Polyacetylene and Polynorbornene Derivatives Carrying TEMPO. Synthesis and Properties as Organic Radical Battery Materials

Summary: 2,2,6,6‐Tetramethylpiperidine 1‐oxyl (TEMPO)‐containing N‐propargylamide HCCCH₂NHCO‐4‐TEMPO ( 1 ), propargyl ester HCCCH₂OCO‐4‐TEMPO ( 2 ), phenylacetylene derivative HCCC₆H₃‐3,4‐(CO₂‐4‐TEMPO)₂ ( 3 ), and norbornene diester monomers, NB‐2,3‐exo,exo‐(CH₂OCO‐4‐TEMPO)₂ ( 4 ), NB‐2,3‐endo,exo‐(COO‐4‐TEMPO)₂ ( 5a ), NB‐2,3‐endo,endo‐(COO‐4‐TEMPO)₂ ( 5b ) (NB = norbornene, TEMPO = 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl) were synthesized and polymerized with rhodium and ruthenium catalysts. Monomers 2 , 5a , and 5b gave polymers with number‐average molecular weights of 47 000–185 000 in 59–100% yields, while 1 , 3 , and 4 gave polymers insoluble in common organic solvents in 88–100% yields. The capacities of cells fabricated with poly( 1 ), poly( 2 ), and poly( 3 ) were 67, 82, and 23 Ah · kg⁻¹ based on the weight, respectively. The capacity of poly( 5a )‐based cell reached the theoretical value (109 Ah · kg⁻¹) of the polymer.

Charge–discharge curves of poly( 5a ) at a current density of 0.13 mA · cm⁻² (100 mA · g⁻¹_{‐cathode active material}) in the voltage range of 2.5–4.2 V.     

Titanium‐Catalyzed Norbornene Oligomerization. Isolation of a Crystalline Heptamer with a 2,3‐exo‐Disyndiotactic Structure

Summary: Norbornene (NB) was oligomerized at 0 °C using AlEt₂Cl‐TiCl₄ at a monomer/titanium molar ratio of about 11. The oligomerization product consists of a fraction soluble in diethyl ether, amorphous by X‐ray examination, and of a crystalline fraction, insoluble in diethyl ether. The crystalline fraction was shown by powder X‐ray diffraction to consist of a NB heptamer. Single‐crystal X‐ray analysis indicated that the heptamer had a stereoregular 2,3‐exo‐disyndiotactic structure. The heptamer adopts a strained, highly irregular, folded conformation in the crystalline state. Structural differences with respect to NB oligomers obtained with zirconocene catalysts are discussed.

A view of the molecular structure of the crystalline NB heptamer.     

Catalytic Synthesis of a Monodisperse Olefin Block Copolymer Using a Living Polymerization System

Polymerization of norbornene has been conducted with [t‐BuNSiMe₂(3,6‐t‐Bu₂Flu)]TiMe₂ ( 1 ) in toluene at 20 °C using modified methylaluminoxane that contained 0.4 mol‐% of triisobutylaluminium (TIBA) (dMMAO(0.4)) or 1.8 mol‐% of TIBA (dMMAO(1.8)). The 1 ‐dMMAO(0.4) catalytic system undergoes a living polymerization of norbornene. The catalysis of norbornene and propylene with the 1 ‐dMMAO(1.8) catalytic system gives markedly different results because of differences in transfer times of the polymers from Ti to TIBA. The successive addition of norbornene and propylene before the complete consumption of the norbornene in the 1 ‐dMMAO(1.8) system gives monodisperse PNB‐block‐poly(propylene‐ran‐norbornene)‐block‐PP terminated with a Ti–PP bond, which is exchanged with TIBA. Hence the repeated addition of the same amount of norbornene and propylene realizes the catalytic synthesis of monodisperse block copolymer in this system.

     

Cyclopentadienyl Nickel and Palladium Complexes/Activator System for the Vinyl‐Type Copolymerization of Norbornene with Norbornene Carboxylic Acid Esters: Control of Polymer Solubility and Glass Transition Temperature

Summary: In non‐polar solvents such as toluene, Cp‐Ni and ‐Pd complexes (Cp = η⁵‐C₅H₅) with appropriate activators have been found to induce the addition polymerization of norbornene in excellent yields, for example (Cp)Pd(allyl)/[Ph₃C][B(C₆F₅)₄] gave 105 120 kg‐polymer/cat‐mol · h at room temperature. While the Cp‐Pd system was not suitable in the presence of ester‐substituted norbornenes, the Cp‐Ni system, for example (Cp)Ni(Cl)(PPh₃)/AlMe₃/B(C₆F₅)₃ can copolymerize norbornene with 5‐norbornene‐2‐carboxylic acid methyl ester in toluene to give high yields (up to 68% in 2 h at room temperature) of copolymer with variable contents of the methyl ester monomer unit (17.4–60.7 mol‐%). These copolymers have high molecular weights ( = 234 100–109 500) and narrow molecular weight distributions ( = 1.78–1.89). In addition, they are soluble in common organic solvents giving flexible and transparent films on casting, that show very high T_g in the range of 352.8 to 316.0 °C. The same Ni‐catalyst system can also copolymerize norbornene derivatives with bulky substituents, i.e., 2‐butyl‐5‐norbornene and 5‐norbornene‐2‐carboxylic acid butyl ester. The T_g of these copolymers are lower (294.9–267.3 °C) than the methyl ester‐based copolymers, demonstrating that the T_g of the polynorbornene copolymer film can be tailored simply by changing the alkyl group of the monomer to within the range of 352 to 267 °C.

Figure showing the addition polymerization of norbornene using Cp‐Ni complex with appropriate activators.     

Preparation of Polar Ethylene–Norbornene Copolymers by Metallocene Terpolymerization with Triisobutylaluminium‐Protected But‐3‐en‐1‐ol

But‐3‐en‐1‐ol has been pre‐protected by triisobutylaluminium and terpolymerized with ethylene and norbornene by rac‐[Et(Ind)₂]ZrCl₂/MAO catalysts. The strong polarity of diisobutyl(but‐3‐en‐1‐oxy)aluminum causes a slight reduction in the catalyst activity and yields a small fraction of crystallinity. The but‐3‐en‐1‐ol content in the terpolymer is as high as 3.2% and can be readily adjusted by varying the reaction conditions. When the norbornene/ethylene ratio is over 10, the norbornene incorporation efficiency is not affected by the polar monomer and is close to that of the copolymerization. Similar to the ethylene/norbornene copolymers, the thermal properties of the obtained terpolymers are mainly determined by their norbornene contents.

     

Polymerization of carboxylic ester functionalized norbornenes catalyzed by (η3‐allyl)palladium complexes bearing N‐heterocyclic carbene ligands

An in situ generated cationic allylpalladium complex bearing N‐heterocyclic carbene (NHC) ligands, derived from the reaction of [(η³‐C₃H₅)Pd(NHC)Cl] with AgX (X = BF₄ or SbF₆), is an active catalyst for the addition polymerization of norbornene and norbornene derivatives [5‐norbornene‐2‐carboxylic acid methyl ester ( b ) and 5‐norbornene‐2‐carboxylic acid n‐butyl ester ( c )] with an ester group containing a large portion of endo‐isomers. The catalytic activities, polymer yields, molecular weights, and molecular weight distributions of polynorbornenes were investigated under various reaction conditions: the catalytic activity was highly dependent on the counteranion, the reaction solvent, and the reaction temperature. For b , as the portion of an endo‐isomer increased, the activity of 13 (SbF) was much higher than those of 14 and 15 , and for c (exo/endo = 95:5), the maximum turn over number (TON) was observed with 15 (SbF). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3042–3052, 2007     

Novel Highly Active Niobium Catalysts for Ring Opening Metathesis Polymerization of Norbornene

Ring‐opening metathesis polymerization (ROMP) of norbornene catalyzed by niobium(V) N,N‐dialkylcarbamates Nb(O₂CNR₂)₅, R = Et ( 1 ), Me ( 2 ) was studied in the presence of methylaluminoxane (MAO) as a cocatalyst. These novel catalytic systems resulted very active in chlorobenzene: 1 in the presence of methylaluminoxane catalyzes the ROMP of norbornene with the highest activity (29 000 kg of polymer/mol of catalyst × hour) never reported up to now for niobium catalysts. The high productivity appears particularly attractive considering that these precursors are rather cheap and easy to synthesize and to handle. Polynorbornenes were characterized by FT‐IR and NMR spectroscopies and by DSC calorimetry. A new FT‐IR method for the swift determination of the cis/trans content of the polymer is presented.

     

Effect of Cocatalysts on the Catalytic Activities of Tantalum‐ and Niobium‐Based Catalysts for Ring‐Opening Metathesis Polymerization of Norbornene

A series of pentavalent tantalum and niobium complexes with aryloxy ligands was prepared, and their catalytic behavior for the ROMP of norbornene was studied in the presence of an alkylaluminum cocatalyst. Tantalum complexes 1 – 4 showed very high activity for the ROMP of NBE in combination with ⁱBu₃Al to give high‐molecular‐weight polymers. In contrast, the niobium complexes 5 and 6 , as well as NbCl₅, exhibited very high activity upon activation with Me₃Al to give high‐molecular‐weight polymers.

     

Polymerization of Vinyl Ethers by (α‐diimine)NiII/Methylaluminoxane Catalysts

Polymerizations of vinyl ethers are carried out with (α‐diimine)nickel(II ) catalysts in the presence of methylaluminoxane. Effects of structural variations of the ligand on the activities of catalysts and polymer microstructure are described. The catalysts prepared by changing the bulkiness of ligand substituents in the ortho aryl position result in no specific trends terms of the yield and molecular weight of polymer. Poly(vinyl ether)s are atactic regardless of the structure of the catalyst used.

     

Synthesis and Polymerization of Optically Active N‐Propargylphosphonamidates: A Novel Helical Polymer Carrying a P‐Chiral Center

Summary: A diastereomeric pair of novel N‐propargylphosphonamidates, HCCCH₂NHP(O)(CH₃)O‐L ‐menthyl was synthesized by the successive condensations of methylphosphonic dichloride with L ‐menthol and propargylamine. The (R)‐P‐isomer ( 1a ) was isolated, and the absolute configuration was determined by XRD. Polymerization of 1a , and a mixture of 1a and (S)‐P‐isomer ( 1b ) was carried out with a zwitterionic Rh complex as a catalyst. cis‐Stereoregular polymers with number‐average molecular weights of 5 600–9 800 were obtained in good yields. Poly( 1a ) and poly( 1a ₂₉‐co‐ 1b ₇₁) exhibited large specific rotations (+408 and −146°), and intense Cotton effects ([θ] = +2.25 and −0.9 × 10⁴ deg · cm² · dmol⁻¹) based on the conjugated polyacetylene backbone around 325 nm in CHCl₃, indicating that these polymers have helical structures, whose predominant helical senses are opposite.

Polymerization of N‐propargylphosphonamidate.     

Glass Transition Temperature and Chain Flexibility of Ethylene‐Norbornene Copolymers from Molecular Dynamics Simulations

Summary: Model chains of ethylene‐norbornene copolymers were built up using the results of ¹³C NMR spectral analysis of copolymer samples synthesized with metallocene‐based catalysts. Our models statistically reproduce the microstructure, composition, and tacticity of the copolymer chains of experimental samples. They were used to test if MD simulations are suitable to investigate the relationships between microstructure and macroscopic properties. In particular, MD simulations were applied to calculate the glass transition temperature and to study the chain flexibility by the analysis of ACF of specific virtual bonds. Plots of specific volume versus temperature computed for models of four copolymer samples having different microstructures and norbornene contents yield T_g values in good agreement with experiments. Moreover, comparison of the ACFs provides some qualitative indications about the relationship between chain stereochemistry and T_g.

ACF functions of the virtual bonds with microstructures NENE (bottom) and ENNE (top).     

Ordering Cylindrical Microdomains for Binary Blends of Block Copolymers with Graphoepitaxy

The morphology of a thin film was studied for a binary mixture of asymmetric PS‐b‐PMMA block copolymers on a flat silicon wafer coated with 50 nm thick silicon oxide. AFM and TEM reveal that the PMMA cylinders orient perpendicular to the substrate by tuning the film thickness. Furthermore, grating substrates with different width and depth are used to guide the alignment of the perpendicular cylinders. As a result, an array of highly ordered, hexagonally packed PMMA cylinders in the PS matrix with a domain spacing of less than 25 nm has been produced.

     

Silyl‐Terminated Ethylene‐co‐Norbornene Copolymers by Organotitanium‐Based Catalysts

Ethylene (E) and norbornene (N) were copolymerized in the presence of PhSiH₃ as chain‐transfer agent with [Ti(η⁵:η¹‐C₅Me₄SiMe₂NBu^t)(η¹‐Me)₂] precatalyst combined with [Ph₃C][B(C₆F₅)₄]. The silane was introduced at chain‐ends of E‐co‐N copolymers with concomitant reinitiation of the growing polymer chain. The concentrations of the silane and polymer molecular weight are inversely correlated. The characteristic signals of  SiH₂Ph chain‐ends were observed by ¹H NMR. The Si heteroatom is predominantly adjacent to ethylene units in E‐co‐N copolymers with high N content.

     

Copolymerization of Propene and 5‐Vinyl‐2‐Norbornene: A Simple Route to Polar Poly(propylene)s

Summary: The metallocenes rac‐C₂H₄(Ind)₂ZrCl₂ ( 1 ), rac‐Me₂Si(Ind)₂ZrCl₂ ( 2 ), and rac‐Me₂Si(2‐Me‐benz[e]Ind)₂ZrCl₂ ( 3 ) efficiently copolymerize propene and 5‐vinyl‐2‐norbornene (VNB). 1 and 2 give a high VNB content and high productivities, whereas 3 gives moderate incorporation. Surprisingly, precatalysts 1 and 2 , which have very closely related structures, showed very different reactivities toward VNB, with 1 having a greater affinity for VNB than for propene. The copolymers are quantitatively converted into polyolefins with polar functionalities.

     

Magnetic Field‐Induced Shape Transitions in Multiphase Polymer‐Liquid Crystal Blends

Summary: This paper presents a computational study of phase separation‐phase ordering‐texturing in blends of polymer coils and rod‐like nematic liquid crystals under the presence of magnetic fields, using an extended version of the Matsuyama‐Evans‐Cates model (Phys. Rev. E 2000 , 61, 2977). This work demonstrates that demixing in these blends leads to droplet morphologies with tunable droplet shapes and director textures. In contrast to filled nematics, where solids are suspended in a nematic liquid crystal matrix, demixing in coil‐mesogenic rods blends leads to nematic emulsions, in which the deformable viscoelastic polymer drops are suspended in a nematic matrix. Under strong anchoring conditions, the imposition of a magnetic field leads to a director re‐orientation that due to strong anchoring produces a droplet shape change. Magnetic field‐induced shape transitions in these blends are shown to be second order with a finite critical field threshold that diverges as anchoring strength vanishes. A morphological‐texture diagram summarizes the magnetic field‐anchoring conditions that promote anisotropic shapes. This work presents additional material processing routes to design and control bi‐phasic morphologies in polymer‐liquid crystal blend.

Computed morphology phase diagram in terms of magnetic field strength Λ_M and anchoring strength. Λ_ϕQ.     

Polymerization of Norbornene with CoCl2 and Pyridine Bisimine Cobalt(II) Complexes Activated with MAO

Addition polymerization of norbornene was performed with several pyridine bis(imine) cobalt dichloride complexes activated with methylaluminoxane (MAO), first described for ethylene polymerization. For the first time, norbornene was also polymerized with CoCl₂ associated to MAO. The influence of several reaction parameters has been investigated. Quite different behavior was observed compared with ethylene polymerization. Moreover, the copolymerization of ethylene and norbornene with these complexes was not possible but led to a mixture of both homopolymers.

The pyridine bis(imine) cobalt dichloride complexes used in this study.     

Reaction of Boranes with TMS Diazomethane and Dimethylsulfoxonium Methylide. Synthesis of Poly(methylidene‐co‐TMSmethylidene) Random Copolymers

Summary: Borane reacts with TDM by a sequence of insertion and disproportionation reactions to yield tris‐(trimethylsilylmethyl)borane. No further addition of TDM occurs. Triallylborane and tris‐(4‐methoxyphenylethyl)borane initiate the copolymerization of TDM and dimethylsulfoxonium methylide. The reactions afford TMS‐substituted polymethylene oligomers. The resultant poly(methylidene‐co‐TMSmethylidene) random copolymers arise from incorporation of TMSmethylidene (CHSiMe₃) and methylidene (CH₂) groups into the growing polymer chain one carbon at a time.

Trialkylborane‐catalyzed copolymerization of trimethylsilyl diazomethane and dimethylsulfoxonium methylide.     

Sequential Electrografting and Ring‐Opening Metathesis Polymerization: a Strategy for the Tailoring of Conductive Surfaces

Summary: An electrografting technique has been combined with ring‐opening metathesis polymerization (ROMP). Poly(allyl methacrylate) chains have been chemisorbed onto steel and carbon plates under an appropriate cathodic potential in N,N‐dimethylformamide. The allyl moieties have been converted into Ru catalysts active in ROMP of norbornene and its derivatives. Initiation of ROMP from the surface is an efficient strategy to prepare strongly adhering coatings of tunable thickness and hydrophilic/hydrophobic balance, depending on the norbornene derivative polymerized at the surface.

The hydrophobicity of the polymer coating may be controlled by hydrolysis of the polynorbornene derivative.     

Supramolecular Thermoresponsive Hyperbranched Polymers Constructed from Poly(N‐Isopropylacrylamide) Containing One Adamantyl and Two β‐Cyclodextrin Terminal Moieties

Poly(N‐isopropylacrylamide) (PNIPAM) oligomer containing one adamantyl (AD) and two β‐cyclodextrin (β‐CD) moieties at the chain terminals, AD‐PNIPAM‐(β‐CD)₂, was synthesized by atom transfer radical polymerization (ATRP) and successive click reactions. In aqueous solution, AD‐PNIPAM‐(β‐CD)₂ spontaneously forms supramolecular thermoresponsive hyperbranched polymers via molecular recognition between AD and β‐CD moieties. To the best of our knowledge, this work represents the first report of the construction of supramolecular thermoresponsive hyperbranched polymers from well‐defined polymeric AB₂ building units.

     

Oligomerization of Electron‐Deficient Vinyl Monomers Through an Ate‐Complex Mechanism: A New Role for B(C6F5)3 Lewis Acid

The Lewis acid B(C₆F₅)₃ in combination with hydrosilanes exhibits remarkable activity in the oligomerization of sulfone‐ and phosphonate‐based monomers. This process opens new routes to high‐tech silicone‐based materials, i.e., thermoplastic elastomers and heat‐resistant polysiloxanes.