One‐component thioxanthone‐based polymeric photoinitiators

The photochemical and photophysical properties of new polymeric photoinitiators (PPIs) containing pendant thioxanthone (TX) and amine moieties are studied. The PPIs are synthesized by copolymerization of tert‐butyl 2‐((9‐oxo‐9H‐thioxanthen‐2‐yloxy)methyl)acrylate (TX1) with N,N‐dimethylaminoethyl methacrylate (DMAEM) at two different ratios using free radical polymerization. UV–vis spectra indicate that PPIs possess similar absorption characteristics to TX1 in the violet range (～400 nm; absorption red‐shift 20 nm). The photochemical mechanisms are studied by electron spin resonance (ESR), steady state photolysis, laser flash photolysis, and cyclic voltammetry. ESR studies indicate formation of two different aminoalkyl radicals on the hydrogen donor amine. The triplet state of the PPIs is short‐lived compared to isopropyl thioxanthone and TX1, due to the built‐in amine functionality. Photopolymerization of trimethylolpropane triacrylate (TMPTA) initiated by these photoinitiators under LED exposure at 385 and 405 nm using real‐time FTIR spectroscopy shows that they exhibit higher efficiency than TX/N‐methyldiethanolamine (MDEA) and TX1/MDEA systems with the advantage of a much higher molecular weight that can be very helpful to overcome migration issues. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3370–3378     

Cyclization tendencies in the free radical polymerization of allyl acrylate derivatives: A computational study

In this study density functional theory (DFT) has been used to model the elementary steps and rationalize the free radical polymerization kinetics in allyl methacrylate (AMA), allyl 2‐cyanoacrylate (ACA) and methyl α‐[(allyloxy)methyl]acrylate. The models used in this study have revealed the fact that while methyl α‐[(allyloxy)methyl]acrylate, cyclopolymerizes via 5‐membered rings, AMA and ACA do not. The cyclization tendency of methyl α‐[(allyloxy)methyl]acrylate is attributed to the similar hybridization (sp³) of C3 and C5 favoring a quasi cyclic structure for the reactive rotamer. On the other hand, the presence of the cyano (CN) group in ACA facilitates the initiation step as compared to AMA. The chain transfer reaction does not seem to play a major role in the monomers of interest. This study highlights the usage of quantum chemistry in determining the cyclization tendencies of allyl acrylate derivatives in their free radical polymerization reactions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and evaluation of new phosphonic acid‐functionalized acrylamides with potential biomedical applications

Phosphorus‐containing acidic monomers are able to interact with the inorganic phase of mineralized tissues such as enamel, dentin, and bone. From this perspective, three phosphonic acid‐containing acrylamide monomers with different lengths of alkyl chains were synthesized to be used for both self‐etching dental adhesives and mineralized hydrogel scaffolds. Monomers were synthesized by the reaction of α‐aminophosphonates (diethyl aminomethylphosphonate, diethyl 2‐aminobutan‐2‐ylphosphonate, and diethyl 2‐aminooctan‐2‐ylphosphonate) with acryloyl chloride followed by the hydrolysis of phosphonate groups by using trimethylsilyl bromide. The properties such as pH in the range of mild self‐etching adhesives, hydrolytic stability, high rate of copolymerizations with 2‐hydroxyethyl methacrylate (HEMA) and HEMA/glycerol dimethacrylate, giving high‐molecular‐weight polymers on thermal polymerization, and strong decalcification ability of hydroxyapatite make these monomers good candidates for self‐etching adhesives, although no appreciable effect of the number and size of the α‐substituents was observed. Hydrogel scaffolds containing phosphonic acid groups were fabricated, characterized, and mineralized. Altogether, the results suggest that these phosphonic acid‐containing monomers have suitable properties to be used in fabrication of biomaterials for both dental and bone tissue engineering applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2755–2767     

Electrically tunable polarisation-independent blue-phase liquid crystal binary phase grating via phase-separated composite films

A simple method for fabricating polarisation-independent blue-phase liquid crystal phase grating is demonstrated by implementing photopolymerisation-induced phase separation through a binary photomask. The dynamic focusing property of the proposed liquid crystal grating is independent of the polarisation state of incident light. The efficiency of various diffraction orders for the phase grating was measured as a function of the applied voltage. Experimental results show that the maximum diffraction efficiency reaches 36% for the ±1 order, which approaches the theoretical limit ~41%. The measured rise time is 1.4 ms and fall time is 2.2 ms. Such a tunable grating has great potential for photonic applications.     

Observation of a martensitic structural distortion in V, Nb, and Ta

Thermal-expansion measurements of the Group 5 elements V, Nb, and Ta reveal a structural distortion below 300 K. Data for single-crystalline Nb and Ta display anisotropic thermal expansion, martensitic in character, that is inconsistent with cubic crystal structures at low temperature. Published results on V show similar behavior. Interstitial impurities suppress the transition.     

Strip yield zones around ring-shaped crack in transversely isotropic thick layer

A ring-shaped crack under uniform load in an infinitely long elastic–perfectly plastic thick layer is considered. The problem is formulated for a transversely isotropic material by using integral transform technique. Due to the geometry of the configuration, Hankel integral transform technique was chosen and the problem was reduced to a singular integral equation which is solved numerically by using Gaussian Quadrature Formulae and the values were evaluated at discrete points. The plastic zone widths were obtained by using the plastic strip model after stress intensity factors were obtained. Numerical results are plotted for various ring-shaped crack sizes and transversely isotropic materials. It was found that the width of the plastic zone at the inner edge of the crack was greater than the outer one.     

高分子担载席夫碱及其Cr(Ⅲ)配合物:合成、表征、抗菌和抗真菌性能评价(英文)

用胺甲基树脂与5-氟-2-羟基苯甲醛,5-氟-3-氯-2-羟基苯甲醛,5-氟-3-甲基-2-羟基苯甲醛反应合成了3种新颖的高分子担载席夫碱和它们Cr(Ⅲ)配合物,并用元素分析、磁化率、IR、1H NMR、UV-Vis、TG/DTA对其进行了表征。就一些革兰氏阳性菌(芽孢杆菌属腊状芽孢杆菌(Bacillus cereus sp),单核细胞增生李斯特菌4b(Listeria monocytogenes 4b),藤黄微球菌(Micrococcus luteus),金黄色葡萄球菌(Staphylococcus aureus)表皮葡萄球菌(Staphylococcus epidermis))和革兰氏阴性菌(布鲁氏菌(Brucella abortus),大肠杆菌(Escherichia coli),恶臭假单胞菌SP(Pseudomonas putida sp.),痢疾志贺氏菌10(Shigella dysenteria type 10),伤寒杆菌H(Salmonella typhi H)和酵母菌(念珠菌)(yeast(Candida albicans))用井扩散法对高分子担载席夫碱和它们Cr(Ⅲ)配合物的生物学活性进行了筛选。     

Synthesis and photopolymerization of new dental monomers from o‐hydroxyaryl phosphonates

Novel aromatic mono‐ and diphosphonate monomers based on t‐butyl α‐bromomethacrylate were prepared for use in dental composites. The synthesis of the two monomers involved three steps: the reaction of diethyl phosphite with phenol or hydroquinone, the rearrangement of the resulting phosphate derivatives into o‐hydroxyaryl phosphonates with lithium diisopropylamide, and the reaction of o‐hydroxyaryl phosphonates with t‐butyl α‐bromomethacrylate. Then, the selective hydrolysis of the t‐butyl ester groups of the monomers with trifluoroacetic acid gave the other carboxylic acid containing monomers. The photopolymerization behaviors of the synthesized monomers with glycerol dimethacrylate and triethylene glycol dimethacrylate were investigated with photodifferential scanning calorimetry at 40 °C with 2,2′‐dimethoxy‐2‐phenyl acetophenone as the photoinitiator. The hydrolysis of the t‐butyl groups of the monomers increased the reactivity and the rates of polymerization of the monomers. The mixtures of the acid monomers showed rates of polymerizations similar to those of homopolymerizations of triethylene glycol dimethacrylate and glycerol dimethacrylate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6775–6781, 2006     

Solid phase extraction and determination of nickel in water samples by using novel thiol-containing sulfonamide polymeric resin and atomic absorption spectrophotometer

Interest in preconcentration techniques for the determination of metals at ultratrace levels still continues increasingly because of some disadvantages of flameless atomic absorption spectrometry as well as the high costs of other sensitive methods in compared to flame atomic absorption spectrometry.In this study,thiol-containing sulfonamide resin was synthesized,characterized and applied as a new sorption material for solid phase extraction of nickel in drinking water samples.After preconcentration procedure,flame atomic absorption spectrometry was used for determinations.Optimum parameters were found to be pH=3.2,contact time =20 min and eluate volume=3 mL.The limit of detection was found to be 0.75 ng · mL-1.The synthesized resin exhibits the superiority in compared to the other adsorption reagents because of the fact that there is no necessity of any complexing reagent,high sorption capacity as well as the relatively fast extraction rate.The Ni concentrations in the studied 21 kind of water samples were found to be in the range of BDL-4.0 ng ·mL-1.     

Synthesis and characterization of cadmium hydroxide nanowires by arc discharge method in de-ionized water

In this study, Cd(OH)₂ nanowires have been synthesized by using arc discharge method in de-ionized water. The morphology and properties of the Cd(OH)₂ nanowires were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and UV–Vis spectroscopy. TEM observations revealed that Cd(OH)₂ nanowires were abundant morphology in synthesized nanostructures, and the diameter of the Cd(OH)₂ nanowires ranges from 5 to 40 nm with several micrometers of length. In addition, the width of nanowires is not uniform and varies throughout the nanowire. XRD analysis revealed that the Cd(OH)₂ nanowires grow along [001] direction. Furthermore, hexagonal- and irregular-shaped Cd(OH)₂ nanoplates were synthesized during arc discharge. It was obtained that required arc current is 50 A for the effective and large scale production of Cd(OH)₂ nanowires. Furthermore, the optical properties of the nanowires have been characterized by UV–Vis spectra. By the means of the optical studies, the direct band gap of Cd(OH)₂ nanowires was found to be 4.0 eV with strong quantum size effect. It is also shown that a simple and cheap method which does not require relatively expensive vacuum and laser equipment stipulates an economical alternative for the synthesis of Cd(OH)₂ nanowires.