Behavior of quaternary ammonium salt photobase generators on initiating free radical photo‐polymerization

Series of quaternary ammonium tetraphenyl borates salt photobase generators (PBGs) were synthesized using p‐methoxyphenacylmethylene and 2‐naphthoymethylene as chromophores, and triethylene diamine, pyridine or 3‐methyl pyridine as tertiary amine. The kinetics for polymerization of trimethylolpropane triacrylate (TMPTA) monomer using PBGs as free radical photo‐initiator was monitored by differential photo‐calorimeter (DPC). It was found that all the quaternary ammonium tetraphenyl borate salt photobase generators synthesized could initiate free radical polymerization of the acrylate monomer TMPTA by exposure to UV irradiation, but the activity was relatively low. Addition of a small amount of polar solvent to the system could largely increase the polymerization rate and final conversion. Photo‐polymerization was also improved by increasing light intensity or raising reaction temperature. PBGs with p‐methoxyphenacylmethylene as chromophore had higher absorbance at around 280 nm and showed higher activity in initiating photo‐polymerization than those with N‐(2‐naphthoylmethyl) as chromophore. Copyright © 2006 Society of Chemical Industry     

The Analysis of Photocuring Behavior of Polyester Acrylate by Means of Differential Photo Calorimeter (DPC) and Rigid-Body Pendulum Rheometer (RPT)

This study aims to understand the different photocuring behaviors of acrylated polyester by adding different photoinitiators and monomers. Differential photo calorimeter (DPC) is used to understand the exothermal effects during photocuring. The self-catalyst model of dynamic analysis software was then used to obtain the relationships between reaction speed, reaction extent, and rate of reaction. In addition, this study also tried to understand the formation of photocuring resin from the rigid-body pendulum rheometer (RPT) experiment. The results showed that the extent of reaction, conversion rate and speed varies directly with the concentration of the photoinitiator and monomer. The reaction level of propoxylated pentaerithritol triacrylate was higher than propoxylated neopentyl-glycol diacrylate. Moreover, the method using RPT shows better view of the molecule reaction status inside the photopolymer.     

On the inhibiting effect of phenolic compounds in the photopolymerization of acrylates under high‐intensity and polychromatic UV/visible lights

The photopolymerization of wood coatings under UV and visible light in industrial type conditions has been investigated. The inhibiting effect of the phenolic compounds found in wood extractives, especially quercetin, on the final properties of the coating (hardness, gel content) as well as the polymerization kinetics (rates, final conversion) has been discussed. Model clear‐coating formulations — based on an acrylate oligomer, a reactive diluent and a bis‐acylphosphine oxide as photo‐initiator — have been used. This article focuses on the influence of the nature of the acrylate oligomer (polyester, epoxy, polyurethane), the type of phenolic derivative (POHs) and the irradiation conditions (UV conveyor, Xe lamp). It appears that lead to through the strong inner‐filter effect in the presence of quercetin is responsible for the loss of all the observed properties. In order to mimic what happens at the wood–coating interface, the role of the diffusion of the phenolic derivatives have been also investigated and discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3285–3298, 2007     

A study on the preparation of polymer/montmorillonite nano‐composite materials by photo‐polymerization

The preparation of polymer/montmorillonite intercalation composite materials was studied by two kinds of photo‐polymerization reaction (photo‐acid generation and photo‐radical generation). Small‐angle X‐ray diffraction was used for the structural characterization of montmorillonite contained in the products. Results indicated that, after chemical modification of montmorillonite, the monomer (methyl methacrylate) and the prepolymer (m‐cresol/HMMM) were able to intercalate into the layers of clay and to polymerize ‘in situ’, thus producing photo‐polymerized composite materials. The advantages and shortcomings of the method of photo‐polymerization for the preparation of these composite materials are discussed. © 2001 Society of Chemical Industry     

Synthesis and characterization of photo‐crosslinkable polyfluorene with acrylate side‐chains

A photo‐crosslinkable polymer, poly[2,7‐(9,9‐dioctylfluorene)‐co‐2,7‐(9‐hexyl‐9‐(2‐acrylate ethyl)‐9H‐fluorene)] (P3), was synthesized and the photo‐crosslinkable acrylate groups were introduced into the side‐chains of the polyfluorene derivative after its polymerization. This method avoids the possible crosslinkage of the crosslinkable groups on the monomers during polymerization in the traditional synthesis route by the polymerization of the monomers with the crosslinkable side‐chains. The soluble and processable polymer P3 could be crosslinked via the acrylate groups in its side‐chains upon exposure to UV light in nitrogen atmosphere. The crosslinking was confirmed by IR spectroscopy: the IR peak of C?C bond at 1635 cm^?1 decreased and that of the vinyl C? H bond at 742 cm^?1 disappeared after the UV exposure. The absorption spectra of P3 remain unchanged after crosslinking, but a longer wavelength emission at 517 nm appeared in the photoluminescent and electroluminescent spectra of the crosslinked P3, which could be attributed to the formation of keto defects during the photo crosslinking. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2336–2342, 2006     

Relationship between mechanical properties of ceramic green body and structures of photo-cured acrylate polymer for ceramic 3D printing based on photo polymerization

3D printing technologies using photo polymerization of photo-curable monomer and oligomers as an organic binder have been studied to fabricate ceramics with a complicated shape. For minimizing distortion of ceramics during the manufacturing process and fast 3D printing of ceramic green body, high mechanical strength of ceramic green body and fast photo polymerization of the photo-curable resin are required, respectively. In this study, the ceramic green bodies with various compositions were fabricated by photo radical polymerization of the slurry-type resin composed of fused silica bead, and tri- or (and) mono-functional acrylate. Photo radical polymerization behaviors of mono-, tri-functional acrylate monomer, and blend of two monomers were analyzed by photo-DSC and FT-IR measurements. The structure analysis of photo-cured polymers made by each monomer was performed by thermo-mechanical analysis. Through mixing of mono- and tri-functional acrylate monomer, we confirmed that polymerization rate more increased compared with those of only mono-, tri-functional monomer. Unreacted vinyl groups in the polymers prepared with blend of two monomers decreased by an addition of mono-functional monomer in tri-functional monomer. The polymers prepared with the blend showed higher storage modulus and broader viscoelastic behavior compared to those fabricated with tri-functional monomer. Thus, to achieve high fracture strength of the green body, we verified that the photo-cured polymer in the green body should have high crosslinking density and low free volume based on reduction of unreacted vinyl groups in the polymer. Additionally, through analysis of cross-sectional SEM of the green body, we confirmed that acrylate monomer should include proper content in the slurry-type resin to maximize the fracture strength of the body regardless of the type of the used acrylate monomer. This was because low content of acrylate monomer in the slurry-type resin makes it difficult to form neckings composed with photo-cured polymers between the silica beads.     

Synthesis and photo‐polymerization of bio‐based furanic compounds functionalized by 2‐hydroxypropyl methacrylate group(s)

Bio‐based compounds (FmHPM and FdHPM) with a furan backbone and photo‐polymerizable 2‐hydroxypropyl methacrylate (HPM) group(s) were synthesized from carbohydrate‐derived furanyl alcohols (furan‐2‐methanol and furan‐2,5‐dimethanol) and their photo‐polymerizing behaviors and mechanical properties after photo‐polymerization were investigated. Half time values (t_1/2) of bio‐based FmHPM and FdHPM were 10.4 s and 3.0 s and their shrinkage ratios were 3.0 and 6.1% during photo‐polymerization, respectively. Tensile‐shear strength of glass and polycarbonate joints bonded by bio‐based furanic compounds appeared in range of 0.2–0.6 MPa and pencil hardness of film coated by bio‐based furanic compounds after photo‐polymerization showed 2H–3H. Newly synthesized bio‐based furanic compounds allowed the feasibility to alternate petroleum‐based Bis‐GMA/TEGDMA, photo‐polymerizable composition widely utilized in a variety of applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of hydrophilic monomer on the surface properties of cationic polyurethane‐fluorinated acrylate hybrid dispersions

Cationic polyurethane‐fluorinated acrylate hybrid dispersions (PUFA) were prepared by the copolymerization of styrene, butyl acrylate, and 2,2,3,4,4,4‐hexafluorobutyl methacrylate in the medium of crosslinked polyurethane via phase inversion polymerization. The said polyurethane was synthesized in acetone from 2,4‐tolyene diisocyanate, N‐methyldiethanolamine, trimethylolpropane, and soft polyester diol block. The influences of hydrophilic monomer on the surface properties, immersion behaviors, particle size and, zeta potential of the dispersions were investigated. The results show that the addition of hydrophilic monomer can be advantaged to the stability of dispersions and yet will increase the surface free energy by more than 19.9%. The PUFA coating films cured at ambient conditions have the lower surface free energy (less than 0.02033 J/m²). At the same time, there is an obvious mobility of fluorinated groups in fluorinated polymer films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Kinetic behavior of photo‐polymerization of UV‐curable resins with carboxylic acid and amino groups

Photo‐polymerization behaviors of bisphenol‐A epoxy diacrylate (EPA) and six kinds of EPA‐derived resins containing different amounts of carboxylic acid, urethane, amide, and imide groups were studied by a photo differential scanning calorimetry. The dark polymerization was performed and pseudo‐steady state assumption of growing radicals was made to obtain the kinetic constants for propagation, bimolecular termination, monomolecular termination, and the concentration of growing radicals of different resins as a function of extent of reaction. Compared with EPA, it was found that the rate of polymerization and kinetic constants of the six resins were relatively small because the mobility of reacting species in resins was restricted by carboxylic acid, urethane, amide, and imide groups. Finally, three different photo‐initiators were used to initiate the polymerization, and their kinetic behaviors were compared. The effect of tertiary amine group of photo‐initiator on the rate of polymerization of resins having carboxylic acid group and the initiator efficiency were discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Templating synthesis of non‐spherical polymer particles and their effect on the fracture toughness of an epoxy‐amine network

Flexible non‐spherical polymer particles were successfully produced via concentrated emulsion polymerization. LUDOX TM‐50 (colloidal silica, 50 wt% suspension in water) was introduced into the continuous phase to strengthen the template and inhibit monomer diffusion between the continuous and dispersed phases. The extent of non‐spherical shape was identified by the roundness value. Transmission electron micrographs showed that the higher the volume fraction of the dispersed phase became, the more non‐spherical were the poly(butyl acrylate) (PBA) particles. As an application, the effect of the non‐spherical particles on the fracture toughness of a modified epoxy‐amine network was studied. Scanning electron micrographs showed that the introduction of the non‐spherical PBA particles improved efficiently the impact strength of the cured epoxy resin. Copyright © 2006 Society of Chemical Industry     

Novel reworkable resins: thermo‐ and photo‐curable di(meth)acrylates

The aim of the study reported in this paper was to develop new di(meth)acrylates having aromatic units and thermally degradable units in their molecules. It was also the aim to clarify the photo‐curing and degradation properties of the new monomers. Di(meth)acrylates having aromatic units and thermally degradable units were synthesized. As thermally cleavable linkages, tertiary ester moieties were incorporated into the di(meth)acrylates. Three types of processes for curing and degradation of the cured resins were studied: thermal curing and thermal degradation; thermal curing and photodegradation; and photo‐curing and thermal degradation. In the thermal curing and photodegradation process, di(meth)acrylate films containing a thermally induced radical initiator and a photoacid generator (PAG) became insoluble in solvents on heating. The cured films became soluble in solvents after ultraviolet irradiation followed by baking. The re‐dissolution behaviors were strongly affected by the structures of the PAGs. A mechanism for the photo‐ or thermo‐curing and photoassisted thermal degradation was studied using Fourier transform infrared, ¹H NMR, thermogravimetric, mass spectrometric and size exclusion chromatographic analyses. Copyright © 2009 Society of Chemical Industry     

Preparation of a self‐compatibility alloy via a seed‐graft concentrated‐emulsion pathway

A novel polymerization procedure, the concentrated‐emulsion graft polymerization of styrene monomer with poly(butyl acrylate) seed, was proposed for the production of a self‐compatibility macromolecule alloy. The effects of the butyl acrylate content, sodium dodecyl sulfate concentration, and polymerization temperature on the graft ratio were investigated. Scanning electron microscopy, transmission electron microscopy, and impact strength were used to characterize the microstructure and mechanical performance of the self‐compatibility macromolecule alloy. The results showed that increasing the butyl acrylate content, reducing the sodium dodecyl sulfate concentration, and improving the polymerization temperature all favored an increased graft ratio, which resulted in increased impact strength of the self‐compatibility macromolecule alloy. Therefore, the concentrated‐emulsion polymerization method is particularly suitable for seed‐graft polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2915–2920, 2002; DOI 10.1002/app.10288     

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     

Effects of Photodegradable o‐Nitrobenzyl Nanogels on the Photopolymerization Process

A series of partially photodegradable o‐nitrobenzyl nanogels (NBNG) with different caged functional groups (COOH, OH, SH) are prepared and compared with a nondegradable nanogel as additives in photocurable materials. Photoinduced nanogel network disruption and photoinitiated polymerization of infiltrating and dispersing monomer could be controlled independently. In triethylene glycol dimethacrylate (TEGDMA), o‐NBNGs that release a COOH or OH functional group upon photodegradation of the o‐nitrobenzyl crosslinker, the reduced chemical crosslinking density of the nanogel network allows greater penetration of monomer into the partially degraded nanogel network, which results in an increase in volumetric shrinkage and polymerization stress. In contrast, the formulation of o‐NBNGs with caged SH groups also can be photodegraded but is able to rebuild the chemical crosslinking through thiol‐based chain transfer reactions when photocured as a dispersion in TEGDMA. As such, it behaves like a photo‐inert nanogel. Dynamic thermomechanical analysis and testing by three‐point bending further confirms the photoinduced crosslink density variation influences mechanical properties of the final polymer networks. This work demonstrates the inherent properties of the nanogel network and the type of crosslinking can alter the performance of the photocured resin while a separate photochemical process can be used to regulate photoinduced polymerization.     

UP树脂光增稠研究

本文介绍了光引发剂、光敏化剂、光源距离和光照时间等对ＵＰ树脂光引发聚合增粘的影响，以及各种单体与ＵＰ树脂的光引发聚合的比较，说明利用光引发聚合可以达到ＵＰ树脂增稠的目的。     

Rheological behavior and thermal properties of poly(butyl acrylate‐co‐2‐ethylhexyl acrylate)‐grafted vinyl chloride resin

The rheological behavior and thermal properties of a poly(butyl acrylate‐co‐2‐ethylhexyl acrylate) [P(BA‐EHA)]‐grafted vinyl chloride (VC) composite resin [P(BA‐EHA)/poly(vinyl chloride) (PVC)] and its materials were investigated. The rheological behavior, thermal stability, and Vicat softening temperature (VST) of P(BA‐EHA)/PVC were measured with capillary rheometry, thermal analysis, and VST testing, respectively. The effects of the P(BA‐EHA) content and the polymerization temperature of grafted VC on the rheological behavior of the composite resin were examined. The weight loss of the composite resin and its extracted remainder via heating were analyzed. The influence of the content and crosslinking degree of P(BA‐EHA) and the polymerization temperature of the grafted VC on VST of the materials was determined. The results indicated the pseudoplastic‐flow nature of the composite resin. The flow property of the modified PVC resin was improved because of the incorporation of the acrylate polymer. The molecular weight of PVC greatly influenced the flow behavior and VST of the composite resin and its materials. The flowability of the composite resin markedly increased, and the VST of its materials decreased as the polymerization temperature of the grafted VC increased. The initial degradation temperature of the composite resin increased as the P(BA‐EHA) content increased. The VST of the samples was enhanced a little as the content of the crosslinking agent increased in P(BA‐EHA). As expected, the composite resin, with good impact resistance, had better heating stability and flowability than pure PVC, whereas the VST of the material decreased little with increasing P(BA‐EHA) content. Therefore, P(BA‐EHA)/PVC resins prepared by seeded emulsion polymerization have excellent potential for widespread applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 419–426, 2005     

Study on spatial–temporal kinetics of photo‐initiated frontal polymerization in stacked reaction cells

The spatial–temporal kinetics for photo‐initiated frontal polymerization(PFP) of isobornyl acrylate with 2,4,6‐trimethylbenzoyldiphenyl phosphine oxide (TPO) as photobleaching initiator was studied experimentally in stacked reaction cells. FTIR and NMR spectroscopy were employed to measure the polymerization conversion, which is dependent on the exposure time, sample depth, light intensity and photo‐initiator concentration. The experimental results are consistent with the theoretical model prediction and show that prolonged irradiation time, higher light intensity and lower photo‐initiator concentration are favorable in enhancing the advance of the polymerization front. The depth‐resolved GPC analysis shows that the average molecular weight of the PFP product dramatically increases with sample depth, while the molecular weight polydispersity reduces steadily with increase in sample depth. Copyright © 2006 Society of Chemical Industry     

Controllable surface modifications of polyamide by photo‐induced graft polymerization using immobilized photo‐initiators

A novel two‐step UV initiated grafting method has been developed and applied on surface modification of polyamide. Anthraquinone‐2‐sulfonate sodium, an acid dye, was chosen as the photo‐initiator. In the first step, photo‐initiators were ionically bonded onto polyamide through a normal acid dye dyeing process. Vinyl monomers such as acrylic acid were then grafted onto polyamide surface in the following step. During UVA irradiation, not only monomers were grafted onto polymer surface, photo‐initiator itself was also covalently bonded onto polymer. The grafted polymers were characterized by Fourier transform infrared spectrometer (FTIR), X‐ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM).The degree of photo‐grafting can be controlled by adjusting concentrations of photo‐initiator and monomer, as well as UVA exposure time. This process demonstrated the feasibility of efficiently modifying polymer surface under low UV intensity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Concentrated emulsion polymerization for preparation of β‐cyclodextrin‐supported chromatography columns

Concentrated inverse emulsion polymerization was used for making chromatography columns (based on crosslinked polystyrene divinylbenzene (PS‐DVB)) with pore sizes less than 10 μm. According to DSC‐thermal gravimetry thermograms, it was confirmed that the residual monomer concentration after polymerization process is negligible. For application of these columns in chiral chromatography, the β‐cyclodextrin is chemically fixed on the PS‐DVB resin pore surface. The presence of hydroxyl groups in the PS‐DVB resin after chemical modification was confirmed by FTIR spectroscopy. By chemical modification of the PS‐DVB resin, thermal stability increased up to 446°C. The structure of columns was analyzed by scanning electron microscopy (SEM). SEM evaluations showed that the porous structure of PS‐DVB resin was maintained intact after the chemical modification with β‐cyclodextrin. According to X‐ray data, presence of the crystalline domain that is related to β‐cyclodextrin is confirmed.© 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 857–863, 2006     

Preparation and characterization of unsaturated poly(ester‐imide) based on 1,4‐bis[2′‐trifluoromethyl‐4′‐(4″‐glycolformate)‐trimellitimidophenoxy]benzene

A novel diimidodialcohol monomer, 1,4‐bis[2′‐trifluoromethyl‐4′‐(4″‐glycolformate)‐ trimellitimidophenoxy]benzene (BGTB), was synthesized and characterized. It was reacted with isophthalic acid, maleic anhydride and propylene glycol to produce a novel unsaturated poly(ester‐imide) (BGTB‐UPEI) with imide and trifluoromethyl groups in the polymer backbone. The BGTB‐UPEI resin was diluted with reactive monomer (styrene) to give a low‐viscous poly(ester‐imide)/styrene (BGTB‐UPEI/St) mixed solution, which was then thermally cured to yield thermosetting BGTB‐UPEI/St composite. The effect of processing parameters such as the curing temperature and curing time, reactive monomer concentration and initiator amount on the curing reaction was systematically investigated. Experimental results indicated that the thermally cured BGTB‐UPEI/St composite exhibited much better thermal, mechanical, electrical insulating properties and chemical resistance than the standard unsaturated polyester/polystyrene composite. Copyright © 2006 Society of Chemical Industry