Search results for "Anionic addition polymerization"

Linear-Hyperbranched Amphiphilic AB Diblock Copolymers Based on Polystyrene and Hyperbranched Polyglycerol

2005

A convenient three-step strategy has been developed for the preparation of well-defined amphiphilic, linear hyperbranched block copolymers by hypergrafting. The synthetic procedure is based on a combination of carbanionic polymerization with the alkoxide-based controlled ring-opening multibranching polymerization of glycidol. A linear AB diblock copolymer polystyrene-block-polybutadiene (PS-b-PB) with narrow polydispersity was obtained by anionic copolymerization. Subsequent hydroxylation by hydroboration led to PS 508 -b-(PB-OH) 56 , used as macro--initiator for the polymerization of glycidol under slow monomer addition conditions.

Temperature Variation Enables the Design of Biobased Block Copolymers via One‐Step Anionic Copolymerization

2021

A one-pot approach for the preparation of diblock copolymers consisting of polystyrene and polymyrcene blocks is described via a temperature-induced block copolymer (BCP) formation strategy. A monomer mixture of styrene and myrcene is employed. The unreactive nature of myrcene in a polar solvent (tetrahydrofuran) at -78 °C enables the sole formation of active polystyrene macroinitiators, while an increase of the temperature (-38 °C to room temperature) leads to poly(styrene-block-myrcene) formation due to polymerization of myrcene. Well-defined BCPs featuring molar masses in the range of 44-117.2 kg mol-1 with dispersities, Ð, of 1.09-1.21, and polymyrcene volume fractions of 30-64% are acc…

Synthesis, characterization and properties of functional star and dendritic block copolymers of ethylene oxide and glycidol with oligoglycidol branch…

2009

Abstract Well-defined, four-arm star block copolymers of ethylene oxide and glycidol were prepared via controlled anionic polymerization using protected glycidol. The length of the poly(ethylene oxide) block was varied from DP = 10 to 50, while the length of the short polyglycidol block remained nearly constant, at DP = 4–6. Star block copolymers with hydroxyl groups at the ends of the arms after conversion to the corresponding alkoxides were used as multifunctional macroinitiators for the sequential polymerization of ethylene oxide and protected glycidol. After deprotection, the branched block copolymers of ethylene oxide and glycidol had narrow molar mass distributions and multiple hydrox…

1993

Effect of Lithium Perchlorate on the Kinetics of the Anionic Polymerization of Methyl Methacrylate in Tetrahydrofuran

1999

The kinetics of the anionic polymerization of methyl methacrylate in the presence of lithium perchlorate (LiClO 4 ) are investigated in THF using 1,1-diphenylhexyllithium as initiator in a flow-tube reactor between -30 and 0 °C. The rate constants of propagation determined in the presence of LiClO 4 are lower than those obtained in the absence of the salt, similar to the effect observed for LiCl. For propagation, the reaction order with respect to active center concentration is found to be 0.5 in both cases, which indicates that LiClO 4 does not effectively perturb the aggregation of the enolate ion pair. The formation of various mixed aggregates is proposed. The polydispersity index of the…

Mechanism of Anionic Polymerization of (Meth)acrylates in the Presence of Aluminium Alkyls IV. Formation of a Co-ordinative Polymer Network via the L…

1996

The polymerization of methyl methacrylate in the presence of aluminium alkyls in toluene deviates from conventional kinetics. This results predominantly from the formation and precipitation of a co-ordinative polymer gel or network. Due to the lower reactivity and accessibility of the living chains in the gel, they are regarded as ’dormant’ and thus the concentration of active species decreases during polymerization. The network formation occurs via co-ordination of the living aluminate chain end group with in-chain ester carbonyl groups. Part of the chains are deactivated by a termination process but they are free of cyclic β-ketoesters which would result from the common ’back-biting’ reac…

Polymerization of styrene

1979

Graft Copolymers with Complex Polyether Structures: Poly(ethylene oxide)-graft-Poly(isobutyl vinyl ether) by Combination of Living Anionic and Photoi…

2014

Polyether Core-Shell Cylinder-Polymerization of Polyglycidol Macromonomers

2005

The synthesis and polymerization of macromonomers containing a polymerizable styrene head group and a tail of ethylene oxide derivatives of different character were investigated. The synthesis of macromonomers was based on living anionic polymerization of oxiranes. Two monomers were used: 1-ethoxyethyl glycidyl ether (glycidol acetal), which after hydrolysis forms hydrophilic glycidol blocks and glycidyl phenyl ether forming hydrophobic blocks. Polymerizable double bonds were introduced by terminating the living chain with p-(chloromethyl)styrene. The radical polymerization of the macromonomers was carried out in water with addition of a non-polar solvent (benzene) and AIBN as initiator. Co…

Group transfer and anionic polymerization: A critical comparison

1990

The mechanism of group transfer polymerization (GTP) of methacrylates in THF is investigated by using data on kinetics of homo- and copolymerization, polymer microstructure and molecular weight distribution. By comparison with corresponding data on anionic polymerization it is concluded that the mechanisms of monomer addition to the active chain end is very similar for both anionic and group transfer polymerization and that GTP is ionic in character. On the other hand, GTP uniquely is characterized by the existence of a catalyst exchange equilibrium. The position of this equilibrium determines the rates of polymerization, and the dynamics determine the molecular weight distribution.