One‐Pot Synthesis of Hyperbranched Polyethylenes Tethered with Pendant Acryloyl Functionalities by Chain Walking Copolymerizations

Chain walking copolymerization of ethylene with 1,4‐butanediol diacrylate at elevated concentrations for the synthesis of low‐viscosity hyperbranched polyethylenes tethered with a controllable amount of acryloyl functionality is reported. At concentrations much higher than the critical gelation concentrations, the diacrylate comonomer is copolymerized predominantly following the mono‐insertion pattern. A range of hyperbranched polyethylenes tethered with acryloyl functionality (1.3–4.8 mol‐%) and having low melt viscosity (ca. 25 Pa · s at 25 °C) and low glass transition temperature (T_g = ?69 °C) has been synthesized. This unique method is specific to the Pd‐diimine‐catalyzed chain‐walking copolymerization system.

     

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.     

Novel Hyperbranched Poly(aryl ether urethane)s Using AB2‐Type Blocked Isocyanate Monomers and Copolymerization with AB‐Type Monomers

A novel AB₂‐type blocked isocyanate monomer was synthesized which was de‐blocked to provide a hyperbranched poly(aryl ether urethane). Copolymerization of this monomer with a functionally similar AB monomer yielded polymers with molecular weights in the range 8.0–310 kDa with a DB of 41–59% that underwent two‐stage decomposition above 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.09 to 1.10 dL · g^?1. End‐group modification of hyperbranched poly(aryl ether urethane)s was carried out with PEG monomethyl ether and 1‐decanol and affected the thermal properties and solubilities of the polymers. T_g of the polymers was reduced significantly from 201 to 71 °C upon incorporation of AB monomer in the copolymerization.

     

Complex Branched Polyolefin Generated from Quasi‐living Polymerization of 4‐Methyl‐1‐pentene Catalyzed by α‐Diimine Palladium Catalyst

Branched α‐olefin 4‐methyl‐1‐pentene (4MP) is polymerized with a cationic α‐diimine palladium catalyst. The influences of polymerization parameters including reaction temperature and monomer concentration on polymer architecture are evaluated in detail. Increasing temperature and lowering monomer concentration can lead to the formation of more complex branched polyolefin because of chain walking. At 0 °C, complex branched polyolefins are generated from quasi‐living polymerization of 4MP with α‐diimine palladium catalyst.

     

Synthesis and Photovoltaic Properties of Conjugated Copolymers with Benzo[1,2‐b:4,5‐b′]dithiophene and Bis(thiophene)phthalimide Units

Two new donor/acceptor copolymers PBDTPhBT1 and PBDTPhBT2 with alternating benzodithiophene ( BDT ) and bisthiophene‐phthalimide ( PhBT ) units were synthesized by Stille coupling reaction. The copolymers showed identical optical bandgaps of 1.98 eV. The HOMO energy levels are ?5.35 and ?5.32 eV for PBDTPhBT1 and PBDTPhBT2 , respectively. The bulk heterojunction solar cell devices based on these copolymers as donors and PC₇₁BM as acceptor displayed high open‐circuit voltages of 0.90–0.93 V and achieved power conversion efficiency of 1.54% under the illumination of AM 1.5, 100 mW · cm^?2.

     

Polymerisation of Norbornene Catalysed by Highly Active Tetradentate Chelated α‐Diimine Nickel Complexes

A series of three recently synthesised tetradentate chelated α‐diimine nickel complexes of the type [NiBr₂(Ar‐BIAN)] (where Ar = 2‐(1‐R‐1H‐1,2,3‐triazol‐4‐yl)phenyl; R = benzyl 1 , 1‐phenylethyl 2 , phenyl 3 ) are used as precatalysts for the polymerisation of norbornene. When activated with MAO, 1 – 3 are highly active catalysts for the production of high molecular weight polynorbornene (e.g., 1.39 × 10⁷ g PNB mol Ni^?1 · h^?1). The catalytic activity and polymer molecular weight increase markedly with the initial concentration of norbornene, but both parameters decrease with the reaction time. The characterisation of the polynorbornenes by NMR, GPC/SEC, X‐ray diffraction, and DSC/TGA leads to the assignment of a structure typical of a polynorbornene originated by a coordination vinyl addition mechanism.

     

Temperature Dependent Studies of Molecular Interactions in a Low‐Molecular Weight Ester Diol Mixed with a Hyperbranched Polyester Additive

In this paper the influence of the hyperbranched polyester based on 4,4‐bis(4‐hydroxyphenyl)valeric acid on the properties of an ester diol oligomer will be discussed. The hyperbranched polyester was added to an ester diol in different amounts and the resulting bulk viscosity values were measured. Surprisingly, the resulting viscosity depends on the mixing temperature of both substances. Glass transition temperatures gave an idea about the phase behavior in the blend. H bond formation in the ester diol was intensively studied by temperature dependent IR measurements. The weakening of H bonds in the ester diol oligomer with increasing temperature was proven by IR measurements and correlates with results from viscosity measurements. These changes allow increased interactions between the ester diol and the hyperbranched polyester which causes different viscosity values depending on the mixing temperature. The overall changes in the behavior of the mixture were proven by temperature dependent AFM measurements.

Frequency dependent viscosity measurement for the mixture containing of 20 wt.‐% of the hyperbranched polyester.     

Synthesis of Heterobifunctional Hyperbranched Polyethylenes Tethered with Dual Acryloyl and 2‐Bromoisobutyryl Functionalities via One‐Pot Chain‐Walking Terpolymerization

A one‐step synthesis of heterobifunctional hyperbranched polyethylenes covalently tethered with dual acryloyl and 2‐bromoisobutyryl functionalities at controllable contents is reported. It is achieved in one pot by chain‐walking terpolymerization of ethylene with two functional acrylate comonomers, 1,6‐hexanediol diacrylate and 2‐(2‐bromoisobutyryloxy) ethyl acrylate. The unique chain‐walking mechanism renders the hyperbranched polymer chain topology and its remarkable capability in incorporating acrylate comonomers enables the incorporation of both comonomers to give two valuable functionalities. The two comonomers exhibit nearly equal vinyl reactivity and are incorporated independently in the terpolymerization with their molar contents controlled by adjusting the comonomer feed concentrations.

     

Diffusion and Reaction of Methylaluminoxane (MAO) within a Silica Membrane

Summary: The self‐diffusion coefficient of MAO confined within a silica membrane is not experimentally accessible by traditional PFG NMR measurements, probably due to a susceptibility effect resulting in rather broad, unobservable resonance lines. A more indirect approach was therefore applied to probe the diffusivity of MAO within a silica membrane. MAO confined in a bulk toluene solution on one side of the membrane was free to diffuse through the membrane (saturated with toluene) and into a corresponding deuterated toluene solution on the other side of the membrane where its proton NMR signal intensity was monitored as a function of time. By introducing a relevant diffusion model, the diffusivities of both toluene and MAO were derived by model‐fitting. By refining the diffusion model, the formation of methane within the silica was explained, and its diffusivity estimated. The results suggest a significant reduction in diffusivities of both MAO and toluene within the silica as compared to the corresponding diffusivities in bulk solution.

¹H NMR spectra as a function of time within the shift region δ = 2.0–2.5 ppm (toluene) acquired during the first 40 h of the diffusion process.     

Synthesis and Characterization of Oxetane‐Functionalized Phosphorescent Ir(III)‐Complexes

In order to incorporate iridium(III) complexes covalently into an oxetane‐bearing hole‐transporting matrix, a new oxetane‐equipped acetoacetate derivative was introduced as an ancillary ligand. Model complexes with an analogical nonpolymerizable ligand were also prepared in order to perform comparative investigations. Therefore, a series of bis‐cyclometalated Ir(III) complexes, showing orange (C?N‐ligand, coumarin 6) and green (C?N‐ligand, phenylpyridine) emission were synthesized and fully characterized. The emission maxima are 569 nm for the orange and 518 nm for the green‐emitting Ir(III) complexes. Entirely solution processed devices, based on crosslinkable hole‐conductors, partially doped with the described orange and green Ir(III) emitters, respectively, were fabricated and tested.

     

Multicyclic Poly(ether ketone)s by Polycondensation of 1,3,5‐Tris(4‐fluorobenzoyl)benzene with Various Diphenols

Summary: 1,3,5‐Tris(4‐fluorobenzoyl)benzene (TFBB) was polycondensed with silylated 4,4′‐dihydroxybiphenyl, bisphenol‐A or 4‐tert‐butylcatechol in N‐methylpyrrolidine with K₂CO₃ as a promoter. The TFBB/diphenol feed ratio was varied from 1.0:1.0 to 1:0:1.5. Partial cross‐linking was observed with the stiff 4,4′‐dihydroxybiphenyl, even at the 1.0:1.0 ratio. With bisphenol‐A, no gelation took place up to a feed ratio of 1.0:1.3, indicating a high cyclization tendency. With 4‐tert‐butylcatechol, no cross‐linking occurred up to the 1.0:1.5 ratio, proving an even higher cyclization tendency. The formation of cyclic, bicyclic and multicyclic oligo‐ and polyethers was detected by means of MALDI‐TOF mass spectrometry for all reaction products. These results demonstrate that increasing chain stiffness reduces the influence of cyclization. Cyclization proved unavoidable, however, and a high cyclization tendency prevents the formation of hyperbranched and networked structures.

     

Polyethylenes Having Well‐Defined Bimodal Molecular Weight Distributions Formed with Bis(phenoxy‐imine) Zr Complexes

Summary: Bis(phenoxy‐imine) Zr complexes with MAO activation can produce polyethylenes with well‐defined bimodal molecular weight distributions. Polymerization behavior indicates that minor changes in the ligand structures can have a significant effect on the modality of the resulting polyethylenes. Although there is no direct relationship between the bimodal catalytic behavior and the structure of a precatalyst complex in solution, a precatalyst complex having a methyl or methoxy group para to the phenoxy‐oxygen inclined to exhibit bimodal behavior whereas that with a pentafluorophenyl group on the imine‐nitrogen displayed unimodal behavior. Polymerization results suggest that bimodal behavior is linked to the presence of two kinds of cationic active species, which arise from different modes of ligand coordination. A qualitative correlation was found between the calculated amounts of possible cationic active species and the uni‐ and bimodal catalytic behavior. Based on the results obtained, we concluded that the bimodal polyethylenes are produced by two kinds of cationic active species having two available cis‐located sites with cis‐N, trans‐O and cis‐N, cis‐O arrangements. The results introduced herein are rare examples of the production of well‐defined bimodal polyethylenes using a single precatalyst.

Bis(phenoxy imine) Zr complexes can produce well‐defined bimodal polyethylenes.     

Synthesis and Study of CdS Nanoparticle‐Doped Poly(1,4‐dihexyloxybenzene)

A simple, economical and high yielding method to prepare poly(1,4‐dihexyloxybenzene), an alkylated derivative of poly(para‐phenylene) (PPP), is reported. We further prepared a composite of poly(1,4‐dihexyloxybenzene) and CdS nanoparticles and studied their structural, optical, stability and transport properties. It was observed that the conductivity of poly(1,4‐dihexyloxybenzene) increased by several orders of magnitude when doped with CdS nanoparticles. Similarly, CdS nanoparticle‐doped PPP showed higher thermal stability, when compared to the neat polymer. As these composites could be processed in the same way as organic polymers, they would find applications in many low‐cost optoelectronic devices.

     

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.

     

Propene Polymerisation with rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2 as a Highly Active Catalyst: Influence of Monomer Concentration,Polymerisation Temperature and a Heterogenising Support

Propene was polymerised at high temperatures (up to 90 °C) using rac‐[Me₂Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)₂]ZrCl₂/MAO as the catalytic system. The increasing deactivation reaction rate of the catalyst for polymerisations above 60 °C was less for a silica supported catalyst compared with the homogeneous one. The isotacticity of polypropene decreases from 99 to 96%. Also the morphology changes with different temperatures.

Increasing of the thermal stability for the rac‐[Me₂Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)₂]ZrCl₂/MAO/SiO₂ with respect of the rac‐[Me₂Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)₂]ZrCl₂/MAO system.     

Synthesis of Narrowly Distributed ω‐Telechelic Hyperbranched Polyethylenes by Efficient End‐Capping of Pd‐Diimine‐Catalyzed Ethylene “Living” Polymerization with Styrene Derivatives

We report herein a quantitative end‐capping chemistry for the efficient synthesis of monotelechelic hyperbranched polyethylenes containing various ω‐end functionalities by quenching Pd‐diimine catalyzed ethylene “living” polymerization with styrene derivatives. This chemistry utilizes the unique reaction of styrene derivatives with cationic Pd‐diimine species to form stable π‐benzyl intermediate complexes, which are inactive for ethylene polymerization. In the synthesis, “living” hyperbranched polyethylene chains were grown with a Pd‐diimine catalyst. Subsequent end‐quenching of the “living” chains with three styrene derivatives renders narrowly distributed telechelic hyperbranched polyethylenes containing different functional ω‐terminal groups.

     

Determination of the Crystal Structure of Syndiotactic 3,4‐Poly(2‐methyl‐1,3‐butadiene) by Molecular Mechanics and X‐Ray Diffraction

Summary: The crystal structure of syndiotactic 3,4‐poly(2‐methyl‐1,3‐butadiene) has been determined by the joint use of molecular mechanics and X‐ray diffraction. Molecular mechanics calculations have been performed both on the isolated chain and on the crystal by the use of various force fields. The energy minimizations predict a model of the crystal structure. The calculated X‐ray powder diffraction pattern is in good agreement with the experimental one. This model has been refined in order to obtain the best agreement with all the experimental data. The space group is Pbcm and the parameters of the unit cell are a = 6.6 Å, b = 13.2 Å, c = 5.27 Å. The presence of defects in the crystal has been taken into account. Analogies and differences with the crystal structure of syndiotactic 1,2‐poly(1,3‐butadiene) are discussed.

X‐ray fiber diffraction pattern of syndiotactic 3,4‐poly(2‐methyl‐1,3‐butadiene).     

Insights into the Ring‐Expansion Polymerization of Thiiranes with 2,4‐Thiazolidinedione

The behavior of the ring‐expansion homopolymerization of 2 (phenoxymethyl)thiirane (PMT) and propylene sulfide (PS), respectively, with thiazolidine‐2,4‐dione (TZD) as a cyclic initiator is investigated. The polymerizations show steadily growing molar masses with increasing monomer conversions. In addition, reversible merging reactions between rings are observed, with up to six merged macrocycles formed. The degree of merging is strongly dependent on the initial monomer concentration, whereas temperature has only a small impact. Under optimized conditions, ring‐poly(PMT) polymer with values of M _n up to 50 250 g mol^?1 and dispersities down to 1.11 can be synthesized. DSC and ESI‐MS measurements of the novel ring‐poly(PS) prove the formation of ring polymer having topological purity above 95%.

     

Synthesis of Ethylene/Acrylonitrile Composite Elastomers with Nanosized Polyacrylonitrile Domains Using α‐Dimine‐[N,N] Nickel Dichloride/EASC

A series of ethylene and acrylonitrile composite elastomers were prepared using (1,4‐bis(2,6diisopropylphenyl)‐acenaphtenediimine‐nickel(II))‐dichloride/ethylaluminum sesquichloride (EASC). The xylene‐soluble polymer fraction showed nitrile bands in infrared spectroscopy at 2 245 and 2 214 cm^?1 and polyacrylonitrile‐enriched structures were detected in the xylene‐insoluble fraction by¹H and ¹³C NMR. In addition, TEM detected nanosized polyacrylonitrile domains dispersed in the polyethylene matrix. Differential scanning calorimetry scans conducted from ?70 to 350 °C measured exothermic bands corresponding to the cyclization and aromatization of the nitrile groups dispersed in the polyethylene matrix.

     

On the Radiation‐Induced Polymerisation of 2,3‐Dihydropyran

Summary: Concentrated (5 mol‐%) solutions of 2,3‐dihydropyran in CFCl₂CF₂Cl matrix were irradiated at 77 K and several intermediates – radical cation, dimer radical cation, dihydropyryl radical and a trapped polymer radical – were observed by low‐temperature EPR spectroscopy. The irradiated solutions yielded after melting a polymeric product, which was characterised by IR spectroscopy and GPC. The polydisperse polymer is assumed to be formed by a cationic process initiated by a dimer carbocation. The polymerization proceeds via the ring double bonds, while ring‐opening reaction occurs in a small extent. The free‐radical mechanism via the dihydropyryl radical leads to low molecular weight oligomers only. The quantum chemical calculations support the interpretation of the experimental results.