Das neue Neodym(III)‐Oxidchlorid‐Oxoselenat(IV) Nd7O5Cl3[SeO3]4

Pale violet, needle‐shaped single crystals of the new neodymium(III) oxide chloride oxoselenate(IV) Nd₇O₅Cl₃[SeO₃]₄ were obtained by the reaction of Nd₂O₃ and NdCl₃ with SeO₂ (molar ratio: 3:1:4) in evacuated silica ampoules within seven days at 775 °C, if an excess of CsCl worked as fluxing agent. Nd₇O₅Cl₃[SeO₃]₄ crystallizes in the triclinic space group P with the lattice parameters a = 694.46(4), b = 944.53(5), c = 1567.92(9) pm, α = 87.821(3), β = 81.849(3), γ = 84.852(3)° and Z = 2. Its structure exhibits seven crystallographically different Nd³⁺ cations, of which (Nd1)³⁺ – (Nd4)³⁺ are coordinated by O^2– anions forming distorted square prisms. The polyhedra of (Nd1)³⁺ and (Nd2)³⁺ receive additional caps by one Cl^– anion each, and (Nd5)³⁺ – (Nd7)³⁺ show mixed square antiprismatic environments of O^2– and Cl^– anions too. However, the polyhedra of (Nd5)³⁺ and (Nd6)³⁺ include two, the polyhedron about (Nd7)³⁺ even three Cl^– anions. Two‐dimensional layers of edge‐ and vertex‐linked [ONd₄]¹⁰⁺ tetrahedra are built up by (O1)^2– – (O5)^2– together with all Nd³⁺ cations. All the other oxygen atoms belong to four crystallographically different Se⁴⁺ cations erecting ψ¹‐tetrahedral oxoselenate(IV) units [SeO₃]^2– with stereochemically active non‐bonding electron pairs (“lone pairs”) pointing into the free space between the layers. Three independent Cl^– anions in threefold coordination of Nd³⁺ cations interconnect the layers to form a three‐dimensional network, thereby achieving the charge balance.     

Cyclic and branched functional polyesters derived from 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane and various dicarboxylic acids

Triethylamine‐promoted polycondensations of 5,5′,6,6′‐tetrahydroxy‐3,3, 3′,3′‐tetramethyl spirobisindane (TTSBI) and α,ω‐alkane dicarboxylic acid dichlorides were performed with equimolar feed ratios. Three different procedures were compared. At a TTSBI concentration of 0.05 mol/L, gelation was avoided, and soluble cyclic polyesters having two OH groups per repeat unit were isolated. These polyesters were characterized with ¹H NMR spectroscopy, MALDI‐TOF mass spectrometry, and SEC and DSC measurements. All polycondensations with sebacoyl chloride resulted in gelation, regardless of the procedure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1699–1706, 2007     

Synthesis of amphiphilic biodegradable glycocopolymers based on poly(ε‐caprolactone) by ring‐opening polymerization and click chemistry

Amphiphilic, biodegradable block glycopolymers based on poly(ε‐caprolactone) (PCL) with various pendent saccharides were synthesized by combination of ring‐opening polymerization (ROP) and “click” chemistry. PCL macroinitiators obtained by ROP of ε‐caprolactone were used to initiate the ROP of 2‐bromo‐ε‐caprolactone (BrCL) to get diblock copolymers, PCL‐b‐PBrCL. Reaction of the block copolymers with sodium azide converted the bromine groups in the PBrCL block to azide groups. In the final step, click chemistry of alkynyl saccharides with the pendent azide groups of PCL‐b‐PBrCL led to the formation of the amphiphilic block glycopolymers. These copolymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography. The self‐assembly behavior of the amphiphilic block copolymers was investigated using transmission electron microscopy and atomic force microscope, spherical aggregates with saccharide groups on the surface were observed, and the aggregates could bind reversibly with Concanavalin A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3583–3594, 2009     

“Click” chemistry for in situ formation of thermoresponsive P(NIPAAm‐co‐HEMA)‐based hydrogels

The strategy for in situ chemical gelation of poly(N‐isopropylacrylamide‐co‐hydroxylethyl methacrylate) [P(NIPAAm‐co‐HEMA)]‐based polymers was demonstrated. Two types of new P(NIPAAm‐co‐HEMA) derivatives with alkyne and azide pendant groups, respectively, were prepared. When the solutions of the two derivatives were mixed together, a crosslinking reaction, a type of Huisgen's 1,3‐dipolar azide‐alkyne cycloaddition, in the presence of Cu(I) catalyst occurs. The morphology, equilibrium swelling ratio, swelling kinetics, and temperature response kinetics of the in situ gelated hydrogels were studied. In comparison with the conventional PNIPAAm hydrogel, because of the spatial hindrance of polymeric chains, the resulted hydrogels had a macroporous structure as well as a fast shrinking rate. The strategy described here presents a potential alternative to the traditional synthesis techniques for the in situ formation of thermoresponsive hydrogels. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5263–5277, 2008     

Photo‐initiated thiol–ene “click” hydrogels from RAFT‐synthesized poly(N‐isopropylacrylamide)

Despite the efficiency and robustness of the widely used copper‐catalyzed 1,3‐dipolar cycloaddition reaction, the use of copper as a catalyst is often not attractive, particularly for materials intended for biological systems. The use of photo‐initiated thiol‐ene as an alternative “click” reaction to synthesize “model networks” is investigated here. Poly(N‐isopropylacrylamide) precursors were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and were designed to have trithiocarbonate moieties as end groups. This structure design provides opportunity for subsequent end‐group modifications in preparation for thiol‐ene “click.” Two reaction routes have been proposed and studied to yield thiol and ene moieties. The advantages and disadvantages of each reaction path were investigated to propose a simple but efficient route to prepare copper‐free “click” hydrogels. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4626–4636     

“Bottom‐Up” Fabrication of BODIPY‐Functionalized Fluorescent Hyperbranched Glycopolymers for Hepatoma‐Targeted Imaging

A novel type of multivalent and highly specific fluorescent hyperbranched glycopolymers h‐P(GalEA‐co‐VBPT‐co‐BYMA) (hPGVB) is designed and prepared successfully via a facile “bottom‐up” strategy. The acetylated hPGVB is prepared by one‐pot reversible addition‐fragmentation chain transfer (RAFT) copolymerization of acrylate‐type galactose monomers AcGalEA and methacrylate‐type fluorescent monomers BYMA in presence of an inimer‐type RAFT chain transfer agent. After deacetylation, the resulting amphiphilic hPGVB can self‐assemble into stable nanoparticles in aqueous media, showing strong green fluorescence with relative high quantum yields and good photostability. The cell viability study indicates the excellent biocompatibility of the hPGVB fluorescent nanoparticles (FNPs) against HepG2 and NIH3T3 cells. More importantly, comparing with the galactose‐free fluorescent hyperbranched polymers h‐P(OEGMA‐co‐VBPT‐co‐BYMA), hPEVB FNPs can be selectively internalized by asialoglycoprotein (ASGP) receptor‐rich HepG2 cells, indicating their potential application in the bioimaging fields.     

A Strontium‐ and Chlorine‐Free Pyrotechnic Illuminant of High Color Purity

The development of a red‐light‐emitting pyrotechnic illuminant has garnered interest from the pyrotechnics community owing to potential regulations by the United States Environmental Protection Agency (U.S. EPA) regarding the use of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium‐based red‐light‐emitting pyrotechnic compositions of high purity and color quality is described. These formulations do not contain strontium or chlorinated organic materials. Rather, the disclosed formulations are based on a non‐hygroscopic dilithium nitrogen‐rich salt that serves as both oxidizer and red colorant. These formulations are likely to draw interest from the civilian fireworks and military pyrotechnics communities for further development as they both have a vested interest in the development of environmentally conscious formulations.     

Synthesis of boronate‐functionalized organic‐inorganic hybrid monolithic column for the separation of cis‐diol containing compounds at low pH

In this work, an organic‐inorganic hybrid boronate affinity monolithic column was prepared via “one‐pot” process using 4‐vinylphenylboronic acid as organic monomer and divinylbenzene as cross‐linker. The effects of reaction temperature, solvents and composition of organic monomers on the column properties (e.g. morphology, permeability, and mechanical stability) were investigated. A series of test compounds including small neutral molecules, aromatic amines, and cis‐diol compounds were used to evaluate the retention behaviors of the prepared hybrid monolithic column. The results demonstrated that the prepared hybrid monolith exhibited mixed‐interactions including hydrophilicity, cation exchange, and boronate affinity interaction. The run‐to‐run, day‐to‐day and batch‐to‐batch reproducibilities of the prepared hybrid monolith for thiourea's retention time were satisfactory with the relative standard deviations (RSDs) less than 0.09, 1.45 and 4.05% (n = 3), respectively, indicating the effectiveness and practicability of the proposed method.     

In situ fabrication of paclitaxel‐loaded core‐crosslinked micelles via thiol‐ene “click” chemistry for reduction‐responsive drug release

In this study, a facile method to fabricate reduction‐responsive core‐crosslinked micelles via in situ thiol‐ene “click” reaction was reported. A series of biodegradable poly(ether‐ester)s with multiple pendent mercapto groups were first synthesized by melt polycondensation of diol poly(ethylene glycol), 1,4‐butanediol, and mercaptosuccinic acid using scandium trifluoromethanesulfonate [Sc(OTf)₃] as the catalyst. Then paclitaxel (PTX)‐loaded core‐crosslinked (CCL) micelles were successfully prepared by in situ crosslinking hydrophobic polyester blocks in aqueous media via thiol‐ene “click” chemistry using 2,2′‐dithiodiethanol diacrylate as the crosslinker. These PTX‐loaded CCL micelles with disulfide bonds exhibited reduction‐responsive behaviors in the presence of dithiothreitol (DTT). The drug release profile of the PTX‐loaded CCL micelles revealed that only a small amount of loaded PTX was released slowly in phosphate buffer solution (PBS) without DTT, while quick release was observed in the presence of 10.0 mM DTT. Cell count kit (CCK‐8) assays revealed that the reduction‐sensitive PTX‐loaded CCL micelles showed high antitumor activity toward HeLa cells, which was significantly higher than that of reduction‐insensitive counterparts and free PTX. This kind of biodegradable and biocompatible CCL micelles could serve as a bioreducible nanocarrier for the controlled antitumor drug release. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 99–107     

A Novel Self‐protection Hydroquinone Electrochemical Sensor Based on Thermo‐sensitive Triblock Polymer PS‐PNIPAm‐PS

A novel self‐protection sensor was successfully constructed based on an interesting thermo‐sensitive triblock polymer PS‐PNIPAm‐PS. At low temperatures (<24 °C), the analyte was able to undergo the redox process at the modified electrode. However, the polymer shrunk and accumulated at high temperatures (>30 °C), which dramatically increased the electron transfer resistance (Rct) of the modified electrode and consequently blocked the occurrence of the redox reaction to protect the electrode from high temperatures and enhance its stability. Under optimized conditions, the proposed sensor showed a good detection range for hydroquinone (6×10^?7 to 2.35×10^?3 M) and a low LOD (490 nM). The sensor was also successfully applied for detecting hydroquinone in real samples. The present work may provide a novel method for electrode protection, high‐temperature alarm, high‐temperature protection of batteries and new sensors production.     

Tragacanth gum‐based pH‐responsive magnetic hydrogels for “smart” chemo/hyperthermia therapy of solid tumors

The drug delivery performances of pH‐responsive magnetic hydrogels (MHs) composed of tragacanth gum (TG), poly(acrylic acid) (PAA), and Fe₃O₄ nanoparticles (NPs) were investigated in terms of physicochemical as well as biological features. The fabricated drug delivery systems (DDSs) were analyzed using Fourier transform infrared spectroscopy, X‐ray diffraction, vibrating sample magnetometer, scanning electron microscopy, and transmission electron microscopy. The synthesized MHs were loaded with doxorubicin hydrochloride (Dox) as a universal model anti‐cancer drug. The MHs showed excellent Dox loading and encapsulation efficiencies, mainly due to strong hydrogen bonding and electrostatic interaction between the drug and polymeric matrix, as well as porous micro‐structures of the fabricated MHs. The drug‐loaded MHs showed negligible drug release values in physiological condition. In contrast, in cancerous condition (pH 5.0), both MHs exhibited highest drug release values that qualified them as “smart” DDSs. The cytocompatibilities of the MHs as well as the cytotoxicity of the Dox‐loaded MHs were investigated against human epidermoid‐like carcinoma (Hela) cells through MTT assay. In addition, hyperthermia therapy induced by Fe₃O₄ NPs was applied to locally raise temperature inside the Hela cells at 45 ± 3°C to promote cell death. As a result, the Dox‐loaded MHs can be considered as potential DDSs for chemo/hyperthermia therapy of solid tumors.     

Hairy PEO‐Silica Nanoparticles through Surface‐Initiated Polymerization of Ethylene Oxide

Summary: The grafting of poly(ethylene oxide) (PEO) onto silica nanoparticles was performed in situ by the ring‐opening polymerization of the oxirane monomer initiated from the mineral surface using aluminium isopropoxide as an initiator/heterogeneous catalyst. Alcohol groups were first introduced onto silica by reacting the surfacic silanols with prehydrolyzed 3‐glycidoxypropyl trimethoxysilane. The alcohol‐grafted silica played the role of a coinitiator/chain‐transfer agent in the polymerization reaction and enabled the formation of irreversibly bonded polymer chains. Silica nanoparticles containing up to 40 wt.‐% of a hairy layer of grafted PEO chains were successfully produced by this technique.

The grafting of poly(ethylene oxide) (PEO) onto silica nanoparticles by in‐situ ring‐opening polymerization of the oxirane monomer.     

Mechanistic investigation inspired “on water” reaction for hydrobromic acid‐catalyzed Friedel–Crafts–type reaction of β‐naphthol and formaldehyde

The mechanism of the HBr‐catalyzed Friedel‐Crafts‐type reaction between β‐naphthol and HCHO was investigated by DFT to improve this reaction. The HBr‐H₂O co‐catalyzed the preferential pathway undergoes the concerted nucleophilic addition and hydrogen shift, stepwise followed by H₂O elimination and the C C bond formation. The origin of the high catalytic activity of HBr is ascribed to C H···Br⁻ and O H···Br⁻ interactions, which suggest that the active species is Br⁻. Moreover, water molecules efficiently assist in improving the activity of Br⁻. The computational results show that solvent polarity profoundly affects the activation barriers. To our delight, the activation barrier of the rate‐determining step for the favored pathway in water is comparable (0.6 kcal/mol difference) with that in acetonitrile. The experimental observation further confirmed our results and demonstrated that the title reaction can be successfully achieved “on water.” Therefore, we open a new efficient and green strategy for the synthesis of biphenol derivatives. © 2017 Wiley Periodicals, Inc.     

Azide/Alkyne‐“Click”‐Reactions of Encapsulated Reagents: Toward Self‐Healing Materials

The successful encapsulation of reactive components for the azide/alkyne‐“click”‐reaction is reported featuring for the first time the use of a liquid polymer as reactive component. A liquid, azido‐telechelic three‐arm star poly(isobutylene) ( = 3900 g · mol⁻¹) as well as trivalent alkynes were encapsulated into micron‐sized capsules and embedded into a polymer‐matrix (high‐molecular weight poly(isobutylene), = 250 000 g · mol⁻¹). Using (Cu^IBr(PPh₃)₃) as catalyst for the azide/alkyne‐“click”‐reaction, crosslinking of the two components at 40 °C is observed within 380 min and as fast as 10 min at 80 °C. Significant recovery of the tensile storage modulus was observed in a material containing 10 wt.‐% and accordingly 5 wt.‐% capsules including the reactive components within 5 d at room temperature, thus proving a new concept for materials with self‐healing properties.

     

Well‐defined epoxide‐containing styrenic polymers and their functionalization with alcohols

Polymers containing electrophilic moieties, such as activated esters, epoxides, and alkyl halides, can be readily modified with a variety of nucleophiles to produce useful functional materials. The modification of epoxide‐containing polymers with amines and other strong nucleophiles is well‐documented, but there are no reports on the modification of such polymers with alcohols. Using phenyloxirane and glycidyl butyrate as low molecular weight model compounds, it was determined that the acid‐catalyzed ring‐opening of aryl‐substituted epoxides by alcohols to form β‐hydroxy ether products was significantly more efficient than that of alkyl‐substituted epoxides. An aryl epoxide‐type styrenic monomer, 4‐vinylphenyloxirane (4VPO), was synthesized in high yield using an improved procedure and then polymerized in a controlled manner under reversible addition‐fragmentation chain‐transfer (RAFT) polymerization conditions. A successful chain extension with styrene proved the high degree of chain‐end functionalization of the poly4VPO‐based macro chain transfer agent. Poly4VPO was modified with a library of alcohols and phenols, some of which contained reactive functionalities, e.g., azide, alkyne, allyl, etc., using either CBr₄ (in PhCN at 90 °C for 2–3 days) or BF₃ (in CH₂Cl₂ at ambient temperature over 30 min) as the catalyst. The resulting β‐hydroxy ether‐functionalized homopolymers were characterized using size exclusion chromatography, ¹H NMR and IR spectroscopy, and thermal gravimetric analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1132–1144     

One‐pot synthesis of surface‐functionalized molecularly imprinted polymer microspheres by iniferter‐induced “living” radical precipitation polymerization

This article describes for the first time the development of a new polymerization technique by introducing iniferter‐induced “living” radical polymerization mechanism into precipitation polymerization and its application in the molecular imprinting field. The resulting iniferter‐induced “living” radical precipitation polymerization (ILRPP) has proven to be an effective approach for generating not only narrow disperse poly(ethylene glycol dimethacrylate) microspheres but also molecularly imprinted polymer (MIP) microspheres with obvious molecular imprinting effects towards the template (a herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D)), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant K_a and apparent maximum number N_max for the high‐affinity sites of the 2,4‐D imprinted polymer were determined by Scatchard analysis and found to be 1.18 × 10⁴ M^?1 and 4.37 μmol/g, respectively. In addition, the general applicability of ILRPP in molecular imprinting was also confirmed by the successful preparation of MIP microspheres with another template (2‐chloromandelic acid). In particular, the living nature of ILRPP makes it highly useful for the facile one‐pot synthesis of functional polymer/MIP microspheres with surface‐bound iniferter groups, which allows their direct controlled surface modification via surface‐initiated iniferter polymerization and is thus of great potential in preparing advanced polymer/MIP materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3217–3228, 2010