Experimental Criteria for Living Polymerizations

Abstract

Seven experimental criteria for living polymerizations are critically reviewed. The limitations of the use of linear plots of Mn (or xn) versus conversion and linear plots of the number of polymer chains versus conversion are illustrated by an example of alkyllithium-initiated polymerization of styrene by incremental additions of styrene with deliberate termination (5% per incremental monomer addition). The experimental criteria of using narrow molecular weight distribution and the formation of block copolymers are illustrated with practical examples and size exclusion chromatography data. The use of the terms 'living polymerization with reversible termination' and 'living polymerization with reversible chain transfer' are proposed. scope and limitations of the experimental criteria for living polymerization are critically reviewed. In particular, the limitations of the use of linear plots of number average molecular weight, A, (or X,, the number average degree of polymerization) versus conversion and plots of the number of polymer molecules versus conversion as critieria for living polymerization systems will be demonstrated. EXPERIMENTAL Chemicals and solventsStyrene, butadiene and benzene were carefully purified as described previously." sec-Butanol (Aldrich, 99Y0) was transferred into a graduated cylinder with a high-vacuum stopcock, degassed on the vacuum line and diluted with benzene. sec-Butyllithium (Lithium Corporation, 12 w t % in cyclohexane) was analyzed by the double titration method with 1,2-dibrom0ethane.~~ PolymerizationsAnionic polymerizations with .wc-butyllithium a s initiator were carried out in benzene solution a t 25°C in allglass, sealed reactors using breakseals or high-vacuum

Microstructure effect in the coupling reactions of polymeric organolithium compounds using chlorosilanes

“…[20][21][22] and chain transfer reactions. [1][2][3][4][5] Recently, the The coupling technique has been applied to a scope of living polymerizations has been extended commercial process for the preparation of A-B-A to include cationic, [6][7][8] transition metal organotype of triblock copolymers. 23,24 Furthermore, the metallic, 9,10 and even radical polymerizations.…”

Methacrylic block copolymers by sulfur free RAFT (SF RAFT) free radical emulsion polymerisation

“…It is evident from the results that SF-RAFT has all of the features of controlled reversible-deactivation polymerisation. 7,68 All chains grow simultaneously and their lifetime is equal to reaction duration, since the vinyl group is always present at the ω-chain end, as well as narrow MWD of the synthesised polymers.…”

Synthesis of poly(styrene-b-tetrahydrofuran-b-styrene) triblock copolymers by transformation from living cationic into living radical polymerization using 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a transforming agent

“…Living anionic polymertention because they exhibit unique behaviors ization has quantitatively given superior block cosuch as forming micelles when in solution and the polymers which have the molecular weights promotion of macrophase separation and microstrictly controlled. [1][2][3][4][5] Some publications have phase segregation in their polymer composites.…”