Polymer‐supported half‐titanocene catalysts for the syndiospecific polymerization of styrene

Monocyclopendienyltitanium trichloride (CpTiCl₃) was supported on polymer carriers with different hydroxyl contents, and the supported catalysts were used for styrene polymerization. The supported catalysts exhibited high activity even at low Al/Ti ratios and increased the molecular weight of the products, indicating that polymer carriers could stabilize the active sites. The polymers prepared with unsupported and supported catalysts were extracted with boiling n‐butanone and characterized by carbon nuclear magnetic resonance (¹³C NMR) and differential scanning calorimetry. The polymers obtained by supported catalysts had a high fraction of boiling n‐butanone‐insoluble part and high melting temperatures, but ¹³C NMR results showed that syndiotacticity decreased compared with that of polymers prepared with an unsupported catalyst. ESR study on the supported catalysts confirmed that the active sites supported on the carrier dropped into the solution and formed active sites the same as those in the unsupported system when they reacted with methylaluminoxane. ¹³C NMR analysis showed that the polymerization mechanism of the supported active sites was an active‐site controlled mechanism instead of a chain‐end controlled mechanism of the unsupported active sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 127–135, 2000     

The Aza‐Morita–Baylis–Hillman Reaction: A Mechanistic and Kinetic Study

The aza‐Morita‐Baylis–Hillman (aza‐MBH) reaction has been studied in a variety of solvents, a selection of imine substrates and with various combinations of PPh₃ and para‐nitrophenol as the catalyst system. The measured kinetic data indicates that the effects of solvent and protic co‐catalyst are strongly interdependent. These results are most easily reconciled with a mechanistic model involving the reversible protonation of zwitterionic intermediates in the catalytic cycle, which is also supported by ³¹P NMR spectroscopy and quantum chemical studies.     

Bifunctional Heterogeneous Catalysis of Silica–Alumina‐Supported Tertiary Amines with Controlled Acid–Base Interactions for Efficient 1,4‐Addition Reactions

We report the first tunable bifunctional surface of silica–alumina‐supported tertiary amines (SA–NEt₂) active for catalytic 1,4‐addition reactions of nitroalkanes and thiols to electron‐deficient alkenes. The 1,4‐addition reaction of nitroalkanes to electron‐deficient alkenes is one of the most useful carbon–carbon bond‐forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA‐supported amine (SA–NEt₂) catalyst enabled selective formation of a double‐alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA–NEt₂ catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA–NEt₂ catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron‐deficient alkenes. The solid‐state magic‐angle spinning (MAS) NMR spectroscopic analyses, including variable‐contact‐time ¹³C cross‐polarization (CP)/MAS NMR spectroscopy, revealed that acid–base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid–base interactions.     

Preparation and application of a novel core–shell‐particle‐supported zirconocene catalyst

The use of functional groups bearing silica/poly(styrene‐co‐4‐vinylpyridine) core–shell particles as a support for a zirconocene catalyst in ethylene polymerization was studied. Several factors affecting the behavior of the supported catalyst and the properties of the resulting polymer, such as time, temperature, Al/N (molar ratio), and Al/Zr (molar ratio), were examined. The conditions of the supported catalyst preparation were more important than those of the ethylene polymerization. The state of the supported catalyst itself played a decisive role in both the catalytic behavior of the supported catalyst and the properties of polyethylene (PE). IR and X‐ray photoelectron spectroscopy were used to follow the formation of the supports. The formation of cationic active species is hypothesized, and the performance of the core–shell‐particle‐supported zirconocene catalyst is discussed as well. The bulk density of the PE formed was higher than that of the polymer obtained from homogeneous and polymer‐supported Cp₂ZrCl₂/methylaluminoxane catalyst systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2085–2092, 2001     

Asymmetric polymerization of N‐substituted maleimides with chiral oxazolidine–organolithium

Asymmetric anionic homopolymerizations of achiral N‐substituted maleimides (RMI) were performed with lithium 4‐alkyl‐2,2‐dialkyloxazolidinylamide. All obtained polymers were optically active, exhibiting opposite optical rotation to that of a corresponding oxazolidinyl group at the terminal of the main chain. This suggests that opposite optical rotation to the corresponding chiral oxazolidine was induced to the polymer main chain. In the polymerization using a fluorenyllithium (FlLi)–oxazolidine complex, the obtained polymer with a fluorenyl group at the polymer end showed a negative specific rotation. This also suggests that asymmetric induction took place in the polymer main chain. The asymmetric induction was supported by the circular dichroism (CD) and GPC analysis with polarimetric detector. Optical activity of the polymer was attributed to different contents of (S,S) and (R,R) structures formed from threo‐diisotactic additions, as supported by the ¹³C‐NMR spectra of the polymers and the model compounds. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 473–482, 1999     

Minimization of the auxiliary reagent loading for direct arylation polymerization (DArP) of 2‐bromo‐3‐hexylthiophene

In this work, we present a powerful set of synthetic strategies aimed at minimization of auxiliary reagent loading for direct arylation polymerization (DArP) of 2‐bromo‐3‐hexylthiophene. As such, we report efficient lowering of Pd(OAc)₂ catalyst loading as well as loading of other auxiliary reagents, such as neodecanoic acid and N,N‐dimethylacetamide. Unprecedented low loadings of catalyst down to 0.0313% (313 ppm) were achieved, while producing polymer in high yield (91% after Soxhlet extraction), with a high molecular weight (24.2 kDa) and carefully controlled chemical structure thus making the optimized DArP protocol significantly more cost‐effective, convenient, sustainable, and environmentally friendly. The resulting polymer samples were thoroughly investigated in terms of their chemical structure as well as optical, thermal, chain ordering and electronic properties using GPC analysis, ¹H NMR, MALDI, UV–vis, GIXRD spectroscopy, DSC, and SCLC hole mobility measurements. The results demonstrate that the reagent lowering strategies increase the polymer regioregularity from 94.6 to 96.5% as evidenced by ¹H NMR spectra and corroborated by GIXRD, DSC, and UV–vis measurements. Additionally, polymer samples obtained at low reagent loading are more uniformly proton‐terminated as evidenced by ¹H NMR and MALDI end‐group analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1492–1499     

Porphyrin‐based polymer‐supported palladium as an excellent and recyclable catalyst for Suzuki–Miyaura coupling reaction in water

A porphyrin‐based polymer with high surface area was synthesized using 5,10,15,20‐tetraphenylporphyrin through a one‐pot Friedel–Crafts alkylation reaction. Pd(II) was successfully supported on this polymer. This strategy provides an easy approach to produce highly stable Pd–porphyrin‐based polymer. The resulting Pd catalyst was characterized using Fourier transform infrared and X‐ray photoelectron spectroscopies, thermogravimetric analysis, scanning and transmission electron microscopies and N₂ adsorption–desorption measurements. This porphyrin‐based polymer‐supported Pd was used as a heterogeneous catalyst for Suzuki–Miyaura coupling reaction in water. The results demonstrated that this Pd catalyst indeed exhibited excellent catalytic activity and recycling performance in water, even for inactive aryl chloride substrate. A new heterogeneous strategy for catalyzing the Suzuki–Miyaura reaction in water is provided.     

Ru–η6‐benzene–phosphine complex‐catalyzed transfer hydrogenation of ketones

Three Ru–η⁶‐benzene–phosphine complexes bearing tri‐(p‐methoxyphenyl)phosphine, triphenylphosphine and tri‐(p‐trifluoromethylphenyl)phosphine were synthesized and characterized by ³¹P{¹H} NMR, ¹H NMR, ¹³C{¹H} NMR and elemental analyses. Complex 1 was further identified by X‐ray crystallography. These complexes exhibit good to excellent activities for the transfer hydrogenation of ketones in refluxing 2‐propanol, and the highest turnover frequency (TOF) is up to 5940 h⁻¹. The effect of electronic factors of these complexes on the transfer hydrogenation of ketones reveals that the catalytic activity is promoted by electron‐donating phosphine and the catalyst stability is improved by electron‐withdrawing phosphine. Copyright © 2011 John Wiley & Sons, Ltd.     

Silica‐Supported P2O5 as an Efficient Heterogeneous Catalyst for the One Pot Synthesis of 3‐Amino‐imidazo[2,1‐b](1,3)benzothiazole under Green Conditions

The new approach involving the solid supported catalyst for the formation of C–N bond followed by cyclization has been reported. In this work we have reported a facile, efficient, and environment‐friendly protocol for the synthesis of some new 3‐amino‐imidazo[2,1‐b](1,3)benzothiazole derivatives by one‐pot condensation of 2‐aminobenzothiazole, indole‐3‐carbaldehyde, and aryl isocyanide in the presence of silica‐supported P₂O₅ as a heterogeneous solid acid catalyst. The reaction was performed using conventional method under green conditions. The present approach offers the advantages of simple methodology, inexpensive acid catalyst, short reaction time, easy work up with excellent yield, simple purification and use of green solvent. All the newly synthesized compounds were characterized in details using physical and chemical techniques such as melting point, ¹H NMR, ¹³C NMR, and FTIR spectroscopy.     

Self‐assembling directed synthesis of a novel terephthalamide‐bridged ladderlike polysiloxane

A novel, soluble terephthalamide‐bridged ladderlike polysiloxane ( L ) was synthesized successfully for the first time by stepwise coupling polymerization. The process involved the hydrogen‐bonding self‐assembly of amido groups, which resulted in the formation of a more highly ordered polymeric structure. A novel monomer, bis(3‐methyldimethoxysilylpropyl) terephthalamide ( M ), was prepared by a hydrosilylation reaction in the presence of dicyclopentadienyl platinum dichloride as a catalyst. The structures of the monomer ( M ) and the polymer ( L ) were characterized by Fourier transform infrared, ¹H NMR, ¹³C NMR, ²⁹Si NMR, mass spectrometry, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry. All the characterization data indicated that the synthesized polymer ( L ) possessed an ordered ladderlike structure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3161–3170, 2002     

Ring‐opening metathesis polymerization as a route to controlled copolymers of ethylene and polar monomers: Synthesis of ethylene–vinyl chloride‐like copolymers

A series of ethylene–vinyl chloride‐like copolymers were prepared by ring‐opening metathesis polymerization (ROMP). The route to these materials included the bulk polymerization of 5‐chlorocyclooctene and 5,6‐dichlorocyclooctene with the first‐generation Grubbs' catalyst, followed by diimide hydrogenation of the resulting unsaturated polymers. In addition, the amount of chlorine in these materials was varied by the copolymerization of 5‐chlorocyclooctene with cyclooctene. These materials were fully characterized by NMR (¹H and ¹³C), gel permeation chromatography, and Fourier transform infrared spectroscopy. Finally, hydroboration was carried out on the ROMP product of 5‐chlorocyclooctene to yield a polymer, which was effectively a vinyl alcohol–vinyl chloride–ethylene terpolymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2107–2116, 2003     

Synthesis and nonlinear optical properties of polyester containing 4‐di‐(2′‐hydroxyethoxy)‐4‐diphenyl‐hydrazonomethyl chromophore

The nonlinear optical property of new polyester has been studied via second harmonic generation (SHG). The values of electro‐optic coefficients, d₃₃ and d₃₁, of the poled polymer film were 3.15 × 10 ^?7 and 1.5 × 10^?7 esu, respectively. Thermal behavior of this polyester was studied through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). 4‐di‐(2′‐hydroxyethoxy)‐4‐diphenyl‐hydrazonomethyl was synthesized from the reaction of 3,4‐dihydroxy‐4‐diphenyl‐hydrazonomethyl with 2–chloro–1‐ethanol in a 1:2 mole ratio and subsequently reacted with terephthaloyl chloride (TPC) in the presence of pyridine, as catalyst, to produce the new nonlinear polyester. The chemical structures of the resulting monomers and polymer were characterized by CHN analysis, ¹H‐NMR, FT‐IR, and UV–Vis spectroscopy. Copyright © 2009 John Wiley & Sons, Ltd.     

Polymerization of methyl methacrylate by 2‐pyrrolidinone and n‐dodecyl mercaptan

The bulk polymerization of methyl methacrylate initiated with 2‐pyrrolidinone and n‐dodecyl mercaptan (R‐SH) has been explored. This polymerization system showed “living” characteristics; for example, the molecular weight of the resulting polymers increased with reaction time by gel permeation chromatographic analysis. Also, the polymer was characterized by Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR techniques. The polymer end with the iniferter structures was found. By the initial‐rate method, the polymerization rate depended on [2‐pyrrolidinone]^1.0 and [R‐SH]⁰. Combining the structure analysis and the polymerization‐rate expression, a possible mechanism was proposed. n‐Dodecyl mercaptan served dual roles—as a catalyst at low conversion and as a chain‐transfer agent at high conversion. Finally, the thermal properties were studied, and the glass‐transition temperature and thermal‐degradation temperature were, respectively, 25 and 80–100 °C higher than that of the azobisisobutyronitrile system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3692–3702, 2002     

Solid‐State NMR investigations of anhydrous proton‐conducting acid–base poly(acrylic acid)– poly(4‐vinyl pyridine) polymer blend system: A study of hydrogen bonding and proton conduction

NMR studies of the structure and dynamics of a system composed of the acidic polymer poly(acrylic acid) (PAA) and the basic polymer poly(4‐vinyl pyridine) (P4VP) are presented. This system aims at the application of anhydrous proton‐conducting membranes that can be used at elevated temperatures at which the proton conduction of hydrated membranes breaks down. The ¹H NMR measurements have been preformed under fast magic angle spinning (MAS) conditions to achieve sufficient resolution and the applied ¹H NMR methods vary from simple ¹H MAS to double‐quantum filtered methods and two‐dimensional ¹H double‐quantum spectroscopy. The dynamic behavior of the systems has been investigated via variable temperature ¹H MAS NMR. ¹³C cross‐polarization MAS NMR provides additional aspects of dynamic and structural features to complete the picture. Different types of acidic protons have been identified in the studied PAA‐P4VP systems that are nonhydrogen‐bonded free acidic protons, hydrogen‐bonded dicarboxylic dimers, and protons forming hydrogen bonds between carboxylic protons and ring nitrogens. The conversion of dimer structures in dried PAA to free carboxylic acid groups is accomplished at temperatures above 380 K. However, the stability of hydrogen‐bonding strongly depends on the hydration level of the polymer systems. The effect of hydration becomes less apparent in the complexes. An inverse proportionality between hydrogen‐bonding strength and proton conduction in the PAA‐P4VP acid–base polymer blend systems was established. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 138–155, 2009     

13Carbon nuclear magnetic resonance of ethylene–propylene–1‐decene terpolymers

Many studies have been reported on the ¹³C NMR characterization of ethylene–α‐olefin copolymers, but only a few have been reported on terpolymers. The incorporation of an α‐olefin into the polyethylene chain changes the structure and, consequently, the properties of the polymer obtained. Looking for new products, we obtained a series of ethylene–propylene–1‐decene terpolymers with the metallocenic system rac‐ethylene bisindenyl zirconium dichloride/methylaluminoxane. We performed a complete ¹³C NMR characterization of these terpolymers qualitatively and quantitatively. Here we present a detailed study of the ¹³C NMR chemical shifts, triad sequence distributions, monomer average sequence lengths, and reactivity ratios for these terpolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2531–2541, 2003     

Synthesis of novel diene polymer via friedel–crafts‐type reaction of polybutadiene with aromatic compounds

This study describes a novel and facile synthesis strategy for a styrene‐butadiene rubber (SBR)‐like polymer via Friedel–Crafts‐type reaction between aromatic compounds and polybutadiene using an aluminum chloride as a catalyst. Although gelation was induced by a reaction of a generated carbocation with olefins in other polybutadiene chains in benzene and toluene because of their low electron densities on their rings, anisole with a higher electron density reacted with the polybutadiene carbocation efficiently. The introduction ratio of anisole increased as the reaction proceeded, and the obtained polymer, BRAN polymer, contained 15% anisoles for olefins in the polybutadiene in 4 h at 80 °C as estimated by ¹H NMR analysis. The glass‐transition temperature (T_g) of the BRAN polymer also increased with anisole content (T_g ~?50 °C when anisole contents 20%). The vulcanizate containing the BRAN polymer showed higher mechanical properties compared to samples using other matrix polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 841–847     

Self‐assembled Pd nanoparticle‐containing ionic liquid: Efficient and reusable catalyst for the Heck reaction in water

A self‐assembled Pd nanoparticle‐containing ionic liquid as metal–organic polymer was successfully prepared. The structure of the catalyst was characterized using Fourier transform infrared and ¹H NMR spectroscopies, scanning electron microscopy and elemental analysis. The catalyst was effectively employed in the palladium‐catalyzed Heck reaction in water as a green solvent. Moreover, due to its stability the catalyst can be recovered simply and effectively and reused nine times without much loss of activity.     

Cyclopolymerization of dipropargylfluorene by transition‐metal catalysts

A fluorene‐containing spiro‐type conjugated polymer, poly(dipropargylfluorene), was synthesized via the cyclopolymerization of dipropargylfluorene by Mo‐ and W‐based transition‐metal catalysts. The polymerization of dipropargylfluorene proceeded well by MoCl₅ catalyst itself to give a quantitative yield of polymer. The Mo‐based catalysts are more effective than those of W‐based catalysts. The structure of poly(dipropargylfluorene) was characterized by various instrumental methods (NMR, IR, and UV–visible spectroscopies) to have the conjugated polymer backbone carrying fluorene moieties. Analysis of the ¹³C NMR spectrum revealed that the polymer structure consists of only six‐membered rings. The resulting poly(dipropargylfluorene)s were brown or black powder and soluble in aromatics and halogenated hydrocarbons such as benzene, chlorobenzene, tetrahydrofuran, chloroform, and methylene chloride. Thermal and morphological properties of the polymer are also discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4101–4109, 2001     

Hydrogen‐Bonding Catalysis of Tetraalkylammonium Salts in an Aza‐Diels–Alder Reaction

A piperidine‐derived tetraalkylammonium salt with a non‐coordinating counteranion worked as an effective hydrogen‐bonding catalyst in an aza‐Diels–Alder reaction of imines and a Danishefsky diene. The hydrogen‐bonding interaction between the ammonium salt and an imine was observed as part of a ¹H NMR titration study.     

New anti‐bacterial polychelates: synthesis,characterization, and anti‐bacterial activities of thiosemicarbazide–formaldehyde resin and its polymer–metal complexes

New polymeric ligand (resin) was prepared by the condensation of thiosemicarbazides with formaldehyde in the presence of acidic medium. Thisemicarbazide–formaldehyde polymer–metal complexes were prepared with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) in 1:2 metal:ligand molar ratio. The polymeric ligand and its polymer–metal complexes were characterized by elemental analysis, thermogravimetric analysis (TGA), FTIR, ¹³C NMR and ¹H NMR. The geometry of central metal ions was conformed by electronic (UV–vis) and EPR spectra. The antibacterial activities of all the synthesized polymers were investigated against Bacillus subtilis and Staphylococcus aureus (Gram‐positive) and Escherichia coli and Salmonella typhi (Gram‐negative). These compounds showed excellent activities against these bacteria using the shaking flask method. Copyright © 2008 John Wiley & Sons, Ltd.