed a more uniform polymer network than the blend of epoxy acrylate and epoxide. Copyright © 2007 Society of Chemical Industry     

A glance at violet LED sensitive photoinitiators based on the spiroxanthene scaffold

A novel photoinitiator based on a spiroxanthene scaffold in the presence of an iodonium salt is proposed for the cationic ring‐opening polymerization of a diepoxide, as well as for the free‐radical polymerization of an acrylate upon violet LED exposure (385 and 405 nm). Good‐to‐excellent rates of polymerization and final conversions are obtained. These systems are characterized by a higher reactivity compared with that of anthracene/iodonium salt used as reference for cationic near UV polymerization. The addition of a poly(ionic liquid) improves the cationic polymerization profiles. The photochemical mechanisms are studied by steady‐state photolysis, fluorescence, and electron spin resonance spin‐trapping techniques. Molecular orbital calculations give an insight into the light absorption properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43213.     

Synthesis and photopolymerization kinetics of polymeric one‐component type II photoinitiator containing benzophenone moiety and tertiary amine

A polymeric one‐component type II photoinitiator (PDABPP) based on 4,4′‐dihydroxybenzophenone (DHBP), acryloyl chloride, and piperazine was synthesized, and its structure was confirmed by GPC and ¹H NMR. The photopolymerization kinetics of the photoinitiator was studied by real‐time infrared spectroscopy. It indicated that PDABPP was a more effective photoinitiator than that of benzophenone (BP)/triethylamine (TEA). The rate of polymerization and final conversion increased, and the induction period shortened with increase of PDABPP concentration, light intensity, and amine concentration. The kinetics of photopolymerization for tripropylene glycol diacrylate (TPGDA) incorporating PDABPP in the presence of different tertiary amines as the initiating system indicated that the PDABPP/TEA combination exhibited the highest polymerization rates among the PDABPP/amines combinations. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

丙烯酸酯/环氧的自由基/阳离子同步光聚合混合体系的研究

科学技术的进步,对新材料的要求逐步向着多功能和高性能的方向发展,单组分材料已难于满足这种要求,在高分子材料方面,人们采用了共混、接枝、嵌段等方法以达到改善和提高性能的目的。感光性高分子是一类很重要的功能材料,至今,大部分采用自由基聚合方式制备。近年来,阳离子引发体系发展很快,特别鎓盐光引发体系受到很大的重视,发展迅速。目前自由基聚合及阳离子聚合已经成为合成感光性高分子材料的二种最     

新型杂化光聚合体系

光固化方式的复合化是对光固化体系进行改性的重要方法。通过将自由基和阳离子以及阳离子和阳离子配合组成新的光固化体系,可以得到优良的固化体系。本论文以多种丙烯酸酯,乙烯基醚,环氧树脂,以及实验室合成的杂化单体等做为基础材料进行混合杂化光聚合体系,杂化单体光聚合体系的光固化动力学比较,并对羟基化合物对各体系的影响进行分析。实验结果表明,杂化单体在转化率,转化速度,对羟基化合物不敏感性等多方面都比混合杂化体系有明显优势。     

Organic sulfur compounds as initiators of polymerization. VII. Polymerization of methyl methacrylate by N-[(p-benzoyl)benzenesulfonyl]benzenesulfonamide

The photopolymerization of methyl methacrylate in bulk using N-[(p-benzoyl)benzenesulfonyl]benzenesulfonamide as a photoinitiator was studied. A kinetic study of the photopolymerization showed that the rate of polymerization is proportional to the square root of the photoinitiator concentration. The decomposition of a sulfur–nitrogen bond and the obtained radicals are suggested to be responsible for the initiation of polymerization. The influence of the photoinitiator on the molecular weight was also studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2083–2086, 1998