Search results for "Living free-radical polymerization"
showing 10 items of 22 documents
Kinetic treatment of slow initiation in living carbocationic polymerization and investigation of benzyl halides as initiators for the polymerization …
1998
In contrast to earlier conclusions it is demonstrated that kinetic analysis of incremental monomer addition (IMA) experiments for living carbocationic polymerizations with slow initiation leads only to the ratio of apparent rate constants of initiation and propagation. The apparent rate constants depend on the true (bimolecular) rate constants and on the positions of the equilibria between dormant and active states of initiator and polymer chain ends, respectively. The same considerations are true for other living processes involving dormant species, e.g., group transfer polymerization or controlled radical polymerization. Slow initiation of living carbocationic polymerization of isobutylen…
Primary radical termination and chain transfer in vinyl polymerization
1974
Cyclodextrins in polymer synthesis: free radical polymerization of cyclodextrin host-guest complexes of methyl methacrylate or styrene from homogenou…
2000
The polymerization of methylated β-cyclodextrin (m-β-CD) 1 : 1 host-guest compounds of methyl methacrylate (MMA) (1) or styrene (2) is described. The polymerization of complexes 1 a and 2 a was carried out in water with potassium peroxodisulfate (K2S2O8)/sodium hydrogensulfite (NaHSO3) as radical redox initiator at 60°C. Unthreading of m-β-CD during the polymerization led to water-insoluble poly(methyl methacrylate) (PMMA) (3) and polystyrene (4). By comparison, analogously prepared polymers from uncomplexed monomers 1 and 2 in ethanol as organic solvent with 2,2′-azoisobutyronitrile (AIBN) as radical initiator showed significantly lower molecular weights and were obtained in lower yields i…
Macromonomers on the basis of 2-phenyl-2-oxazoline
1988
By initiation of the ring-opening polymerization of 2-phenyl-2-oxazoline (1) with p-iodomethylstyrene a macromonomer with a styrene end-group (2) is obtained. The degree of polymerization was varied between 10 and 16. The radical copolymerization of 2 with styrene is described. 1 forms with methyl triflate a very stable oxazolinium salt which is a good initiator for the bulk polymerization of 1 at temperatures of 50–70°C. It was conclusively proved that under these conditions the polymerization proceeds by a living mechanism. By termination with N, N-dimethylaminopropylmeth-acrylamide a macromonomer (5) was obtained. 5 can be radically homopolymerized. This comb-like polymer 6 has the typic…
Radical Polymerization of Styrene Controlled by Half-Sandwich Mo(III)/Mo(IV) Couples: All Basic Mechanisms Are Possible
2001
Density functional calculations of bond dissociation energies (BDEs) have been used as a guide to the choice of metal system suitable for controlling styrene polymerization by either the stable free radical polymerization (SFRP) or the atom transfer radical polymerization (ATRP) mechanism. In accord with the theoretical prediction, CpMo(eta(4)-C(4)H(6))(CH(2)SiMe(3))(2), 2, is not capable of yielding SFRP of styrene. Still in accord with theoretical prediction, CpMo(eta(4)-C(4)H(6))Cl(2), 1, CpMo(PMe(3))(2)Cl(2), 3, and CpMo(dppe)Cl(2) (dppe = 1,2-bis(diphenylphosphino)ethane), 4, yield controlled styrene polymerization by the SFRP mechanism in the presence of 2,2'-azobisisobutyronitrile (A…
Star-Like Polymers of tert -Butyl Acrylate via Controlled Radical Polymerization - Synthesis and Properties
2011
Summary: Star polymers with different numbers and lengths of poly(tert-butyl acrylate) arms were obtained by the core-first method via atom transfer and iodine mediated radical polymerization. Multifunctional initiators with different numbers of initiating groups (from 3 to 28) were used to initiate the polymerization of tert-butyl acrylate, yielding stars with different numbers of arms. The structures of the stars were characterized by NMR and gel permeation chromatography with refractive index, multiangle laser light scattering and viscosimetric detectors.
Tailored Semiconducting Polymers: Living Radical Polymerization and NLO-Functionalization of Triphenylamines
2002
This paper describes the preparation of various polymers with triarylamine side groups. High molecular weight materials were obtained by free radical polymerization utilizing the gel effect. Polymers with a marrow polydispersity and a predetermined molecular weight could be prepared by living radical polymerization. The T g could, thereby, be controlled between 50 and 140°C either by using different monomers or by varying the molecular weight. Living radical polymerization allowed in addition the preparation of block copolymers. The triarylamine side groups could be transformed into NLO-chromophores by reaction with tetracyanoethylene. This leads to the incorporation of tricyanoethylene. Th…
Cyclodextrins in Polymer Synthesis: Free-Radical Polymerization of Methylated β-Cyclodextrin Complexes of Methyl Methacrylate and Styrene Controlled…
2000
Half-sandwich molybdenum(III) compounds containing diazadiene ligands and their use in the controlled radical polymerization of styrene
2002
Abstract The reaction of CpMoCl2 with diazadiene ligands RNCHCHNR (R2dad) affords the corresponding paramagnetic complexes CpMoCl2(R2dad) (R=Ph, 1; p-Tol, 2; C6H3Pr2i-2,6, 3; and Pri, 4). All compounds have been characterized by EPR spectroscopy and have been investigated by cyclic voltammetry. They display one-electron oxidation and reduction processes, these being reversible or irreversible depending on the nature of R. The irreversibility of the reduction wave is due to a chemical follow-up process which consists of chloride loss from the reduced product. This phenomenon is suppressed in the presence of excess chloride in solution. An X-ray structure of 3 verifies the mononuclear na…
How the interplay of different control mechanisms affects the initiator efficiency factor in controlled radical polymerization: An investigation usin…
2007
International audience; Compound CpMoI2(iPr2dad) (iPr2dad = iPrNdouble bondCHsingle bondCHdouble bondNiPr), obtained by halide exchange from CpMoCl2(iPr2dad) and NaI, has been isolated and characterized by EPR spectroscopy, cyclic voltammetry, and X-ray crystallography. Its action as a catalyst in atom transfer radical polymerization (ATRP) and as a spin trap in organometallic radical polymerization (OMRP) of styrene and methyl acrylate (MA) monomers has been investigated and compared with that of the dichloro analogue. Compound CpMoCl2(iPr2dad) catalyzes the ATRP of styrene and MA with low efficiency factors f (as low as 0.37 for MA and ethyl 2-chloropropionate as initiator), while it irre…