نتایج جستجو برای: opening polymerization

تعداد نتایج: 78293  

Journal: :Dalton Transactions 2021

Iron, cobalt and copper complexes bearing [2 + 2] Schiff-base macrocycles have been isolated screened as catalysts for the ring opening polymerization (ROP) of cyclic esters.

Journal: :Polyhedron 2014
Melanie A Pribisko Tonia S Ahmed Robert H Grubbs

Two new Ru-based metathesis catalysts, 3 and 4, have been synthesized for the purpose of comparing their catalytic properties to those of their cis-selective nitrate analogues, 1 and 2. Although catalysts 3 and 4 exhibited slower initiation rates than 1 and 2, they maintained high cis-selectivity in homodimerization and ring-opening metathesis polymerization reactions. Furthermore, the nitrite ...

Journal: :Organometallics 2010
Benjamin K Keitz Robert H Grubbs

Ru-based olefin metathesis catalysts containing carbohydrate-derived NHCs from glucose and galactose were synthesized and characterized by NMR spectroscopy. 2D-NMR spectroscopy revealed the presence of Ru-C (benzylidene) rotamers at RT and the rate of rotation was measured using magnetization transfer and VT-NMR spectroscopy. The catalysts were found to be effective at ring-opening metathesis p...

Journal: :Dalton transactions 2014
Jing Ma Ke-Qing Zhao Mark Walton Joseph A Wright David L Hughes Mark R J Elsegood Kenji Michiue Xinsen Sun Carl Redshaw

Reaction of the ligand 2,4-tert-butyl-6-[(2-methylquinolin-8-ylimino)methyl]phenol (L(1)H) with [VOCl3] in the presence of triethylamine afforded the complex [VOCl2L(1)] (1), whereas use of [VO(OnPr)3] led to the isolation of [VO2L(1)] (2) or [VO2L(1)]·2/3MeCN (2·2/3MeCN). Reaction of 2-((2-(1H-benzo[d]imidazol-2-yl)quinolin-8-ylimino)methyl)-4,6-R(1),R(2)-phenols (R(1) = R(2) = (t)Bu; L(2)H), ...

2010
Magnus Eriksson

Telechelic polyesters have successfully been synthesized with lipasecatalyzed polymerization. The produced telechelics had a high degree of difunctionalization, high purity (requiring little or no workup) and controlled degree of polymerization. The syntheses were performed in one-pot one-step reaction systems. Two different types of lipase-catalyzed polymerizations were applied – ring-opening ...

Journal: :Macromolecular Materials and Engineering 2021

Polymerization processes with high reproducibility, traceability, and nontoxic compounds are required for biomedical applications. Here an automated solvent-free polymerization of hyperbranched polyglycerol has been established on a multiple-hundred gram scale. Performed is anionic ring-opening multibranching (ROMB) slow addition glycidol. The approach avoids commonly used organic solvents duri...

2014
Oleg I. Kazakov Partha P. Datta Meghedi Isajani Elizabeth T. Kiesewetter Matthew K. Kiesewetter

Thiourea (TU)/amine base cocatalysts are commonly employed for well-controlled, highly active "living" organocatalytic ring-opening polymerizations (ROPs) of cyclic esters and carbonates. In this work, several of the most active cocatalyst pairs are shown by 1H NMR binding studies to be highly associated in solution, dominating all other known noncovalent catalyst/reagent interactions during RO...

2002
M. R. Kessler S. R. White

The cure kinetics of polydicyclopentadiene (pDCPD) prepared by ringopening metathesis polymerization with three different concentrations of Grubbs’ catalyst was examined using differential scanning calorimetry (DSC). The experimental data were used to test several different phenomenological kinetic models. The data are best modeled with a “model-free” isoconversional method. This analysis revea...

Journal: :Molecules 2014
Urszula Piotrowska Marcin Sobczak

Biodegradable or bioresorbable polymers are commonly used in various pharmaceutical fields (e.g., as drug delivery systems, therapeutic systems or macromolecular drug conjugates). Polyesters are an important class of polymers widely utilized in pharmacy due to their biodegradability and biocompatibility features. In recent years, there has been increased interest in enzyme-catalyzed ring-openin...

2002
M. R. KESSLER S. R. WHITE

The cure kinetics of polydicyclopentadiene prepared by ring-opening metathesis polymerization with three different concentrations of Grubbs’ catalyst were examined with differential scanning calorimetry. The experimental data were used to test several different phenomenological kinetic models. The data were best modeled with a model-free isoconversional method. This analysis revealed that the a...

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