Ethoxylated Bisphenol A Dimethacrylate Research Articles

Antibacterial Dental Composites with Chlorhexidine and Mesoporous Silica

One of the leading causes for the failure of dental composite restorations is secondary caries. Effectively inhibiting cariogenic biofilms and reducing secondary caries could extend the service life of composite restorations. Dental composites releasing antibacterial agents such as chlorhexidine (CHX) have shown biofilm-inhibitory efficacy, but they usually have poor physical and mechanical properties. Herein, we present a study of a new method to encapsulate and release CHX from dental composite using mesoporous silica nanoparticles (MSNs). SBA-15 MSNs were synthesized according to a reported procedure. CHX (62.9 wt%) was encapsulated into dried MSN from 0.3 M CHX ethanol solution. The dental composites containing 0% (control), 3%, 5%, and 6.3% CHX or the same amounts of CHX entrapped in MSN (denoted as CHX@MSN) were fabricated with methacrylate monomers and silanized glass fillers (CHX or CHX@MSN + glass filler particle = 70 wt%). The monomer mixture consisted of bisphenol A glycidyl methacrylate (BisGMA), hexanediol dimethacrylate (HDDMA), ethoxylated bisphenol A dimethacrylate (EBPADMA), and urethane dimethacrylates (UEDMA) at a weight ratio of 40:30:20:10. The composites were tested for CHX release and recharge, flexural strength and modulus (at 24 hr and 1 mo), surface roughness, in vitro wear, and antibacterial activity against Streptococcus mutans and Lactobacillus casei (in both planktonic growth and biofilm formation). The results showed that the composites with CHX@MSN largely retained mechanical properties and smooth surfaces and showed controlled release of CHX over a long time. In contrast, the composites with directly mixed CHX showed reduced mechanical properties, rough surfaces, and burst release of CHX in a short time. The composites with CHX either directly mixed or in MSN showed strong inhibition to S. mutans and L. casei. This research has demonstrated the successful application of MSNs as a novel nanotechnology in dental materials to inhibit oral biofilm without sacrificing materials’ mechanical properties and surface integrity.

Influence of the base and diluent monomer on network characteristics and mechanical properties of neat resin and composite materials.

This study evaluated the effect of the combination of two dimethacrylate-based monomers [bisphenol A diglycidyl dimethacrylate (BisGMA) or bisphenol A ethoxylated dimethacrylate (BisEMA)] with diluents either derived from ethylene glycol dimethacrylate (ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate) or 1,10-decanediol dimethacrylate (D3MA) on network characteristics and mechanical properties of neat resin and composite materials. The degree of conversion, maximum rate of polymerization and water sorption/solubility of unfilled resins and the flexural strength and microhardness of composites (after 24 h storage in water and 3 months storage in a 75 vol% ethanol aqueous solution) were evaluated. Data were analyzed with two-way ANOVA and Tukey's test (α = 0.05). The higher conversion and lower water sorption presented by BisEMA co-polymers resulted in greater resistance to degradation in ethanol compared with BisGMA-based materials. In general, conversion and mechanical properties were optimized with the use of long-chain dimethacrylate derivatives of ethylene glycol. D3MA rendered more hydrophobic materials, but with relatively low conversion and mechanical properties.

Polycaprolactone/oligomer compound scaffolds for cardiac tissue engineering

Polycaprolactone (PCL), a synthetic biocompatible and biodegradable polymer generally used as a scaffold material for tissue engineering applications. The high stiffness and hydrophobicity of the PCL fiber mesh does not provide significant cell attachment and proliferation in cardiac tissue engineering. Towards this goal, the study focused on a compound of PCL and oligomer hydrogel [Bisphenol A ethoxylated dimethacrylate (BPAEDMA)] processed into electrospun nanofibrous scaffolds. The composition, morphology and mechanical properties of the compound scaffolds, composed of varying ratios of PCL and hydrogel were characterized by scanning electron microscopy, infrared spectroscopy and dynamic mechanical analyzer. The elastic modulus of PCL/BPAEDMA nanofibrous scaffolds was shown to be varying the BPAEDMA weight fraction and was decreased by increasing the BPAEDMA weight fraction. Compound fiber meshes containing 75 wt % BPAEDMA oligomer hydrogel exhibited lower modulus (3.55 MPa) and contact angle of 25(o) . Rabbit cardiac cells cultured for 10 days on these PCL/BPAEDMA compound nanofibrous scaffolds remained viable and expressed cardiac troponin and alpha-actinin proteins for the normal functioning of myocardium. Cell adhesion and proliferations were significantly increased on compound fiber meshes containing 75 wt % BPAEDMA, when compared with other nanofibrous scaffolds. The results observed that the produced PCL/BPAEDMA compound nanofibrous scaffolds promote cell adhesion, proliferation and normal functioning of cardiac cells to clinically beneficial levels, relevant for cardiac tissue engineering.

Synthesis, Characterization, Antimicrobial Activity, and Adhesive Property of Amino Benzyl Group Substituted Acrylic/Methacrylic Polymers and Their Copolymers

The monomers 2-aminobenzylacrylate (2-ABA) and 2-aminobenzyl methacrylate (2-ABMA) were synthesized. The homopolymers and various compositions of copolymers with ethoxylated bisphenol-A-dimethacrylate (EBPADMA) were synthesized using free radical polymerization. The polymers were characterized by FT-IR, 1H NMR, and 13C NMR spectral techniques. The thermal property of the polymers was determined by thermogravimetric analysis and differential scanning calorimeter. The prepared adhesives were tested on leather and metal surfaces using single-lap-joint shear test method. The antimicrobial activity of polymers and copolymers has been studied using Mueller Hinton Broth method.

Development of dental resinous systems composed of bisphenol a ethoxylated dimethacrylate and three novel methacrylate monomers: Synthesis and characterization

AbstractThree novel monomers with a methacrylate unit, different chain lengths, and functional groups were synthesized and proposed as possible diluent monomers in dental resinous systems containing bisphenol A ethoxylated dimethacrylate (BisEMA) aiming at their use in dental resin mixtures. The monomers were mixed with BisEMA and photopolymerized in the presence of a photoinitiator system. The unfilled formulations were evaluated regarding their degree of conversion, thermal properties, Vickers microhardness, water sorption, water solubility, and surface morphology. The monomers presented a high conversion degree compared to control groups and have affected the glass transition temperature of the samples. Their hardness values were similar to or higher than the value found for the control group. The specimens evaluated presented a homogeneous matrix and stability throughout the water sorption and solubility tests. Considering their simplicity and effective application in synthesis, as well as the results obtained for the polymerized formulation groups, the new monomers presented here represent promising photocurable dental monomers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Low shrinkage light curable dental nanocomposites using SiO2 microspheres as fillers

Commercial resin matrixes of dental composites generally utilize diluents such as triethylene glycol dimethacrylate (TEGDMA) to reduce viscosity. However, the diluents exhibited adverse effects such as higher volume shrinkage and diminished mechanical properties of the dental composites. To overcome these adverse effects, developing of both inorganic fillers and resin monomers is necessary to improve the properties of dental composite. In this work, monodispersed silica microspheres with a diameter of 400nm were synthesized via the Stöber process. The as-prepared particles were silanized with 3-methacryloxypropyltrimethoxysilane (γ-MPS) and used as fillers. Additionally, ethoxylated bisphenol A dimethacrylate (EBPADMA) with lower viscosity and higher molecular mass was introduced as a base resin monomer, which could be used as resin matrixes with a low amount of diluent. Various resin mixtures of EBPADMA, bisphenol A diglycidyl dimethacrylate (Bis-GMA) and TEGDMA were prepared, which had a similar filler content (71wt.%), and their mechanical properties, volume shrinkage, depth of cure and light transmission were examined. Among them, the resin mixture containing 70% EBPADMA and 30% TEGDMA exhibited the best compression strength (238.1±5.4MPa), depth of cure (4.02±0.04mm) and the lowest volume shrinkage (2.27%).

Detection and quantification of monomers in unstimulated whole saliva after treatment with resin‐based composite fillings in vivo

Resin-based dental restorative materials contain allergenic methacrylate monomers, which may be released into saliva after restorative treatment. Monomers from resin-based composite materials have been demonstrated in saliva in vitro; however, studies analyzing saliva after restorative therapy are scarce. The aim of this study was to quantify methacrylate monomers in saliva after treatment with a resin-based composite filling material. Saliva was collected from 10 patients at four start points--before treatment, and 10 min, 24 h, and 7 d after treatment--and analysed by combined chromatography/mass spectrometry. The monomers bisphenol-A diglycidyl methacrylate (Bis-GMA), 2-hydroxyethyl methacrylate (HEMA), and urethane dimethacrylate (UDMA) were detected and quantified in the samples collected shortly (10 min) after treatment. The amounts detected ranged from 0.028 to 9.65 μg ml(-1) for Bis-GMA, from 0.015 to 0.19 μg ml(-1) for HEMA, and from 0.004 to 1.2 μg ml(-1) for UDMA. Triethyleneglycol dimethacrylate (TEGDMA) was detected in four of the samples. Ethoxylated bisphenol-A dimethacrylate (Bis-EMA) was not detected. Monomers were not detected in saliva samples collected before treatment, or 24 h or 7 d after treatment, with the exception of one sample, 24 h after treatment, in which HEMA was detected. In conclusion, monomers from the investigated resin-based composite and adhesive system were present in saliva shortly after treatment. One week after treatment, no monomers could be detected in patients' saliva samples.

Novel self-directed dual surface metallisation via UV-curing technique for flexible polymeric capacitors

Polymer composites with metal nanoparticles have attracted considerable attention over the past years due to numerous solid state potential applications in organic electronics and microelectronic devices. Here we report the first example of a novel, rapid and convenient self-directed dual surface nano-silvering of a polymer film by a simple single-stage process of free-radical photopolymerisation (UV-curing). The major component of the composite is bisphenol A ethoxylate dimethacrylate (BEMA) which can be photopolymerised by a photo-reactive initiator (Darocur 1173) under UV light. Under the same conditions of UV irradiation, silver nitrate decomposes and the silver ion is deposited as metal while the pyrrole is oxidised to polypyrrole. It is demonstrated that this versatile method can open up promising prospective in obtaining innovative composite polymeric capacitors for highly flexible and/or non-planar electronics application. The obtained films are characterised by Scanning Electron Microscopy (SEM) and electrical measurements.

Thermal degradation and isoconversional kinetic analysis of light-cured dimethacrylate copolymers

Thermal degradation kinetics of copolymers based on bis-phenol A ethoxylated dimethacrylate (Bis-EMA) with triethylene glycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) with TEGDMA in wt/wt ratios 30/70, 50/50, or 70/30 were investigated using thermogravimetric analysis as a means to provide specific information regarding the internal structures of these resins. Thermogravimetric scans were taken at four different heating rates to perform an isoconversional analysis to determine the change of the effective activation energy as a function of conversion. A two-step degradation mechanism was found to occur in almost all copolymer compositions attributed to the existence of inhomogeneities in the macromolecular structure and the formation of weak links inside the polymeric network.

Preparation and characterization of UV-cured acrylic nanocomposites based on modified organophilic montmorillonites

UV-cured nanocomposites have been prepared through the photopolymerization of the acrylic resin BEMA (Bisphenol A ethoxylate dimethacrylate) added with organophifilic montmorillonites. Two types of commercially available nanoclays namely Cloisite 30B and Cloisite Na+ were further modified with organic compatibilizers (dodecylsuccinic anhydride, octadecylamine, octadecanoic alcohol and octadecanoic acid) in order to increase their basal spacing and improve the dispersion in the acrylic matrix. The modification with the organic compatibilizers determined an increase of the interlayer distance, as revealed by XRD (X-Ray Diffraction) analysis. The different types of the modified nanoclays were then dispersed in BEMA monomer at 5% m/m concentration and UV-cured in order to prepare the nanocomposites. XRD measurements performed on the nanocomposites showed a slight increase of the interlayer distance indicating the formation of intercalated structures. The photopolymerization reaction was monitored through real-time FT-IR (Fourier Transform Infrared Spectroscopy) in order to check any influence of the nanofillers on the cure kinetics. The nanocomposites were investigated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetric) analyses and compared to the neat UV-cured resin. The presence of the nanofillers did not influence the glass transition temperature (Tg) of the acrylic resin; in addition an increase of the thermal stability in air of the nanocomposites was evidenced through TG analysis.

Influence of BisGMA, TEGDMA, and BisEMA contents on viscosity, conversion, and flexural strength of experimental resins and composites

Different monomer structures lead to different physical and mechanical properties for both the monomers and the polymers. The objective of this study was to determine the influence of the bisphenylglycidyl dimethacrylate (BisGMA) concentration (33, 50 or 66 mol%) and the co-monomer content [triethylene glycol dimethacrylate (TEGDMA), ethoxylated bisphenol-A dimethacrylate (BisEMA), or both in equal parts] on viscosity (eta), degree of conversion (DC), and flexural strength (FS). Eta was measured using a viscometer, DC was obtained by Fourier transfer Raman (FT-Raman) spectroscopy, and FS was determined by three-point bending. At 50 and 66% BisGMA, increases in eta were observed following the partial and total substitution of TEGDMA by BisEMA. For 33% BisGMA, eta increased significantly only when no TEGDMA was present. The DC was influenced by BisGMA content and co-monomer type. Mixtures containing 66% BisGMA showed a lower DC compared with mixtures containing other concentrations of BisGMA. The BisEMA mixtures had a lower DC compared with the TEGDMA mixtures. The FS was influenced by co-monomer content only. BisEMA mixtures presented a statistically lower FS, followed by TEGDMA + BisEMA mixtures, and then by TEGDMA mixtures. Partial or total replacement of TEGDMA by BisEMA increased eta, which was associated with the observed decreases in DC and FS. Although the BisGMA content influenced the DC, it did not affect the FS results.

Amorphous Calcium Phosphate Composites and Their Effect on Composite–Adhesive–Dentin Bonding

This study evaluates the bond strength and related properties of photo-polymerizable, remineralizing amorphous calcium phosphate (ACP) polymeric composite–adhesive systems to dentin after various periods of aqueous aging at 37°C. An experimental ACP base and lining composite was made from a photo-activated resin comprising 2,2-bis[p-(2′-hydroxy-3′-methacryloxypropoxy)phenyl]propane (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA) and zirconyl dimethacrylate (ZrDMA); designated BTHZ. An experimental orthodontic composite was formulated from a photo-activated resin comprising ethoxylated bisphenol A dimethacrylate (EBPADMA), TEGDMA, HEMA and methacryloxyethyl phthalate (MEP); designated ETHM. In both composite series three fillers were compared: (i) freshly precipitated zirconium-modified ACP (as-prepared Zr-ACP), (ii) milled Zr-ACP and (iii) an ion-leachable fluoride glass. In addition to the shear bond strength (SBS), work to fracture and failure modes of the orthodontic composites were determined. The SBS of the base and lining ACP composites appeared unaffected by filler type or immersion time. In the orthodontic ACP composite series, milled ACP composites showed initial mechanical advantages over as-prepared ACP composites and produced higher incidence of a failure mode consistent with stronger adhesion. After six months of aqueous exposure, 80% of specimens failed at the dentin–primer interface, with a 42% overall reduction in bond strength. BTHZ and ETHM based ACP composites are potentially effective anti-demineralizing–remineralizing agents with possible clinical utility as protective base-liners and orthodontic cements, respectively. The analysis of the bond strength and failure modalities suggests that milled ACP composites may offer greater potential in clinical applications.

Degree of vinyl conversion in experimental amorphous calcium phosphate composites

An experimental dental composite, based on amorphous calcium phosphate (ACP) with the potential to arrest caries development and regenerate mineral-deficient tooth structures has recently been developed. The aim of this study was to assess the degree of vinyl conversion (DVC) attained in experimental composites based on zirconia-modified ACP. Photo-activated resins were based on ethoxylated bisphenol A dimethacrylate (EBPADMA) [ETHM series with varying EBPADMA/triethylene glycol dimethacrylate (TEGDMA) molar ratios assigned 0.5-ETHM I, 0.85-ETHM II and 1.35-ETHM III], or 2,2-bis[p-(2′-hydroxy-3′-methacryloxypropoxy)phenyl]-propane (Bis-GMA) [BTHZ series]. To asses a possible effect of filler particle size on DVC, composites containing 60 mass % resin and 40 mass % of either milled ACP (mACP; median diameter d m = 0.9 μm) or coarse ACP (cACP; d m = 6.0 μm) were prepared, and irradiated with LED curing unit for 40 s. The DVC was calculated as the % change in the ratio of the integrated peak areas between the aliphatic and aromatic absorption bands determined by Fourier transform infrared spectroscopy (FTIR). The highest DVCs values were attained in mACP-BTHZ, cACP-BTHZ and mACP-ETHM III formulations. DVC of tested ACP composites (on average (76.76 ± 4.43)%) compares well with or exceeds DVCs values reported for the majority of commercial materials.

Accelerated controlled radical polymerization of methacrylates

AbstractBACKGROUND: Nitroxide adducts 1,1‐ditertbutyl‐1‐(1‐methyl‐1‐cyanoethoxy)‐amine (AIBN/DBN), 1,1‐ditertbutyl‐1‐(benzoylperoxy)‐amine (BPO/DBN) and 2,2,6,6,‐tetramethyl‐4‐oxo‐1‐(1‐methyl‐1‐cyanoethoxy)‐piperidine (AIBN/4‐OXO‐TEMPO) were prepared and evaluated as stabilized unimolecular initiators for controlled radical polymerization of methacrylate monomers using sulfuric acid as an accelerating additive. Their effectiveness was evaluated from polymerization rates, molecular weight control and dispersity (D) of the polymers. Thermal stabilities of the polymers were also examined. The monomers used were methyl methacrylate, triethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (EBPADMA).RESULTS: Polymerization was accomplished at 70 and 130 °C in 5 min to 144 h. The value of D of poly(methyl methacrylate) (PMMA) was 1.05–1.22. The glass transition temperature (Tg) for PMMA was 122–127 °C. The activity of the chain ends was established by chain extension and controlled polymerization was established by plotting Mn versus monomer conversion. First‐order kinetics in monomer consumption was established and an electron paramagnetic resonance study was conducted. Decomposition temperature (Td) for PMMA was 360–380 °C, for poly(TEGDMA) was 300–380 °C and for poly(EBPADMA) was 360–440 °C. Photoinitiation without additive yielded no polymer. Thermal initiation by AIBN/4‐OXO‐TEMPO was the fastest.CONCLUSIONS: The initiators are applicable in low‐temperature additive‐enhanced controlled polymerization of methacylates and dimethacrylates, producing polymers with excellent attributes and a low value of D. Copyright © 2008 Society of Chemical Industry

Light-Cured Dimethacrylate-Based Resins and Their Composites: Comparative Study of Mechanical Strength, Water Sorption, and Ion Release

This study explored how resin type affects selected physicochemical properties of complex methacrylate copolymers and their amorphous calcium phosphate (ACP)-filled and glass-filled composites. Two series of photo-polymerizable resin matrices were formulated employing 2,2-bis[p-(2'-hydroxy-3'-methacryloxypropoxy)phenyl]propane (Bis-GMA) or an ethoxylated bisphenol A dimethacrylate (EBPADMA) as the base monomer, Unfilled copolymers and composites filled with a mass fraction with 40 %, 35 % and 30 %, respectively, of ACP or the un-silanized glass were assessed for biaxial flexure strength (BFS), water sorption (WS) and mineral ion release upon immersion in HEPES-buffered saline solution for up to six months. Substituting EBPADMA for Bis-GMA significantly reduced the WS while only marginally affected the BFS of both dry and wet copolymers. Independent of the filler level, both dry and wet ACP composites formulated with either BTHM or ETHM resins were mechanically weaker than the corresponding copolymers. The BFS of ACP composite specimens after 1 month in saline did not further decrease with further aqueous exposure. The BFS of glass-filled composites decreased with the increased level of the glass filler and the time of aqueous exposure. After 6 months of immersion, the BFS of glass-filled BTHM and ETHM composites, respectively, remained 58 % and 41 % higher than the BFS of the corresponding ACP composites. Ion release data indicated that a minimum mass fraction of 35 % ACP was required to attain the desired solution supersaturation with respect to hydroxyapatite for both the BTHM and ETHM derived composites.

Contraction Stress Determinants in Dimethacrylate Composites

The influence of composite organic content on polymerization stress development remains unclear. It was hypothesized that stress was directly related to differences in degree of conversion, volumetric shrinkage, elastic modulus, and maximum rate of polymerization encountered in composites containing different BisGMA (bisphenylglycidyl dimethacrylate) concentrations and TEGDMA (triethylene glycol dimethacrylate) and/or BisEMA (ethoxylated bisphenol-A dimethacrylate) as co-monomers. Stress was determined in a tensilometer. Volumetric shrinkage was measured with a mercury dilatometer. Elastic modulus was obtained by flexural test. We used fragments of flexural specimens to determine degree of conversion by FT-Raman spectroscopy. Reaction rate was determined by differential scanning calorimetry. Composites with lower BisGMA content and those containing TEGDMA showed higher stress, conversion, shrinkage, and elastic modulus. Polymerization rate did not vary significantly, except for the lower value of the 66% TEGDMA composite. We used linear regressions to evaluate the association between polymerization stress and conversion (R(2)=0.905), shrinkage (R(2)=0.825), and modulus (R(2)=0.623).

Copolymerization kinetics of dental dimethacrylate resins initiated by a benzoyl peroxide/amine redox system

AbstractThe copolymerization of four dental dimethacrylates initiated by a benzoyl peroxide/4‐N,N‐dimethylamino phenethyl alcohol redox system at 37°C was studied with differential scanning calorimetry. The studied dimethacrylates were viscous bisphenol A glycidyl dimethacrylate (Bis‐GMA), bisphenol A ethoxylated dimethacrylate (Bis‐EMA), and urethane dimethacrylate (UDMA), which were characterized as base monomers, and low‐viscosity triethylene glycol dimethacrylate (TEGDMA), which was characterized as a diluent. Also, three series of dimethacrylate copolymers were prepared by incremental additions (12.5 wt %) of TEGDMA to a base comonomer (Bis‐GMA, UDMA or Bis‐EMA). The maximum rate of homopolymerization of the dimethacrylates followed the order of Bis‐GMA > UDMA > TEGDMA > Bis‐EMA, and the final degree of conversion of the corresponding homopolymers followed the order of TEGDMA > UDMA > Bis‐EMA > Bis‐GMA. A reaction–diffusion‐controlled termination region was clear in all monomers and started earlier in bulky and rigid Bis‐GMA and Bis‐EMA (followed by the more flexible UDMA and TEGDMA) but lasted longer in the Bis‐EMA polymerization. The maximum rate of copolymerization and degree of conversion of copolymers of a base monomer with TEGDMA changed monotonically with an increase in the TEGDMA content in the initial comonomer mixture. A synergistic effect was clear only in the final double‐bond conversion of Bis‐GMA/TEGDMA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Thermal degradation of light-cured dimethacrylate resins: Part I. Isoconversional kinetic analysis

The thermal degradation of resins based on bis-phenol A glycidyl dimethacrylate (Bis-GMA), bis-phenol A ethoxylated dimethacrylate (Bis-EMA), urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) was investigated using thermogravimetric analysis. Four different heating rates were employed for its polymer in order to have adequate data to perform an isoconversional analysis. Activation energies were estimated as a function of the extent of degradation using a differential and an integral method. The observed differences were interpreted in terms of degradation mechanisms, which are highly depended on the structural characteristics of the corresponding resin. The existence of only a small number of defects in the network structure of Bis-GMA and Bis-EMA resins together with their stiff aromatic nuclei lead to the formation of a rigid network with high thermal stability and to decomposition in one-step. In contrast, inhomogeneities in the network structure of TEGDMA and UDMA resins, mainly due to the formation of primary cycles during polymerization, result in a two-step degradation mechanism at much lower temperatures. The hydrogen bonding ability of Bis-GMA and UDMA monomer units was also found to play an important role during thermal degradation of these resins.

Accelerant‐promoted free radical polymerization of methacrylates by stabilized nitroxide unimolecular initiators: synthesis and characterization

AbstractBACKGROUND: This investigation evaluates the effectiveness of initiator adducts for living and controlled polymerization of methacrylates, crosslinking of dimethacrylates and thermal stabilities of the resulting polymers. Adducts of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy with benzoyl peroxide and with azobisisobutyronitrile were prepared and evaluated as stabilized unimolecular initiators for the free radical polymerization of methacrylate monomers using sulfuric acid as catalyst. The monomers used were methyl methacrylate, triethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (EBPADMA).RESULTS: Successful polymerization was achieved at 70 and 130 °C with reaction times ranging from 45 min to 120 h. The dispersity (D) of poly(methyl methacrylate) (PMMA) was 1.09–1.28. The livingness and extent of control over polymerization were confirmed with plots of Mn evolution as a function of monomer conversion and of the first‐order kinetics. The glass transition temperature (Tg) for PMMA was 123–128 °C. The degradation temperature (Td) for PMMA was 350–410 °C. Td for poly(TEGMA) was 250–310 °C and for poly(EBPADMA) was 320–390 °C.CONCLUSION: The initiators are suitable for free radical living and controlled polymerization of methacrylates and dimethacrylates under mild thermal and acid‐catalyzed conditions, yielding medium to high molecular weight polymers with low dispersity, high crosslinking and good thermal stability. Copyright © 2008 Society of Chemical Industry

Sorption and desorption parameters of water or ethanol in light‐cured dental dimethacrylate resins

AbstractTwo cycles of sorption/desorption of water or ethanol by light‐cured dental resins of bisphenol A glycol dimethacrylate (Bis‐GMA), bisphenol A ethoxylated dimethacrylate (Bis‐EMA) urethane dimethacrylate (UDMA) triethylene glycol dimethacrylate and decanediol dimethacrylate (D3MA) were studied. The experimental curves mt = f(t) taken for the first water sorption by poly‐Bis‐GMA, poly‐Bis‐EMA and poly‐UDMA showed a maximum. A maximum was also observed in the curve obtained for first sorption of ethanol by poly‐Bis‐GMA. In all other cases, the curves for sorption or desorption of water or ethanol showed Fickian behavior. The experimental data obtained for first sorption of water or ethanol were perfectly fitted to a new proposed equation, which predicts water or ethanol sorption with simultaneous extraction of unreacted the monomer. This equation gave us the possibility for the determination of the diffusion coefficient of the extraction of the unreacted Bis‐GMA during the water and ethanol sorption, as well as the diffusion coefficient of the extraction of the unreacted Bis‐EMA and UDMA during the water sorption. The maximum water or ethanol absorbed at equilibrium and the diffusion coefficient are determined from the second sorption/desorption cycle during which the extraction of the monomer is negligible. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008