Monomers for adhesive polymers, 17.a Synthesis,photopolymerization and adhesive properties of polymerizable phosphonic acids bearing urea groups

Four polymerizable phosphonic acids bearing urea groups 4a, 4b, 9a, and 9b as well as the 10-(methacryloyloxy)decylphosphonic acid 10 were synthesized in four to six steps. They were characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy and by high-resolution mass spectroscopy. Contrary to methacrylates 4a and 4b, methacrylamides 9a and 9b were hydrolytically stable in deuterated water/deuterated ethanol solutions. The photopolymerization behavior of acidic monomers 4a, 4b, 9a, 9b, and 10 and their corresponding phosphonates were studied using a differential scanning calorimeter. Homopolymerizations and copolymerizations with N-butyl-N-ethylacrylamide were carried out. The presence of a urea group was found to significantly increase the rate of polymerization. Monomers bearing a phosphonic acid group were more reactive than their corresponding phosphonates. Self-etch adhesives based on monomers 4a, 4b, 9a, and 9b were able to provide a strong bond between a composite and the dental hard tissues (dentin and enamel). The presence of a urea group led to a significant increase in the shear bond strength to both dentin and enamel.     

Monomers for Adhesive Polymers, 9–Synthesis,Radical Photopolymerization,and Properties of (Meth)acrylamido Dihydrogen Phosphates

5‐Methacrylamidopentyl ( 3a ), 10‐(N‐methylacrylamido)decyl ( 3b ), or 11‐(N‐methylacrylamido)undecyl dihydrogen phosphate ( 3c ) are synthesized by (meth)acrylation of the corresponding ω‐aminoalkane‐1‐ols with methacrylic anhydrid or acryloyl chloride followed by phosphorylation of the formed ω‐(meth)acrylamidoalkane‐1‐ols. The monomers show a significantly improved hydrolytic stability compared to the corresponding methacrylate‐based dihydrogen phosphates. The photopolymerization of 3a–c with a bis(acrylamide) crosslinker confirms a high reactivity in the free‐radical copolymerization. These monomers enable the mediation of a strong bond between the enamel or dentin surface and a restorative composite under self‐etching conditions.

     

Monomers for Adhesive Polymers, 10‐Synthesis,Radical Photopolymerization and Adhesive Properties of Methacrylates Bearing Phosphonic Acid Groups

Syntheses of eight novel methacrylates bearing phosphonic acid groups were synthesized in three to five steps. The interaction of these monomers with hydroxyapatite was investigated using ¹³C‐NMR spectroscopy. Free radical homopolymerizations were carried out in a mixture ethanol/water (2.5/1, v/v) using 2,2′azo(2‐methylpropionamidine) dihydrochloride as initiator. The copolymerization of these monomers with a mixture HEMA/GDMA (5/3, mol/mol) was investigated by photo‐DSC. Dentin shear bond strength measurements showed that 2‐methacryloyloxy‐3‐(1,1,2,2‐tetrafluoroethoxy)propylphosphonic acid 4b , 2,3‐dimethacryloyloxypropylphosphonic acid 18 and 3‐(methacryloyloxy)‐2,2‐(di[(dihydroxyphosphoryl)methyl])propyl methacrylate 23 are promising candidates for dental adhesives.

     

Synthesis and photopolymerization of phosphonic acid monomers for applications in compomer materials

Novel methacrylate monomers bearing phosphonic acid groups 1 and 2 as well as new sulfur methacrylates 9 and 10 have been prepared in good yields from thiophenol. They have been fully characterized by ¹H‐NMR, ¹³C‐NMR, ³¹P‐NMR, and HRMS. Their copolymerization with a bis‐GMA : TEGDMA (1 : 1) blend has been investigated with photodifferential scanning calorimetry at 50°C with camphorquinone as a photoinitiator and ethyl 4‐(dimethylamino)benzoate (EDAB) as a coinitiator. The higher the content of acidic monomer 1 or 2 incorporated in the bis‐GMA : TEGDMA (1 : 1) blend, the lower the mixtures reactivity. The phosphonic acid group has been proved to be responsible for this drop of reactivity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

New Radiopaque Bromine‐Containing Monomers for Dental Restorative Materials

Four bromine‐containing methacrylates 1 – 4 are synthesized from pentaerythritol tribromide and 2,2,2‐tribromoethanol and are characterized by ¹H and ¹³C NMR spectroscopy. Their free radical polymerization is performed in dimethylformamide (DMF), using 2,2′‐azobis(2‐methylpropionitrile) as initiator. The photopolymerization behavior of monomers 1–4 is investigated using a differential scanning calorimeter. Homopolymerizations and copolymerizations with 2‐hydroxyethyl methacrylate are carried out. Both the presence of a carbamate group and of bromine atoms result in an increase of the polymerization rate. Dental resins are prepared by replacing a certain amount of 2‐(4‐cumyl‐phenoxy)ethyl methacrylate by monomers 3 and 4 in a model formulation. The incorporation of these methacrylates leads to a significant increase of the radiopacity. Resins based on mono­mer 4 exhibit improved mechanical properties.

     

Monomers for adhesive polymers, 8a crosslinking polymerization of selected N‐substituted bis(acrylamide)s for dental filling materials

The free‐radical polymerization of bis‐(N‐ethylacrylamido)‐ethylenglycol ( I ), N,N′‐dimethyl‐1,6‐bis (acrylamido)‐hexan ( II ), and N,N′‐diethyl‐1,3‐bis(acrylamido)‐propan ( III ) were investigated. The cross‐linking polymerization was followed in bulk by using the ampoules technique and gravimetry. Polymerizations exhibited an abnormal kinetic behavior. For the monomer II , for example, the reaction order to 2,2′‐ azobisisobutyronitril (AIBN) initiator of 1.28, and the polymerization overall activation energy of 151 kJ/mol between 50 and 75°C were determined. The increasing temperature and decreasing initiator concentration resulted in an increase of double bonds consumption in the formed polymer network. At 75°C the residual unsaturation was under 2%, compared with 9.9% at 50°C. The monomer conversion‐time dependences were complemented also with differential scanning calorimetry (DSC) recording the heat released during polymerization. The extension of peak time with decreasing the instant heat flow rate at this point sort the studied bis(acrylamide)s according the reactivity in the following sequence: monomer III > I > II . The polymer samples sol–gel analyses in ethanol allowed the determination of the molecular weight M_c between the network crosslinks. The presence of microgel particles at the very beginning of polymerization and the changes in chain conformation with temperature we consider as the way in which was affected the polymerization kinetics of these monomers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Brominated phenol–formaldehyde resin as an adhesive for plywood

A brominated phenol–formaldehyde resin was investigated as a plywood adhesive to study the effect of bromine on the physical and flammability properties of this resin. The results of these studies showed that brominated phenol–formaldehyde resin of 10% bromine content by weight of the phenol–formaldehyde resin was suitable to be used as a plywood adhesive. The optimal compressing temperature and compressing time were 110°C and 30 min, respectively. The prepared plywood obtained from the optimal condition gave a high shear strength, good flame retardancy, and good resistance to both hot and cold water. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1918–1924, 2003     

Aromatic–Aliphatic acrylic monomers and polymers: Synthesis and characterization

Two new ester‐type monomers were synthesized by the condensation of acrylic acid with the products of the hydroxyethylation of 4‐nonylphenol or 4‐tert‐butylphenol. The hydroxyethylation reaction was performed with 1,3‐dioxolan‐2‐ona in the presence of alkalies. By hydroxyethylation, the phenols were changed into alcoholic derivatives able to react with acrylic acid to give acrylic esters. The insertion of the aryl–alkyl groups into the structure of the acrylic esters, and implicitly of the corresponding polymers, was carried out with the intention of increasing their thermostability and improving their behavior as pressure‐sensitive adhesives on the whole. The monomers and the polymers were characterized by elemental and thermogravimetric analyses, IR and ¹H‐NMR spectroscopy, and other special methods. The results of these investigations confirmed the formulated suppositions. The inherent viscosities of the resulting polymers were in the range of 47–64 mL/g, and their thermal stability was up to 315–320°C, far higher than that of the polyacrylates used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 802–814, 2002     

Photo‐curing behaviors of bio‐based isosorbide dimethacrylate by irradiation of light‐emitting diodes and the physical properties of its photo‐cured materials

Bio‐based isosorbide (1,4:3,6‐dianhydroglucitol), which was obtained from biomass‐derived carbohydrates, has recently attracted much attention as an alternative to bisphenol A (BPA) because of its rigidity and transparency. BPA is still widely used for a variety of chemical applications even though it is known to be an endocrine‐disrupting chemical. BPA is a key precursor to most photo‐curable materials ranging from encapsulants of electronic devices to dental sealants. In this study, photo‐curable isosorbide dimethacrylate (ISDM) was synthesized from bio‐based isosorbide as a substitute for BPA, and the photo‐curing behaviors of ISDM by irradiation with light‐emitting diode (LED) light were investigated. The photo‐curing conversion and rates of ISDM formation were determined based on the change in the peak corresponding to the double bond within the methacrylate groups using attenuated total reflectance Fourier transform infrared (ATR–FTIR) spectroscopy. The effects of initiators and the wavelength of LED light on the photo‐curing conversion and rates of ISDM formation were examined, and a comparative study was carried out with 2,2‐bis[4(2‐hydroxy‐3‐methacryloyloxy‐propyloxy)phenylpropane] (Bis‐GMA), which is a photo‐curing material bearing a BPA moiety. In addition, the mechanical properties, such as surface hardness, adhesion strength, and transparency, after photo‐curing of ISDM were evaluated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42726.     

Polystyrene foams. II. Structure–impact properties relationships

In the first part of this series of articles, the relations between the foaming conditions and the microstructure of expanded polystyrene (EPS) were explored. In this part, the effects of the foaming conditions and the microstructure of EPS on impact properties are discussed. Regression analysis was conducted on the data and expressions were developed to quantify these relationships. Moreover, the importance of the individual structural parameters was determined. Statistical analysis of the data showed that foaming time was the most important factor determining the impact strength, while foaming temperature was the most important factor controlling the specific impact strength. The deformation of cells at the crack tip, as a result of bending and/or buckling of cell walls, can increase the failure strain, which leads to an increase in failure energy. In expanded polymers, the majority of the absorbed energy during impact loading is dissipated as plastic work. The transition of plane stress conditions to plane strain conditions, due to expansion, can be considered as another source of toughening in EPS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1421–1426, 2003     

Polystyrene foams. III. Structure–tensile properties relationships

In the previous two parts of this series of articles, the relations among the foaming conditions, microstructure, and impact properties of expanded microcellular polystyrene (EPS) were discussed. In this article, the effects of the foaming conditions and structure on the tensile properties of EPS were investigated. A systematic investigation was performed based on a statistical experimental design. Various processing conditions were used and a wide range of cellular structures was developed. Regression analysis was conducted on the data and expressions were developed to quantify the relationship between the tensile properties and the cellular structure. Foaming time and foaming temperature were the most important processing parameters influencing the tensile modulus and strength. The tensile modulus and strength increased with an increasing foam density, but they decreased slightly when the cell size increased. Two different approaches were used to develop models relating the modulus to the foam density of EPS. Both models fitted the experimental data quite well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1427–1434, 2003     

Monomers for Adhesive Polymers 12 Synthesis and Free‐Radical Homo‐ and Copolymerization of 2‐Ethoxycarbonylallyl 5‐(1,2‐dithiolane‐3‐yl)‐pentanoate

The 2‐ethoxycarbonylallyl 5‐(1,2‐dithiolane‐3‐yl)‐pentanoate monomer (AODS) includes in its molecular structure C?C and S? S reactive bonds allowing it to behave as a bi‐functional monomer, possessing two groups, however, with different reactivity for use in polymer chain building. The polymerization‐specific features of this monomer are the absence of auto‐acceleration and polymer chain crosslinking. Polymerization proceeds readily through most free‐radical initiators. One exception, carboxy‐peroxides are rapidly decomposed without the production of free radicals. AODS is partially converted to a gel without the consumption of double bonds during monomer dissolution in certain organic solvents and after being mixed in solution with carboxy‐peroxides. The determined AODS‐co‐MMA copolymerization parameters are r₁ = 2.61, r₂ = 0.23 if Luperco peroxide is used as a polymerization initiator, and r₁ = 2.71, r₂ = 0.38 if AIBN is used.

     

Synthesis of acidic vinylcyclopropanes for dental applications

The multistep synthesis of four new acidic vinylcyclopropanes is described. These monomers were fully characterized using ¹H NMR, ¹³C NMR and ³¹P NMR spectroscopy and high‐resolution mass spectrometry. The homopolymerization of the corresponding polymerizable di‐tert‐butyl phosphates as well as the copolymerization of each acidic monomer with 1,1‐diethoxycarbonyl‐2‐vinylcyclopropane were investigated using photo‐differential scanning calorimetry with bis(4‐methoxybenzoyl)diethylgermane as photoinitiator. Self‐etch adhesives based on the synthesized acidic vinylcyclopropanes are able to achieve a strong bond between a dental composite and both dentin and enamel. Flowable composites containing these acidic vinylcyclopropanes exhibit good mechanical properties. The replacement of methacrylates by vinylcyclopropanes leads to a significant reduction of the shrinkage stress of flowable composites. © 2017 Society of Chemical Industry     

Structure–property relationships in one‐component polyurethane adhesives for wood: Sensitivity to low moisture content

The causes of strength loss of wood joints and their consequent delamination from one‐component polyurethane adhesives used for bonding structural wood when used at a low moisture content was investigated by testing wood joint strength and elongation at rupture at different wood moisture contents and by ¹³C‐NMR spectroscopy and scanning electron microscopy of the hardened bond line. The combination of the relative proportion of the still‐reactive free ? NCO groups on the polyurethane, of the wise choice of degree of polymerization of the resin, and of a slower rate of reaction were the three parameters found to be important in overcoming the problem of poor or no bonding of wood at low to very low moisture contents from one‐component polyurethane adhesives. The results obtained indicated that one‐component polyurethane adhesives that had a combination of a higher proportion of still‐unreacted ? NCO groups, a lower degree of polymerization, and a slower reaction rate were capable of overcoming the problem of the high sensitivity of polyurethane gluing at low to very low wood moisture contents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4181–4192, 2006     

Polyurethane ionomers. I. Structure–properties relationships of polyurethane ionomers

The influence of chemical structure on mechanical properties of polyurethane ionomers (PU ionomers) has been examined. NCO-terminated prepolymers prepared from primarily 4,4-methylene bis(phenyl isocyanate) (MDI) and poly(oxytetramethylene) glycol (PTMO) were chain extended with tertiary amine-containing diols and the ionomers obtained by quaternization of the prepolymers. The N-methyldiethanolamine chain extender gave the best physical properties. The mechanical properties of the PU ionomers were improved with decreasing chain length of PTMO and with increasing concentration of quaternary ammonium centers (or NCO/OH ratio of PU prepolymers). A lower degree of quaternization resulted in a decrease in the mechanical properties of the resulting PU ionomers, but their properties could be improved by post-quaternization. The adhesion of the PU ionomers to aluminum and the glass transition temperature increased with increasing concentration of quaternizing centers.     

New polymer syntheses. IX. Synthesis and properties of new conducting polyazomethine polymers containing main chain cycloalkanone and pyridine moieties

Novel polyazomethines containing cycloalkanones or pyridine moieties were synthesized by the polycondensation of 2,5‐bis(m‐aminobenzylidene)cyclopentanone (BMAP, IV), 2,6‐bis(m‐aminobenzylidene)cyclohexanone (BMAH, V), 2,6‐bis(p‐aminobenzylidene)cyclohexanone (BPAH, VI), and 2,6‐bis(m‐aminostyryl)pyridine (BMAS, VIII) diamines with terephthalaldehyde in EtOH at 25°C. These polymers were yellow to orange in color, had reduced viscosities up to 1.42 dL/g, and had electric conductivities as high as 10⁻¹¹–10⁻¹² S cm⁻¹. All the polyazomethines were insoluble in common organic solvents but dissolved completely in concentrated sulfuric acid. However, they were readily hydrolyzed in concentrated H₂SO₄. X‐ray diffraction diagrams showed that the crystallinities of the polyazomethines were low. These azomethine polymers showed high thermal and thermooxidative stability and exhibited no appreciable decomposition up to 400°C in air. The electronic spectra of the polymers indicated a large bathochromic shift of the π–π* absorption band (∼360 nm) that was due to the presence of CN bonds in the polymer main chain. Doping with iodine dramatically raised the conductivity and produced dark brown to black colored semiconductive polymers with a maximum conductivity on the order of 10⁻⁷ S cm⁻¹. Furthermore, the morphology of selected examples of the four polyazomethines was examined by scanning electron microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1218–1229, 2000     

Synthesis and application of modified starch as a shell–core main adhesive in a foundry

To be used as an alternative adhesive for sand cores in a foundry, a solid water‐soluble modified starch [carboxymethyl starch (CMS)] was synthesized by a new dry reaction process. With this process, a series of CMS products was obtained with degrees of substitution (DSs) ranging from 0.25 to 0.78 at a high reaction efficiency and characterized with regard to their molecular structure and aqueous solution viscosity. On the basis of the dry synthesis of CMS, the properties of CMS‐bonded shell–core sand were investigated, and practical production experiments were carried out. The results show that there was a new sharp peak in the infrared spectrum that represented the carboxymethyl groups and formation of CMS. The viscosity of the CMS aqueous solution increased with increasing DS and amount of CMS. When DS was in the range 0.3–0.5 and the mass fraction was 5–7%, the CMS aqueous solution had a suitable viscosity, which was helpful for the improvement of the properties, such as flowability, permeability, and strength, of the CMS core sand. In addition, a CMS shell–core with an appropriate wall thickness (10–20 mm) for the purpose of obtaining both sufficient strength and permeability could be made with the CMS‐bonded core sand and a hot‐core‐box process. The final pouring results prove that high‐quality iron castings with smooth inner cavities could be produced with the CMS‐bonded shell–core and that it (namely the CMS‐bonded shell‐core) could be used as a replacement for the furan resin‐bonded sand core. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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