Cationic half-sandwich scandium complex for the synthesis of polyisobutylene with high molecular weight under mild conditions

2017 ◽  
Vol 56 (5) ◽  
pp. 467-470 ◽  
Author(s):  
Ke Yang ◽  
Tingting Li ◽  
Rui Tan ◽  
Kaihua Shen ◽  
Yang Li
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Mild Conditions ◽  
Half Sandwich

Synthesis of high molecular weight isobutylene-α-methylstyrene copolymers containing alkenyl groups with a half sandwich scandium initiator system under mild conditions

2019 ◽  
Vol 10 (14) ◽  
pp. 1724-1729 ◽  
Author(s):  
Ke Yang ◽  
Hui Niu ◽  
Hui Yu ◽  
Jinghan Dong ◽  
Jing Wang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Random Copolymers ◽  
Mild Conditions ◽  
Initiator System ◽  
Half Sandwich

Copolymerizations of isobutylene and two alkenyl functionalized α-MeSt derivatives respectively, catalyzed by [(C5Me4SiMe3)Sc(CH2SiMe3)2THF], at −35 °C produced high Mn random copolymers with pendant alkenyl groups.

Synthesis and characterization of high molecular weight and low dispersity polystyrene homopolymers by RAFT polymerization

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Cheng Jin ◽  
Chun Liu ◽  
Bo Jiang ◽  
Qin-jian in
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Polymerization Temperature ◽  
Polymer Molecular Weight ◽  
Mild Conditions ◽  
Reversible Addition ◽  
Polymerization Method

AbstractHigh molecular weight polystyrene homopolymers with low dispersity were synthesized by a reversible addition-fragmentation chain transfer (RAFT) polymerization method using 0.03 and 0.3 wt% of cumyl dithiobenzoate (CDB) vs. styrene (St) and the azobis(isobutyronitrile) initiator, at the polymerization temperature of 60 or 70 °C. The optimal high molecular weight polystyrene via this synthetic scheme shows Mw = 46.5×104, Mn = 33.3×104, and a dispersity of 1.40. The polystyrene chain contains a dithiobenzoate C=S moiety and thus can be used as a macro-chain-transfer agent for the polymerization of other monomers and for the synthesis of diversified block copolymers under mild conditions. The changes of the polystyrene molecular weight and dispersity were studied by the influences of the initial concentration ratio of CDB to styrene ([CDB]0/[St]0), the polymerization temperature, and the polymerization time. The PS molecular weight is inversely proportional to the [CDB]0/[St]0 ratio. Decreasing CDB from 0.3 to 0.03 wt%, a high MW PS was obtained, while the dispersity was observed to increase from 1.10 to 1.40. The PS molecular weight increases with the increase of the reaction time, while the dispersity of PS varies little from 1.12 to 1.23. The molecular weight and dispersity increase with the increase of the polymerization temperature. As the temperature arises from 60°C to 70°C, the conversion increases considerably from 25.8% to 39.9%, and the dispersity increases slightly from 1.15 to 1.17. As the temperature reaches 80°C, the conversion increases considerably to 64.7%, and the dispersity increases to 1.53. The polymer molecular weight of the polystyrene prepared by the RAFT method is suitable for the applications of engineering materials.

scholarly journals NEW AROMATIC DINITRODERIVATIVES OF CHLORAL AS MONOMER FOR SYNTHESYS OF POLYESTER AND POLYHETERO-ARYLENE

2018 ◽  
Vol 61 (2) ◽  
pp. 4
Author(s):  
Ruslan M. Kumykov ◽  
Arsen K. Vologirov
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Strength Properties ◽  
High Reactivity ◽  
Activation Mechanism ◽  
Aromatic Diamines ◽  
Synthesis Conditions ◽  
Mild Conditions ◽  
Methods Of Synthesis ◽  
Methylene Groups

The synthesis of aromatic dinitroderivatives of chloral effectively used in production of soluble, heat and fire resistant polyester and polyhetero arylenes using in the reaction of aromatic nucleophilic replacement was studied. The groups of new aromatic dinitroderivatives containing chloral as central groups between the phenyl nuclei: dichlorethelyne, carbonyl, acetylene and methylene groups were considered. The synthesis conditions were improved for polyester polyesterketones, polyesteretherketones, poliftalimides and polynaphtalamids without substantially affecting the thermal and solid characteristics achieved under relatively mild conditions using nucleophilic polynitro substitution. The search of new functional groups used in the condensation reactions, is an urgent task of polymer chemistry. Such groups must be determined by enough high reactivity of the monomers, without reducing their availability and without increasing their toxicity. It has decisive importance in the structure of initial monomers, which would be determined by the properties of polymers and the solubility of the target. In this aspect, dinitro compounds containing diphenyl, phthalimide and naftalimidnye cycles are presented their unique structures. It is known that improvement in meltability and solubility of the polymers without significant effect on the thermal and strength properties achieved by the introduction of these "carded" groups bulky substituents or phenyl phenoxide, flexible "bridge" fragments and introduced into the aromatic nuclei of the starting compounds bulk chlorine atoms. As part of this review it was made an attempt to describe methods of synthesis and properties of aromatic dinitropro- derivatives containing combinations of bulky substituents and flexible "bridged" groups using as initial compounds the simplest derivatives of chloral. The mostly known polyimides and polyetherimides prepared by reacting dianhydrides of aromatic tetracarboxylic acids with aromatic diamines with two-staged process where the first stage, a poly (o-carboxy) imides, and the second, due to thermal or catalytic imidization of polyamides with low solubility in organic solvents. It should be noted that the second stage -thermal or catalytic imidization not always results in a totally cycling polyamides that reduces the possibility of a relatively high molecular weight of polymers. At using aromatic dinitro- compounds containing a phthalimide and naftalimide cycles as comonomers bis-phenols, the problem of the extent of cyclization is absent. It was noted that an important determinant of obtaining high molecular weight of polymers is using nucleophilic polinitro-substitution in a process flow on the first stage under relatively mild conditions in a medium of DMSO or DMSO / toluene at 70 °C for 2 h in a completely dry environment. The review deals with some aspects of activation mechanism of nitro groups in nucleophilic polynitro-substitution. The processes of synthesis of condensation monomers of dinitro-derivatives using chloral were considered in detail. The methods of preparation and some properties of aromatic dinitroarilene, dinitroftalimide and dinitronaftalimide with dichlorethylenes, ketones, acetylene and methylene "bridged" groups between the phenyl nuclei are given. Forcitation:Kumykov R.M., Vologirov A.K. New aromatic dinitroderivatives of chloral as monomer for synthesys of polyester and polyhetero- arylene. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 4-14

Synthesis of high molecular weight polybenzimidazole using a highly pure monomer under mild conditions

2017 ◽  
Vol 66 (12) ◽  
pp. 1812-1818 ◽  
Author(s):  
Eun-Ki Kim ◽  
So Young Lee ◽  
Sang Yong Nam ◽  
Sung Jong Yoo ◽  
Jin Young Kim ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Mild Conditions

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

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