Fluorescence from fluorescent dye based polyurethane ionomer(III)

A series of reactive fluorescent dyes were successfully synthesized and their structure was proven by IR spectra, NMR spectra, elemental analysis, and mass spectra. The fluorescence performance 6‐amino‐2(‐3‐phenyl‐propyl)‐benzo[de]isoquinoline‐1,3‐dione and 2‐benzyl‐6‐hydroxy‐benzo[de]isoquinoline‐1,3‐dione appears at around 276 and 437.4 nm, respectively, and their quantum yields are 0.662 and 0.562, respectively. It is important to indicate that the fluorescence performance is better for 6‐amino‐2(‐3‐phenyl‐propyl)‐benzo[de]isoquinoline‐1,3‐dione than for as a result of more electron donating groups linked to the 6‐amino‐2(‐3‐phenyl‐propyl)‐benzo[de]isoquinoline‐1,3‐dione molecule. These fluorescent dyes further react with toluene diisocyanate and other additives to form fluorescent dye based polyurethane (PU) ionomer molecules, and their structures are demonstracted by IR spectra. In aqueous solution, the fluorescence performance appears to be better for 6‐amino‐2(‐3‐phenyl‐propyl)‐benzo[de]isoquinoline‐1,3‐dione based PU ionomer than for 6‐amino‐2‐phenyl‐ethyl‐benzo[de]isoquinoline‐1,3‐dione based PU ionomer. For the fluorescent dye based PU ionomer molecule system, the number‐average particle sizes of the fluorescent dye based PU ionomer molecules in water increase with increasing concentration of the fluorescent dye, as a result of the increased free volume of the ionomer molecule. This may be the result of increased intermolecular interactions between ionomer– molecules themselves. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 455–465, 2005     

Novel regenerable N‐halamine polymeric biocides. I. Synthesis,characterization, and antibacterial activity of hydantoin‐containing polymers

Two novel cyclic‐amine monomers, i.e., 3‐allyl‐5,5‐dimethylhydantoin (ADMH) and 7,8‐benzo‐3 allyl‐1,3‐diazasprio[4.5]decane‐2,4‐dione (BADDD) were synthesized with good yields by reacting allyl bromide with 5,5‐dimethylhydantoin (DMH) and 7,8‐benzo‐1,3‐diazasprio[4.5]decane‐2,4‐dione (BDDD), respectively. The synthesized monomers were characterized by FTIR and ¹H‐NMR spectra, and copolymerized with acrylonitrile (AN), vinyl acetate (VAC), and methyl methacrylate (MMA) in a small monomer ratio of ADMH and BDDD, respectively. The copolymers were characterized by FTIR, ¹H‐NMR, and DSC studies. The N‐halamine derivatives of the corresponding copolymers were found to exhibit high antibacterial activities against Escherichia coli, and the antibacterial properties were durable and regenerable. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2460–2467, 2001     

Study of fluorescence from fluorescent dye‐based polyurethane ionomer

6‐Amino‐2‐(3‐chloro‐2‐hydroxy‐propyl)‐ benzo[de]isoquinoline‐1,3‐dione (DYE‐A) and 2‐benzyl‐6‐hydroxy‐benzo[de]isoquinoline‐1,3‐dione (DYE‐B) have been successfully synthesized in our lab, and their structures have been proven by IR, NMR, and mass spectra. The fluorescence performance appears to be better for DYE‐A than for DYE‐B as a result of DYE‐A having more electron donating substituents that are strongly excited when absorbing UV light. These fluorescent dyes have further reacted with toluene diisocyanate and other additives to form the fluorescent dye‐based polyurethane (PU) ionomer molecules, and the structures of these molecules have been demonstrated by IR spectra. In aqueous solution, our experimental results indicate that the fluorescence performance is seen to be better for DYE‐A than for DYE‐B. Increased concentration of DYE‐A molecule attached to the backbone of the PU ionomer molecule may reduce the fluorescence performance of this PU ionomer molecule, resulting from the intramolecular interaction between ionomer molecule itself. For the fluorescent dye‐based PU ionomer molecule system, the average particle size of the fluorescent dye‐based PU ionomer molecule in water increases with increasing concentration of the fluorescent dyes, as a result of increased free volume of the ionomer molecules. Our experimental results also illustrate that the tensile strength of self‐cured film made by the fluorescent dye‐based PU ionomer appears to increase with an increase in the concentration of DYE‐A. This is the result of increased intermolecular interaction between ionomer molecules. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2723–2737, 2003     

Synthesis and characterization of light‐absorbing cyclopentadithiophene‐based donor–acceptor copolymers

Cyclopentadithiophene and benzothiadiazole based donor–acceptor polymers are fast emerging as the most promising class of materials for organic solar cells. Here we report on a series of Cyclopentadithiophene and benzothiadiazole based conjugated polymers, namely poly[4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole] (P1), poly[4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole‐alt‐9‐(heptadecan‐9‐yl)‐2,7‐bis(4,4,5,5‐tetramethyl)‐1,3,2‐dioxaborolan‐2‐yl)‐9H‐carbazole] (P2) and poly[4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole‐alt‐5,11‐bis(2‐hexyldecyl)‐3,9‐bis(4,4,5,5‐tetramethyl)‐1,3,2‐dioxaborolan‐2‐yl)‐5,11‐dihydroindolo[3,2‐b]carbazole] (P3), with alternating donor and acceptor units and discuss their photophysical and electrochemical properties. Stille coupling of 2‐tributylstannyl‐4,4‐dioctylcyclopenta[2,1‐b:3,4‐b′]dithiophene with 4,7‐dibromobenzo[1,2,5]thiadiazole generated the alternating donor–acceptor monomer 4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole (CPDT‐BT‐CPDT). Homopolymer P1 of CPDT‐BT‐CPDT was synthesized by oxidative polymerization using FeCl₃. Copolymers P2 and P3 were synthesized by palladium‐catalysed Suzuki polycondensation. The synthesized polymers showed good solubility in common organic solvents, and UV‐visible measurements showed that the absorption maxima of the polymers lie in the range 624 to 670 nm. The energy gaps of these polymers were found to lie in the range 1.29 to 1.50 eV. Gel permeation chromatography measurements against polystyrene standards showed the number‐average molecular weight to be in the range (2.2–6.0) × 10⁴ g mol^?1. Thermogravimetric analysis showed the polymers to possess high thermal stability. A preliminary study of photodiode devices prepared using polymers P1, P2 and P3 when blended with the PC₇₁BM electron acceptor found that P2 is the optimum chemical structure for pursuing further device optimization.© 2015 Society of Chemical Industry     

Synthesis and photovoltaic device studies of azo‐linked low‐bandgap polymers

We report the synthesis of a series of new polymers containing azo linkage as a part of the main chain. The monomer 1,2‐bis(7‐bromo‐9,9‐dioctyl‐9H ‐fluoren‐2‐yl)diazene was synthesized using a precursor approach which avoids non‐selective bromination and was copolymerized with various donor or acceptor units. The homopolymer poly[1,2‐bis(9,9‐dioctyl‐9H ‐fluoren‐2‐yl)diazene] ( P1 ) as well as the copolymers poly[1‐(9,9‐dioctyl‐9H ‐fluoren‐2‐yl)‐2‐(9,9,9′,9′‐tetraoctyl‐9H ,9′H ‐[2,2′‐bifluoren]‐7‐yl)diazene] ( P2 ), poly[1‐(9,9‐dioctyl‐7‐(4‐octylthiophen‐2‐yl)‐9H ‐fluoren‐2‐yl)‐2‐(9,9‐dioctyl‐9H ‐fluoren‐2‐yl)diazene] ( P3 ) and poly[4‐(7‐((9,9‐dioctyl‐9H ‐fluoren‐2‐yl)diazenyl)‐9,9‐dioctyl‐9H ‐fluoren‐2‐yl)benzo[c ][1,2,5]thiadiazole] ( P4 ) were synthesized by Suzuki polymerization. The copolymers poly[1‐(7‐(4,4‐dioctyl‐4H ‐cyclopenta[1,2‐b :5,4‐b ′]dithiophen‐2‐yl)‐9,9‐dioctyl‐9H ‐fluoren‐2‐yl)‐2‐(9,9‐dioctyl‐9H ‐fluoren‐2‐yl)diazene] ( P5 ) and poly[4‐(5‐(7‐((9,9‐dioctyl‐9H ‐fluoren‐2‐yl)diazenyl)‐9,9‐dioctyl‐9H ‐fluoren‐2‐yl)‐4‐octylthiophen‐2‐yl)‐7‐(4‐octylthiophen‐2‐yl)benzo[c ][1,2,5]thiadiazole] ( P6 ) were synthesized by direct arylation polymerization reaction. Polymers synthesized using the direct arylation method show good molecular weight, with absorption maxima in the range 500 to 532 nm. P5 and P6 possess low optical bandgaps of 1.81 and 1.86 eV, respectively. A power conversion efficiency of 0.53% with open circuit voltage of 0.53 V, short circuit current density of 3.1 mA cm^?2 and fill factor of 29% has been achieved with C71‐PCBM as acceptor in bulk heterojunction solar cells fabricated with P5 as donor. © 2016 Society of Chemical Industry     

Anionic copolymerization of diglycidyl ether of bisphenol A with Meldrum's acid derivatives initiated by 4‐(N,N‐dimethylamino) pyridine

The anionic copolymerization of diglycidyl ether of bisphenol A with 2,2,5,5‐tetramethyl‐4,6‐dioxo‐1,3‐dioxane or 6,6‐dimethyl‐(4,8‐dioxaspiro[2.5]octane‐5,7‐dione) with 4‐(N,N‐dimethylamino) pyridine as an initiator to form thermosets was studied with differential scanning calorimetry, and the kinetics were evaluated with isoconversional procedures. The evolution during the curing process of the epoxide, lactone, and linear ester bands was evaluated with Fourier transform infrared spectroscopy in the attenuated total reflection mode to clarify the reactions taking place. The shrinkage during curing, thermomechanical properties, and thermal degradability of the materials obtained by copolymerization with the different derivatives of Meldrum's acid were evaluated and related to the chemical structure of the final network. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Graft copolymerization of methyl methacrylate with an N‐substituted maleimide–liquid‐crystalline copolymer by atom transfer radical polymerization

The synthesis of novel copolymers consisting of a side‐group liquid‐crystalline backbone and poly (methyl methacrylate) grafts were realized by the use of atom transfer radical polymerization (ATRP). In the first stage, the bromine‐functional copolymers 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate and (2,5‐dioxo‐2,5‐dihydro‐1H‐pyrrole‐1‐yl)methyl 2‐bromopropanoate were synthesized by free‐radical polymerization. These copolymers were used as initiators in the ATRP of methyl methacrylate to yield graft copolymers. Both the macroinitiator and graft copolymers were characterized by ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP graft copolymerization was supported by an increase in the molecular weight of the graft copolymers compared to that of the macroinitiator and also by their monomodal molecular weight distribution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Microwave‐Assisted Syntheses of Benzimidazole‐Containing Selenadiazole Derivatives That Induce Cell‐Cycle Arrest and Apoptosis in Human Breast Cancer Cells by Activation of the ROS/AKT Pathway

The use of selenium‐containing heterocyclic compounds as potent cancer chemopreventive and chemotherapeutic agents has been well documented by a large number of clinical studies. In this study we developed a new approach to synthesize four benzimidazole‐containing selenadiazole derivatives (BSeDs). The method uses a combination of peptide coupling reagents and microwave irradiation. This strategy features milder reaction conditions, higher yields, and shorter reaction times. The synthetic BSeDs were identified as potent antiproliferative agents against the human MCF‐7 and MDA‐MB‐231 breast cancer cell lines. Compounds 1 b (5‐(6‐methyl‐1H‐benzo[d]imidazol‐2‐yl)benzo[c][1,2,5]selenadiazole), 1 c (5‐(6‐chloro‐1H‐benzo[d]imidazol‐2‐yl)benzo[c][1,2,5]selenadiazole), and 1 d (5‐(6‐bromo‐1H‐benzo[d]imidazol‐2‐yl)benzo[c][1,2,5]selenadiazole) were found to show greater cytotoxicity against the triple‐negative breast cancer cell line MDA‐MB‐231 than MCF‐7, and to exhibit dose‐dependent inhibition of cell migration, in which a significant decrease in the zone of cell monolayer wound closure was observed relative to untreated controls. Our results demonstrate that BSeDs can cause cell‐cycle arrest and apoptosis in MDA‐MB‐231 cells by inducing DNA damage, inhibiting protein kinase B (AKT), and activating mitogen‐activated protein kinase (MAPK) family members through the overproduction of reactive oxygen species (ROS). Taken together, the results of this study provide a facile microwave‐assisted strategy for the synthesis of selenium‐containing organic compounds that exhibit a high level of anticancer efficacy.     

Merging Allosteric and Active Site Binding Motifs: De novo Generation of Target Selectivity and Potency via Natural‐Product‐Derived Fragments

The de novo design of molecules from scratch with tailored biological activity is still the major intellectual challenge in chemical biology and drug discovery. Herein we validate natural‐product‐derived fragments (NPDFs) as excellent molecular seeds for the targeted de novo discovery of lead structures for the modulation of therapeutically relevant proteins. The application of this de novo approach delivered, in synergy with the combination of allosteric and active site binding motifs, highly selective and ligand‐efficient non‐zinc‐binding ( 3 : 4‐{[5‐(2‐{[(3‐methoxyphenyl)methyl]carbamoyl}eth‐1‐yn‐1‐yl)‐2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidin‐1‐yl]methyl}benzoic acid) as well as zinc‐binding ( 4 : 4‐({5‐[2‐({[3‐(3‐carboxypropoxy)phenyl]methyl}carbamoyl)eth‐1‐yn‐1‐yl]‐2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidin‐1‐yl}methyl)benzoic acid) uracil‐based MMP‐13 inhibitors presenting IC₅₀ values of 11 nM ( 3 : LE=0.35) and 6 nM ( 4 : LE=0.31).     

Use of allyl‐functional benzoxazine monomers as replacement for styrene in vinyl ester resins

New vinyl ester systems are prepared using allyl‐functional benzoxazine monomers, 3‐allyl‐6‐methyl‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazine (pC‐ala) or bis(3‐allyl‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazin‐6‐yl)methane (BF‐ala), as reactive diluents for vinyl ester resins derived from an epoxy resin, diglycidyl ether of bisphenol A, instead of using styrene. Different initiators are used to investigate the copolymerization of allyl function from pC‐ala with vinyl function from vinyl ester resin prepolymer. The temperature dependence of viscosity is studied to demonstrate the retention of processability of the new vinyl ester resins. Dynamic mechanical and thermogravimetric analyses are used to investigate the dynamic mechanical properties and thermal stability of the new resins. Copyright © 2012 Society of Chemical Industry     

Nitrative Spirocyclization Mediated by TEMPO: Synthesis of Nitrated Spirocycles from N‐Arylpropiolamides,tert‐Butyl Nitrite and Water

A new method for the nitrative spirocyclization of alkynes is described. This method involves the oxidative difunctionalization of alkynes initiated by a radical attack pathway using t‐BuONO (tert‐butyl nitrite) combined with water as the nitro source and TEMPO [(2,2,6,6‐tetramethyl‐piperidin‐1‐yl)oxyl] as the initiator, and it represents a new example of oxidative alkyne difunctionalization via the formation of C N/C C bonds for the assembly of nitroalkene unit‐containing spirocycles.

     

Effect of penta- and tetramethyl HALS on the radiation resistance of polypropylene

2,2,6,6-Tetramethyl-4-piperidinyl methacrylate (TMPM), a new pentamethyl HALS 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate (PMPM), their homopolymers (PTMPM and PPMPM), and their copolymers, [i.e., TMPM or PMPM copolymerized with monomers methyl methacrylate (MMA), methacrylic acid (MAA), acrylic acid (AA), and styrene (St) separately] were synthesized. PMPM shows an extremely excellent stabilizing effectiveness on improving the radiation resistance of polypropylene (PP) in comparison with other low molecular weight (LMW) HALS or polymeric HALS. Polymeric HALS shows a much higher thermal stability and better extraction resistance than that of LMW HALS. It is found that the Eb values of the PP-added pentamethyl HALS series are higher than those of PP with the corresponding tetramethyl HALS series at a given irradiation dose. A conclusion can be drawn that the pentamethyl HALS series has a higher stabilizing effectiveness than that of the tetramethyl HALS series. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2649–2656, 1998     

Structural Optimization of Berberine as a Synergist to Restore Antifungal Activity of Fluconazole against Drug‐Resistant Candida albicans

We have conducted systematic structural modification, deconstruction, and reconstruction of the berberine core with the aim of lowering its cytotoxicity, investigating its pharmacophore, and ultimately, seeking novel synergistic agents to restore the effectiveness of fluconazole against fluconazole‐resistant Candida albicans. A structure–activity relationship study of 95 analogues led us to identify the novel scaffold of N‐(2‐(benzo[d][1,3]dioxol‐5‐yl)ethyl)‐2‐(substituted phenyl)acetamides 7 a – l , which exhibited remarkable levels of in vitro synergistic antifungal activity. Compound 7 d (N‐(2‐(benzo[d][1,3]dioxol‐5‐yl)ethyl)‐2‐(2‐fluorophenyl)acetamide) significantly decreased the MIC₈₀ values of fluconazole from 128.0 μg mL^?1 to 0.5 μg mL^?1 against fluconazole‐resistant C. albicans and exhibited much lower levels of cytotoxicity than berberine toward human umbilical vein endothelial cells.     

Nitroxide‐mediated homopolymerization and copolymerization of 2‐vinylpyridine with styrene

Homopolymerization and copolymerization of 2‐vinylpyridine (2VP) with styrene (S) at 125°C in the presence of 2,2,6,6‐tetramethyl piperidin‐1‐yloxyl (TEMPO) radicals have been studied. The homopolymerization was carried out with 2,2′‐azobis(isobutyronitrile) (AIBN) as a thermal initiator or without AIBN in the initial reaction mixture. In the copolymerization initiated with AIBN, the molar fraction of 2VP in the feed, F_2VP, varied in the range of 0.1–0.9; F_2VP = 0.65 was found to be the azeotropic composition. The linear semilogarithmic time–conversion plots demonstrated a pseudoliving nature of the polymerizations under study. The molecular weight–conversion dependences indicated the participation of side reactions, diminishing the number of TEMPO‐terminated polymer chains. The synthesized homopolymers and copolymers were characterized using size‐exclusion chromatography (SEC), nitrogen analysis, and NMR spectroscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2024–2030, 2001     

A New Class of 1‐Aryl‐5,6‐dihydropyrrolo[2,1‐a]isoquinoline Derivatives as Reversers of P‐Glycoprotein‐Mediated Multidrug Resistance in Tumor Cells

A number of aza‐heterocyclic compounds, which share the 5,6‐dihydropyrrolo[2,1‐a]isoquinoline (DHPIQ) scaffold with members of the lamellarin alkaloid family, were synthesized and evaluated for their ability to reverse in vitro multidrug resistance in cancer cells through inhibition of P‐glycoprotein (P‐gp) and/or multidrug‐resistance‐associated protein 1. Most of the investigated DHPIQ compounds proved to be selective P‐gp modulators, and the most potent modulator, 8,9‐diethoxy‐1‐(3,4‐diethoxyphenyl)‐3‐(furan‐2‐yl)‐5,6‐dihydropyrrolo[2,1‐a]isoquinoline‐2‐carbaldehyde, attained sub‐micromolar inhibitory potency (IC₅₀: 0.19 μm ). Schiff bases prepared by the condensation of some 1‐aryl‐DHPIQ aldehydes with p‐aminophenol also proved to be of some interest, and one of them, 4‐((1‐(4‐fluorophenyl)‐5,6‐dihydro‐8,9‐dimethoxypyrrolo[2,1‐a]isoquinolin‐2‐yl)methyleneamino)phenol, had an IC₅₀ value of 1.01 μm . In drug combination assays in multidrug‐resistant cells, some DHPIQ compounds, at nontoxic concentrations, significantly increased the cytotoxicity of doxorubicin in a concentration‐dependent manner. Studies of structure–activity relationships and investigation of the chemical stability of Schiff bases provided physicochemical information useful for molecular optimization of lamellarin‐like cytotoxic drugs active toward chemoresistant tumors as well as nontoxic reversers of P‐gp‐mediated multidrug resistance in tumor cells.     

Exploration of Sulfur‐Containing Analogues for Imaging Vesicular Acetylcholine Transporter in the Brain

Sixteen new sulfur‐containing compounds targeting the vesicular acetylcholine transporter (VAChT) were synthesized and assessed for in vitro binding affinities. Enantiomers (?)‐(1‐(3‐hydroxy‐1,2,3,4‐tetrahydronaphthalen‐2‐yl)piperidin‐4‐yl)(4‐(methylthio)phenyl)methanone [(?)‐ 8 ] and (?)‐(4‐((2‐fluoroethyl)thio)phenyl)(1‐(3‐hydroxy‐1,2,3,4‐tetrahydronaph‐thalen‐2‐yl)piperidin‐4‐yl)methanone [(?)‐ 14 a ] displayed high binding affinities, with respective K_i values of 1.4 and 2.2 nm for human VAChT, moderate and high selectivity for human VAChT over σ₁ (≈13‐fold) and σ₂ receptors (>420‐fold). Radiosyntheses of (?)‐[¹¹C] 8 and (?)‐[¹⁸F] 14 a were achieved using conventional methods. Ex vivo autoradiography and biodistribution studies in Sprague–Dawley rats indicated that both radiotracers have the capacity to penetrate the blood–brain barrier, with high initial brain uptake at 5 min and rapid washout. The striatal region had the highest accumulation for both radiotracers. Pretreating the rats with the VAChT ligand (?)‐vesamicol decreased brain uptake for both radiotracers. Pretreating the rats with the σ₁ ligand YUN‐122 (N‐(4‐benzylcyclohexyl)‐2‐(2‐fluorophenyl)acetamide) also decreased brain uptake, suggesting these two radiotracers also bind to the σ₁ receptor in vivo. The microPET study of (?)‐[¹¹C] 8 in the brain of a non‐human primate showed high striatal accumulation that peaked quickly and washed out rapidly. Although preliminary results indicated these two sulfur‐containing radiotracers have high binding affinities for VAChT with rapid washout kinetics from the striatum, their σ₁ receptor binding properties limit their potential as radiotracers for quantifying VAChT in vivo.     

Synthesis of novel polyimides containing side‐chain azo‐2‐naphthol moieties

An amine‐ester derivative of isoeugenol was prepared in three steps. This amine‐ester was converted to diazonium salt and subsequently was reacted with 2‐naphthol and a novel isoeugenol ester‐azo derivative as a new monomer was obtained in quantitative yield. This monomer was characterized by high‐field ¹H‐NMR, IR, and elemental analysis and then was used for the preparation of model compound and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione was allowed to react with this new monomer. The reaction was very fast and gave only one double adduct by Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer with bistriazolinediones [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] were carried out in N,N‐dimethylacetamide at room temperature. The reactions were exothermic, fast, and gave novel heterocyclic polyimides by repetitive Diels–Alder‐ene polyaddition reactions. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1942–1951, 2003     

Efficient Catalytic Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid by Magnetic Laccase Catalyst

2,5‐Furandicarboxylic acid (FDCA) is a bio‐based platform chemical for the production of polyethylene furanoate (PEF) and other valuable furanic chemicals. A magnetic laccase catalyst with (2,2,6,6‐tetramethyl‐piperidin‐1‐yl)oxyl (TEMPO) as the mediator has the remarkable capability of oxidizing 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA). Under optimal reaction conditions, a quantitative yield (90.2 %) of FDCA with complete HMF conversion was obtained after 96 h of reaction. More importantly, the magnetic laccase catalyst exhibited good recyclability and stability, maintaining 84.8 % of its original activity following six reuse cycles. This is the first report on the efficient catalytic oxidation of HMF to FDCA by using an immobilized enzyme catalyst.     

The effect of TIBA on metallocene/MAO catalyzed synthesis of propylene oxazoline copolymers and their use in reactive blending

Oxazoline‐functionalized polypropylenes were synthesized by using the rac‐Et[1‐Ind]₂ZrCl₂/MAO catalyst system. The used comonomers were 2‐(9‐decene‐1‐yl)‐1,3‐oxazoline (R‐Ox1), 2‐(9‐decene‐1‐yl)‐4,4‐dimethyl‐1,3‐oxazoline (R‐Ox2), and 2‐(4‐(10‐undecene‐1‐oxy)phenyl)‐1,3‐oxazoline (R‐Ox3). The oxazolines reduce the catalyst activity in the order R‐Ox3 > R‐Ox1 > R‐Ox2. By the addition of triisobutylaluminum (TIBA), the catalyst poisoning is reduced and is most pronounced in the R‐Ox1‐ and R‐Ox2‐containing systems. The oxazoline‐containing copolymers were melt blended with carboxylic acid end‐functionalized polystyrene (PS‐COOH) at 200°C. Strong changes in the morphology of the reactive blends compared to the nonreactive blends, especially the cocontinuous morphology in a poly(propylene‐co‐R‐Ox3)/PS‐COOH blend, indicate the usefulness of the modified copolymers in the reactive blending processes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2174–2181, 2002