In this article, the synthesis and self‐assembly of a novel well‐defined biocompatible amphiphilic POEGMA‐PDMS‐POEGMA triblock copolymer were studied. The copolymer was synthesized by atom transfer radical polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) using α,ω‐dibromo polydimethylsiloxane macroinitiator (Br‐PDMS‐Br). Br‐PDMS‐Br was synthesized through the esterification of α,ω‐hydroxypropyl polydimethylsiloxane and 2‐bromoisobutyryl bromide. The structures of the copolymers were confirmed by proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The copolymers showed reversible aggregation in response to temperature cycles with a lower critical solution temperature (LCST) between 61 and 66 °C, as determined by ultraviolet‐visible spectrophotometry and dynamic light scattering. The LCST values increased in proportion to the length of the hydrophilic block and were lower than that of the POEGMA homopolymer. The self‐assembly behavior of the copolymers in aqueous solution was investigated by fluorescence spectroscopy and transmission electron microscopy. The critical micelle concentration value (1.08–0.26 10−6 mol L−1) decreased as the length of the POEGMA chain increased. The POEGMA‐PDMS‐POEGMA copolymers can easily self‐assemble into spherical micelles in aqueous solution. Such biocompatible block copolymers may be attractive candidates as ‘‘smart'' thermo‐responsive drug delivery systems. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2684‐2691

To explore the applications of click chemistry in polyurethane materials, a series of novel linear polyurethane-triazoles (PUTs) are prepared using the in situ click reaction of propargylterminated polyurethanes with 1,4-dibromobutane in the presence of sodium azide. The PUT structures are confi rmed by 1 H NMR, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis, and the number-average molecular weights of PUTs range from (3.74-11.16) × 10 4 g mol −1 , determined by gel permeation chromatography. The triazole ring content is characterized and the effects of incorporating the triazole rings on the properties and morphologies of PUTs are examined. Because of the extra dipole-dipole interaction and hydrogen bonds of 1,4-disubstituted triazole in the hard segments, microphase separation of the PUTs is enhanced compared with conventional polyurethane extended with 1,4-butanediol. The tensile strengths of PUTs, from 21.8 to 39.0 MPa, are higher than conventional polytriazole elastomers, owing to the physical crosslinks formed by the hydrogen bonds in the PUTs. However, the thermal stability of the PUTs decreases as the hard segment content increases. regard to health hazards of the isocyanates used, and possible side or unwanted reactions, such as reaction with water or with preformed urethane groups. [6][7][8] Since the copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click reaction" was introduced by Sharpless [ 9 ] and Meldal [ 10 ] independently, it has become a useful tool for connecting polymer fragments to form linear, [11][12][13] star, [14][15][16] and dendrimer architectures, [17][18][19] because of its high effi ciency, regioselectivity and mild reaction conditions. Polymers constructed using regular triazole linkages through click polymerization of small diynes and bisazides, called polytriazoles, are very brittle and show poor processability. [20][21][22] To improve the polymer properties, researchers have inserted polyols, such as PEG [ 23,24 ] and PDMS [ 25,26 ] into the structure to obtain polytriazole elastomers. However, relatively low mechanical properties of these polytriazole elastomers have been observed even after chemical crosslinking. Side chain post-functionalization of PUs by click methodologies has also been reported. PUs with clickable side chain groups, such as

Two kinds of diols containing 1,2,3‐triazole units were synthesized through the azide‐alkyne cycloaddition reaction between propargyl alcohol and 1,4‐diazidobutane. One of the diols, (butane‐1,4/1,5‐diylbis[1H‐1,2,3‐triazole‐1,4/1,5‐diyl])dimethanol (BDTDO‐1), containing 1,4/1,5‐disubstituted 1,2,3‐triazole regioisomers, was directly prepared under thermal condition without Cu(I) catalyst. The other diol, (butane‐1,4‐diylbis[1H‐1,2,3‐triazole‐1,4‐diyl])dimethanol (BDTDO‐2), containing 1,4‐disubstituted 1,2,3‐triazoles, was prepared by Cu(I) catalyzed click chemistry. Then, two kinds of 1,2,3‐triazole modified polyurethane elastomers (PUEs) were prepared from the reaction of 4,4′‐methylenebis(phenyl isocyanate) and poly(tetramethylene ether) glycol, with BDTDO‐1 or BDTDO‐2 as the chain extender (CE). It was found that the introduction of 1,2,3‐triazoles and their substitution positions had significant influences on the hydrogen bonding, thermal and mechanical properties of PUEs. Compared with the PUE prepared from 1,4‐butanediol as the CE, the PUE containing symmetric 1,4‐disubstituted 1,2,3‐triazoles units in the main chains shows higher values of hydrogen bonding, physical crosslinking density, Young's modulus, tensile strength and melting temperature, while lower glass transition temperature, resulting from the rigid structure and the ability to form more hydrogen bonds. However, the introduction of asymmetric 1,4/1,5‐disubstituted 1,2,3‐triazole moieties decreases the values of hydrogen bonding, thermal and mechanical properties of PUE appreciably due to the destruction of the ordered structure of the hard segments.

Morphology and electronic-structure modulation are of widespread interest when designing oxygen-evolution-reaction (OER) electrocatalysts for use in fuel cells. In this study, we prepared a NiTe2/NF@CuFe catalyst using replacement reactions and hydrothermal reduction. NiTe2-nanoparticle morphology was adjusted by the introduction of multiple Fe centers and Cu replacement, which resulted in a NiTe2/NF@CuFe catalyst that exhibited excellent OER performance. The thus-prepared catalyst showed a low overpotential of 228 mV and a Tafel slope of 33 mV dec–1 at 10 mA cm–2 in 1 M KOH as the electrolyte. The catalyst is remarkably stable compared to the reference catalyst during electrocatalytic oxygen evolution over 12 h. Density function theory calculations confirmed that the Cu atoms not only facilitate neighboring charge-transfer processes but also build isolated areas of NiTe2 nanoparticles. Net charges and the electron localization function reveal that the well-distributed doped Fe atoms significantly stabilize the NiTe2 nanoparticles on the surface and improve its electronic activity during the OER process. This work provides an effective concept for the synthesis of highly efficient overall water-splitting electrocatalysts.

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