Search results for "copolymer"

Quantitative description of temperature induced self-aggregation thermograms determined by differential scanning calorimetry

2012

A novel thermodynamic approach for the description of differential scanning calorimetry (DSC) experiments on self-aggregating systems is derived and presented. The method is based on a mass action model where temperature dependence of aggregation numbers is considered. The validity of the model was confirmed by describing the aggregation behavior of poly(ethylene oxide)-poly(propylene oxide) block copolymers, which are well-known to exhibit a strong temperature dependence. The quantitative description of the thermograms could be performed without any discrepancy between calorimetric and van 't Hoff enthalpies, and moreover, the aggregation numbers obtained from the best fit of the DSC exper…

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…

Introducing an amine functionality at the block junction of amphiphilic block copolymers by anionic polymerization strategies

2011

A series of block copolymers bearing a single amino in-chain functionality was synthesized via anionic polymerization of styrene and ethylene oxide. By means of both a conventional and a continuous setup, living polystyrene was quantitatively end functionalized with an oxirane (DBAG) prior to the polymerization of the poly(ethylene oxide) segment. The in-chain amine was conjugated with a fluorescent dye.

Linked cyclopentadienyl-amido titanium catalysts supported on pyridylethylsilane-modified silica for heterogeneous ethylene homo- and copolymerization

2003

Abstract Linked cyclopentadienyl-amido titanium dimethyl and dichloro complexes, Ti(η 5 :η 1 -C 5 Me 4 SiMe 2 N t Bu)X 2 (X=Me, Cl), were reacted with trityl tetrakis(pentafluorophenyl)borate (TB), Ph 3 C + [B(C 6 F 5 ) 4 ] − , and methylaluminoxane (MAO), followed by treatment with toluene suspension of pyridylethylsilane-modified silica, to give two new supported-type titanium catalysts, PySTiTB and PySTiMAO. PySTiTB polymerized ethylene in the presence of triisobutylaluminum (TIBA) in hexane at 60 °C and 5 bar with slightly higher activity than the corresponding homogeneous system under the same conditions. PySTiMAO showed relatively high activity even without any use of alkylaluminum co…

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…

Evaluation of Mechanical and Structure Properties of Electron Beam Cross-Linked Ethylene-Octene Copolymer Nanocomposites with Multi-Walled Carbon Nan…

2016

Recently, ionizing radiation has found an application in nanotechnology especially attributed to the improvement of nanocomposites. In the present paper, we have developed and evaluated radiation cross-linked nanocomposites made of ethylene-octene copolymer (EOC) with 0-15 wt.% of multi-walled carbon nanotubes (MWCNTs) and irradiated by 5 MeV accelerated electrons. The influence of combined factors of MWCNT filler content and the irradiation up to 150 kGy on the tensile stress-strain properties at 25–50°C was analysed. The cross-linking efficiency was also evaluated. The results indicated improvement in tensile properties with an increase of MWCNT content and the irradiation up to 150 kGy d…

Structural analysis of linear/branched ethylene block copolymers

2017

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 …

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…