Photoinduced Specific Acylation of Phenolic Hydroxy Groups with Aldehydes

A convenient method is reported to specifically acylate phenolic hydroxyl groups through a radical pathway. When a mixture of an aldehyde and a phenol in ethyl acetate is irradiated with blue light in the presence of iridium and nickel bromide catalysts at ambient temperature, phenoxyl and acyl radicals are transiently generated in situ and cross‐couple to furnish an ester. Aliphatic hydroxy groups remain untouched under the reaction conditions.     

Role of the interface in multicomponent materials

Studies of the relationship between interfacial structure and mechanical properties in multicomponent materials are reviewed in this article. The following categories are considered for role of the interface in multicomponent systems: Interpenetrating polymer network(IPN), catalytic effect of silane coupling agent, morphological differences of filler surface, particle-particle interaction and particle size of the filler. The interfacial role in terms of the reinforcement mechanism of the composite and the behavior in the melt state is also discussed in the multicomponent system.     

Polyether-bridged bis(tert-butyl nitroxide) paramagnetic hosts showing receptor ability to calcium(II) and barium(II) ions

The title compounds, Ph2bNO and Ph3bNO, were designed as a biradical paramagnetic host, and their chelation ability was confirmed by inclusion of a size-matched alkaline-earth metal ion. The crystal structures of [Ca(hfac)₂(Ph2bNO)] and [Ba(hfac)₂(Ph3bNO)] were determined, where Hhfac stands for 1,1,1,5,5,5-hexafluoropentane-2,4-dione. The solution electron paramagnetic resonance spectra showed switching behavior. Five lines were found for Ph3bNO and charecterized as the hyperfine splitting due to the two nitrogen atoms. After addition of barium(II) ion, the spectrum turned to be three lines. Removal of the barium ion recovered the five line pattern. The present system can be regarded as a reversible magnetic-coupling switch by means of a supramolecular technique.     

Intrinsic self‐initiating thermal ring‐opening polymerization of 1,3‐benzoxazines without the influence of impurities using very high purity crystals

A phenol/aniline type monofunctional benzoxazine monomer, PH‐a , is synthesized and highly purified to study the intrinsic thermal ring‐opening polymerization of benzoxazines without the influence of any impurity. The successful synthesis of the monomer and its corresponding chemical structure are confirmed by Fourier transform infrared spectroscopy (FTIR) and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. Purity of the compound is evaluated through differential scanning calorimetry (DSC) as well as elemental analysis (EA). Moreover, the thermal behavior of benzoxazine monomer toward polymerization is also studied by DSC, indicating that the highly purified benzoxazine monomer actually polymerize upon heating. The results present evidence of an intrinsic tendency for 1,3‐benzoxazines to undergo thermally induced ring‐opening polymerization upon heating only without any impurity participating during the reaction. This reveals that polybenzoxazines can be obtained by both the traditional thermally accelerated (or activated) polymerization, where impurities or purposefully added initiators are involved in the reaction; or, by the classic thermal polymerization, where only heat is enough to initiate the reaction. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3434–3445     

Monotonicity recovering and accuracy preserving optimization methods for postprocessing finite element solutions

We suggest here a least-change correction to available finite element (FE) solution. This postprocessing procedure is aimed at recovering the monotonicity and some other important properties that may not be exhibited by the FE solution. Although our approach is presented for FEs, it admits natural extension to other numerical schemes, such as finite differences and finite volumes. For the postprocessing, a priori information about the monotonicity is assumed to be available, either for the whole domain or for a subdomain where the lost monotonicity is to be recovered. The obvious requirement is that such information is to be obtained without involving the exact solution, e.g. from expected symmetries of this solution.The postprocessing is based on solving a monotonic regression problem with some extra constraints. One of them is a linear equality-type constraint that models the conservativity requirement. The other ones are box-type constraints, and they originate from the discrete maximum principle. The resulting postprocessing problem is a large scale quadratic optimization problem. It is proved that the postprocessed FE solution preserves the accuracy of the discrete FE approximation.We introduce an algorithm for solving the postprocessing problem. It can be viewed as a dual ascent method based on the Lagrangian relaxation of the equality constraint. We justify theoretically its correctness. Its efficiency is demonstrated by the presented results of numerical experiments.     

Synthesis,characterization, photo‐induced alignment,and surface orientation of poly(9,9‐dioctylfluorene‐alt‐azobenzene)s

Three types of bi‐functionalized copolymers ( P1FAz , P2FAz , and P3FAz ) with different numbers of fluorene units and an azobenzene unit were synthesized and characterized using UV–vis and polarized absorption spectroanalysis. The trans‐cis photoisomerization was conformed under 400 nm light irradiation for all copolymers in chloroform. However, in the film state, only the trans‐cis photoisomerization occurred by mono‐fluorene attached copolymer poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐4,4′‐azobenzene)] ( P1FAz ). Photo‐induced alignment was achieved using the P1FAz film after irradiation with linear polarized 400 nm light and subsequent annealing at 60 °C. Surface orientation of a spin‐coating film of poly(9,9‐didodecylfluorene) ( F12 ) was achieved using the photo‐induced alignment layer of the P1FAz film after annealing at 90 °C. The photo‐induced alignment layer of P1FAz has potential application to the surface orientation technique for appropriate polymers, which will be useful for the fabrication of optoelectronics devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

q-Moduli of Continuity in H( ), p>0, and an Inequality of Hardy and Littlewood

Some aspects of the interplay between approximation properties of analytic functions and the smoothness of its boundary values are discussed. One main result describes the equivalence of a special q-modulus of continuity and an intrinsic K-functional. Further, a generalization of a theorem due to G. H. Hardy and J. E. Littlewood (1932, Math. Z.34, 403–439) on the growth of fractional derivatives is deduced with the help of this K-functional.