Synthesis and photopolymerization of ethylene glycol 3‐morpholine‐propionate methacrylate for potential dental composite application

2,2‐Bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy) phenyl]‐propane (bis‐GMA), triethylene glycol dimethylacrylate (TEGDMA), camphorquinone (CQ), ethyl‐4‐dimethylaminobenzoate (EDMAB), or 2‐(dimethylamine)ethyl methacrylate (DMEM) were composed of the modern dental composite system and acted as resin, diluent, photoinitiator, and coinitiator, respectively. In this study, ethylene glycol 3‐morpholine‐propionate methacrylate (EGMPM) was synthesized via Michael addition reaction to replace both the TEGDMA as a diluent and the nonpolymerizable amine EDMAB as a coinitiator. Mixtures of bis‐GMA/TEGDMA/CQ/EGMPM and bis‐GMA/TEGDMA/CQ/DMEM were found to have almost the same rate of polymerization and reach final double bond conversion at 58%, slightly lower than that of the bis‐GMA/TEGDMA/CQ/EDMAB (63%) and bis‐GMA/EGMPM/CQ (60%) under comparable visible light irradiation conditions. In addition, the results of dynamic mechanical analysis showed that all of the four samples had approximately the same modulus and the glass transition temperature. The water sorption and solubility of bis‐GMA/TEGDMA/CQ with different amines (EDMAB, DMEM, and EGMPM) had almost the same value except that the water sorption of bis‐GMA/EGMPM/CQ was out of the range of the ISO 4049 (2000) standards. The results indicated that EGMPM was potentially a coinitiator for dental composite, because there are no significant differences in photopolymerization characteristic and physical properties when compared with traditional system (bis‐GMA/TEGDMA/CQ/EDMAB). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4589–4594, 2006     

A comparison of efficiency of two photoinitiators for polymerization of light‐cure dental composite resins

The purpose of the study was to compare the effect of two photoinitiators, (?)camphorquinone (CQ) and 1‐phenyl‐1,2‐propanedione (PPD) on curing performance of light‐cure dental composite resins. Bisphenol A‐glycidyl methacrylate (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) monomer mixture was used as the resin matrix. The resin matrix was mixed with CQ and/or PPD along with 0.25% of 4‐(dimethyl amino) phenethyl alcohol (DMAPEA) catalyst. The effect of photoinitiator on curing performance was evaluated and compared in terms of properties such as depth of cure, diametral tensile strength (DTS), flexural strength (FS), flexural modulus (FM), vickers hardness number (VHN), water sorption (WS), and solubility of cured composite. Statistical evaluation using Analysis of Variance (single factor) showed that the photosensitization efficiency of CQ and PPD are comparable. However, their combination showed synergistic effect for properties such as DTS and solubility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Iodonium salt improves the dentin bonding performance in an experimental dental adhesive resin

The aim of this study was to evaluate the influence of an iodonium salt on the immediate and long-term microtensile bond strength to dentin of an experimental dental two-step, self-etching adhesive system. A model dental adhesive resin was formulated using bisphenol A glicidyl dimethacrylate (Bis-GMA), triethylene glicol dimethacrylate (TEGDMA), and hydroxyethyl methacrylate (HEMA), which was polymerized using four combinations of photo-initiators and coinitiators. A group using only camphorquinone (CQ), two binary systems (CQ and ethyl 4-dimethylamine benzoate (CQ+EDAB), CQ and diphenyliodonium hexafluorphosphate (CQ+DPIHFP)) and a ternary system (CQ+EDAB+DPIHFP) was investigated. Clearfil SE Bond (CSEB) was used as a commercial reference. Bond strength to bovine dentin was assessed through microtensile bond tests measured in MPa in a universal testing machine. The beam specimens were stored in distilled water at 37 °C for 24 h and 1 year. Two-way ANOVA and Student–Newman–Keuls' post-hoc tests were used to compare means of groups (α=5%) and failure modes classified under magnification. After 24 h, the ternary system showed a bond strength similar to that of the binary system CQ+EDAB and the commercial material. After 1 year of storage, the μTBS values of the group CQ+EDAB+DPIHFP showed a bond strength significantly higher (p<0.05) than those of the CQ, CQ+DPIHFP, and CQ+EDAB groups and no difference from that of the CSEB group. The ternary photo-initiator system with iodonium salt maintained increased bond strength to dentin of model self-etching adhesive systems after 1 year of aging.     

Crosslinking behavior of dextran modified with hydroxyethyl methacrylate upon irradiation with visible light—Effect of concentration,coinitiator type,and solvent

This study presents the synthesis of a crosslinkable dextran as starting material for the development of new hydrogels as drug delivery system in dental applications. 2‐Hydroxyethyl methacrylate (HEMA) was coupled to dextran after activation with carbonyldiimidazole as monitored by FTIR and ¹H‐NMR spectroscopy. The Dex‐HEMA was crosslinked by visible light in the presence of camphorquinone (CQ) as photoinitiator and a coinitiator in a proper solvent. Aliphatic or aromatic amines were used as coinitiators and the content of the coinitiator was varied from 0.25 to 3.0 mol %. Diphenyliodonium chloride was added as a third component to the above photoinitiation system. It was observed that, the degree of swelling decreased upon an increase of Dex‐HEMA concentration and the water content in the solvent system due to formation of more crosslinking points, that is, increasing crosslink density (P_x). The type of coinitiator shows a prominent impact on the swelling behavior and crosslinking efficiency of hydrogels. Special cryofixation and cryofracture techniques were used to investigate the surface and interior of swollen Dex‐HEMA hydrogel samples by SEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Cyclic acetal as coinitiator for bimolecular photoinitiating systems

Cyclic acetals were used to replace the conventional amines in bimolecular photoinitiating systems. The mixtures of benzophenone derivatives and cyclic acetals were used to initiate the UV photopolymerization of 1,6-hexanedioldiacrylate (HDDA). Camphorquinone (CQ)/1,3-benzodioxole (BDO) combinations were used to initiate the visible light photopolymerization of 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) (70/30 wt%) for dental application. The kinetics was recorded by real-time infrared spectroscopy (RTIR). Ethyl 4-N,N-dimethylaminobenzoate (EDMAB) was used as control in the same photocuring condition. The results showed that the addition of cyclic acetals greatly increased the rate of polymerization (R_p) and final double bond (DC) of HDDA. Combination of p-chlorobenzophenone (CBP)/BDO had the highest initiating reactivity. BDO also showed an effective coinitiator for camphorquinone-based initiator system. Comparing with EDMAB, CBP/BDO and CQ/BDO indicated comparable initiating reactivity. Moreover, the natural component characteristics of BDO made it a promising alternative to commercial amine in biomolecular photoinitiating system.     

Efficiency of 2,2‐dimethoxy‐2‐phenylacetophenone for the photopolymerization of methacrylate monomers in thick sections

The efficiency of 2,2‐Dimethoxy‐2‐phenylacetophenone (DMPA) for the photopolymerization of methacrylate monomers in thick sections was assessed. DMPA is an efficient photoinitiator for thick sections (≈2 mm) because a fast reaction and high conversions are obtained with concentrations as low as 0.25 wt % DMPA. The polymerization rate increased when the DMPA content increased from 0.125 wt % to 0.25 wt %. However, the conversion versus irradiation time profiles in resins containing 0.25 wt % or 0.5 wt % DMPA were similar. This is attributed to the screening effect caused by excessive levels of DMPA. In addition, the consumption of DMPA under UV irradiation was accompanied by the appearance of light absorbing photoproducts. Because the absorbing species nearest to the light source absorb part of it, the light fails to reach the deeper layers of the sample. The overall effect of light screening is a reduced photoinitiation rate and double bond conversion along the irradiation path. This effect was compensated by the use of irradiation sources of higher intensity; which increased the initiation rate by increasing the production of primary radicals. DMPA is colorless and it does not require the presence of amine as coinitiator. These properties make DMPA attractive as photoinitiator of dental composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of novel antibacterial monomers (UDMQA) and their potential application in dental resin

To prepare antibacterial dental resin, a series of novel urethane dimethacrylates quaternary ammonium methacrylate monomers (UDMQAs) with different substituted alkyl chain length were synthesized, and their structures were confirmed by FTIR and ¹H‐NMR spectra. The obtained UDMQAs were used to replace 2,2‐Bis[4‐(2‐hydroxy‐3‐methacryloyloxypropyl)‐phenyl]propane (Bis‐GMA) totally as base monomers of dental resin and mixed with Tri‐ethyleneglycol dimethacrylate (TEGDMA) at the mass ratio of 50/50. The properties of these prepared resins like antibacterial activity, double bond conversion (DC), polymerization shrinkage, flexural strength (FS), and modulus (FM), water sorption and sol fraction were investigated. The most commonly used dental resin Bis‐GMA/TEGDMA (50wt/50wt) was chosen as a reference. The results showed that UDMQAs could endow dental resin with antibacterial activity. Compared with Bis‐GMA‐based dental resin, UDMQAs‐based resin had the same or higher DC, lower polymerization shrinkage, lower flexural strength and modulus, and higher water sorption and sol fraction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚氨酯型高分子硫杂蒽酮光引发剂的制备及性能研究

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

新型的含葡萄糖胺的水溶性高分子型硫杂蒽酮光引发剂

将硫杂蒽酮光引发剂（TX）和共引发剂葡萄糖胺（GA）引入同一个高分子链上,合成新型水溶性高分子型硫杂蒽酮光引发剂（PTX-GA）.通过改变PTX-GA中TX与GA的比例,合成了PTX-GA1、PTX-GA2、PTX-GA3,并通过光膨胀计实验研究了3种引发剂引发丙烯酰胺聚合的能力.研究表明这种水溶性高分子型硫杂蒽酮光引发剂即使在没有共引发剂胺的情况下,引发丙烯酰胺（AAM）的聚合效率也非常显著.同时由于它具有水溶性,而且含有生物分子,有利于改善光引发剂的生物相容性.     

Hybrid organic–inorganic macromolecular photoinitiator system for visible-light photopolymerization

Hybrid organic–inorganic macrophotoinitiator bearing pendant tertiary amine groups (OI-AH) was prepared by hydrolytic condensation of a silane containing amino groups. The macromolecular amino-functionalized photoinitiator was used in combination with camphorquinone (CQ) for visible-light photo-polymerization. The OI-AH was incorporated into methacrylate resins at loadings between 1 and 10 wt.%. The photodecomposition of the CQ/OI-AH in methacrylate monomers under visible light irradiation (λ = 470 nm) was examined. The photolysis products of CQ/OI-AH were transparent at the irradiating wavelengths; consequently, the consumption of the CQ is accompanied by increased light intensity in the underlying lays. The clean and rapid photobleaching of CQ in combination with OI-AH makes this photoinitiator system very attractive for polymerization of thick sections. The evolution of monomer conversion versus irradiation time showed that the OI-AH is an efficient co-initiator of CQ because a fast reaction and high conversion of methacrylate groups result after 60 s irradiation with a LED source of 140 mW.     

Impact of radiation attenuation and temperature evolution on monomer conversion of dimethacrylate‐based resins with a photobleaching photoinitiator

The photopolymerization process of a dimethacrylate copolymer system activated by the camphorquinone (CQ)/amine photoinitiator system (1 wt%), was experimentally studied under nonisothermal conditions in 1‐ and 2‐mm thick samples by measuring double bond conversion, temperature rise and radiation attenuation through the sample during polymerization. The peak temperature in 1‐ or 2‐mm thick samples irradiated at 5 mW/cm² was 29 and 38°C, respectively. The temperature evolution during polymerization was also predicted by solving the energy balance coupled with the kinetic expressions for the reaction rate. Radiation attenuation as a function of depth by the photobleachable CQ results in spatial and temporal variation in the local rates of the kinetic steps involved. General relationships for spatiotemporal variations in concentration of a photobleaching initiator, in systems where attenuation and initiator consumption are taken into account, were used to compute local polymerization rates. The effects of radiation attenuation, photobleaching of the photoinitiator and variation of cure temperature at different depths into the resin, all compete to determine the double bond consumption. The increased radiation attenuation in the 2‐mm thick sample was accompanied by a higher cure temperature compared with the 1‐mm thick sample, and as a result, the monomer conversion averaged over the sample thickness in the 1‐ and 2‐mm thick samples was the same. Results obtained in this research highlight the inherent interlinking of thermal and radiation attenuation effects in bulk photopolymerizing systems. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Photopolymerization kinetics of dimethacrylate‐based light‐cured dental resins

The influence of certain factors [structure and concentration of tertiary amines as coinitiators, monomer composition, presence of inorganic pigments, and incident light intensity (I₀)] on the polymerization rates (R_p), polymerization quantum yields, and conversions of bisphenol A–bis(glycidyl methacrylate) (Bis‐GMA)/triethylene glycol dimethacrylate based resins was studied. The initial rate of bulk polymerization increased and the final conversion decreased with the content of Bis‐GMA in the mixture. In contrast, it was established that, for all monomer compositions, the R_p grew when increasing the I₀, the R_p being directly proportional to the square root of I₀. Such behavior is in agreement with the well‐known kinetic expression for the ideal radical photoinitiated polymerization in solution of monofunctional monomers, in spite of the complexity of the dimethacrylate mixtures that were studied. Both the structure and the concentration of reducing amine affected the efficiency of the initiator system and therefore the kinetic behavior of polymerization of these formulations under irradiation. The rate of polymerization increased with the increase of coinitiator concentration over the interval of 0–1%, but later it diminished when increasing the amine content, suggesting that the excess coinitiator retards the polymerization process. The study of the photoreduction of camphorquinone in the presence of different amines showed that the efficiency of the coinitiator depends not only on its ability to photoreduce camphorquinone, forming amine‐derived radicals, but also on the reactivity of these radicals toward the initiation of acrylic monomer polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1016–1023, 2005     

Efficient visible photoinitiator with high‐spectrum stability in an acid medium for free‐radical and free‐radical‐promoted cationic photopolymerization based on erythrosine B derivatives

Three dye‐linked photoinitiators with excellent spectral stability in an acid medium were synthesized by the covalent bonding of a coinitiator (tertiary amine) and a benzoyl group or two coinitiators to the phenolic and carboxyl group position of erythrosine B. The combination of the iodonium salt and free tertiary amino used to initiate the free‐radical/cationic visible photopolymerization was investigated to acquire the relationship between the structure and performance. The photoinitiating ability of the derivative with the phenolic position bearing a coinitiator was poorer than of the derivative with the carboxyl group bearing one because of the strong back electron transfer of the former. For the derivative with a linked coinitiator on the carboxyl position, the proximity effect between the sensitizer and the coinitiator moiety resulted in an excellent photoinitiating ability for radical/cationic polymerization; this suggested its potential for application. Although radical/cationic photopolymerization could be initiated by the derivative/coinitiator/iodonium salt, the different component ratios between them had different effects on these two polymerizations; this provided useful information for the design of effective photoinitiators for different polymerizations. On the basis of the fluorescence quenching and photopolymerization results, a corresponding synergistic mechanism was proposed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43035.     

含共引发剂胺的聚氨酯型高分子光引发剂的制备及性能研究

通过异佛尔酮二异氰酸酯（IPDI）、2-（2,3-二羟基）丙氧基硫杂蒽酮（HPTX）及N取代的二乙醇胺进行逐步聚合反应,将硫杂蒽酮结构及共引发剂胺结构都引入到同一高分子链上,得到侧链含有硫杂蒽酮、主链含有共引发剂胺的聚氨酯型高分子光引发剂（PU-IBTX、Pu—IMTX和Pu．IPTX）。傅立叶红外变换光谱和核磁共振氢谱证实了高分子光引发剂的结构。紫外光谱证实了高分子链的结构对硫杂蒽酮单元的最大紫外吸收几乎没有影响。用光致差示量热计研究聚氨酯型高分子光引发剂引发聚氨酯丙烯酸酯（PUA）树脂的光聚合反应,结果表明,Pu—IPTX是引发PUA光聚合最有效的光引发剂。     

Selective removal of 1,2‐propanediol and 1,2‐butanediol from bio‐ethylene glycol by catalytic reaction

Ethylene glycol (EG), synthesized from biomass, frequently contains refractory 1,2‐propanediol (PDO) and 1,2‐butanediol (BDO). Selective removal of PDO and BDO was realized herein by catalytic dehydration to form volatile aldehydes, ketones, and acetals. Various acidic and basic catalysts were screened under a range of conditions for the conversion of a mixture containing 73 wt % EG, 20 wt % PDO, and 7 wt % BDO. Over H‐Beta 26 zeolite, the most selective catalyst among tested, PDO and BDO conversions reached 99.1 and 99.3%, respectively, after 4 h reaction at 453 K, with separation factors over 2. The activation energies for EG, PDO, and BDO dehydration were ca. 99.3, 69.9, and 54.0 kJ/mol, respectively, accounting for the high reactivity of PDO and BDO. The dehydration largely proceeded in the micropores of H‐Beta and depended on the number of strong Brønsted acid sites, but excessively strong acid sites enhanced the polymerization of EG. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4032–4042, 2017     

Polymeric Michler's ketone photoinitiator containing coinitiator amine

Novel polymeric photoinitiator based on Michler's ketone (MK) (PMKPR) was synthesized by introducing coinitiator amine and MK into the same polymeric chain as well as the low‐molecular weight model compounds. UV–vis spectra show that PMKPR has the characteristic UV–vis absorption of MK. The photobleaching behavior of PMKPR and the model compounds were studied, indicating that the photobleaching rate of PMKPR is much faster than that of model compounds. Two types of monomer with different functionality, 2,2‐bis[4‐(acryloxypolyethoxy)phenyl] propane (A‐BPE‐10) and trimethylopropane triacrylate (TMPTA), were chosen to be initiated by these photoinitiators. The result indicates that PMKPR is an efficient photoinitiator for polymerization of A‐BPE‐10 and TMPTA. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

A low migration phosphine to overcome the oxygen inhibition in new high performance photoinitiating systems for photocurable dental type resins

The objective of this work was to propose a novel low migration additive (i.e. a phosphine) to overcome the oxygen inhibition in a camphorquinone (CQ) base photoinitiating system for the polymerization of methacrylates (e.g. a bisphenol A‐glycidyl methacrylate (Bis‐GMA)/triethyleneglycol dimethacrylate (TEGDMA) blend (70%/30% w/w)) upon exposure to a commercial blue light emitting diode centred at 477 nm. CQ/amine/phosphine derivative or CQ/amine/iodonium salt/phosphine derivative combinations were studied. Real‐time Fourier transform IR and photo‐DSC experiments were used to monitor the polymerization profiles. Remarkably, it was found that the addition of the new phosphine derivative to CQ/amine or CQ/amine/iodonium salt noticeably improved the rate of polymerization and the final conversion in air. A low migration was found for this additive as shown by HPLC experiments in agreement with a copolymerizable behaviour. No additional yellowing of the film was observed. Electron spin resonance spectrometry was used to detect the produced radicals. The overall chemical mechanisms are investigated and discussed. © 2016 Society of Chemical Industry     

Effects of composition and extrusion parameters on the morphological development and rheological properties of PP/PC blends. Co-continuity investigation

In this work, a new dimethacrylate monomer named ??,????-Bis(4-(2??-hydroxy- 3??methacryloyloxy-propoxy)-3,5-dimethylphenyl)-1,4-diisopropyl-benzene (??,????-BHMPDDB) was synthesized to replace 2,2-bis[4-(2??-hydroxy-3??-methacryloyloxy-propoxy)-phenyl]propane (Bis-GMA) as one component of dental composite materials. The structures of ??,????-BHMPDDB and its intermediate product ??,????-Bis(4-oxiranylmethoxy-3,5-dimethylphenyl)-1,4-diisopropylbenzene (??,????-BODDB) were confirmed by FT-IR, ¹H-NMR, and elemental analysis. ??,????-BHMPDDB was mixed with TEGDMA to form a new dental resin, and double bond conversion, polymerization shrinkage, contact angle, water sorption and solubility, flexural strength and modulus before and after water immersion of this new dental resin were studied. Compared with the commonly used Bis-GMA/TEGDMA dental resin, ??,????-BHMPDDB/TEGDMA had higher double bond conversion (60.5?±?0.3?%), lower polymerization shrinkage (5.6?%), and comparable flexural strength before water immersion (94.1?±?3.9?MPa), which made ??,????-BHMPDDB/TEGDMA having potential to replace Bis-GMA/TEGDMA as matrix phase of dental composites materials. However, ??,????-BHMPDDB/TEGDMA also had drawbacks, such as higher water sorption (5.06?±?0.17?%), water solubility (2.37?±?0.1?%), and lower flexural strength after water immersion (71.4?±?14.6?MPa).     

Novel N‐ethyl‐2‐styrylquinolinium iodides as sensitizers in the photoinitiated free‐radical polymerization of trimethylolopropane triacrylate. II

Results of kinetic studies of two‐component photoinitiator systems used in the visible‐light photoinduced polymerization of 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate are presented. Nine different styrylquinolinum dyes coupled with n‐butyltriphenylborate as a coinitiator have been used as photoinitiating systems. Reactive radicals that initiate the polymerization are formed by the well‐known mechanism of photoinduced electron transfer between dye cations acting as electron acceptors and borate anions acting as electron donors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of a dimethacrylates monomer with low shrinkage and water sorption for dental application

In this study, a dimethacrylates monomer 1,3-bis[2-(4-(2′-hydroxy-3′-methacryloyloxy-propoxy)phenyl)-2propyl]benzene (BMPB) was synthesized to replace 2,2-bis[4-(2′-hydroxy-3′-methacryloyloxy-propoxy)phenyl]propane (Bis-GMA) as one component of dental restorative material with the aim of reducing polymerization shrinkage and water sorption. The structure of BMPB was confirmed by FTIR, ¹H-NMR, and elemental analysis. Double bond conversion, polymerization shrinkage, contact angle, water sorption, solubility, flexural strength, and flexural modulus of BMPB/tri(ethylene glycol) dimethacrylate (TEGDMA) based resin were measured. Bis-GMA/TEGDMA based resin was used as reference. The results illustrated that double bond conversion, polymerization shrinkage, water sorption, and solubility of BMPB/TEGDMA were lower than that of Bis-GMA/TEGDMA (P < 0.05). BMPB/TEGDMA had the same flexural strength with Bis-GMA/TEGDMA (P > 0.05), but higher flexural modulus (P < 0.05). Therefore, BMPB could possibly replace Bis-GMA as one component of dental restorative materials with the advantages of similar mechanical properties, being slightly more hydrophobic but presenting less shrinkage. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012