Search results for "Copolymerization"
showing 10 items of 38 documents
Ethene/norbornene copolymerization with (isodicyclopentadienyl)titanium complex-MAO catalyst
2007
Norbornene (NB) homopolymerization and ethene/NB copolymerizations with a silylene-bridged (isodicyclopentadienyl)(tert-butylamido)titanium dichloride-methylalumoxane (MAO) catalyst system were investigated. This catalytic system shows no efficiency towards NB homopolymerization but produces poly(ethene-co-norbornene)s. An increase in the initial NB feed content leads to a loss of copolymerization activity as well as NB copolymer incorporation. The structure of the isodicyclopentadienyl fragment (IsodiCp) has a strong limiting effect on comonomer incorporation possibilities.
Acid‐Cleavable Poly(ethylene glycol) Hydrogels Displaying Protein Release at pH 5
2020
Abstract PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring‐opening copolymerization of ethylene oxide with 3,4‐epoxy‐1‐butene (EPB) and subsequent modification to introduce acid‐degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross‐linking. Copolymers with different molar ratios of EPB, molecular weights (M n) up to 10 000 g mol−1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG‐co‐isoEPB)MA copolymer and the hydrogels showed pH‐…
Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: A Robust Approach for Modeling Precipitation and Dispersion Kinetics
2012
A kinetic model is developed for the heterogeneous free-radical copolymerization of vinylidene fluoride and hexafluoropropylene in supercritical CO 2. The model accounts for polymerization in both the dispersed (polymer-rich) phase and in the continuous (polymer-free) supercritical phase, for radical interphase transport, diffusion limitations, and chain-length-dependent termination in the polymer-rich phase. A parameter evaluation strategy is developed and detailed to estimate most of the kinetic parameters a priori while minimizing their evaluation by direct fitting. The resulting model predictions compare favorably with the experimental results of conversion and MWD at varying monomer fe…
Copolymerization of ethylene with norbornene or 1-octene using supported ionic liquid systems
2016
Copolymerization of ethylene with norbornene (E/NB) and ethylene with 1-octene (E/Oct) is performed using supported ionic liquid (SIL) systems, in which metallocene (Cp2VCl2) or post-metallocene [VCl2(salenCl2)] vanadium catalysts are immobilized in pyridinium chloroaluminate ionic liquid supported on silica. The studied SIL catalysts show higher activities as well as stability than their non-supported analogues. In addition, higher activities and better comonomer incorporation are observed for norbornene (above 30 mol%). The comonomer incorporation has considerable influence on copolymer molecular weight (M w), melting temperature, crystallinity degree, and microstructure of the copolymers…
The effect of the comonomer on the copolymerization of ethylene with long chain α-olefins using Ziegler–Natta catalysts supported on MgCl2(THF)2
2000
Abstract The effect of the type of the comonomer (1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene) on the copolymerization of ethylene with α-olefin over vanadium (VOCl3 and VCl4) and titanium (TiCl4) catalysts supported on MgCl2(THF)2 and activated by Et2AlCl was studied. The results show that the introduction of a longer α-olefin in the ethylene polymerization feed depresses the catalytic activity of all investigated catalysts. The catalyst activity does not depend on the type of the comonomer applied but changes with the comonomer concentration in the feed. The incorporation of α-olefin in the polymer chain was found to be dependent on the type and concentration of the comonomer i…
Synthesis and structural characterization of ethylene copolymers containing double-decker silsesquioxane as pendant groups and cross-linkage sites by…
2018
Abstract The copolymers of ethylene with the double-decker silsesquioxane (DDSQ) were synthesized by copolymerization with the use of metallocene and bis(phenoxy-imine) catalysts. The influence of the kind of the catalyst and polyreaction conditions on the performance of copolymerization as well as on the properties of the copolymers was studied. Depending on polyreaction parameters, the DDSQ contents in the copolymer varied in the range of 0.93–11.53 wt% which determined the compositions and the structural properties of copolymers. DDSQ incorporated into the polymer chain could constitute pendant groups in the main chain or it could act as a cross-linking agent. The ethylene/DDSQ copolymer…
Dichlorovanadium(IV) diamine-bis(phenolate) complexes for ethylene (co)polymerization and 1-olefin isospecific polymerization
2018
Abstract Two vanadium complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor, [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)2}Cl2] (1) and [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)(CH2-2-O-C6H4)}Cl2] (2), were synthesised and characterized by FTIR and 1H NMR spectroscopy. Upon activation with Al(iBu)3/Ph3CB(C6F5)4, these complexes became active catalysts for 1-octene polymerization giving highly stereoregular polymers (mmmm ∼ 90%) having regioirregularly arranged units. The catalytic activity of the catalysts in ethylene homo- and copolymerization, and their ability to incorporate a comonomer were highly dependent on both the activator type and the complex structure. 1/EtAlCl2 exhi…
MRI-Visible Poly(ε-caprolactone) with Controlled Contrast Agent Ratios for Enhanced Visualization in Temporary Imaging Applications
2013
International audience; Hydrophobic macromolecular contrast agents (MMCAs) are highly desirable to provide safe and efficient magnetic resonance (MR) visibility to implantable medical devices. In this study, we report on the synthesis and evaluation of novel biodegradable poly(ε-caprolactone)-based MMCAs. Poly(α-propargyl-ε-caprolactone-co-ε-caprolactone)s containing 2, 5, and 10 mol % of propargyl groups have been prepared by ring-opening copolymerization of ε-caprolactone and the corresponding propargylated lactone. In parallel, a diazido derivative of the clinically used diethylenetriaminepentaacetic acid (DTPA)/Gd3+ complex has been synthesized. Finally, MRI-visible poly(ε-caprolactone)…
Synthesis and characterisation of ordered arrays of mesoporous carbon nanofibres
2009
A facile and reproducible one-step pathway has been developed for preparing ordered arrays of mesoporous carbon nanostructures within the pores of anodized aluminium oxide (AAO) membranes, through the confined self-assembly of phenol/formaldehyde resol and amphiphilic copolymer templates. The morphology of the mesoporous carbon nanostructures can be controlled by varying the copolymer surfactant, the quantity of the resol–surfactant precursor sol used and the amount of phenol–formaldehyde resol introduced into the resol–surfactant sol. One-dimensional (1-D) carbon nanostructures, such as carbon fibres with a core–shell structure and carbon ribbons with circular mesopores running parallel to…
Ethylene/POSS copolymerization behavior of postmetallocene catalysts and copolymer characteristics
2017
Copolymerization of ethylene with iso-butyl substituted monoalkenyl(siloxy)- or monoalkenylsilsesquioxane (POSS) comonomers over bis(phenoxy-imine) and salen-type titanium and zirconium catalysts was studied. It was found that the polyreaction performance was significantly depended by the kind of the catalyst and by the structure and concentration of POSS in the feed. The POSS comonomer was efficiently incorporated into the polymer chain at up to 0.2 mol %. The differences in the copolymer compositions as the functions of the catalyst kind and the POSS comonomer were observed, including the varied number-average sequence length of ethylene and unsaturated end groups, as determined by 1H NMR…