The Development of Stereoerrors During the Homo‐ and Copolymerization of Propylene Using C2‐Symmetric Metallocene Catalysts – A Cautionary Note

Summary: A recent paper described the development of atactic sequences during the copolymerization of propylene and 1‐pentene using the C₂‐symmetric metallocene catalyst rac‐dimethylsilyl‐bis(2‐methylbenz(e)indenyl) zirconium dichloride. We have found similar stereoerrors, and showed that atactic material could in fact be extracted from the material, indicating that the catalyst in question had probably isomerized in solution, leading to a mixture of isotactic and atactic polymers.

     

“One‐pot” Synthesis of 1‐Vinyl‐2‐pyrrolidone with Protic Functional Groups in 3‐Position

A synthetic route that allows modification of 1‐vinyl‐2‐pyrrolidone with an alcohol or thiol group in its 3‐position in a one‐pot reaction without using protecting groups is described. The strategy used to achieve this goal is the reaction of the carboxamide anion of 1‐vinyl‐2‐pyrrolidone with cyclic precursors of these functionalities. It is furthermore shown that VP‐monomers functionalized with OH groups are suitable for the preparation of the corresponding copolymers with pure VP. As a second application of the new compounds, we also describe the synthesis of the first asymmetric crosslinker based on VP.

     

Protonation of Sulfonated Poly(4,4′‐diphenylether‐1,3,4‐oxadiazole) Membranes

This work describes the effect of sulfuric acid protonation on the properties of SPOD‐DPE membranes using FT‐IR and impedance spectroscopic analyses. The IR spectra showed the protonation of nitrogen atoms from oxadiazole rings, with a broad band complex in the region 3 000–2 100 cm^?1 with two centered peaks at 2 590 and 2 440 cm^?1. The S?O characteristic absorption bands in SPOD‐DPE and sulfuric acid were specially studied in the region of 1 800–900 cm^?1. The band shifts are associated to the interaction between acid groups and oxadiazole ring nitrogen atoms. The IR spectra evidenced the presence of three absorption species (HSO, SO and free H₂SO₄) depending on the sulfuric acid concentration. For the protonated SPOD‐DPE membranes, a proton conductivity around 10 mS · cm^?1 was reached at 50 °C.

     

Anionic Copolymerization of 5‐(N,N‐Dialkylamino)isoprenes

Summary: The anionic copolymerization of various 5‐(N,N‐dialkylamino)isoprenes initiated by sec‐butyllithium in hexane is investigated. The bulkiness of the alkyl side chains has a strong influence on the copolymerization behavior, monomer reactivity decreasing in the order of alkyl groups methyl > ethyl ≈ propyl > isopropyl. Polymer structures vary from nearly block over tapered and gradient to random, depending on the relative reactivities of comonomers. Since the basicity of the tertiary amino groups depends on the nature of the alkyl groups, it is possible to vary the basicity along the polymer backbone by a suitable choice of the comonomers. Copolymerization kinetics do not seem to follow first‐ or second‐order with respect to monomer conversion and they cannot be described using the terminal model.

General structure of obtained polymers.     

Control of the radical polymerization by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl and its sodium salt

The control of the radical polymerization of styrene by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl is reported here in bulk at 90 °C, 120 °C and in miniemulsion. Similarly, the control by its sodium complex is reported in bulk at 90 °C.

M _n vs. conversion for 3 , 3Na , and TEMPO.     

High‐Pressure Kinetics of Oxidative Copolymerization of Styrene with α‐Methylstyrene

This is the first report on the study carried out on high‐pressure free‐radical initiated oxidative copolymerization of styrene (STY) with α‐methylstyrene (AMS) at various temperatures (45–65 °C) at constant pressure (100 psi) and then at various pressures (50–300 psi) keeping the temperature (50 °C) constant. The compositions of the copolyperoxides obtained from the ¹H NMR spectra were utilized to determine the reactivity ratios of the monomers. The reactivity ratios indicate that STY forms an ideal copolyperoxide with AMS and the copolyperoxide is richer in AMS. The effect of temperature and oxygen pressure on the reactivity ratios of the monomers was studied. The rates of copolymerization (R_P) were used to determine the overall activation energies (E_a) and activation volume (ΔV^#) of copolymerization. The unusually higher values of the ΔV^# may be due to the pressurizing fluid oxygen which itself is a reactant in the copolymerization, the side reactions, and the chain‐transfer reactions occurring during copolymerizations.

The Arrhenius plots for the rate of the copolymerization of STY‐AMS‐O₂ system at 100 psi of oxygen pressure.     

Pseudo‐Living Anionic Telomerization of Buta‐1,3‐diene

Low‐molecular‐weight liquid polybutadienes (1 000–2 000 g · mol^?1) consisting of 60 mol‐% poly(buta‐1,2‐diene) repeating units were synthesized via anionic telomerization. Maintaining the initiation and reaction temperature at less than 70 °C minimized chain transfer and enabled the polymerization to occur in a living fashion, which resulted in well‐controlled molecular weights and narrow polydispersity indices. MALDI‐TOF mass spectrometry confirmed that the end groups of liquid polybutadienes synthesized via anionic telomerization contained one benzyl end and one protonated end. In comparison, the end groups of liquid polybutadienes synthesized via living anionic polymerization contained one sec‐butyl or butyl end and one protonated end.

     

Poly(carbazole)‐Based Copolymers Containing Deep‐Blue Chromophore for Polymer Light‐Emitting Diode Applications

A new series of two poly(carbazole)‐based copolymers (poly(9‐hexyl‐carbazole‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PCVz) and poly(9,9‐dioctylfluorene‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PFCVz)) containing carbazoylphenylquinoline pendant groups were synthesized via the Suzuki coupling reaction for polymer light‐emitting diode applications. The electro‐optical properties of ITO/PEDOT/Polymer/PBD/LiF/Al devices based on these copolymers were investigated using UV‐visible, photoluminescence, and electroluminescence spectroscopy. The turn‐on voltages of the copolymer devices were found to be 6.0–8.0 V. The maximum brightness and luminescence efficiency of the copolymers device were found to be 230 cd · m^?2 and 0.28 cd · A^?1 at 11 V, respectively.

     

Synthesis of Silica‐Supported Metallocene Catalysts for Olefin Polymerization

Four supported metallocene catalysts were synthesized directly on silica [Si(CpZrCp), Si(CpZrInd), Si(IndZrCp), and Si(IndZrInd)]. The first ligand was chemically tethered to silica (internal ligand) while the second was free from silica (external ligand). The polymerization of ethylene and the copolymerization of ethylene with hexene were investigated. The activity of the catalysts and the molecular weights of the polymers were found to depend on the position of the ligands. In all cases, high‐molecular‐weight polyethylene with moderate polydispersity was obtained. Moreover, the copolymerization of ethylene with hexene provided a homogeneous polymer.

Reaction of ZrCl₄(OC₄H₈)₂ with modified silica (SiCp).     

Proton‐Conducting Zirconium Pyrophosphate/Poly(2,5‐benzimidazole) Composite Membranes Prepared by a PPA Direct Casting Method

Zirconium pyrophosphate (ZPP)/poly(2,5‐benzimidazole) composites were prepared by polymerization of 3,4‐diaminobenzoic acid with zirconium hydrogen phosphate in polyphosphoric acid. The composite membranes for polymer electrolyte membranes were prepared by casting the polymerization solutions directly onto stainless steel plates. Membranes doped in 60 wt.‐% phosphoric acid solution had high proton conductivity values of more than 0.12 S · cm^?1 (at 180 °C and 1% RH). Physical properties of the doped membranes, including the mechanical strength and dimensional stability, improved as ZPP content in the composites increased to 10–20 wt.‐%.

     

Water‐Soluble Conjugated Polyelectrolyte‐Based Fluorescence Enzyme Coupling Protocol for Continuous and Sensitive β‐Galactosidase Detection

A simple, rapid, continuous and homogeneous fluorescent assay for β‐galactosidase was developed, combining an enzyme‐coupled reaction and signal amplification property of conjugated polyelectrolytes (CPs). The procedure is based on a sequence of two coupled biocatalytic steps in which the β‐galactosidase hydrolyzes its substrate to a phenol derivative followed by conversion to quinone (secondary product) with fluorescence quenching ability by the tyrosinase. The fluorescence of PFP?SO is efficiently quenched by the quinone via an electron transfer process. The limit of detection (LOD) of this assay is less than 0.0005 U · mL^?1, which is better than that of electrochemical method and is comparable to that of most sensitive chemiluminescent techniques. In principle, this sensor mechanism will extend the application window of CPs for wide‐spectrum enzyme detections. This “mix‐and‐detect” approach could be expanded to a high‐throughput manner.

     

Polyrotaxanes of Pyrene–Triazole Conjugated Azomethine and α‐Cyclodextrin with High Fluorescence Properties

The paper reports on the preparation of a new 2‐rotaxane monomer through an acid coupling reaction between 1‐pyrenecarboxaldehyde and α‐CD/3,5‐diamino‐1,2,4‐triazole inclusion complex. Pyrenyl groups are large enough to provide a blocking effect toward cyclodextrin de‐threading. The oxidative C? C coupling of 2‐rotaxane in the presence of RuCl₃ catalyst afforded conjugated azomethine polyrotaxanes. The expected modifications of the solubility, morphology, film forming ability for rotaxane polymer were proved. As shown by fluorescence and UV‐vis spectroscopy, a material with optical properties appropriate for use in photonics was obtained.

     

Synthesis and Photophysical Investigations of Novel Polymerizable Blue Emitting Fluorophores – Combination of a Hindered Amine with a Benzo[de]isoquinoline‐1,3‐dione

Summary: New monomeric benzo[de]isoquinoline‐1,3‐dione blue emitting fluorophores, containing hindered amine stabilizer fragment have been synthesized under phase transfer catalysis conditions and their ability for “one‐step” optical bleaching and stabilization of poly(methyl methacrylate) has been demonstrated. During the co‐polymerization, no changes in the chromophoric system of the fluorophore occurred. The chemical bonding of the synthesized monomers in the polymer chain was confirmed spectrophotometrically. The absorption and some basic photophysical characteristics of the low and high molecular weight fluorescent brighteners have been determined. Photostability of the new monomeric fluorophores and their influence on the photostability of the blue emitting side‐group co‐polymers obtained have been established. A significant stabilizing effect against photodegradation was determined.

     

Photocurable Shape‐Memory Copolymers of ε‐Caprolactone and L‐Lactide

Biodegradable and photocurable block copolymers of ε‐caprolactone and L ‐lactide were synthesized by polycondensation of PLLA diol ( = 10 000 g · mol^?1), PCL diol ( = 10 000 g · mol^?1), and a chain extender bearing a coumarin group. The effect of copolymer composition on the thermal and mechanical properties of the photocured copolymers was studied by means of DSC and cyclic tensile tests. An increase in Young's modulus and a decrease in the tensile strain with increasing PLLA content was observed for the block copolymers. Block copolymers with high PCL content showed good to excellent shape‐memory properties. Random copolymers exhibited R_f and R_r values above 90% at 45 °C for an extremely large tensile strain of 1 000%.

     

Syndiospecific Homopolymerisation of Higher 1‐Alkenes with Two Different Bridged [(RPh)2C(Cp)(2,7‐tert‐BuFlu)]ZrCl2 Catalysts

Summary: Syndiotactic polymers of 1‐pentene, 1‐hexene and 1‐octene were obtained with the C_S‐symmetric metallocene catalysts [Ph₂C(Cp)(2,7‐tert‐Bu₂Flu]ZrCl₂ and [(4‐MePh)₂C(Cp)(2,7‐tert‐Bu₂Flu)]ZrCl₂, which have already been proven to give high molar masses and excellent tacticities in propene polymerisation. The monomers were polymerised in bulk and in solution processes at temperatures between 0 and 60 °C using methylaluminoxane as a cocatalyst. The effects on catalyst activity as well as on polymer microstructure and molar mass were determined. Polymers with high syndiotacticities and molar masses (up to 550 000 g · mol^?1 in the 1‐octene polymerisation) compared to other metallocenes were obtained.

     

Hydrolytic Polycondensation of Bisphenol‐A‐Bischloroformate Catalyzed by Phase‐Transfer Catalysts

The hydrolytic interfacial polycondensation of bisphenol‐A‐bischloroformate was performed with four different phase‐transfer (PT) catalysts: N‐butylpyridinium bromide, triethylbenzylammonium (TEBA) chloride, tetrabutylammonium hydrogen sulfate, and tetraphenylphosphonium bromide. These polycondensations were conducted at 5 or 35 °C initial reaction temperature. The resulting polycarbonates were characterized by viscosity and SEC measurements and by MALDI‐TOF mass spectrometry. The four PT catalysts gave quite different results with respect to molecular weight and formation of cyclic polycarbonates. The highest molecular weights (number average, and weight average, ) were obtained with TEBA‐Cl. Lower temperatures and high feed ratios of TEBA‐Cl proved to be favorable for both high molecular weights and high fractions of cycles. Cyclic polycarbonates were detectable in the mass spectra up to 14 kDa (technical limit of the measurements). Low molecular weights in combination with unreacted chloroformate groups proved that the other PT‐catalysts were less efficient under the given reaction conditions.

MALDI‐TOF mass spectrum of the polycarbonate No. 3b .     

Metathetic Selective Degradation of Polyisoprene: Low‐Molecular‐Weight Telechelic Oligomer Obtained from Both Synthetic and Natural Rubber

Summary: Degradation studies of cis‐1,4‐polyisoprene were carried out using first and second generation Grubbs catalysts to achieve end‐functionalized acetoxy oligomers in both an organic solvent and a latex phase at room temperature. Well‐defined acetoxy telechelic polyisoprene structures were obtained in a selective manner with a range of from 10 000 to 30 000, with a polydispersity index of around 2.5.

Structure produced by the metathetic depolymerization of hydroxy telechelic cis‐1,4‐polyisoprene.     

Synthesis and Hole‐Transporting Property of a Novel Poly(N‐vinylcarbazole) Copolymer with Metal‐Coordination Sites

Summary: Hole transporting poly(N‐vinylcarbazole) copolymers with phenylazomethine dendron units acting as metal ligation sites were synthesized. These polymers possess both hole‐transport and metal‐collecting units with simple σ‐bond linkages. Complexation in the phenylazomethine dendron unit within these copolymers by SnCl₂ has been successfully observed by the change in the UV‐vis spectra. The complexation changes the HOMO/LUMO energy gap that results in a spectral red‐shift. Using copolymers as a hole‐transport layer, only complexation with metal ions leads to an enhanced maximum luminescence. Such a complexation results in a high electroluminescence efficiency because the p‐type‐doped structure acts as the hole‐transport layer.

Copolymerization for the preparation of DPAGn(x)‐Cbz(y).     

Solid‐State Olefin Metathesis: ADMET of Rigid‐Rod Polymers and Ring‐Closing Metathesis

Summary: Solid‐state olefin metathesis of rigid‐rod acyclic diene metathesis (ADMET) polymers and ring‐closing metathesis (RCM) have been investigated. 1,4‐Dipropoxy‐2,5‐divinylbenzene ( 4 ) was synthesized and used in a bulk ADMET polymerization to produce oligomers of dialkoxy poly(phenylene vinylene). The reaction was continued in the solid state, effectively doubling the molecular weight. Solid‐state RCM was investigated with a variety of solid dienes and metathesis catalysts, and demonstrated in low conversions using amide diene 5 with catalysts 9 , 13 , and 14 .

     

Activation of Titanium‐Based Single‐Site Catalysts for Ethylene Polymerization Using Supports of Type MgCl2/AlRn(OEt)3–n

Summary: Easy and effective immobilization and activation of a range of Ti‐based single‐site catalysts for ethylene polymerization has been achieved, without methylaluminoxane or borate activators, using MgCl₂/AlR_n(OEt)_3–n supports obtained by reaction of AlR₃ with adducts of magnesium chloride and ethanol. The use of relatively low catalyst loadings leads to efficient uptake by the support and gives high catalyst activity. Catalyst immobilization using these MgCl₂‐based supports also leads to stable polymerization kinetics, with negligible decay in catalyst activity during polymerization. Metallocene, half‐metallocene, and non‐metallocene catalysts have been used, particularly high activities being obtained using cyclopentadienyl titanium trichloride and its analogues. The polyethylenes obtained have narrow molecular weight distribution, with generally in the range 2–3, indicating retention of single‐site catalyst characteristics after immobilization. Spherical polymer particle morphology was achieved, without reactor fouling.

Temperature profile of ethylene polymerization using [(Indenyl)TiCl₃] immobilized on a MgCl₂/AlEt_n(OEt)_3–n support (?: internal temperature; ?: cooling mantle temperature).