Search results for "Monomer"
showing 10 items of 857 documents
Long-Chain Alkyl Epoxides and Glycidyl Ethers: An Underrated Class of Monomers.
2020
Long-chain epoxides and specifically alkyl glycidyl ethers represent a class of highly hydrophobic monomers for anionic ring-opening polymerization (AROP), resulting in apolar aliphatic polyethers. In contrast, poly(ethylene glycol) is known for its high solubility in water. The combination of hydrophobic and hydrophilic monomers in block and statistical copolymerization reactions enables the synthesis of amphiphilic polyethers for a wide range of purposes, utilizing micellar interactions in aqueous solutions, e.g., viscosity enhancement of aqueous solutions, formation of supramolecular hydrogels, or for polymeric surfactants. Controlled polymerization of these highly hydrophobic long-chain…
Fast Access to Amphiphilic Multiblock Architectures by the Anionic Copolymerization of Aziridines and Ethylene Oxide.
2018
An ideal system for stimuli-responsive and amphiphilic (block) polymers would be the copolymerization of aziridines with epoxides. However, to date, no copolymerization of these two highly strained three-membered heterocycles had been achieved. Herein, we report the combination of the living oxy- and azaanionic ring-opening polymerization of ethylene oxide (EO) and sulfonamide-activated aziridines. In a single step, well-defined amphiphilic block copolymers are obtained by a one-pot copolymerization. Real-time 1H NMR spectroscopy revealed the highest difference in reactivity ratios ever reported for an anionic copolymerization (with r1 = 265 and r2 = 0.004 for 2-methyl- N-tosylaziridine/EO …
Glycidyl Tosylate: Polymerization of a “Non‐Polymerizable” Monomer permits Universal Post‐Functionalization of Polyethers
2019
Abstract Glycidyl tosylate appears to be a non‐polymerizable epoxide when nucleophilic initiators are used because of the excellent leaving group properties of the tosylate. However, using the monomer‐activated mechanism, this unusual monomer can be copolymerized with ethylene oxide (EO) and propylene oxide (PO), respectively, yielding copolymers with 7–25 % incorporated tosylate‐moieties. The microstructure of the copolymers was investigated via in situ 1H NMR spectroscopy, and the reactivity ratios of the copolymerizations have been determined. Quantitative nucleophilic substitution of the tosylate‐moiety is demonstrated for several examples. This new structure provides access to a librar…
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…
Competition between α and γ phases in isotactic polypropylene: effects of ethylene content and nucleating agents at different cooling rates
2001
Abstract The influence of ethylene content, nucleating agents and cooling rate upon the formation of γ phase in isotactic polypropylene is investigated. Detailed analysis of wide angle X-ray diffraction shows that some γ phase can appear even in copolymers of very low ethylene content (0.5 mol.%). Differential scanning calorimetry shows a double melting peak. Nucleating agents of different types are found to enhance γ phase crystallization, even in high molecular weight homopolymers. In any of the materials studied the amount of γ phase decreases with increasing cooling rate, going to zero at a cooling rate of about 10°C s−1. We interpret the observations in terms of the kinetics of growth …
Titanium complexes having chelating diaryloxo ligands bridged by tellurium and their catalytic behavior in the polymerization of ethylene
2000
A series of titanium complexes having tellurium-bridged chelating bis(aryloxo) ligands, [TiX2{2,2‘-Te(4-R-6-R‘-C6H2O)2}]2 (5b, X = Cl, R = Me, R‘ = tBu; 6a, X = OiPr, R = R‘ = H; 6b, X = OiPr, R = Me, R‘ = tBu), were prepared. 5b and 6b were determined by X-ray crystallography to have chloro- and isopropoxo-bridged dimeric structures. The structural data for these complexes indicated that the Ti−Te coordination bonds were stronger than the similar Ti−S coordination bonds in the corresponding sulfur-bridged complexes. The reaction of (C5R5)TiCl3 (R = H, Me) with 2,2‘-Te(4-R-6-R‘-C6H2OLi)2 gave monocyclopentadienyl derivatives, (C5R5)TiCl{2,2‘-Te(4-Me-6-tBu-C6H2O)2} (7, R = H; 8, R = Me). The…
Polypropylene and poly(ethylene-co-1-octene) effective synthesis with diamine-bis(phenolate) complexes: Effect of complex structure on catalyst activ…
2017
A series of group 4 metal complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor: (μ-O)[Me2N(CH2)2N(CH2-2-O-3,5-tBu2-C6H2)2ZrCl]2 (1a), R2N(CH2)2N(CH2-2-O-3-R1-5-R2-C6H2)2TiCl2 (R = Me, R1, R2 = tBu (2a), R = iPr, R1, R2 = tBu (2b), R = iPr, R1 = tBu, R2 = OMe (2c)), and Me2N(CH2)2N(CH2-2-O-3,5-tBu2-C6H2)(CH2-2-O-C6H4)TiCl2 (2d) are used in ethylene and propylene homopolymerization, and ethylene/1-octene copolymerization. All complexes, upon their activation with Al(iBu)3/Ph3CB(C6F5)4, exhibit reasonable catalytic activity for ethylene homo- and copolymerization giving linear polyethylene with high to ultra-high molecular weight (600·× 103–3600·× 103 g/mol). The activi…
Amino Functional Poly(ethylene glycol) Copolymers via Protected Amino Glycidol
2010
The synthesis of poly(ethylene glycol) (PEG) copolymers with multiple amino functionalities within the chain is described, relying on an epoxide comonomer bearing a protected amino group. N,N-dibenzyl amino glycidol (DBAG) and ethylene oxide (EO) were copolymerized via anionic polymerization, leading to well-defined polymers with varied comonomer content and low polydispersities (Mw/Mn in the range of 1.1 to 1.2). Subsequent hydrogenolysis with Pearlman’s catalyst afforded poly(ethylene glycol-co-amino glycerol)s (PEG-co-PAG) with a precisely adjusted number of randomly incorporated amino groups in the range of 2−15%. For the first time, the kinetics of an EO copolymerizations have has been…
Effective copolymerization of ethylene with α,ω-alkenols and homopolymerization of α,ω-alkenols catalyzed by aminophenolate zirconium complex
2019
Abstract A zirconium complex of diamine-bis(phenolate) ligand, [(tBu2O2NN’)ZrCl]2(μ-O) where (tBu2O2NN’) = Me2N(CH2)2N(CH2–2-O−-3,5-tBu2-C6H2)2, activated with (iBu)3Al/Ph3CB(C6F5)4, was for the first time used in copolymerization of ethylene with unsaturated alcohols (CH2 = CH(CH2)nCH2OH, where n = 7, 8, 3). The hydroxyl groups of comonomers were protected with R3-xAlClx (where x = 0 or 1, R = iBu, Et). In contrast to the formerly reported catalysts, the activity of this catalyst is much higher in ethylene/alkenols copolymerization than in ethylene homopolymerization and its lifetime is long. Moreover, the copolymers with high polar comonomer contents (up to 16.4 mol%, 52.3 wt%) were produ…