Dendrimers as scaffolds for Reversible Addition Fragmentation Chain Transfer (RAFT) agents: A route to star-shaped block copolymers
Hao, X., Malmström, E., Davis, T. P., Stenzel, M. H., & Barner-Kowollik, C. (2005) Dendrimers as scaffolds for Reversible Addition Fragmentation Chain Transfer (RAFT) agents: A route to star-shaped block copolymers. Australian Journal of Chemistry, 58(6).
Star-shaped block copolymers of styrene and n-butyl acrylate having three, six, and twelve pendent arms were successfully synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. Dendritic cores (based on 1,1,1-trimethylolpropane) of generation 0, 1, and 2 have been functionalized with 3-benzylsulfanylthiocarbonylsulfanylpropionic ester groups and have subsequently been employed to mediate the polymerization of styrene and n-butyl acrylate to generate macro-star-RAFT agents as starting materials for chain extension. The chain extension of the macro-star-RAFT agents with either styrene or n-butyl acrylate by bulk free radical polymerization at 60°C gives narrowly distributed polymer (final polydispersities close to 1.2) increasing linearly in molecular weight with increasing monomer-to-polymer conversion. However, with an increasing number of arms (i.e., when going from three- to twelve-armed star polymers), the chain extension becomes significantly less efficient. The molecular weight of the generated block copolymers was assessed using 1H NMR spectroscopy as well as size exclusion chromatography calibrated with linear polystyrene standards. The hydrodynamic radius, Rh, of the star block copolymers as well as the precursor star polymers was determined in tetrahydrofuran by dynamic light scattering (90°) at 25°C. Interestingly, the observed Rh-Mn relationships indicate a stronger dependence of Rh on Mn for poly(butyl acrylate) stars than for the corresponding styrene polymers. Rh increases significantly when the macro-star-RAFT agent is chain extended with either styrene or n-butyl acrylate. © CSIRO 2005.
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|Item Type:||Journal Article|
|Additional Information:||Cited By :28
Export Date: 5 September 2016
Correspondence Address: Barner-Kowollik, C.; Centre for Advanced Macromolecular Design, School of Chemical Engineering and Industrial Chemistry, University of New South Wales, Sydney, NSW 2052, Australia; email: firstname.lastname@example.org
|Keywords:||Block copolymers, Gravimetric analysis, Molecular weight, Nuclear magnetic resonance spectroscopy, Polymerization, Polystyrenes, Protons, Size exclusion chromatography, Butyl acrylate, Coupling reactions, Low-field resonances, Reversible addition fragmentation chain transfer (RAFT), Dendrimers|
|DOI:||10.1071/CH05036 10.1021/CR990119U; Hawker, C.J., (1995) Angew. Chem. Int. Ed. Engl., 34, p. 1456. , doi:10.1002/ANIE.199514561;|
|Divisions:||Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > Institutes > Institute for Future Environments
Current > QUT Faculties and Divisions > Science & Engineering Faculty
|Deposited On:||22 Sep 2016 04:50|
|Last Modified:||22 Sep 2016 04:50|
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