Search results for "Copolymers"

Vanadium catalysts for ethylene-norbornene copolymerization

2020

Kopolimery cyklicznych olefin (COCs) stanowią obiecującą grupę materiałów o specyficznych, możliwych do zaprojektowania właściwościach. Szczególnym zainteresowaniem w tej grupie związków cieszą się kopolimery etylenu z norbornenem. Do ich syntezy stosuje się różnorodne kompleksy metali przejściowych, przede wszystkim pierwiastków z grupy 4. Artykuł stanowi przegląd literatury dotyczącej wykorzystania katalizatorów wanadowych z różnego rodzaju ligandami w syntezie kopolimerów etylenu z norbornenem. Opisano wpływ ligandów i warunków prowadzenia reakcji na aktywność oraz wybrane właściwości otrzymanych kopolimerów.

Studies of ethylene/1-hexene copolymerization over zirconocene catalyst supported on MAO-modified MgCl2(THF)2. The effect of copolymerization conditi…

2003

Composition of catalytic system and copolymerization reaction conditions influence on heterogeneity of ethylene/1-hexene copolymers obtained over MgCI2(THF)2/MAO/Cp2ZrCl2/MAO catalyst was studied. One of the DSC techniques, i.e. successive self-nucleation/annealing (SSA) method allowing separation of the polymer into fractions with differing chemical composition in result of alternating crystallization and melting cycles was applied. It was found that the intermolecular heterogeneity exists inside all studied samples irrespective of the reaction conditions (temperature and time) and the catalyst composition (Al/Zr molar ratio). It was also confirmed that catalyst composition has a considera…

Supramolecular Modification of ABC Triblock Terpolymers in Confinement Assembly

2018

The self-assembly of AB diblock copolymers in three-dimensional (3D) soft confinement of nanoemulsions has recently become an attractive bottom up route to prepare colloids with controlled inner morphologies. In that regard, ABC triblock terpolymers show a more complex morphological behavior and could thus give access to extensive libraries of multicompartment microparticles. However, knowledge about their self-assembly in confinement is very limited thus far. Here, we investigated the confinement assembly of polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or SVT) triblock terpolymers in nanoemulsion droplets. Depending on the block weight fractio…

Naturally Occurring Oxazole Structural Units as Ligands of Vanadium Catalysts for Ethylene-Norbornene (Co)polymerization

2021

1,3-Oxazole and 4,5-dihydro-1,3-oxazole are common structural motifs in naturally occurring peptides. A series of vanadium complexes were synthesized using VCl3(THF)3 and methyl substituted (4,5-dihydro-1,3-oxazol-2-yl)-1,3-oxazoles as ligands and analyzed using NMR and MS methods. The complexes were found to be active catalysts both in ethylene polymerization and ethylene-norbornene copolymerization. The position of methyl substituent in the ligand has considerable impact on the performance of (co)polymerization reaction, as well as on the microstructure, and thus physical properties of the obtained copolymers.

Titanium and Vanadium Catalysts with 2-Hydroxyphenyloxazoline and Oxazine Ligands for Ethylene-Norbornene (co)Polymerization

2019

A series of titanium and vanadium complexes with oxazoline 2-(4,5-dihydro-1,3-oxazol-2-yl)phenol (L1), 2-(4-methyl-4,5-dihydro-1,3-oxazol-2-yl)phenol (L2), and oxazine 2-(5,6-dihydro-4H-1,3-oxazin-2-yl)phenol (L3) ligands were synthesized, and their structures were determined by NMR and MS methods as (L)2MtCl2. The vanadium complexes were found to be highly active in ethylene (7300 kgPE/(molV&middot

EVALUATION OF BIODEGRADABILITY ON POLYSPARTAMIDE-POLYLACTIC ACID BASED NANOPARTICLES BY CHEMICAL HYDROLYSIS STUDIES POLYMER DEGRADATION AND STABILITY

2015

Here, the synthesis of two graft copolymers based on α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) and poly(lactic acid) (PLA), the O-(2-aminoethyl)-O′-galactosyl polyethylene glycol (GAL-PEG-NH2) or the methoxypolyethylene glycol amine (H2N-PEG-OCH3) is described. Starting from the obtained PHEA-PLA-PEG-GAL and PHEA-PLA-PEG copolymers, polymeric nanoparticles were prepared by high pressure homogenization–solvent evaporation method. To demonstrate their biodegradability as a function of the matrix composition, a chemical stability study was carried out until 21 days by incubating systems in two media mimicking physiological compartments (pH 7.4 and pH 5.5). The degradability of both nan…

Evaluation of biodegradability of novel polymeric nanoparticles based on amphiphilic polylactide-polyaspartamide derivatives.

2015