Abstract
A novel dinitroxide mediating agent that was suitable for stable free-radical polymerization was synthesized and used in the block copolymerization of styrene and t-butyl styrene. Quantitative yields of a novel dinitroxide based on 1,6-hexamethylene diisocyanate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy were obtained. Various experimental parameters, including the nitroxide-to-initiator molar ratio, were examined, and it was determined that the polymerization was most controlled under conditions similar to those of conventional 2,2,6,6-tetramethyl-1-piperidi-nyloxy-mediated stable free-radical polymerization. Moreover, the dinitroxide mediator proved to be a viable route for the facile two-step synthesis of triblock copolymers of styrene and t-butyl styrene. However, the dinitroxide mediation process resulted in a higher than expected level of nitroxide decomposition, which resulted in polymers possessing a terminal alkoxyamine and an adjacent hydroxylamine rather than a preferred internal bisalkoxyamine. This decomposition resulted in the formation of diblock copolymer species during the triblock copolymer synthesis. Gel permeation chromatography was used to monitor the chain-end decomposition kinetics, and the determined observed rate constant (5.89 × 10 -5s-1) for decomposition agreed well with previous studies for other dinitroxide mediating agents.
Original language | English (US) |
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Pages (from-to) | 1547-1556 |
Number of pages | 10 |
Journal | Journal of Polymer Science, Part A: Polymer Chemistry |
Volume | 42 |
Issue number | 7 |
DOIs | |
State | Published - Apr 1 2004 |
Externally published | Yes |
Keywords
- Block copolymers
- Gel permeation chromatography (GPC)
- Radical polymerization
ASJC Scopus subject areas
- Polymers and Plastics
- Organic Chemistry
- Materials Chemistry