Solvent effect on molecular characteristics of polybutadiene and on the kinetic heterogeneity of catalytic systems based on TiCl4

2010 ◽  
Vol 83 (3) ◽  
pp. 487-491
Author(s):  
I. R. Mirgalieva ◽  
E. A. Glukhov ◽  
I. A. Ionova ◽  
A. G. Mustafin ◽  
Yu. B. Monakov
2021 ◽  
Vol 18 (38) ◽  
pp. 27-37
Author(s):  
Eldar N. MIFTAKHOV ◽  
Svetlana A. MUSTAFINA ◽  
Ildus Sh NASYROV ◽  
Azat Kh DAMINOV

Background: the polymer product obtained in the presence of microheterogeneous catalytic systems is characterized by fairly molecular weight distribution (MWD), resulted from kinetically nonequivalent active centers (ACs) in the system that initiate the polymerization process. The nature and composition of ACs are determined by setting and solving an inverse problem on the formation of MWD. This problem is acute because revealing the nature of the kinetic heterogeneity explains changes in the molecular and consumer parameters of the product for different catalyst compositions and propagation modes in polymerizations. Aim: This study aimed to develop methods and algorithms for interpreting gel chromatograms to analyze the kinetic heterogeneity of a polymer product obtained industrially in microheterogeneous catalytic systems. Methods: the solution method is based on the assumption that the formed MWD is a superposition of distributions inherent in each type of ACs. Since the problem in the final formulation refers to the Fredholm integral equations of the first kind, the regularization method of A. N. Tikhonov is used for its numerical solution, with the original problem being preliminary discretized. This methodology and the developed software algorithms were used to determine the kinetic heterogeneity of titanium- and neodymium-containing catalytic systems. Results and discussion: The MWD analysis revealed two types of ACs with an average molecular weight of ATi-lnM = 11.3 and BTi-lnM = 13.2 in the titanium catalyst and three types of ACs ANd-lnM = 11.1, BNd-lnM = 12.7 and CNd-lnM = 14 for the neodymium catalyst, respectively. Conclusions: repeated computational experiments under different polymerization conditions and requirements for the preparation of a catalytic system make it possible to reveal a relationship with the resulting heterogeneity of ACs. It allows us to set and solve problems of controlling the molecular characteristics of the resulting polymer product.


2014 ◽  
Vol 4 (3) ◽  
pp. 773 ◽  
Author(s):  
Qinzhuo Zhou ◽  
Bo-Geng Li ◽  
Suyun Jie ◽  
Na Zheng

2007 ◽  
Vol 61 (1) ◽  
Author(s):  
V. Poláčková ◽  
Š. Toma

AbstractSimple catalytic systems for the Suzuki—Miyaura reaction of aryl chlorides under microwave conditions were tested. Microwave irradiation facilitated the reaction course. The catalyst, base, and solvent effect were studied and two reaction systems offered reasonable to high yields within a short time.


Author(s):  
Эльдар Наилевич Мифтахов ◽  
Светлана Анатольевна Мустафина ◽  
Семен Израилевич Спивак

Построена математическая модель, описывающая процесс получения полиизопрена в присутствии микрогетерогенных титансодержащих каталитических систем с учетом динамики активных центров. Построение модели носило поэтапный характер, при котором модель, описывающая периодический процесс, была дополнена рекуррентными соотношениями с целью описания процесса в каскаде реакторов идеального перемешивания. Численное решение прямой задачи позволило провести анализ молекулярно-массового распределения получаемого продукта в зависимости от исходной загрузки. The aim of this work is building a mathematical model that describes the process of producing polyisoprene in the presence of microheterogeneous titanium-containing catalytic systems, taking into account the dynamics of active centers and numerical calculation of the main physicochemical properties of the resulting product. The main methodology for compiling the mathematical model is the application of the kinetic approach, which consists of compiling and numerically solving the kinetic equations for all types of particles involved in the process. Previously, the distribution of active centers of the applied catalytic system was studied. The confirmed polycentricity of the used catalyst, represented by two types of active centers, is reflected in the nature of the description of the mathematical model. To reduce the system of differential equations to the final form, the method of moments was applied, which allows evaluating the complex properties of the obtained product by its averaged molecular characteristics. A model that permits describing the scale of batch reactors was modified by a macrokinetic module that takes into account possible energy and hydrodynamic laws of the process. For this, recurrence relations were introduced that are valid for the description of continuous mixing reactors. The software package developed by the authors of the work allows carring out a computational experiment for various technological conditions for conducting a continuous process. Based on the results of its launch, the dependences of conversion and averaged molecular characteristics on time in the context of each polymerizer were obtained. Thus, the numerical solution of the direct problem is capable analyzing the molecular weight distribution of the obtained product depending on various parameters of the initial load, for both the batch and continuous modes of the process. The dependences obtained by calculation showed satisfactory agreement with experimental data


2007 ◽  
Vol 48 (4) ◽  
pp. 556-561 ◽  
Author(s):  
N. N. Sigaeva ◽  
F. F. Saitova ◽  
E. A. Glukhov ◽  
A. R. Gareev ◽  
E. R. Maksyutova ◽  
...  

Author(s):  
Afzana Anwer ◽  
S. Eilidh Bedford ◽  
Richard J. Spontak ◽  
Alan H. Windle

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.


1970 ◽  
Vol 39 (2) ◽  
pp. 207-214
Author(s):  
Nazma Akter ◽  
RH Sarker ◽  
MI Hoque

DOI: 10.3329/bjb.v39i2.7490Bangladesh J. Bot. 39(2): 207-214, 2010 (December)


1972 ◽  
Vol 69 (4) ◽  
pp. 659-688 ◽  
Author(s):  
V. Stanescu ◽  
R. Stanescu ◽  
J. A. Szirmai

ABSTRACT Microchemical determinations of glycosaminoglycans and collagen were preformed in isolated histological zones from sections of tibial epiphyseal plate biopsies obtained from children with growth disorders (pituitary dwarfism, congenital myxoedema, Turner's syndrome, Noonan's syndrome, mucopolysaccharidosis type VI, vitamin D resistant rickets and achondroplasia). Alternate sections were used for histochemical localization of glycosaminoglycans and proteins. The values were compared with those found in comparable zones of the growth plate from normal children of the same age. The chondroitin sulphate concentration (% of defatted dry wt.) in the normal epiphyseal plate increased from the resting zone towards the proliferating/hypertrophic zone; collagen exhibited a reverse trend. In some of the pathological biopsies the concentration of chondroitin sulphate was slightly decreased whereas that of collagen was slightly increased. A marked increase in the collagen concentration was found in achondroplasia. The solubility profiles of the cetylpyridinium complexes of the chondroitin sulphate fraction showed three main peaks with slight but characteristic differences in the various zones of the normal cartilage plate. Significant shifts in the proportion of these peaks were observed in several pathological biopsies, indicating possible deviations from the normal molecular characteristics of the chondroitin sulphate. Analysis of the main chondroitin sulphate fraction, obtained from pooled samples of normal tibial growth plate after fractionation on the macroscale, indicated that all three peaks contained both chondroitin-4 sulphate and chondroitin-6 sulphate and that they probably differed in their molecular weight.


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