Photopolymerization Properties Research Articles

Preparation of polyoxometalate-chalcone hybrid and its photo-polymerization property

Photo-sensitive polyoxometalate-based hybrid materials have attracted much attention in recent years due to their unique photo-responsive properties. Here we represent a new type of photo-sensitive polyoxometalate-based hybrid by covalently tethering chalcone moieties onto Anderson cluster. Various techniques including nuclear magnetic resonance (NMR), Fourier transform infrared spectoscopy (FT-IR), electrospray ionization-mass spectrometry (ESI-MS) and single-crystal X-ray diffraction have been utilized to characterize the structure and composition of the resultant hybrid. The 1H and 13C NMR spectra show well resolved peaks that can be unambiguously assigned and are in good accordance with the molecular structure. Characteristic stretching vibrations of MO and Mo–O–Mo bonds can be found at 940 and 668 cm - 1 in the FT-IR spectrum respectively, whilst the chalcone moieties give stretching bands at 1665/1593 cm–1 (C=O–C=C) and 1568/1511 cm - 1 (C=C). The ESI-MS spectrum of the hybrid provides us more convincing structural in- formations. For instance, the isotopic peaks observed at m / z =2167.81 can be clearly ascribed to the anionic fragment of {[( n -C4H9)4N]2[(MnMo6O24){(CH2)3CNHCOCH2OC6H4C2H2COC6H5}2]} - , suggesting the successful modification of Anderson cluster with chalcone molecules. Single-crystal X-ray diffraction analysis reveals that the hybrid crystallizes in a mono-clinic system with a C2 / c space group, where organic chalcone moieties are covalently bonded to the Anderson cluster via μ 3-oxo bridging ligands. The photo-polymerization properties of the hybrid have been investigated in detail using UV-Vis spectroscopy, 1H NMR, and gel permeation chromatography. For example, when irradiated at UV light of 365 nm the hybrid undergoes a [2 π +2 π ] cycloaddition reaction, leading to an absorbance decrease at wavelength of 332 nm in the UV-Vis spectrum. Meanwhile, a new absorbance peak attributed to the generated cyclobutane structure is observed at 245 nm. This process gives a total photo-polymerization conversion of 37.45%, and is found able to restore when exposed to UV light of 254 nm. After five cycles of alternative irradiation at 365 and 254 nm, the amount of the hybrid monomer can still maintain at 85% of the original ones. The 1H NMR spectrum of the hybrid also shows significant changes when irradiated at UV light of 365 nm. Signals of the unsaturated carbonyl groups of the chalcone moieties at δ 7.83 and 7.73 shift to high field after irradiation, and give corresponding cyclobutane signal at δ 4.80. These results are in accordance with the results of UV-Vis spectroscopy. Weight-average molecular weight of the resulting hybrid polymer is 9.78×105 g/mol as demonstrated by the gel permeation chromatography analysis. This work may provide a new pathway for the fabrication and functional application of novel photo-sensitive polyoxometalate-based hybrids.

Monomers for adhesive polymers, 18. Synthesis, photopolymerization and adhesive properties of polymerizable α-phosphonooxy phosphonic acids

Four polymerizable α-phosphonooxy phosphonic acids 7a, 7b, 9 and 16 were synthesized in seven steps. They were characterized by 1H, 13C and 31P NMR spectroscopy and by high-resolution mass spectroscopy. The copolymerization of acidic monomers 7a, 7b, 9 and 16 with 2-hydroxyethyl methacrylate was studied using a differential scanning calorimeter. Due to the presence of two acidic groups, those monomers are significantly more reactive than 10-methacryloyloxydecylphosphonic acid (MDPA) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP). Self-etch adhesives based on monomers 7a, 7b, 9 and 16 were formulated and used to mediate a bond between a dental composite and the dental hard tissues (dentin and enamel). These adhesives exhibit excellent performances and provide significantly higher dentin and enamel shear bond strength than adhesives based on MDP or MDPA.

Monomers for adhesive polymers, 17.a Synthesis, photopolymerization and adhesive properties of polymerizable phosphonic acids bearing urea groups

Four polymerizable phosphonic acids bearing urea groups 4a, 4b, 9a, and 9b as well as the 10-(methacryloyloxy)decylphosphonic acid 10 were synthesized in four to six steps. They were characterized by 1H, 13C, and 31P NMR spectroscopy and by high-resolution mass spectroscopy. Contrary to methacrylates 4a and 4b, methacrylamides 9a and 9b were hydrolytically stable in deuterated water/deuterated ethanol solutions. The photopolymerization behavior of acidic monomers 4a, 4b, 9a, 9b, and 10 and their corresponding phosphonates were studied using a differential scanning calorimeter. Homopolymerizations and copolymerizations with N-butyl-N-ethylacrylamide were carried out. The presence of a urea group was found to significantly increase the rate of polymerization. Monomers bearing a phosphonic acid group were more reactive than their corresponding phosphonates. Self-etch adhesives based on monomers 4a, 4b, 9a, and 9b were able to provide a strong bond between a composite and the dental hard tissues (dentin and enamel). The presence of a urea group led to a significant increase in the shear bond strength to both dentin and enamel.

Monomers for adhesive polymers. XV. Synthesis, photopolymerization, and adhesive properties of polymerizable β-ketophosphonic acids

Monomers for adhesive polymers. XV. Synthesis, photopolymerization, and adhesive properties of polymerizable β-ketophosphonic acids

Novel polymeric photoinitiators with side-chain benzophenone: Facile synthesis and photopolymerization properties without coinitiator

Abstract A novel polymeric photoinitiator, poly(glycidyl benzophenone ether) (PGBE), with a side-chain benzophenone (BP) group was synthesized from poly(epichlorohydrin) and 4-hydroxybenzophenone. The structure of PGBE was characterized by IR and 1H NMR. The light absorption of PGBE was detected by UV spectrophotometer with the maximum absorption wavelength at 283 nm in acetonitrile solvent, which were red-shifted compared with BP. The obvious advantage of this initiator was the elimination of amine based hydrogen donors and to provide alternative hydrogen donors with easy availability and non-toxicity. The photopolymerizations of tripropylene glycol diacrylate (TPGDA) and trimethylolpropane triacrylate (TMPTA) initiated by PGBE and BP/EDAB were studied by real-time FT-IR. The polymeric initiator was found to have higher efficiency than BP/EDAB.

Synthesis, UV-curing behavior and surface properties of fluorine-containing vinyl ether polymers

Five fluorine-containing vinyl ether monomers were prepared by the reaction between 2-vinyloxy ethanol, a fluorinated alcohol and hexafluorobenzene in the presence of sodium hydride in dimethylformamide. Two representative properties of these monomers, UV-curing behavior initiated by a cationic photo-initiator PAG 201 and surface free energy of coating films, were investigated. Photo-polymerization proceeded both rapidly and completely with a high double-bond conversion (> 90%) and a fast curing rate (maximum curing time < 21 s) for three monomers. The surface energies of the monomers and the resulting polymer films were then investigated. The minimum surface free energy of the UV-cured homopolymer films reaches 7.1 mJ/m2. X-ray photoelectron spectroscopy data show that the low surface tension is influenced by fluorine content in the soft segments and fluorinated chains’ migration to the surface. The five monomers exhibit low viscosity, low surface energy, good thermal stability and good photo-polymerization properties, which make them great candidates for UV coating and photoresist applications.

Synthesis and photo-curing behaviors of silicon-containing (vinyl ether)-(allyl ether) hybrid monomers

A series of silicon-containing (vinyl ether)–(allyl ether) hybrid monomers used in nano-imprint lithography resists were synthesized and subjected to photo-initiated polymerization. The surface energies of the monomers and the resulting polymer films were then investigated. The surface energies of the monomers were very low at less than 15 mJ m–2. The photo-curing behaviors of the five hybrid monomers were investigated using real-time Fourier transform infrared spectroscopy. The monomers were sequentially initiated with cationic (PAG201) and mixed (cationic initiator PAG201, radical initiator ITX or TPO) initiators. The vinyl ether double bond polymerized both rapidly and completely, whereas the allyl ether double bond remained when PAG201 was used as the photo-initiator and polymerized completely with mixed initiators. The different double bonds of the silicon-containing (vinyl ether)–(allyl ether) hybrid monomer increased the efficiency of the polymerization and overcame the intrinsic limitations of the free radical and cationic polymerization processes, including strong oxygen inhibition, large volume shrinkage and high humidity sensitivity. The five monomers with low viscosity, low surface energy, good thermal stability and good photo-polymerization properties were suitable for nano-imprint photoresists. © 2013 Society of Chemical Industry

Two-Photon Induced Photopolymerization Using Photoinitiator with an Intramolecular Radical Quenching Moiety for Nanolithography

We have investigated the photoinitiating properties of the photoinitiator 3,6-bis[2-(4-nitrophenyl)-ethynyl]-9-(4-methoxy-benzyl)-carbazole (BNMBC), which has an intramolecular radical quenching group "p-methoxybenzyl," in the substrate lines fabrication of two-photon induced photopolymerization (TPIP). Another photoinitiator 3,6-bis[2-(4-nitrophenyl)-ethynyl]-9-benzyl-carbazole (BNBC) with similar chemical structure but not radical quenching group was studied for comparison. Their photopolymerization properties were studied with resins in which BNBC and BNMBC were used as photoinitiators with a molar ratio of 0.02%, respectively. The linewidth of polymer lines fabricated by TPIP of the photoresist that contained BNMBC could be decreased to 65% of those using BNBC. Besides, we introduced a radical quencher, phenyl methyl ether (PhOCH3), to BNBC and further studied the photopolymerization properties by using BNBC, BNBC/PhOCH3 and BNMBC as photoinitiators with a molar ratio of 0.1%. The results further indicated that BNMBC was effective to confine the radical diffusion in polymerization due to the radical quenching effect of moiety. This intramolecular radical quenching moiety exhibited more effective confining effect of radical diffusion compared to the intermolecular radical quencher PhOCH3. Furthermore, arbitrary complex three-dimensional (3D) microstructure was achieved using the photoresist with photoinitiator BNMBC. The approach could open up broad prospect for improving the resolution in TPIP.

Self-floating ability and initiating gradient photopolymerization of acrylamide aqueous solution of a water-soluble polysiloxane benzophenone photoinitiator

Three water-soluble polysiloxane benzophenone photoinitiators (W-Si-HBP2-A/B/C) with various silicon content used for preparing a gradient polymer were synthesized based on the traditional photoinitiator 4-hydroxybenzophenone (HBP) and aminopolysiloxane. The structures were confirmed by proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC). The water solubility of the photoinitiators, the effect of the silicon content on their triplet state lifetimes and photopolymerization property and the self-floating ability in the water system, and the internal connection between the surface morphology and property of the gradient polymer and film initiated by the photoinitiators were investigated. All three photoinitiators showed relatively good solubility in water, and longer triplet lifetimes and a smaller rate constant than HBP. It is found that the photoinitiator with the highest silicon content had the best floating capability due to lower surface tension and energy of polysiloxane. By using this photoinitiator, the gradient polymer with a significant molecular weight gradient was obtained. In addition, the polysiloxane-based photoinitiators can decrease the dispersion surface energy of the gradient polymer, and the increase of photoinitiator content can change the microstructure of the gradient polymer film. The new green method for preparing gradient polymeric material by using the polymerization technology and the water-soluble polysiloxane-based photoinitiators may have potential applications in the green chemical industry.

Microstructure and surface property of macroscopic gradient polymer initiated by polysiloxane benzophenone photoinitiators with different silicone chain lengths

This paper reported three kinds of polysiloxane benzophenone photoinitiators (HBP-Si-A/B/C) with different silicon contents, which were synthesized based on traditional photoinitiator 4-hydroxy benzophenone (HBP) and epoxy polysiloxane. The effect of silicon content in the photoinitiator molecule on its photopolymerization property, the ability to float up and surface morphology and the property of the gradient polymer film initiated by it was investigated. It is proved by UV absorption and gel permeation chromatography (GPC) measurements that HBP-Si-A/B/C with different silicon content had different abilities to float up. As a result, the gradient polymer with more significant molecular weight gradients could be obtained by using the polysiloxane benzophenone photoinitiator with higher silicon content, which had a better ability to float up caused by lower surface tension and energy, and the surface property was connected with the surface microstructure. The increase of silicon content in the polysiloxane-based photoinitiator could decrease the dispersion surface energy of gradient polymer film initiated by it and generate a more hydrophobic surface by a change of microstructure. In addition, the polysiloxane-based photoinitiator could also restrain the forming of wrinkling on the surface of the UV-curable film due to mitigation of oxygen inhibition in radical photopolymerization, and it may have potential in controlling patterned microstructures and surface property.

Novel photoinitiator with a radical quenching moiety for confining radical diffusion in two-photon induced photopolymerization

We designed and synthesized a novel two-photon induced photoinitiator with radical quenching moiety, 3,6-bis[2-(4-nitrophenyl)-ethynyl]-9-(4-methoxybenzyl)-carbazole (BNMBC), and successfully demonstrated its optical properties, high initiating efficiency in two-photon induced polymerization (TPIP) and capability to fabricate 3D structures with high resolution. The high resolution in TPIP using BNMBC was achieved as compared to the reported photoinitiator 3,6-bis[2-(4-nitrophenyl)-ethynyl]-9-benzylcarbazole (BNBC). BNMBC was confirmed to have a large two-photon absorption cross-section of 2367 GM by Z-scan measurement. We investigated the photopolymerization properties of resins R1–R3 in which BNBC, BNBC/phenyl methyl ether (PhOMe) and BNMBC were used as photoinitiators, respectively. The TPIP fabrication experiments exhibited that BNMBC possessed high TPIP initiating efficiency and an effective radical quenching effect. The volumes of polymer fibers fabricated by the TPIP of the photoresist using BNMBC as the photoinitiator were decreased to 20%–30% of those synthesised using BNBC as a photoinitiator. The introduction of a radical quenching group to the photoinitiator resulted in the effective confining effect of radical diffusion compared to the addition of the same molar ratio of radical quencher. This kind of photoinitiator with radical quenching group should benefit the fabrication of precise structures.

Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions: Photopolymerization properties

A novel approach toward the preparation of newly UV-curable polyurethane coatings composed of multifunctional thiol- and ene-terminated polyurethane aqueous dispersions is presented. By a synergistic combination of polyurethane dispersions synthesis and thiol-ene chemistry, strategies for the preparation of newly UV-curable polyurethane coatings are developed. Photo-DSC, real-time FTIR, DMA and tensile tests measurements are used to investigate the photopolymerization and mechanical behaviors of newly UV-curable polyurethane coatings. The newly polyurethane coatings have 1.5 times higher polymerization rate and final 99% functional groups conversion in air conditions compared to current urethane-acrylate based UV-curable polyurethane dispersions coatings. UV-cured polyurethane films prepared by this method are also found to exhibit increase in Young's modulus and tensile strength at break by 25% and 10%, respectively. These experiment facts suggest that the incorporation of thiol-ene chemistry to the polyurethane dispersion coatings increase their polymerization rate, producing a high degree of cross-linking. This confirms the preparation of the targeted novel UV-curable polyurethane coatings and reveals the dramatic effect that changes in incorporation of thiol-ene chemistry can have on the photopolymerization behaviors of UV-curable polyurethane dispersions coatings systems.

Synthesis and properties of novel polyurethane acrylate containing 3-(2-hydroxyethyl) isocyanurate segment

Novel UV curable multi-functional polyurethane acrylate (PUA) containing 3-(2-hydroxyethyl) isocyanurate (THEIC) segment was synthesized through three step reactions, the ring-opened reaction of ɛ-caprolactone with THEIC under the catalysis of tetrabutyl titanate (TBT), the polyaddition reaction between formed hydroxyl compounds and isophorone diisocyanate (IPDI) and condensation reaction between the product of the second step and pentaerythritol triacrylate (PETA). The chemical structure of PUA oligomer and some influence factors in synthesis process were characterized with GPC, 1H NMR and FTIR. And its photopolymerization process and properties of cured films were also investigated.

Photopolymerization property of a novel benzophenone derivative photoinitiator containing Si

The photopolymerzation property of a novel benzophenone derivative photoinitiator containing Si (HBSiBH) was investigated by real-time FTIR (RTIR) and X-ray photoelectron spectroscopy (XPS). It is noted that both of the polymerization rate and final conversion of the system increased with increase concentration of HBSiBH. Addition of small amount of HBSiBH can greatly improved the photopolymerization rate of radical photopolymerization. XPS experiment showed that the new photoinitiator containing Si had ability to float up to the surface of UV-curable system. It could more effectively mitigate inhibition of oxygen in radical photopolymerization and provide a new approach to improving surface performance of UV-curable materials.

Photoinitiating monomers based on di‐ and triacryloylated hydroxylamine derivatives

AbstractThe purpose of our study was to design a new class of acrylate‐based monomers with an UV‐cleavable heteroatom bond, offering the possibility to initiate radical polymerization upon irradiation with UV‐light. A method to derive the double bond conversion from the ATR‐IR spectra of the monomers and the cured polymers was employed, that enabled us to calculate the theoretical polymerization heats of the new monomers. Their photopolymerization properties were determined by Photo Differential Scanning Calorimetry. Surprisingly, some of these new compounds exhibited high photoinitiation activity, comparable to well‐established Type II photoinitiator systems like benzophenone/triethanolamine. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 392–403, 2009

Photoinitiating Monomers Based on Diacrylamides

Novel monomers with reactive diacrylamide units were developed as alternatives to common acrylate- or acrylamide-based functional groups. By using photo differential scanning calorimetry and ATR-IR spectroscopy, we were able to determine their theoretical polymerization heats and photopolymerization properties. Surprisingly, these new monomers exhibited high polymerization reactivity due to cyclopolymerization and showed self-initiating behavior under irradiation with UV light. As absorption of these photoinitiating monomers tails out at 320 nm, sensitizers were successfully employed to expand the spectral range of sensitivity.

Preparation of Fullerene (C60) Based SiO2 Sonogel Hybrid Composites: UV Laser Induced Photo-Polymerization, Morphological, and Optical Properties

Preparation of Fullerene (C₆₀) Based SiO₂ Sonogel Hybrid Composites: UV Laser Induced Photo-Polymerization, Morphological, and Optical Properties

Characterization of optically active and photocurable ORMOSIL thin films deposited using the Aerosol process

Aerosol-gel process is a deposition method based on the sol-gel polymerization of a liquid film produced from an ultrasonically sprayed aerosol. This process offers an attractive alternative for the deposition of photocurable SiO2—TiO2 ORMOSIL films. 3-(trimethoxysilyl) propylmethacrylate and tetraisopropyl-orthotitanate complexed with methacrylic acid were used as sol-gel precursors. Doping with a terbium:sulphosalicylic acid complex was also studied to test the deposition of spectroscopically active photocurable films. FTIR spectroscopy has been used to study the precursor solutions and ORMOSIL films. It is shown that titanium precursor incorporation enhances the solution reactivity, which yields optical quality thin films. Photopolymerization and photoluminescence properties of the films are reported and discussed with respect to the experimental parameters. The results allow envisaging the UV-imprinting fabrication of Aerosol-gel-derived active waveguides.

Spectroscopic properties and photopolymerization activities of water soluble 1-substituted derivatives of 2-hydroxy-3-(9-oxo-9 H-thioxanthene-4-yloxy)- N, N, N-trimethyl-1-propanaminium chloride salt

The spectroscopic, photochemical and photopolymerization properties of four novel 1-substituted water soluble 2-hydroxy-3-(9-oxo-9 H-thioxanthene-4-yloxy)- N, N, N-trimethyl-1-propanaminium chloride salts are examined. From absorption and fluorescence and phosphorescence analysis substitution in the 1-position by halogen groups induces more charge-transfer character than aliphatic alkyl groups. The photoreduction quantum yields of all the 1-substituted derivatives in the presence of a tertiary amine are lower than that for the unsubstituted derivative which is again indicative of the higher degree of charge-transfer content of the lowest excited states. The reduced activity of the 1-substituted derivatives is also reflected in the microsecond flash photolysis data on radical and radical anion formation. The addition of a tertiary amine, however, enhances the formation of both species probably due to triplet exciplex formation. Photopolymerization and photoinitiation rates for acrylamide are also reduced by 1-substitution. The data are discussed in terms of the nature of 1-substitution increasing the degree of charge-transfer character of the lowest excited singlet and triplet states.

Surface-pressure-induced reversible color change of a polydiacetylene monolayer at a gas–water interface

The photopolymerization properties and the surface pressure dependence of excitonic absorption of polydiacetylene (PDA), i.e., poly-(heptacosa-10,12-diynoic acid), are investigated by in situ reflection spectra of a monolayer at a N2 gas–water (pure water, CdCl2 aqueous solution) interface. The electronic structure of the initially appearing PDA is strongly dependent on the packing condition of diacetylene monomer, the blue- and red-form PDAs that initially appear in loose and close packing conditions, respectively. A reversible color change induced by a change in surface pressure is found for the first time in a partially polymerized PDA monolayer on pure water, in which blue and red form PDAs appear predominantly at low and high surface pressures, respectively. Further, two metastable phases, observed at wavelengths about 40 nm longer than those of the blue form, are thought to be induced by the rheological process of the substitutional sidegroups. Our results suggest that these color changes are closely related to a strain on the acetylenic backbone structure which is induced by the deformation of substitutional alkyl sidegroups.