End‐group analyses of the oligo‐ and polypropylenes produced with bis(phenoxy‐imine) Zr and Hf complexes with methylaluminoxane (MAO) indicate that the polymerization is initiated by two consecutive 1,2‐insertions and is terminated by a β‐H transfer following a 2,1‐insertion. Our data indicate that chain propagation occurs with prevailing 1,2‐regiochemistry but with considerable regioerrors, and with virtually no stereoselectivity.
The polymerization of propylene mediated by bis(phenoxy‐imine) Zr and Hf complexes with MAO. 相似文献
The catalytic properties of bis(phenoxy‐imine) Zr and Hf complexes incorporating perfluorophenyl groups with methylaluminoxane were investigated. The fluorinated complexes produced far higher‐molecular‐weight polyethylenes and ethylene/propylene copolymers with increased activities compared with the non‐fluorinated congeners. Moreover, the fluorinated complexes displayed a higher incorporation ability for propylene.
A simple and efficient polymer grafting onto hydrothermal carbonization (HTC)‐derived materials is described. The method pertains to the Diels–Alder cycloaddition reaction of furan moieties present on the surface of a HTC material with the maleimide groups stemming from a maleimide protected poly(ethylene glycol) (Me‐PEG‐MI) by a retro Diels‐Alder reaction. The precursor polymer, HTC material, and final product are characterized. Successful grafting is confirmed by elemental analysis, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and dispersion studies.
Copolymerization of hepta‐1,6‐diene with ethylene using a cobalt–bis(imino)pyridine complex affords a polymer that contains trans‐1,2‐five‐membered rings in the repeating unit from hepta‐1,6‐diene. The ratio of the repeating units of diene to those of ethylene is controlled from 3: 97 to 50:50, depending on the reaction conditions. Isotope‐labeling reactions reveal that the major chain transfer pathway involves β‐hydrogen elimination of the polymer end formed after ethylene insertion.
Summary: A class of new, soluble, π‐conjugated polymers containing a fumaronitrile unit in the main chain were synthesized by the reaction between di(4‐bromophenyl)fumaronitrile and bis(2,2‐dimethylpropane‐1,3‐diyl)‐1,4‐dialkoxyphenylene‐2,5‐diborate employing palladium catalysts. All the polymers were photoluminescent and electrochemically active.
The new soluble π‐conjugated polymers 1a – d with photoluminescence and electrochemical activity synthesized here. 相似文献
Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in‐situ polymerization. During the process fibrillar complex of FeCl3 and methyl orange (MO), acting as a reactive self‐degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.
TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min. 相似文献
The mechanistic interpretation of kinetic anomalies in reversible addition–fragmentation chain transfer (RAFT)‐mediated polymerization is critically reviewed. The main conclusion of this exercise is that available data do not allow model discrimination between the two prevailing mechanistic schemes, i.e., the slow fragmentation model and the intermediate radical termination model. However, assessment of the rate parameters reveals that the incompatibilities may not be as large as previously reported in literature. Dedicated kinetic studies on model compounds should be performed to shed further light on the seemingly incompatible data that currently exists in literature.
Miniemulsion polymerization with an amphiphilic poly(acrylic acid)‐block‐polystyrene reversible addition–fragmentation chain transfer agent as a surfactant and polymerization mediator is used to synthesize highly uniform nanocapsules. The nanocapsules with uniform structures, which include particle size, shell thickness, and shape symmetry, could be achieved by the post‐addition of a small amount of sodium dodecyl sulfate. Although the solid particles seem unavoidable, the ‘pure’ uniform core–shell structures are easily collected by centrifugation.
Novel side‐chain‐type sulfonated poly(arylene ether) with pendant sulfoalkyl group copolymers (PSA‐SPAE‐6F) have been synthesized by direct copolymerization from a new sulfonated monomer, sodium 3‐(4‐(2,6‐difluorobenzoyl)phenyl)propane‐1‐sulfonate. The sulfonate content could be easily controlled by adjusting the sulfonated and the unsulfonated monomer feed ratio. The obtained copolymers all show good thermal and mechanical properties. It should be noted that the most highly sulfonated copolymer, PSA‐SPAE‐6F90 with an ion exchange capacity of 1.30 mequiv · g−1, shows a proton conductivity of 0.11 S · cm−1 and a water swelling ratio of only 12.9% at 100 °C, which indicates its high proton conductivity and excellent dimensional stability in hot water.
Summary: The evolution of the morphologies in blends of epoxy/4,4′‐methylenebis(2,6‐dimethylaniline)/polyethersulfone was followed by time‐resolved light scattering, optical microscopy and scanning electron microscopy. The results suggest that, once the diffusion of epoxy molecules cannot follow the geometrical growth, a secondary phase separation occurs, even in the droplet morphology, in which the size of the epoxy‐rich domain grows as usual. The viscoelastic effect of polyethersulfone is also discussed.
Development of morphologies followed by OM: bicontinuous phase separation in the PES‐15.9 blend cured at 140 °C after 80 s. 相似文献
We report here a facile synthesis of high performance electro‐active polymer actuator based on a sulfonated polyimide with well‐defined silver electrodes via self‐metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer‐metal composite actuators. Also, the self‐metallized silver electrodes exhibit outstanding metal‐polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion‐based actuators.
Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L ‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.
Structures of the polymer gelators synthesized here. 相似文献
Densities and viscosities of a series of blends of poly(ethylene glycol) (PEG) and poly(ethylene glycol‐ran‐propylene glycol) (PEG‐ran‐PPG) were measured at a temperature above the melting point. The density and viscosity data were fitted with analytical functions involving the volume fraction of PEG, ϕPEG. Stress relaxation curves for the pure components and blends were obtained through Monte Carlo (MC) simulations. A typical stress relaxation curve exhibits a fast mode that represents energetic‐interactions‐driven motion and a slow mode that originates from the entropy‐driven motion. Flory–Huggins interaction parameters (χ) for the blends are much smaller than the critical values (χcritical). The calculation of χ and χcritical provides important clues for polymer blend processing.
This paper studies a kind of hollow nanospheres prepared by self‐assembly β‐cyclodextrins (β‐CDs) and poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (pluronic F127) for gene delivery. It was found that this kind of hollow nanospheres enable load PEI10K/DNA and the resulting F127 NH2 βCD/(PEI10K/DNA) with 0.08 µg/well DNA display equal or higher gene delivery capability compared to PEI10K/DNA with 1 µg/well DNA in the absence or presence of serum. The cytotoxicity of the nanospheres was over 100 times lower than that of PEI10K.
Vapor phase polymerization was used to synthesize high conductivity poly(3,4‐ethylenedioxyphenylene) (PEDOT). The monomer is presented to an oxidant‐rich substrate in vapor form and even for short polymerization times, 10–30 min, Fe(III) tosylate has a propensity for water absorption leading to crystal formation. Poor oxidant treatment before polymerization or high humidity during polymerization can create holes in the PEDOT film decreasing its conductivity. The addition of an amphiphilic copolymer poly(ethylene glycol)‐ran‐poly(propylene glycol) suppresses crystal growth allowing better film formation. The humidity level during synthesis was optimized at 35% relative humidity (RH), producing a conductivity of 761 S · cm−1. Additionally, the copolymer extends the RH range that is tolerable for polymer synthesis.
The synthesis, layer‐by‐layer deposition, and electro‐copolymerization of precursor polyelectrolyte multilayer ultrathin films with thiophene and carbazole electroactive groups are described. The interest is in observing an electrochemical cross‐linking approach towards a highly ordered ultrathin film that contains two types of monomers to result in possible layer‐limited homo‐ and copolymerization. A uniform linear growth with alternate deposition of the polyelectrolytes is observed. The multilayer films were then electrochemically polymerized anodically by cyclic voltammetry (CV), which results in copolymerization between two different electroactive groups. Cross‐linking of the layers was verified by CV and spectroelectrochemistry data with very good linear electro‐copolymerizability.
A new versatile synthesis strategy for macromonomers has been developed that uses the living ring‐opening metathesis polymerization (ROMP) with commercial Grubbs first generation ruthenium initiators. Homopolymers as well as diblock copolymers were end‐functionalized with norbornene derivatives to serve as macromonomers. The graft copolymerization of the macromonomers was also carried out employing ROMP. Well‐defined and highly functional graft copolymers are accessible by this new synthetic route.
The synthesis and polymerization of novel diallyldimethylammonium ionic liquid monomers is described. A free‐radical polymerization follows a ring‐closing cyclopolymerization mechanism similar to the one observed previously for diallyldimethylammonium halides that leads to pyrrolidinium functional polymers. As previously observed in other families of polymeric ionic liquids, their physico‐chemical properties are seriously affected by the nature of the counter‐anion. As an example, the thermal stability increases following the trend SCN− < < < bis(trifluoromethane)sulfonamide. Interestingly, this polymerization route may lead to the synthesis of a new family of random copolymers that have a similar poly(diallyldimethylammonium) backbone and a mixture of counter‐anions determined by the comonomer selection.
