Stereoblock copolymers and tacticity control in controlled/living radical polymerization
Jean-François Lutz1, Dorota Neugebauer, Krzysztof Matyjaszewski
1Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.
Journal of the American Chemical Society
|June 5, 2003
Summary
Controlled radical polymerization techniques like atom transfer radical polymerization (ATRP) and reversible addition-fragmentation transfer (RAFT) polymerization, enhanced by Lewis acids, successfully produced isotactic poly(N,N-dimethylacrylamide) and stereoblock copolymers.
Area of Science:
- Polymer Chemistry
- Materials Science
Background:
- Controlled/living radical polymerization (CLRP) methods are crucial for synthesizing polymers with defined architectures.
- Lewis acids can influence polymer tacticity, impacting material properties.
- N,N-dimethylacrylamide (N,N-DMA) polymerization offers a platform to study stereochemical control.
Purpose of the Study:
- To investigate the efficacy of ATRP, RAFT, and NMP in controlling the tacticity of poly(N,N-DMA).
- To explore the use of Lewis acids, specifically Y(OTf)(3) and Yb(OTf)(3), in enhancing isotacticity during polymerization.
- To achieve the first one-pot synthesis of stereoblock copolymers via radical polymerization.
Main Methods:
- Atom Transfer Radical Polymerization (ATRP) with a specific initiating system and CuCl/Me(6)TREN.
- Reversible Addition-Fragmentation Transfer (RAFT) polymerization utilizing a cumyl dithiobenzoate transfer agent.
- Nitroxide-Mediated Polymerization (NMP) employing SG1 nitroxide.
- Addition of Lewis acids (Y(OTf)(3), Yb(OTf)(3)) to influence polymerization and tacticity.
Main Results:
- ATRP and RAFT in the presence of Y(OTf)(3) yielded poly(N,N-DMA) with controlled molecular weight, low polydispersity (<1.2), and high isotacticity (~85% meso dyads).
- NMP combined with Lewis acids showed less control over chain architecture and microstructure (~65% meso dyads).
- Successful one-pot synthesis of atactic-b-isotactic poly(N,N-DMA) stereoblock copolymers was demonstrated using ATRP/Y(OTf)(3) and RAFT/Y(OTf)(3) systems.
Conclusions:
- ATRP and RAFT polymerization, when combined with Y(OTf)(3), provide effective control over poly(N,N-DMA) tacticity.
- These Lewis acid-mediated CLRP systems enable the synthesis of well-defined stereoblock copolymers in a single pot.
- The findings open avenues for creating advanced polymer materials with tailored microstructures and properties.
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