scholarly journals Control of molecular weight in Ni(ii)-catalyzed polymerization via the reaction medium

2008 ◽  
pp. 4965 ◽  
Author(s):  
Damien Guironnet ◽  
Thomas Rünzi ◽  
Inigo Göttker-Schnetmann ◽  
Stefan Mecking
Keyword(s):  
Molecular Weight ◽  
Reaction Medium ◽  
Catalyzed Polymerization

A Strategy for Increasing Molecular Weight of Polyester by Lipase-Catalyzed Polymerization

2001 ◽  
Vol 30 (8) ◽  
pp. 798-799 ◽  
Author(s):  
Hiroki Ebata ◽  
Kazunobu Toshima ◽  
Shuichi Matsumura
Keyword(s):  
Molecular Weight ◽  
Catalyzed Polymerization

scholarly journals Keggin-Type Heteropolyacid for Ring-Opening Polymerization of Cyclohexene Oxide: Molecular Weight Control

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Ahmed Aouissi ◽  
Zeid Abdullah Al-Othman ◽  
Abdurrahman Salhabi
Keyword(s):  
Molecular Weight ◽  
Reaction Time ◽  
Acetic Anhydride ◽  
Ring Opening ◽  
Weight Control ◽  
Reaction Medium ◽  
Resonance Spectroscopy ◽  
Cyclohexene Oxide ◽  
Scanning Calorimetry ◽  
Catalyst Amount

Polymerization of 1,2-cyclohexene oxide (CHO) in dichloromethane was catalyzed by 12-tungstophosphoric acid (H3PW12O40·13H2O) as a super solid acid. The effect of polymerization parameters such as reaction time, temperature, and catalyst amount was investigated. The effect of acetic anhydride as a ring-opening agent was also investigated. The resulting poly(1,2-cyclohexene oxide) (PCHO) was characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance spectroscopy (1HNMR), gel-permeation chromatography (GPC), and differential scanning calorimetry (DSC). It has been found that the PCHO prepared over H3PW12O40·13H2O has a stereoregularity higher than that prepared over clay and Aluminium alkoxide catalysts. TheTgvalue obtained is due to the microstructure but not to molecular weight. The yield and the molecular weight of the polymer depend strongly on the reaction conditions. Molecular weights can be readily controlled by changing reaction temperature, reaction time, and catalyst amount. Contrary to most polymerization reactions, the molecular weight increases with the temperature increase. Addition of acetic anhydride to the reaction medium increased the yield threefold.

scholarly journals ДІЄТИЧНА ДОБАВКА ІМУНОТРОПНОЇ ДІЇ НА ОСНОВІ ПРОДУКТІВ ДЕСТРУКЦІЇ ПРОБІОТИЧНИХ БАКТЕРІАЛЬНИХ КУЛЬТУР

2018 ◽  
Vol 82 (1) ◽  
Author(s):  
Антоніна Іванівна Капустян ◽  
Наталля Кирилівна Черно
Keyword(s):  
Molecular Weight ◽  
Dietary Supplement ◽  
Bacterial Cell ◽  
Degradation Products ◽  
General Scheme ◽  
Animal Experiments ◽  
Reaction Medium ◽  
Low Molecular Weight ◽  
Toxic Substances ◽  
Absorption Bands

У роботі розглянуто можливість отримання імунотропної дієтичної добавки на основі низькомолекулярних продуктів деградації пептидогліканів клітинних стінок пробіотичних бактерій. Встановлено раціональні режими автолізу біомаси як первинного етапу деструкції пептидогліканів бактеріальних клітинних стінок. Показано, що найбільш інтенсивний лізис клітин відбувається при експозиції культуральної рідини при 90°C протягом 15 хв після 8-ї години культивування, про що свідчить максимальне накопичення амінокислот у реакційному середовищі (1,8 мг/см3). Проведено оптимізацію процесу деструкції пептидогліканів бактеріальних клітин, які піддавали лізису, ферментним препаратом панкреатином. Ефективність ферментолізу визначали за накопиченням імунотропних низькомолекулярних пептидів залежно від концентрації ферменту (СЕ), субстрату (СS) в реакційній суміші та тривалості процесу (τ). Встановлено, що раціональний режим ферментолізу, який забезпечує максимальне накопичення низькомолекулярних пептидів (0,569 мг/см3, досягається за наступних значень факторів: СЕ=12,5 мг/см3, СS=70,0 мг/см3, τ=245,6 хв. Зразок низькомолекулярних пептидів, отриманий за раціональних режимів деструкції, досліджено методом ІЧ-спектроскопії. Встановлено, що у його ІЧ-спектрі присутні смуги поглинання, які відповідають коливанням аміногруп, пептидних зв’язків, піранозної форми глюкози, залишки якої входять до складу мурамової кислоти, та N-ацетилглюкозаміну пептидоглікану. Приведено загальну схему, що ілюструє послідовність процесів виробництва імунотропної дієтичної добавки .У дослідах на щурах встановлено ефективну дозу отриманої дієтичної добавки –0,06 мг/кг маси тіла.  The possibility of obtaining an immunotropic dietary supplement based on low molecular weight degradation products of cell wals peptidoglycans of lactic and bifidobacteria composition has been considered. Rational regimes of autolysis of biomass as the primary stage of degradation of peptidoglycans of bacterial cell walls have been established. It was shown that the most intensive lysis of cells takes place when the culture liquid is treated at a temperature of 90 °C for the 8th hour of cultivation, as indicated by the maximum accumulation of amino acids in the reaction medium (1.8 mg/cm3). Optimization of the destruction process of bacterial cell peptidoglycans exposed to lysis, by enzyme preparation with pancreatin, was carried out by the mathematical planning method of the multifactorial experiment. The effectiveness of enzymatic hydrolysis was determined by the accumulation of immunotropic low molecular weight peptides, depending on the concentration of the enzyme (CE), the substrate (CS) in the reaction mixture and the duration of the process (τ). The rational value of the factors CE, CS and τ that provide the maximum concentration of low molecular weight peptides (0.569 mg/cm3) in the enzymatic hydroltsate are CE=12.5 mg/cm3, Cs=70.0 mg/cm3, τ=245.6 min. A sample of low molecular weight peptides obtained from rational degradation regimes was investigated using the IR spectroscopy method. It has been established that in its spectrum absorption bands corresponding to fluctuations of amino groups, peptide bonds are presentred, which, in fact, take place in the structure of peptides. Fluctuations of the pyranose glucose form, which is included in the muramic acid and N-acetylglucosamine of peptidoglycan, have also been observed. The general scheme of the sequence of production processes of an immunotropic dietary supplement has been given. In animal experiments, it has been established that this additive, in accordance with the classification of chemicals substances to the degree of danger, belongs to class 4 (low-toxic substances). The effective dose of the obtaned dietary supplement is 0.06 mg/kg body weight.

THE MECHANISM OF SODIUM-INITIATED POLYMERIZATION OF DIOLEFINS

1948 ◽  
Vol 26b (9) ◽  
pp. 657-667 ◽  
Author(s):  
R. E. Robertson ◽  
Léo Marion
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
General Formula ◽  
Chain Termination ◽  
Low Molecular Weight ◽  
Initiation Of Polymerization ◽  
Catalyzed Polymerization

An analysis of the products of sodium-catalyzed polymerization of butadiene and isoprene in the presence of toluene suggests that initiation of polymerization takes place by the formation of a disodium addend rather than a free radical. The diaddend reacts with toluene to yield butene-2 and sodium benzyl. Since all of the low molecular weight polymers analyzed were shown to conform to the general formula C6H5CH2(monomer)nH, sodium benzyl is considered to be the chief chain initiator. Chain termination took place by reaction with toluene to regenerate the chain carrier, sodium benzyl. The nature of the acids separated on carbonation of a polymerizing system supports this conclusion.

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

2003 ◽  
Vol 68 (10) ◽  
pp. 1745-1790 ◽  
Author(s):  
Jan Sedláček ◽  
Jiří Vohlídal
Keyword(s):  
Molecular Weight ◽  
Ionic Liquids ◽  
Weight Distribution ◽  
Chemical Structure ◽  
Reaction Medium ◽  
Polymer Chains ◽  
Rhodium Catalysts ◽  
High Tolerance ◽  
Polymer Molecules ◽  
Living Polymerizations

In the last fifteen years, a large variety of specialty polymers of diverse chemical structure and functionality have been synthesized with the rhodium-based catalysts. The high tolerance to the reaction medium and functional groups of monomers, as well as ability to control various structure features of the polymer formed are typical properties of these catalysts. In addition, some rhodium catalysts can be anchored to inorganic or organic supports or dissolved in ionic liquids to form heterophase polymerization systems, which opens the way to pure, well-defined polymers free of the catalyst residues, as well as to recycling rhodium catalysts. This review provides a survey on the polymerization reactions induced with rhodium-based catalysts, in which one or more structure attributes of the polymer formed are subject to control. The structure attributes considered are (i) sequential arrangement of monomeric units along polymer chains; (ii) head-tail isomerism of polymer molecules; (iii) configurational structure of polymer molecules; (iv) conformation of polymer molecules; and (v) molecular weight and molecular-weight distribution of the polymer formed. A review with 188 references.

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