Formulation of Visible Light-Curable Glass-Ionomer Cements Containing N-Vinylpyrrolidone

Abstract

The best graft ratio of the light-curable N-vinylpyrrolidone (NVP) modified terpolymers (LC NVPM TPs) with the molar ratio of 8:2:1 (acrylic acid:itaconic acid:NVP) and the optimal formulation for this light-curable glass-ionomer cement, based on the best graft ratio, were determined. Statistical models were utilized to predict the optimal formulations. The terpolymer was prepared using a free-radical polymerization reaction. The LC NVPM TPs were produced by grafting 2-isocyanatoethyl methacrylate (IEM) onto the terpolymer. Cements were formed by both light-curing and the reaction with glass particles. Compressive strength was used as the basic screening property to find the optimal formulation. Diametral tensile and flexural strengths were also used to evaluate the mechanical properties. The strength values were recorded on the specimens conditioned in distilled water at 37&C for 24 hours or 7 days. The best graft ratio for IEM in this system was 15% of the terpolymer by a molar ratio. The optimal formulation was found to be at the weight ratio of 55:15:30 [LC NVPM TP:2-hydroxyethyl methacrylate (HEMA): H₂O]. Stress-strain curves showed that a relatively high amount of water in the formulation led to higher elastic modulus and proportional limit and lower malleability, whereas a relatively high amount of HEMA gave the opposite results. The light-curable NVP modified glass-ionomer cements showed statistically significantly higher values in compressive, diametral tensile, and flexural strengths than the commercial Vitremer^TM.     

Synthesis and formulation of vinyl-containing polyacids for improved light-cured glass-ionomer cements

Vinyl-containing poly(acrylic acid-co-itaconic acid) copolymers were synthesized and used to formulate light-curable cements containing reactive glass fillers (Fuji II LC). The conditions for light curing were studied and optimized. Effects of molecular weight (MW), grafting ratio, comonomer, liquid composition, powder/liquid (P/L) ratio, glass powder and aging were evaluated. The results show that the vinyl-containing glass-ionomer cements (GICs) prepared in this study exhibit higher compressive strength (CS, 225.6 MPa), diametral tensile strength (DTS, 28.4 MPa) and much higher flexural strength (FS, 116.4 MPa), as compared to commercial Fuji II LC GIC (186.6 in CS, 19.1 in DTS and 57.1 in FS). The optimal light-exposure time was found to be around 10 min, and concentrations of CQ and DC were 0.5% (by weight) and 1.0%, respectively. Effects of MW, grafting ratio, P/L ratio and content of polymer in the liquid formulation were significant. The highest strengths were found for the optimal formulations where the MW was 15,000 (weight average), grafting ratio 25 mol%, P/L ratio 2.7 and liquid composition 50:20:30. During aging, the cement showed an increase of strength over the first week and then no change for a month. SEM analysis suggests that more integrated microstructures and smaller glass particles can lead to higher FS and higher polymer content in GICs leads to tough fracture surface and plastic deformation.     

PREPARATION AND EVALUATION OF ACRYLIC ACID,ITACONIC ACID,AND N-METHACRYLOYLGLUTAMIC ACID COPOLYMERS FOR USE IN GLASS-IONOMER TYPE DENTAL RESTORATIVES

A series of copolymers containing various molar ratios of acrylic acid, itaconic acid and N-methacryloylglutamic acid were prepared in aqueous solution, using standard free-radical polymerization conditions. Specimens for mechanical property studies were prepared by mixing water solutions of the copolymers (50:50, wt:wt) with a commercial, calcium-fluoroaluminosilicate glass powder, with curing or hardening achieved by salt-bridge formation. The glass powder used in the formulation(s) was the same as that used in Fuji II (GC America) glass-ionomer. The working and setting times of the various formulations were evaluated. The compressive strength was used as the basic screening property to find the optimum molar ratio of the three monomers. The diametral tensile strength, flexural strength and Knoop surface hardness of the cured materials were also determined. All mechanical properties were measured after the specimens were conditioned in distilled water for 7 days at 37°C. Based on the compressive strength (CS), poly (AA-co-IA-co-MGA) with a monomers ratio of 8:1:1, respectively, showed the highest CS (269.9 MPa). The 8:1:1 copolymer with different molecular weights were also prepared to evaluate the effect of MW on the compressive strength. The optimum MW copolymer gave a glass-ionomer having the compressive strength improved by 30%, compared to Fuji II (293.9 MPa vs. 224.9 MPa). The same polymer solution was also mixed with glass powders used in other commercial glass-ionomers, i. e., Ketac-Molar (ESPE, Seefeld, Germany), α-Fil and α-Silver (DMG, Hamburg, Germany) to produce conventional glass-ionomers test specimens. The mechanical properties of these materials were also obtained and compared to the Fuji II, Ketac-Molar, α-Fil and α-Silver controls.     

Improved Flexural Strength of N-Vinyl-Pyrrolidone Modified Acrylic Acid Copolymers for Glass-Ionomers

Abstract

The flexural strengths of N-vinylpyrrolidone modified glass-ionomer cements were investigated. The optimal molar ratio of the monomers in copolymers, composed of the three components acrylic acid, itaconic acid and N-vinylpyrrolidone, was determined using a SAS statistical program. The copolymers were prepared using a free-radical polymerization process. The viscosities of aqueous solutions of these polymers were determined. Cements were formed by the reaction of these solutions with glass particles. Flexural strength (FS) was used as the basic screening property to find the optimum molar ratio. Statistical models were applied to predict the optimum molar ratios. All strength values were recorded on the specimens conditioned in distilled water at 37°C for 7 days. The optimal molar ratio for these copolymers was 7:1:3 for poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone), based on flexural strength and viscosity. The effect of molecular weight (MW) on FS was also evaluated. Copolymer with a MW of 10, 800 (M_n) showed 85% higher FS than the Ketac-Molar (KM) system, along with a reasonable working viscosity.     

Novel resin modified glass-ionomer cements with improved flexural strength and ease of handling

Poly(acrylic acid-co-itaconic acid) copolymers containing pendent methacrylates were synthesized and used to formulate redox-initiated in situ cured glass-ionomer cements (GICs) by mixing with reactive glass fillers (Fuji II LC). Various formulations for the redox initiator were studied, and flexural strength (FS) was used as a screening tool for optimization. Effects of molecular weight (MW), grafting ratio, comonomer, polymer content in the liquid composition, powder/liquid (P/L) ratio, and aging on FS were investigated. The results show that the in situ cured GICs demonstrated higher FS (89.6-123.2 MPa), as compared to commercial Fuji II LC GIC (57.1 MPa). The optimal concentrations for redox initiators were found to be 0.15% (by weight) for K₂S₂O₈ and 0.2% for ascorbic acid (or 0.6% for microencapsulated ascorbic acid), respectively. Effects of MW, grafting ratio, P/L ratio and polymer content in the liquid formulation were significant. During aging, the cement showed an increase in strength over 24 h and then no change for time periods up to six months. SEM analysis supports the strength data associated with the formulations. The exotherm and setting time suggest that novel redox-initiated resin-modified GICs hold promise as biocompatible and workable cement for orthopedic applications.     

Removal of Pb2+ and Cd2+ ions from aqueous solutions using guanidine modified hydrogels

In this study, experimental measurements have been made on the batch adsorption of cadmium and lead ions from aqueous solutions using poly(guanidine modified 2‐acrylamido‐2‐methylpropan sulfonic acid/acrylic acid/N‐vinylpyrrolidone/2‐Hydroxyethyl methacrylate), P(AMPSG/AAc/NVP/HEMA) hydrogels. The guanidyl end group bearing AMPSG monomer was synthesized from the reaction of AMPS and guanidine. The hydrogels were prepared by UV‐curing technique. The morphology of the dry H10‐hydrogel sample was examined by SEM. The influence of the uptake conditions, such as pH, functional monomer per cent, contact time, initial feed concentration, and foreign metal ions on the metal ion binding capacity of hydrogel, was also tested. The selectivity of the hydrogel toward the different metal ions tested was Hg(II) > Pb(II) > Au(III) > Cd(II). The adsorption isotherm models were applied to the experimental data, and it was seen that the Langmuir isotherm model was the best fit for the adsorption of Cd(II) and Pb(II) ions on P(AMPSG/AAc/NVP/HEMA) hydrogel. It was found that adsorbed lead and cadmium ions on P(AMPSG/AAc/NVP/HEMA) hydrogel can be effectively desorbed by acid leaching and the regenerated P(AMPSG/AAc/NVP/HEMA) hydrogel can be reused almost five times less without any loss of adsorption capacity. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of amino acid-containing polyacids and their application in self-cured glass-ionomer cement

Six methacrylate or acrylate derivatives of natural amino acids were synthesized and characterized. Based upon these monomers, six terpolymers [poly(acrylic) acid-co-itaconic acid-co-amino acid] were prepared and characterized. The synthesized polymers were used to formulate glass-ionomer cements (GICs) using Fuji II glass filler. The effects of the molecular weight (MW) and powder/liquid (P/L) ratio were evaluated. Scanning electron microscopy (SEM) was used to examine the fracture surfaces of the selected cement specimens. Results show that all the amino acid modified GICs exhibited higher compressive strengths (CS, 193-236 MPa) and much higher flexural strengths (FS, 55-71 MPa) as compared to commercial Fuji II GIC (191 in CS and 16 in FS). Both MW and P/L ratio affected the strength of the formed cement. It was important to find the optimal MW and P/L ratio to obtain the highest FS. In this study, optimized MW (number average) of the polyacids and P/L ratio were around 50,000 and 2.7/1, respectively. The microstructures of the fracture surfaces helped to explain the strength differences among the materials tested in the study. SEM analysis suggests that more integrated microstructures and fewer defects can lead to higher FS.     

New photoluminescent copolymers of naphthalene-2,7-diol dimethacrylate and N-vinyl-2-pyrrolidone

Syntheses of the new photoluminescent copolymers: 2,7-(2-hydroxy-3-methacryloyloxypropoxy)naphthalene with N-vinyl-2-pyrrolidone (NVP) are presented. The obtained compound was copolymerised with different ratios of active diluent (NVP). Thermo- and photo-polymerisations of the compositions with use of the initiators: α,α′-azoiso-bis-butyronitrile and 2,2-dimethoxy-2-phenyl-acetophenone were carried out. The following properties were determined: density, polymerisation shrinkage, glass transition temperature, Young’s modulus, hardness and tensile strength. Moreover, the dynamic-mechanical, thermal and photoluminescent properties were studied. These materials may have potential use as luminophores and coatings filtering harmful UV radiation.     

Evaluation of Organically Modified Layered Double Hydroxides as Fillers for the Preparation of Polymer Nanocomposites in Miniemulsion Polymerization

Latexes of poly(n‐butyl acrylate‐co‐methyl methacrylate) [P(BA‐co‐MMA)] filled with magnesium–aluminum layered double hydroxides (MgAl‐LDHs) are synthesized using miniemulsion polymerization. Three commercial LDHs organically modified with different types of anions are used as fillers (Perkalite F100S, Perkalite A100, and Perkalite AF50) and three different types of surfactants are tested to stabilize the miniemulsions including a cationic, an anionic, and a nonionic one. Stable LDH‐containing miniemulsions are prepared with a mixture of sodium dodecyl sulfate and Triton X‐405 and the polymerizable co‐stabilizer octadecyl acrylate. They are then polymerized to yield nanocomposite latexes. Depending on the type of LDH used, the presence of the inorganic material in the reaction medium affects the polymerization kinetics. X‐ray diffraction analysis of the resulting nanocomposite films suggests exfoliation of the inorganic material. The glass transition temperature of the nanocomposites is not affected by the LDHs and the decomposition temperature of the nanocomposites determined by thermogravimetric analysis is greater than that of the pure polymer.     

Synthesis and Characterization of p—[Perfluoro—1—（2—fluorosulfonylethoxy）]ethylated Polystyrene

A new fluorinated polystyrene bearing a p-sulbstiuted perfluoro[1-(2-fluorosulfonylethoxy)]ethyl group was synthesized via one-electron oxidation of polystyrene by perfluoro[2-(2-fluorosulfonylethoxy)]propionyl peroxide at different peroxide to polystyrene molar ratios.The yield of perfluoroalkylation decreases with the increase of the reactant molar ratio.The modified polymer has been characterized by various techniques:the ring pefluoro[1-(2-fluorosulfonylethoxy)]ethylation has been proved by FT-IR and ^19FNMR;the X-ray photoelectron spectra(XPS) show the maximum binding energy of F18,O18,C18(two kinds of carbon atoms,namely C-H and C-F)and S2p,respectively; desulfonylation of the fluorinated polystyrene appearing at 217℃ has been found by its thermogravimetric analysis (TGA).The determinations of contact angle,refractive index and glass transition temperature of the modified polymer have disclosed that when the contact angle increases with the increase of the molar ratio,the refractive index and glass transition temperature decrease.The polydispersity values indicate that the degradation of the polymer chains did not occur during the reaction.     

Fluorinated modification of hyperbranched polyesters used for improving the surface property of UV curing coatings

The commercial hyperbranched aliphatic polyols (Hn) were modified by thioglycolic acid (TA) and hexafluorobutyl acrylate (HFBA) or dodecafluoroheptyl methacrylate (DFHMA) to prepare a series of fluorinated hyperbranched polyesters. For comparison, a linear fluorinated polymer, poly(n-BMA-co-DFHMA), was synthesized through the copolymerization of n-butyl methacrylate (BMA) and DFHMA. The molecular structures were characterized by ¹H NMR spectroscopic analysis. The synthesized polymers were incorporated into UV-curable formulations as additives, and exposed to a UV lamp. After UV curing, the wettability of the films was investigated by contact angle measurement with water and 1-bromonaphthalene. The results showed that both the hydrophobicity and oleophobicity were greatly enhanced. Moreover, the fluorinated hyperbranched polymers possessed better water and oil repellency than the copolymer poly(n-BMA-co-DFHMA) at a very low concentration. The surface F/C ratio values of the cured films were detected by XPS analysis, and the film with TAH20-DFHMA showed the highest F/C ratio value, indicating its most efficient aggregation effect at the film surface.     

Synthesis and properties of oxetane‐based polysiloxanes used for cationic UV curing coatings

The polysiloxanes end‐capped with oxetane group (PSiO‐H and PSiO‐L) were synthesized via hydrosilylation reaction based on α,ω‐dihydrogen‐terminated polydimethylsiloxanes with a higher (0.23%, PDSi‐H) and lower (0.12%, PDSi‐L) hydrogen amount. The molecular structures were characterized by FT‐IR and ¹H NMR spectroscopy. The polysiloxanes were added into a commercial oxetane‐based resin, 3,3′‐(oxydi(methylene)) bis(3‐ethyloxetane) (DOX), as an additive to prepare a series of cationic UV curable formulations. The photo‐DSC results showed that the maximum photopolymerization rate decreased while the oxetane conversion increased with the polysiloxane content increasing. The surface hydrophobic property of cured films was improved having the water contact angles of 97° and 99° compared with 82° of the cured DOX film with only 1 wt% PSiOs, respectively. The dynamic mechanical thermal analysis results showed that both the storage modulus on the rubbery plateau region and the glass transition temperature decreased with increasing PSiO‐H loading. Moreover, the decrease became more obvious as PSiO‐L was added instead of PSiO‐H due to its lower concentration of oxetane group. The thermal stability of cured films was enhanced by the addition of PSiOs from the thermogravimetric analysis. And the DOX/PSiO‐H film possessed higher thermal degradation temperatures than DOX/PSiO‐L film. Copyright © 2011 John Wiley & Sons, Ltd.     

RADIATION SYNTHESIS AND CHARACTERIZATION OF POLY(AA-co-NVP)/CLAY HYDROGELS

The pH-sensitive P(AA-co-NVP)/clay hydrogels were prepared with the monomers of acrylic acid(AA)and N-vinyl-2-pyrrolidone(NVP)based onγ-ray irradiation technique.The influence of pH values of buffer solutions and contents of clay and NVP on the equilibrium swelling ratio(SR)and compressive properties of the hydrogels was investigated in detail.The results of swelling property tests showed that,with the increase of clay content,the SR of hydrogels increases in the same buffer solution,and the SR of hydrog...     

Liquid Chromatorgraphic Separation of the Enantiomers of Phenylthiohydantoin α-Amino Acids Derivatives on Polysaccharide-Based Chiral Stationary Phases

ABSTRACT

The liquid chromatographic enantioseparation of the phenylthiohydantoin (PTH) derivatives of various amino acids on four commercial polysaccharide-derived chiral stationary phases (CSPs) is described. Chiralcel OF and Chiralpak AS showed better performance than the other CSPs for resolution of the enantiomers of PTH amino acid derivatives. The enantiomers of all amino acids as their PTH derivatives were well separated on Chiralcel OF and/or Chiralpak AS. The (-)(L) or (-)-enantiomers of all analytes examined were preferentially retained on Chiralpak AS, whereas the (+)(D) or (+)-enantiomers of most of analytes were preferentially retained on Chiralcel OF.     

纳米铜/石墨烯-壳聚糖复合膜修饰电极及其对葡萄糖的直接测定

以石墨烯-壳聚糖复合膜修饰玻碳电极,并在此复合膜上电沉积纳米铜,用于葡萄糖的无酶检测。以扫描电镜、傅立叶红外光谱及电化学交流阻抗谱对该复合膜微观形态进行表征,以循环伏安法、计时电流法对该电极的电化学行为进行研究。实验结果表明,在0.1 mol/L Na OH溶液中修饰电极对葡萄糖具有良好的催化氧化作用,该电极对葡萄糖的检测线性范围为5.6×10-5~1.2×10-3mol/L,检出限(S/N=3)为2.3×10-5mol/L。该修饰电极对样品的检测具有良好的稳定性、重现性。     

Characterization of complexation of PVP copolymer with DNA

Interactions of amphiphilic copolymer poly(N‐vinylpyrrolidone‐co‐N‐t‐Boc‐ tryptophanamido‐N′‐methacrylthiourea) [P(NVP‐co‐TrpAMT)] and poly(N‐vinylpyrrlidone) (PVP) with DNA were studied with the aim to understand the difference in their complexation efficiencies when considered as a potential non‐viral delivery vector. Fluorescence spectroscopy, ethidium bromide (EB) quenching, ζ potential measurement, and agarose gel electrophoresis were all carried out in Tris‐HCl (pH 7.4) solution to assess the degree of interaction between the (co)polymers P(NVP‐co‐TrpAMT) and DNA. All of these measurements show that the high affinity of the copolymer for DNA can be demonstrated. We also found that P(NVP‐co‐TrpAMT)‐I (PVP/PTrpAMT molar ratio was 100:2.88) exhibited a high DNA cleavage activity and induced the supercoiled form of the plasmid cleavage in the nicked and linear forms. Moreover, P(NVP‐co‐TrpAMT)‐I exhibited stronger affinity for DNA than PVP and P(NVP‐co‐TrpAMT)‐II (PVP/PTrpAMT molar ratio of 100:6.35). This phenomenon is believed to be related to the structure of TrpAMT and the hydrophobic nature of the copolymer. P(NVP‐co‐TrpAMT)‐II with higher hydrophobic segments creates a strong hydrophobic interaction and induces a steric barrier which hinders their complexation with DNA. The study reveals important information about the inner mechanisms involved in the interaction of the PVP copolymer with DNA, which aids in the design of novel efficient non‐ionic gene carriers. Copyright © 2008 John Wiley & Sons, Ltd.     

Energetic mixing of anti‐SNAP25 on lipid monolayers: degree of saturation of C18 fatty acids

In our study, various mixtures of C18 fatty acids with different degrees of saturation in their hydrocarbon chain, namely stearic acid (SA), oleic acid (L1), linoleic acid (L2), and linolenic acid (L3), and a polyclonal antibody, anti‐synaptosome‐associated protein of 25 kDa (SNAP25) (AS25), have been investigated using the Langmuir–Blodgett (LB) technique accompanied by atomic force microscopy (AFM) imaging. The cis‐double bonds in unsaturated lipids (L1, L2, and L3) have kinks in their molecular conformation and thus could not pack as tightly and uniformly as SA. The bends and kinks in the molecular structure may interfere with the packing of the lipid monolayer which will promote fluidity as shown in the analyzed compressibility modulus (C_s^?1 ) data. The negative values of Gibbs free energy of mixing (ΔG _mix ) of C18 fatty acids/AS25 confirm the spontaneity interaction of AS25 molecules on the monolayers. The amount of AS25 incorporated into the monolayer strongly affected the thermodynamic properties of the lipid monolayers. AFM surface roughness analyses also indicate that AS25 molecules are strongly bounded on the surface membrane as predicted by the obtained energetic data. In comparison to all C18 fatty acids studied, the strongest intermolecular interaction is observed in L1 at the investigated ranges. In particular, at mole ratio of 26:1, the most negative ΔG _mix is observed at L1. Thus, we can draw the conclusion that AS25 is best mixed with L1. This L1/AS25 ratio mimicking a half bilayer membrane serves as a very useful reference in preparing fatty‐acid nanoimmunoliposomes as the targeted drug‐delivery vehicles for cancer therapy. Copyright © 2016 John Wiley & Sons, Ltd.     

Copolymerization of Methacrylic Acid and N-Vinylpyrrolidone in Aqueous Solution

The monomer reactivity ratios for the copolymerization of methacrylic acid (MA) and N-vinylpyrrolidone (NVP) in aqueous media at 30°C were determined as a function of pH (range 2-10), by use of both the modified differential (YBR) and integrated copolymerization equation to process the data at high conversions (< 70% by weight). The reactivity ratio r₁ (for MA) ranges from 0.92 to 8.3 and that for NVP (r₂) is very small except at pH 7 and 8. The ri values show two minima: 2.9 at pH 4 and 0.92 at pH 8, nearly corresponding to the pKa values of the monomer MA and the polymer, respectively. Addition of 1 M sodium chloride results in an increase of n values, and the values are still lower than those of the undissoeiated acid. The trend of r_xwith pH is seen to follow that of the homopolymerization behavior of MA reported in the literature. The r₁ and r₂ are of the same order as those obtained in dimethylformamide in the literature.     

顺丁烯二酸β-环糊精酯-N-乙烯基吡咯烷酮水溶性聚合物的合成及其吸附疏水性药物的研究

以γ射线引发顺丁烯二酸β-环糊精酯(CDM)和N-乙烯基吡咯烷酮(NVP)发生自由基链式反应,制备了顺丁烯二酸β-环糊精酯-N-乙烯基吡咯烷酮聚合物(CDM-NVP).优化后的CDM-NVP聚合物的合成条件为: CDM∶NVP为1∶0.7(w/w, CDM 3.6 g 和 NVP 2.52 g),辐照剂量4 kGy,DMF溶液用量为20 mL.在此条件下制备聚合物的产率为84%,重均分子量为20 kDa.结果表明,此聚合物可以同纳他霉素(NM)和多菌灵(MBC)形成稳定复合物.研究了复合物抑菌活性,测定了其表观稳定常数.利用紫外光谱、核磁图谱和相溶解度对药物复合物进行结构表征.303 K下,NM-CDM-NVP和 MBC-CDM-NVP复合物的表观稳定系数分别为12988.54和865.94 L/mol.抑菌实验结果表明,NM-CDM-NVP和 MBC-CDM-NVP复合物可以显著提高NM和MBC的溶解性和抑菌活性.     

丙烯酸β-羟丙酯/乙烯基吡咯烷酮水凝胶的合成和热敏行为的研究

用自由基共聚法合成了一系列 β -羟丙酯 ( β -HPAT)和乙烯基吡咯烷酮 (NVP)的共聚物及其水凝胶。发现共聚物的水溶液有敏锐的温敏行为 ,最低汇溶温度 (LCST)随NVP含量的增加而升高 ,随着反应单体总浓度的增加 ,相变敏锐性下降且LCST也随之下降。通过考察水凝胶的溶胀率 (SR) ,发现共聚凝胶在适当的单体浓度 ,交联剂浓度和较宽的单体浓度配比范围内 ,有较灵敏的温敏行为。