Search results for "Radical polymerization"

New hyaluronic acid based brush copolymers synthesized by atom transfer radical polymerization.

2013

Abstract In this work, an efficient method for the synthesis of hyaluronic acid based brush copolymers using atom transfer radical polymerization (ATRP) has been reported. At first, two different hyaluronic acid (HA) based macroinitiators have been prepared and then they have been used for the polymerization via ATRP of hydrophilic or hydrophobic molecules carrying vinyl portions. In particular, by linking 2-bromo-2-methylpropionic acid (BMP) to the primary hydroxyl groups of tetrabutyl ammonium salt of HA (HA–TBA) or to amino groups of the ethylenediamino derivative of HA–TBA (HA–TBA–EDA), two macroinitiators (HA–TBA–BMP and HA–TBA–EDA–BMP) have been obtained. Then they have been used for …

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

2014

Novel initiating systems for the living polymerization of acrylates and methacrylates

1998

The polymerization of methyl methacrylate with lithiated initiators in the presence of aluminium alkyls in toluene has living character but it deviates from conventional first-order kinetics and the polymers have fairly broad molecular weight distributions. This results from the formation and precipitation of a coordinative polymer network in which the lithium ions of the living chain ends are coordinated to the in-chain ester carbonyl groups. Thus, the network formation can be prevented by adding Lewis bases like methyl pivalate which coordinate to the living chain ends instead ofthe polymer. Alternatively, one can introduce tetraalkylammonium salts aiming at an exchange of the lithium ion…

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…

Pyrene Containing Polymers for the Non-Covalent Functionalization of Carbon Nanotubes

2009

Pyrene containing diblock copolymers based on poly(methyl methacrylate) were synthesized and investigated regarding their adsorption on carbon nanotubes (CNT). The pyrene units were introduced using a reactive ester monomer for the build up of the second block which later on was reacted polymer-analogously with amine functionalized pyrene derivatives. As we started from the same reactive ester intermediate, full block length identity is given. We varied the length of the anchor block to find an optimal block length and used pyren-1-yl-methylamine as well as 4-pyren-1-yl-butylamine as anchor units. For both anchor units a maximal adsorption was found for 13 and 20 anchor units, respectively.…

Polymeric mesoions, 4. Synthesis of polymerizable mesoionic 4,6-dioxo-1,3-diazines derived from vinylbenzylmalonic acid

2000

Vinylbenzylmalonic acid (4) was condensed with N,N'-diphenylformamidine (5a), N,N'-diphenylacetamidene (5b), S-propyl-1,3-diphenylisothiourea (6) and anilinopyridine (7) in the presence of dicyclohexylcarbodiimide (DDC). The resulting new mesoionic monomers 8a-d were polymerized with 2,2'-azoisobutyronitrile (AIBN) as an initiator and dodecanethiol as a chain transfer agent. The low molecular weight model compounds 5-benzyl-pyrido[1,2-a]pyrimidine-2,4-dione (9a) and 5-hexadecyl-4,6-dioxo-1,3-diphenyl-2-hexadecylthio-1,3-diazine (9b) were prepared for X-ray diffraction analysis and comparison of spectrospical data.

Cyclodextrins in polymer synthesis: polymerization of methyl methacrylate under atom-transfer conditions (ATRP) in aqueous solution

2000

Host guest complexes of methyl methacrylate (MMA) and randomly methylated β-cyclodextrin (m-β-CD, 1 a) were polymerized in aqueous medium using atom-transfer radical polymerization. Ethyl 2-bromoisobutyrate (EBIB) was used as an initiator, copper(I) bromide as the catalyst, and bipyridine (bipy) or 4,4′-di-(5-nonyl)-2,2´-bipyridine (dNbipy) as ligands. The unthreading of m-β-CD during the polymerization led to water-insoluble poly(methyl methacrylate) (PMMA). It was found that using dNbipy resulted in higher monomer conversion than using bipy as the ligand under similar conditions. Furthermore, it is shown that the polymerization of MMA under these conditions has a living character. The pol…

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.

Preparation of Hyperbranched Polyacrylates by Atom Transfer Radical Polymerization. 2. Kinetics and Mechanism of Chain Growth for the Self-Condensing…

1997

The self-condensing vinyl polymerization (SCVP) of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) has resulted in the formation of hyperbranched polyacrylates. The polymerization mechanism used to polymerize the BPEA was atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization. This paper details the study of the kinetics of polymerization and the growth of the macromolecule during the polymerization. The results obtained in the polymerization were compared to the theoretical predictions for SCVP. It was determined that the polymerization deviated from the ideal case, as a consequence of the establishment of a dynamic equilibrium in ATRP resulting in the add…

Polymerization of 3-alkylthiophenes with FeCl3

1992

We report on the mechanism of direct oxidation of 3-alkylthiophenes using ferric chloride (FeCl3) as the polymerization oxidant/catalyst to produce high molecular weight poly(3-alkylthiophenes) (P3ATs), conjugated polymers that have potential as electrically and optically active polymers. This study shows that the FeCl3 must exist in the solid state in the reaction mixture to be active as an oxidant in the polymerization of P3AT. A feasible polymerization mechanism for 3-alkylthiophene was developed on the basis of the crystal structure of FeCl3 and quantum chemical computations of thiophene derivatives. The polymerization is hypothesized to proceed through a radical mechanism rather than a…