Photopolymerization Studies Research Articles

A comparative study of electropolymerization and photopolymerization for the determination of molnupiravir and their application in an electrochemical sensor via computationally designed molecularly imprinted polymers

A comparative analysis of molecularly imprinted polymers based on different synthesis techniques was performed for the recognition of molnupiravir (MOL). The polymerizations were performed with 3-thienyl boronic acid (3-TBA) as a functional monomer by electropolymerization (EP) and with guanine methacrylate (GuaM) as a functional monomer by photopolymerization (PP). Morphological and electrochemical characterizations of the developed sensors were investigated to verify the constructed sensors. Moreover, quantum chemical calculations were used to evaluate changes on the electrode surface at the molecular and electronic levels. The dynamic linear range of both designed sensors under optimized experimental conditions was found to be 7.5 × 10−12–2.5 × 10−10 M and 7.5 × 10−13–2.5 × 10−11 M for EP and PP, respectively. The effect of various interfering agents on MOL peak current was assessed for the selectivity of the study. In the presence of 100 times more interfering agents, the RSD and recovery values were determined. The RSD values of GuaM/MOL@MIP/GCE and poly(Py-co-3-PBA)/MOL@MIP/GCE sensors were found to be 1.99% and 1.72%, respectively. Furthermore, the recovery values of the MIP-based sensors were 98.18–102.69% and 98.05–103.72%, respectively. In addition, the relative selectivity coefficient (k′) of the proposed sensor was evaluated, and it exhibited good selectivity for MOL with respect to the NIP sensor. The prepared sensor was successfully applied to determine MOL in commercial serum samples and capsule form. In conclusion, the developed sensors provided excellent reproducibility, repeatability, high sensitivity, and selectivity against the MOL molecule.Graphical

Directing network degradability using wavelength-selective thiol-acrylate photopolymerization

Thiol-acrylate photoresin containing dynamic disulfide bonds undergoes wavelength-selective photopolymerization under green vs. UV light to produce a degradable step-growth network vs. permanent chain-growth network.

Influence of Photoinitiator Type and Curing Conditions on the Photocuring of Soft Polymer Network

The presented work deals with the photocuring of telechelic macromonomers derived from plant-based fatty acids to obtain a soft polymer network. Compositions were made by mixing macromonomers with three different concentrations (0.5, 1, and 2%) of two type I photoinitiators (Omnirad 2022 and Omnirad 819). All formulations were then subjected to photopolymerization studies by applying UV-assisted differential scanning calorimetry (UV-DSC) measurements at isothermal conditions at 37 °C with a narrow light source wavelength of 365 nm and irradiation (light intensity) of 20 and 50 mW/cm2. The percentage conversions, reaction orders, and constants were estimated based on autocatalytic Sestak–Berggen and Avrami models. In this work, for the first time, the influence of the curing conditions on the photopolymerization process, such as the photoinitiator concentration, light intensity, and oxygen presence/absence, were investigated for these novel systems. The results indicated significant differences between the two commercially available photoinitiators and their effects on photopolymerization kinetics. The maximum reaction rate was found to be considerably higher for Omnirad 2022 (which is a blend of three different compounds), especially at a lower light intensity, i.e., 20 mW/cm2, compared to Omnirad 819. However, it led to lower maximum conversion in an air atmosphere. The dynamic thermomechanical analysis (DMTA) revealed that light intensity, photoinitiator concentration, and oxygen presence had a strong effect on the storage modulus and loss modulus values. It was concluded that the chemical structure of the photoinitiator and curing conditions had a strong effect on the photopolymerization kinetics and properties of the prepared soft polymer networks.

(Invited) The Importance of Characterizing and Calibrating Light Engines in Vat Photopolymerization Additive Manufacturing

Vat photopolymerization (VP) is an additive manufacturing technique that uses spatially patterned light to cure liquid resins into solid materials. As an additive manufacturing technique, parts with complex geometries can be manufactured that would not be possible with conventional techniques. Large scale VP has found wide adoption by a range of industries including automotive, dental, consumer goods, and prototyping. On a smaller scale, hobbyist level users have found innumerable uses for VP and this market, in particular, has fueled the development of a plethora of low-cost printers. Common to all VP printers is the need for a light engine which illuminates the resin and initiates the photopolymerization process. Historically, this light engine was a UV laser with relatively simple optical properties including low divergence, narrow spectral bandwidth, and fixed wavelength – spatial extent of the photopolymerization was controlled by rastering the focused beam across the build plate. More recently, digital micromirror device (DMD) and liquid crystal display (LCD) based light engines have been developed which expose the resin in a parallel fashion by controlling the exposure in a 2-dimensional pixelated manner. These more recent light engine designs tend to rely upon light emitting diodes (LEDs) as the photon source and these have more complex properties including high divergence (i.e. Lambertian emitter), broad spectral bandwidth, and less well-defined wavelength. Many printer manufacturers have developed multi-emitter light engine designs that compound these characteristics. As VP manufacturing continues to mature, the reproducibility of parts, both in terms of dimensional and functional properties, is becoming more and more critical. Here, we present our work on characterizing existing VP printer light engines. We show the types of heterogeneity that are present in these light engines and how they can directly impact printed parts. This then leads us to a discussion about what optical properties are important to control in VP light engines for improved print reproducibility. Finally, we discuss our latest efforts to develop a fully calibrated and characterized uniform light engine for performing careful photopolymerization studies that inform on the underlying photopolymerization physics without convolving light engine heterogeneity with the underlying photophysics. Figure 1

Kinetic study of photopolymerization and depolymerization in C60 films using in situ Fourier-transform infrared spectroscopy for development of C60-based thermoelectric materials

Kinetics of photopolymerization and thermal-induced depolymerization in C60filmsfound that the proportion of the monomer, dimer, and oligomers was saturated to be 4, 72, and 24%, respectively,after40 h irradiation of ultraviolet light. Depolymerization kinetics of the photopolymerized C60film obtainedthe activation energy (Ea) of depolymerization for (C60)2dimerto be 1.26 eV, whereasEafor (C60)noligomers to be 1.78 eV. The difference inEabetween them can be utilized to change their proportion distributions by iterations of photoirradiation/thermal-depolymerization cycle to control the physicochemical properties (such as the electronic and thermal conductivities) of photopolymerized C60film.

Visible light-induced photopolymerization of Deep Eutectic Monomers, based on methacrylic acid and tetrabutylammonium salts with different anion structures

Deep Eutectic Monomers were prepared by dissolution of selected tetrabutylammonium salts serving as hydrogen bond acceptors (HBA) in methacrylic acid (MAA) acting both as hydrogen bond donor (HBD) and vinyl monomer. In this study, we systematically investigate the influence of chloride, nitrate, hydrogensulphate and fluoroborate anions on properties of DEMs and the course of radical photopolymerization. By Combining FTIR, 1H and 13C NMR spectroscopy we found the that degree of coordination of MAA in DEMs by anions follows the order: Cl− > NO3– > HSO4− ≫ BF4−. Moreover, the studies indicated that the strength of hydrogen bonds between HBD and HBA in DEMs is lower than in MAA dimers. Real-time FT-IR spectroscopy studies of photopolymerization of DEMs indicate that the mixtures formed from MAA and tetrabutylammonium fluoroborate show significant lower initial photopolymerization rate in comparison with other investigated DEMs, which polymerize with similar rates.

X-ray diffraction and Raman study of pressure-assisted photopolymerization in the ferrocene-doped C60 crystals

X-ray diffraction and Raman study of pressure-assisted photopolymerization in the ferrocene-doped C60 crystals

Kinetic Studies of Photopolymerization of Monomer‐Containing Deep Eutectic Solvents

AbstractThe kinetics of photopolymerization in deep eutectic solvents (DESs) is investigated through real‐time Fourier transform‐infrared spectrometry (RT‐FTIR). The systems of this study are choline chloride (ChCl) DESs made of acrylic acid and methacrylic acid (DES monomers) and a nonreactive analog isobutyric acid (IBA). The DES consisting of the analog also contains the monomer methyl methacrylate (MMA). Analysis of the evolution of conversion indicates dramatic increase in polymerization rate when comparing the polymerization of the DES monomers to pure monomer polymerization. A significant increase in polymerization rate is also seen in the systems that include a methyl ester derivative of the hydrogen bond donor monomer (e.g., MMA) in a nonpolymerizable DES (e.g., IBA−ChCl). It is proposed that the increased solvent viscosity, preorganization due to hydrogen bonding, and the polarity of the DES around the monomers play a role in the enhancement of the polymerization rate.

Stimuli-responsive poly(hydroxyethyl methacrylate) hydrogels from carboxylic acid-functionalized crosslinkers.

Tailoring hydrogel properties by modifications of the crosslinker structure is a good method for the design of hydrogels with a wide range of properties. In this study, two novel carboxylic acid-functionalized dimethacrylate crosslinkers (1a and 2a) are synthesized by the reaction of poly(ethylene glycol) or 2-hydroxyethyl disulfide with tert-butyl α-bromomethacrylate followed by cleavage of tert-butyl groups using trifluoroacetic acid. Their copolymerization reactivity with 2-hydroxyethyl methacrylate (HEMA) investigated by photopolymerization studies performed on photo-differential scanning calorimetry shows higher reactivity of 2a compared to 1a. These crosslinkers are then used at different ratios for fabrication of pH- and redox-responsive poly(2-hydroxyethyl methacrylate)-based hydrogels. The swelling behavior of the hydrogels is found to be dependent on the structure of the crosslinker, degree of crosslinking, pH, and CaCl2 concentration. The redox-responsive behavior is demonstrated by degradation of the hydrogel upon exposure to 1,4-dithiothreitol. The dye Rhodamine 6G and the drug resorcinol are used as models to demonstrate the pH and redox dependent release of loaded compounds from the hydrogels. The electrostatic interactions between the carboxylate groups and the positively charged R6G are found to govern the release profile in DTT and counteract the diffusion of dye molecules and significant amount of release (79% in 120 hr) occurs only at highly acidic conditions. The degradation mediated release in DTT is observed better in case of resorcinol (around 88% in 5 hr). Overall, these hydrogels can be regarded as good candidates for several applications, such as matrices for controlled release, tissue repair, and regeneration.

Photopolymerization with Light Fields Possessing Orbital Angular Momentum: Generation of Helical Microfibers

Photopolymerization is a powerful technique to create arbitrary micro-objects with a high spatial resolution. Importantly, to date all photopolymerization studies have been performed with incident light fields with planar wavefronts and have solely exploited the intensity profile of the incident beam. We investigate photopolymerization with light fields possessing orbital angular momentum, characterized by the topological charge l. We show both experimentally and theoretically that, as a consequence of nonlinear self-focusing of the optical field, photopolymerization creates an annular-shaped vortex-soliton and an associated optical fiber, which breaks up into |l| solitons or microfibers. These microfibers exhibit helical trajectories with a chirality determined by the sign of l due to the orbital angular momentum of the light field and form a bundle of helical-microfibers. This research opens up a new application for light fields with orbital angular momentum, and our generated microfibers may have appli...

Urea dimethacrylates functionalized with bisphosphonate/bisphosphonic acid for improved dental materials

ABSTRACTIncorporation of bisphosphonate/bisphosphonic acid groups in dental monomer structures should increase interaction of these monomers with dental tissue as these groups have strong affinity for hydroxyapatite. Therefore, new urea dimethacrylates functionalized with bisphosphonate (1a, 1b) and bisphosphonic acid (2a, 2b) groups are synthesized and evaluated for dental applications. Monomers 1a and 1b are synthesized from 2‐isocyanatoethyl methacrylate (IEM) and two bisphosphonated amines (BPA1 and BPA2), prepared as reported elsewhere. Selective dealkylation of the bisphosphonate ester groups of 1a and 1b using trimethylsilyl bromide (TMSBr) gives monomers (2a and 2b) with bisphosphonic acid functionality. X‐ray diffractometer (XRD), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS) analyses of monomer‐treated HAP particles show that 2a induces formation of stable monomer‐calcium salts, similar to 10‐methacryloyloxydecyl dihydrogen phosphate (MDP), with higher chemical interaction than 2b. The photopolymerization studies indicate good copolymerizability with commercial dental monomers. In vitro studies on NIH 3T3 mouse embryonic fibroblast cells have clearly shown that the tested monomers (1b and 2b) are not toxic according to the MTT standards. All these properties make these monomers suitable as biocompatible cross‐linkers/adhesives for dental applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3195–3204

Kinetic study of acrylamide photopolymerization in the presence of silver salt

The solution polymerizations of acrylamide (AAm) initiated by the photoinitiator DAROCUR 2959 (DAR) and UV light were studied. The kinetics of acrylamide polymerization in the presence of silver salt was investigated. Dilatometry was implemented to follow continuously the fast photopolymerization. The polymerization rate vs conversion curve of the photopolymerization of AAm was described by two nonstationary-state intervals. The abrupt increase in the initial rate was attributed to the accumulation of the reaction loci. The continuous decrease in the polymerization rate with conversion was discussed in terms of the increased termination based on the intra- and intermolecular chain transfer to polymer. The deactivation of the excited states of initiator and initiating radicals by their interaction with reaction products (silver nanoparticle–polymer nanocomposites) is also taken into account. The irradiation of silver salt and AAm led to the formation of silver–polymer nanocomposites. The small silver nanoparticles grow during the photolysis (or polymerization and storing) to microparticles and large agglomerates.

Synthesis, Characterization, and Photopolymerization of Polyisobutylene Phenol (Meth)acrylate Macromers

Polyisobutylene (PIB) phenol (meth)acrylates were produced by reacting di- or triphenol-terminated PIB with (meth)acryloyl chloride. 1H NMR, GPC, and MALDI-TOF MS characterization showed that meth(acrylate) end-functionality was 2 and 3, respectively, and that targeted molecular weights and relatively low polydispersities were achieved. Comparative aliphatic PIB triol triacrylate was prepared by end-quenching living polyisobutylene with 4-phenoxy-1-butyl acrylate. A photopolymerization study of PIB diphenol di(meth)acrylates with Mn about 3000 g/mol, PIB triphenol tri(meth)acrylates with Mn about 4000 and 10 000 g/mol, and control aliphatic PIB triol triacrylate with Mn about 10 000 g/mol was conducted. Darocur 1173 and Irgacure 819 and 651 photoinitiators were studied, and FTIR reaction monitoring showed that Darocur 1173 afforded the highest rate of photopolymerization and final conversion, apparently due to its higher solubility in PIB. At Mn ≅ 4000 g/mol, the rate of photopolymerization and conversion...

Photopolymerization study and adhesive properties of self-etch adhesives containing bis(acyl)phosphine oxide initiator

ObjectiveThis paper investigates the photo-co-polymerization behavior of a blend of a diacrylamide (DEBAAP) with a phosphonylated acidic monomer using either bis(acyl)phosphine oxide or camphorquinone/amine as photo-initiator and studies the effect of variation of the structure of the phosphonylated acidic monomer on the shear bond strength to human dentin. MethodsPhotopolymerization kinetics has been assessed through the use of photo-DSC with either initiating system and with and without a phosphonic acid monomer, while the shear bond strengths (SBS) of dentin bonding agents formulated with several phosphonylated acidic monomers have been evaluated by macro SBS testing on human dentin. ResultsPhoto-DSC results show that bis(acyl)phosphine oxide initiates a faster polymerization than camphorquinone/amine and that both photopolymerizations are accelerated by the phosphonic acid monomer. Similar results were obtained between adhesives based on camphorquinone/amine and a commercial adhesive (AdheSE, Ivoclar-Vivadent, Schaan, Liechtenstein). The best performances were obtained when BAPO was used as the initiator, in many cases far better than the commercial adhesive. Adhesive SEA6 based on difluoromethylphosphonic acid C demonstrated the best adhesion results of this study.Significance The bis(acyl)phosphine oxide photo-initiator causes faster photopolymerization of two-step self-etching dental adhesive, and its use could yield better bonding performance.

Inhibition effect of N,N-diglycidyl-4-glycidyloxy aniline on photosensitized cationic polymerization of formulations involving resorcinol diglycidyl ether and poly(propylene glycol)diglycidyl ether

Abstract Cationic photopolymerization studies of poly(propylene glycol)diglycidyl ether with and without 25 wt% of resorcinol diglycidyl ether were carried out in presence of bis(4-methylphenyl)iodonium hexafluorophosphate as photoinitiator. Analyses were carried out using polychromatic radiation at different temperatures in a photo differential scanning calorimeter. The formulations showed an enhancement in the rate of polymerization on addition of resorcinol diglycidyl ether. The same formulations when subjected to photosensitized polymerization in presence of 1-chloro-4-propoxy-9H-thioxanthen-9-one, showed a reverse behavior in rate due to partial absorption of radiation by resorcinol diglycidyl ether. Studies carried out on by the addition of N,N-diglycidyl-4-glycidyloxy aniline as inhibitor on the photosensitized formulations showed higher scavenging activity by inhibitor. The addition of nitrogen containing epoxy monomer as inhibitor can lead to its possible crosslinking within the matrix on polymerization along with a decrease in rate of polymerization without compromising on the final observed conversion. This effect can occur readily for non vitrifying systems. Thus, this observation provides an insight into its possible usage in a rate controlled photopolymerizable epoxy formulations. The photopolymerization kinetics were found to depend on the nature of generation, propagation and scavenging of active centers which are heavily dependent on diffusional restrictions imparted by in situ viscosity of the system. The kinetic estimations as well as evaluation of autocatalytic kinetic model are investigated.

Synthesis, characterization and kinetic study of photocrosslinkable prepolymer: 2-hydroxy-3-[p-(1-{p-[2-hydroxy-3-(vinylcarbonyloxy)propoxy]phenol}-1-phenylethyl)phenoxy]propyl acrylate

New photocrosslinkable prepolymer, 2-hydroxy-3-[p-(1-{p-[2-hydroxy-3-(vinylcarbonyloxy)propoxy]phenol}-1-phenylethyl)phenoxy]propyl acrylate (HVPA) was synthesized from p-[1-(p-hydroxyphenyl)-1-phenylethyl]phenol (HPPP), 1, 1-bis{p-[(2-oxiranyl)methoxy]phenyl}-1-phenylethane with acrylic acid and was characterized by 1H NMR, 13C NMR and FT-IR spectroscopy. The photocrosslinking studies were carried out by irradiating the mixture containing the prepolymer, HVPA (75%), with the diluent, tri(ethyleneglycol)diacrylate (25%), in the presence of a photoinitiator, Irgacure 651 (DMPA), under medium pressure mercury vapour lamp at various time intervals and various DMPA concentrations. The kinetics of the photopolymerization, percent double bond conversion and the rate of polymerization of the photocrosslinked polymers were studied using FT-IR spectroscopy. The result showed that an increasing DMPA concentration increases percent double bond conversion. The effect of viscosity of system on kinetics of photopolymerization was studied. It was found that percent double bond conversion increased with decrease in the viscosity of the system. The percent gel content and hardness of the photocrosslinked polymers were studied, and it was observed that the percent gel content and hardness of the photocrosslinked polymers were increased with increasing irradiation time and DMPA concentration. The photopolymerization studies of the synthesized prepolymer, HVPA, were compared to the commercial prepolymer, bisphenol-a-glycerolate (1-glycerol/phenol) diacrylate (BISGA). The results showed that percent double bond conversion of synthesized prepolymer, HVPA, was higher than commercial prepolymer, BISGA. This showed that HVPA was more suitable for industrial applications than BISGA.

Novel imidazole-containing thioxanthone derivative for photopolymerization

A novel, highly efficient, imidazole-containing thioxanthone photoinitiator, 2-(2-hydroxy-3-imidazole) propoxythioxanthone (IPTX) was synthesized by introducing imidazole to thioxanthone moieties. Another thioxanthone photoinitiator with aliphatic tertiary amine moiety 2-(2-hydroxy-3-methylhydroxyethylamido) propoxythioxanthone (APTX) and 2-(2,3-dihydroxy) propoxythioxanthone (HPTX) were synthesized to evaluate the photoefficiency of IPTX. FT-IR and 1H NMR confirmed the structures of photoinitiators. UV–vis spectra of the three photoinitiators are similar and all exhibit the maximal absorption near 400 nm. Fluorescence spectra show IPTX has the lowest fluorescence intensity among all photoinitiator systems. Photopolymerization studies indicate that IPTX, with imidazole moiety as coinitiator, is more efficient for the polymerization of trimethylolpropane triacrylate (TMPTA) than those with aliphatic tertiary amine group.

Water‐soluble and polymerizable thioxanthone photoinitiator containing imidazole

ABSTRACTA novel free radical photoinitiator, 3‐allyl‐1‐[2‐hydroxy‐3‐(thioxanthen‐9‐one‐2‐yl)oxypropyl]imidazolium chloride ([AIPTX]Cl), is synthesized by the addition reaction of 2‐(2,3‐epoxy)propoxylthioxanthone (ETX) with a heterocyclic compound imidazole firstly, and the achieved intermediate 1‐[2‐hydroxy‐3‐(thioxanthen‐9‐one‐2‐yl)oxypropyl]imidazole (IPTX) is then reacted with allyl chloride. IPTX is chosen to evaluate the photoefficiency of [AIPTX]Cl. FTIR and 1H‐NMR confirm the structures of [AIPTX]Cl and IPTX. UV‐Vis spectra of the two photoinitiators are similar and both exhibit the maximal absorption about 400 nm. Fluorescence spectra show [AIPTX]Cl/IMZ has slightly higher fluorescence intensity than IPTX system. Photopolymerization studies indicate that [AIPTX]Cl/IMZ is more efficient for the polymerization of water‐soluble monomer than IPTX. Moreover, due to its advantages of water solubility and polymerizability, [AIPTX]Cl is an environmental‐friendly photoinitiator and has potential for application in UV‐curing systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40659.

Photopolymerization Kinetics of Block Polyether Based Terminal Urethane Methacrylate with/without Cross‐Linker

ABSTRACTThe present work deals with the photopolymerization of difunctional macromonomer with a polyether chain and urethane methacrylate terminations. Macromonomeric formulations were prepared by mixing macromonomer with two different concentrations of photoinitiator. Formulations were also prepared by the addition of 10 wt% of soft‐segmented difunctional cross‐linker to the abovementioned macromonomic formulations. All formulations were then subjected to photopolymerization studies and the effects of light intensity on the photopolymerization kinetics were studied at two different isothermal conditions using photo differential scanning calorimetry (Photo DSC) with polychromatic radiation. The isothermal heat flow against time was recorded for all formulations and the kinetic parameters were noted. It was observed that the rate of maximum polymerization as well as peak maximum time showed a general trend. However, the ultimate conversion as well as the conversion at maximum rate did not show any trend due to diffusional restrictions imparted by the increase in viscosity with conversion. The photopolymerization of the formulations and curing kinetics including evaluation of autocatalytic model are discussed.

Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one as a visible photoinitiator

Photoinitiators that operate in the visible range of the electromagnetic spectrum have widespread applications. Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one (TX-MPA) was synthesized and the characterization of this initiator was confirmed by spectral analysis methods. TX-MPA has excellent absorption properties in the visible range (ε480nm=3576L/mol.cm). Photophysical studies; fluorescence quantum yield (Фf=0.22, DPA), phosphorescence lifetime (τp=115ms) and triplet lifetime (τ=190ns) were explored. To explore the initiation mechanism of TX-MPA, besides the photophysical and photochemical studies, the polymer (PMMA) obtained from the photopolymerization studies was subjected to a phosphorescence study and τp was found to be 105ms compared to 115ms for the initiator TX-MPA which proved attachment of the initiator to the polymer. Possibly both intermolecular and intramolecular hydrogen abstraction, occur during the initiation stage depending on the concentration of the initiator.