Naphthodioxinone‐1,3‐benzodioxole as photochemically masked one‐component type II photoinitiator for free radical polymerization

A 1,3‐benzodioxole derivative of naphthodioxinone, namely 2‐(benzo[d][1,3]dioxol‐5‐yl)‐9‐hydroxy‐2‐phenyl‐4H‐naphtho[2,3‐d][1,3]dioxin‐4‐one was synthesized and characterized. Its capability to act as caged one‐component Type II photoinitiator for free radical polymerization was examined. Upon irradiation, this photoinitiator releases 5‐benzoyl‐1,3‐benzodioxole possessing both benzophenone and 1,3‐dioxole groups in the structure as light absorbing and hydrogen donating sites, respectively. Subsequent photoexcitation of the benzophenone chromophore followed by hydrogen abstraction generates radicals capable of initiating free radical polymerization of appropriate monomers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Hydrophobic coatings from photochemically prepared hydrophilic polymethacrylates via electrospraying

Linear poly(hydroxyethyl methacrylate‐co‐methyl methacrylate) P(HEMA‐co‐MMA) and poly(dimehylaminoethyl methacrylate‐co‐methyl methacrylate) P(DMAEMA‐co‐MMA) and their corresponding hyperbranched copolymers were synthesized by conventional photoinitiated free radical polymerization and self‐condensing vinyl polymerization (SCVP) using Type I and Type II photoinitiators, respectively. Then, the polymers were processed by electrospraying in N, N‐dimethylformamide. The surface of the resulting electrospray coatings was examined by SEM, XPS, and WCA then compared with those prepared by drop casting. Regardless of the structural nature of the polymers, electrospraying allows the preparation of rough surface that shows more hydrophobic behavior. Electrospray coatings with linear and hyperbranched copolymers exhibited WCA as ～150° and ～130°, respectively, indicating that branching reduces the WCA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1338–1344     

Preparation of 1,2- and 1,4-dihydro derivatives of 6,7-dimethyl-2,3-diphenylquinoxaline <Emphasis Type="Italic">via</Emphasis> its dianion formed by reductive metallation

Treatment of 6,7-dimethyl-2,3-diphenylquinoxaline with sodium in tetrahydrofuran formed a monomeric dianion. The chemical behavior of this dianion was investigated by a variety of reagents. As the result, alkylation reactions gave 1,2-dihydro derivatives, while acylation reactions occured at 1,4-positions. Annulation of the pyrazine ring system was accomplished by treating the dianion with oligomethylene dichlorides, Cl(CH₂) _n Cl, n = 2–4. Correspondence: Seniz Kaban, Department of Chemistry, Yildiz Technical University, Davutpasa Campus, Esenler-Istanbul 34220, Turkey.     

Synthesis,characterization, and thermally activated curing of oligosiloxanes containing benzoxazine moieties in the main chain

Oligosiloxanes containing thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diallyl functional monomer is synthesized through the Mannich and ring closing reaction of 4,4′‐isopropylidenediphenol (bisphenol A), formaldehyde and allylamine. Hydrosilylation reaction of the resulting diallylic monomer (B‐ala) with 1,1,3,3‐tetramethyldisiloxane (TMDS) in the presence of Pt catalyst yields the corresponding poly(B‐ala‐tetramethyl disiloxane)s (PBTMDS) with the molecular weights in the range of 1800–4100 Da. The structures of the precursor diallyl monomer and the resulting polymers are confirmed by FT‐IR and ¹H NMR analysis. Curing behavior of both the monomer and polymers has also been studied by Differential Scanning Calorimetry (DSC). Flexible free standing transparent films of the oligosiloxanes are obtained by solvent casting from dichloromethane solution on Teflon plates. The films preserve shape and, to some extent, toughness after thermal curing between 100 and 180 °C. Thermal properties of the cured polymers are also investigated by thermogravimetric analysis (TGA). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 804–811, 2009     

Quasi-phase-matched grating characterization using minimum-phase functions

Measurement of the second-harmonic power generated by a quasi-phase-matched (QPM) grating as a function of the frequency detuning parameter yields the Fourier transform (FT) magnitude of the complex nonlinear coefficient profile along the QPM device. This FT magnitude can be measured by tuning either the wavelength of the fundamental laser beam or the temperature of the QPM grating. However, the measured magnitude of the FT cannot be unambiguously inverted without the FT phase to uniquely recover the complex nonlinear coefficient profile of the QPM grating. As we demonstrate in this work, this ambiguity can be completely eliminated by placing a stronger and thinner nonlinear sample against the input or output of the QPM device of interest and measuring the detuning curve of this composite structure. By construction, the nonlinear profile of this assembly has a sharp peak due to the thinner sample, followed by the weaker, broader profile of the QPM grating, which essentially constitutes a minimum-phase function. Therefore, its FT phase can be calculated uniquely from its measured FT magnitude, for example by applying to the FT amplitude the logarithmic Hilbert transform or an iterative error-reduction algorithm. This processing then enables the full recovery of the complex nonlinear coefficient profile of the QPM device from its measured detuning curve. In this paper, we demonstrate with numerical examples that this powerful new technique can accurately recover the period, envelope, and chirp parameters of any QPM grating.     

Developing teachers' models for assessing students' competence in mathematical modelling through lesson study

Applications and modelling have gained a prominent role in mathematics education reform documents and curricula. Thus, there is a growing need for studies focusing on the effective use of mathematical modelling in classrooms. Assessment is an integral part of using modelling activities in classrooms, since it allows teachers to identify and manage problems that arise in various stages of the modelling process. However, teachers’ difficulties in assessing student modelling work are a challenge to be considered when implementing modelling in the classroom. Thus, the purpose of this study was to investigate how teachers’ knowledge on generating assessment criteria for assessing student competence in mathematical modelling evolved through a professional development programme, which is based on a lesson study approach and modelling perspective. The data was collected with four teachers from two public high schools over a five-month period. The professional development programme included a cyclical process, with each cycle consisting of an introductory meeting, the implementation of a model-eliciting activity with students, and a follow-up meeting. The results showed that the professional development programme contributed to teachers’ knowledge for generating assessment criteria on the products, and the observable actions that affect the modelling cycle.