scholarly journals C–H Bond Activation of Silyl-Substituted Pyridines with Bis(Phenolate)Yttrium Catalysts as a Facile Tool towards Hydroxyl-Terminated Michael-Type Polymers

Catalysts ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 448
Author(s):  
Thomas M. Pehl ◽  
Moritz Kränzlein ◽  
Friederike Adams ◽  
Andreas Schaffer ◽  
Bernhard Rieger
Keyword(s):  
Bond Activation ◽  
Catalyst Activity ◽  
Group Analysis ◽  
Earth Metal ◽  
Bioactive Molecules ◽  
Size Exclusion ◽  
Hydroxyl Groups ◽  
Nmr Studies ◽  
Initiation Mechanism ◽  
End Group

Herein, silicon-protected, ortho-methylated hydroxy-pyridines were reported as initiators in 2-aminoalkoxy-bis(phenolate)yttrium complexes for rare earth metal-mediated group-transfer polymerization (REM-GTP) of Michael-type monomers. To introduce these initiators, C−H bond activation was performed by reacting [(ONOO)tBuY(X)(thf)] (X = CH2TMS, thf = tetrahydrofuran) with tert-butyl-dimethyl-silyl-functionalized α-methylpyridine to obtain the complex [(ONOOtBuY(X)(thf)] (X = 4-(4′-(((tert-butyldimethylsilyl)oxy)methyl)phenyl)-2,6-di-methylpyridine). These initiators served as functional end-groups in polymers produced via REM-GTP. In this contribution, homopolymers of 2-vinylpyridine (2VP) and diethyl vinyl phosphonate (DEVP) were produced. Activity studies and end-group analysis via mass spectrometry, size-exclusion chromatography (SEC) and NMR spectroscopy were performed to reveal the initiator efficiency, the catalyst activity towards both monomers as well as the initiation mechanism of this initiator in contrast to commonly used alkyl initiators. In addition, 2D NMR studies were used to further confirm the end-group integrity of the polymers. For all polymers, different deprotection routes were evaluated to obtain hydroxyl-terminated poly(2-vinylpyridine) (P2VP) and poly(diethyl vinyl phosphonate) (PDEVP). Such hydroxyl groups bear the potential to act as anchoring points for small bioactive molecules, for post-polymerization functionalization or as macroinitiators for further polymerizations.

KINETIC ASPECTS OF THE COPOLYMERIZATION OF TETRAHYDROFURAN WITH PROPYLENE OXIDE. I

1966 ◽  
Vol 44 (22) ◽  
pp. 2679-2689 ◽  
Author(s):  
L. P. Blanchard ◽  
J. Singh ◽  
M. D. Baijal
Keyword(s):  
Vapor Pressure ◽  
Propylene Oxide ◽  
Chemical Reduction ◽  
Group Analysis ◽  
Vapor Pressure Osmometry ◽  
Hydroxyl Groups ◽  
Internal Reference ◽  
Boron Fluoride ◽  
Co Catalysts ◽  
End Group

Tetrahydrofuran and propylene oxide were copolymerized in the presence of the catalyst boron fluoride ethyl ether, and various co-catalysts, such as 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol. Ethylene chloride was used as a solvent and as an internal reference for analytical purposes. Reactions were carried out at 0 °C and at atmospheric pressure. Monomer concentrations were determined by vapor phase chromatography, and copolymer molecular structure analyses were carried out by physical and chemical methods including infrared spectroscopy, vapor pressure osmometry, hydroxyl end-group analysis, and chemical reduction of unsaturated linkages.The homopolymerization of tetrahydrofuran did not take place, whereas that of propylene oxide proceeded at a rapid rate. In the copolymerization of tetrahydrofuran with propylene oxide, the rate of disappearance of tetrahydrofuran was found to be independent of its concentration, but varied directly with the concentration of propylene oxide. Under similar conditions, the rate of disappearance of propylene oxide was found to be (a) proportional to the square of its concentration, and (b) inversely proportional to the concentration of tetrahydrofuran.Reactivity ratios varied between 1.3 and 1.8 for propylene oxide and between 0.1 and 0.6 for tetrahydrofuran. Molecular weights obtained by vapor pressure osmometry ranged between 460 and 740, and those obtained by hydroxyl end-group analysis ranged between 520 and 1 660. Infrared spectra confirmed the presence of hydroxyl groups and ether linkages in the copolymers prepared. Results on terminal unsaturation were negative.

Preparation of a Certified Reference Material of Trifunctional Polypropylene Oxide

2011 ◽  
Vol 284-286 ◽  
pp. 1961-1968 ◽  
Author(s):  
Jing Xia Wang ◽  
Xiao Dong Fan ◽  
Wei Tian ◽  
Guang Wen Cheng ◽  
Juan Li Li
Keyword(s):  
Molecular Weight ◽  
Reference Material ◽  
Certified Reference Material ◽  
Storage Stability ◽  
Group Analysis ◽  
Size Exclusion ◽  
Distribution Model ◽  
Polypropylene Oxide ◽  
Exclusion Chromatography ◽  
End Group

Due to the lack of trifunctional polypropylene oxide (TPPO) certified reference material (CRM) with precise molecular weight on the market, it is therefore very important to prepare such CRM to calibrate the molecular weight testing equipments, and assure the quality in polyurethanes manufacture. In this paper, the certification of TPPO CRM was introduced based on the size-exclusion chromatography with a multi-angle laser light scattering (SEC-MALLS) method and end-group analysis method. First, TPPO was synthesized via controlled ring-opening polymerization of propylene oxide in the condition of both high temperature and pressure using double metal cyanide (DMC) complexes as catalyst, and TPPO oligomer as coinitiator. Then, the molecular weight homogeneity of TPPO CRM was evaluated by using the F-distribution model, and the storage stability of the molecular weight of TPPO CRM was assessed. All potential uncertainty factors for the certification of TPPO CRM were evaluated using cause-effect diagram. The results showed that the chemical structure of TPPO CRM was an anticipatory structure, which was confirmed by IR. The molecular weight homogeneity of TPPO CRM was qualified. The storage stability period of the final product was one year with respect to its molecular weight, and the certification results of TPPO CRM obtained by SEC-MALLS and end-group analysis were 4996±162 and 5025±146, respectively.

scholarly journals THE ISOTOPE DERIVATIVE METHOD OF PROTEIN AMINO END-GROUP ANALYSIS

1951 ◽  
Vol 190 (2) ◽  
pp. 733-740 ◽  
Author(s):  
Sidney. Udenfriend ◽  
Sidney F. Velick
Keyword(s):  
Group Analysis ◽  
Derivative Method ◽  
End Group

scholarly journals Fibrillar pharmacology of functionalized nanocellulose

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sam Wong ◽  
Simone Alidori ◽  
Barbara P. Mello ◽  
Bryan Aristega Almeida ◽  
David Ulmert ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Fluorescent Dyes ◽  
Pharmacokinetic Profile ◽  
Water Soluble ◽  
Size Exclusion ◽  
Hydroxyl Groups ◽  
Target Tissue ◽  
Exclusion Chromatography ◽  
Specific Accumulation

AbstractCellulose nanocrystals (CNC) are linear organic nanomaterials derived from an abundant naturally occurring biopolymer resource. Strategic modification of the primary and secondary hydroxyl groups on the CNC introduces amine and iodine group substitution, respectively. The amine groups (0.285 mmol of amine per gram of functionalized CNC (fCNC)) are further reacted with radiometal loaded-chelates or fluorescent dyes as tracers to evaluate the pharmacokinetic profile of the fCNC in vivo. In this way, these nanoscale macromolecules can be covalently functionalized and yield water-soluble and biocompatible fibrillar nanoplatforms for gene, drug and radionuclide delivery in vivo. Transmission electron microscopy of fCNC reveals a length of 162.4 ± 16.3 nm, diameter of 11.2 ± 1.52 nm and aspect ratio of 16.4 ± 1.94 per particle (mean ± SEM) and is confirmed using atomic force microscopy. Size exclusion chromatography of macromolecular fCNC describes a fibrillar molecular behavior as evidenced by retention times typical of late eluting small molecules and functionalized carbon nanotubes. In vivo, greater than 50% of intravenously injected radiolabeled fCNC is excreted in the urine within 1 h post administration and is consistent with the pharmacological profile observed for other rigid, high aspect ratio macromolecules. Tissue distribution of fCNC shows accumulation in kidneys, liver, and spleen (14.6 ± 6.0; 6.1 ± 2.6; and 7.7 ± 1.4% of the injected activity per gram of tissue, respectively) at 72 h post-administration. Confocal fluorescence microscopy reveals cell-specific accumulation in these target tissue sinks. In summary, our findings suggest that functionalized nanocellulose can be used as a potential drug delivery platform for the kidneys.

scholarly journals Genetic Polymorphism in Caseins of Cow's Milk. V. End-Group Analysis of β-Caseins A, B, and C

1965 ◽  
Vol 48 (7) ◽  
pp. 884-887 ◽  
Author(s):  
E.B. Kalan ◽  
M.P. Thompson ◽  
Rae Greenberg ◽  
L. Pepper
Keyword(s):  
Genetic Polymorphism ◽  
Group Analysis ◽  
Cow’S Milk ◽  
Cow's Milk ◽  
End Group
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