Dendrimers as scaffolds for reversible addition fragmentation chain transfer (RAFT) agents: A route to star-shaped block copolymers
2005 (English)In: Australian journal of chemistry (Print), ISSN 0004-9425, Vol. 58, no 6, 483-491 p.Article in journal (Refereed) Published
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 degrees 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 H-1 NMR spectroscopy as well as size exclusion chromatography calibrated with linear polystyrene standards. The hydrodynamic radius, R-h, of the star block copolymers as well as the precursor star polymers was determined in tetrahydrofuran by dynamic light scattering (90 degrees) at 25 degrees C. Interestingly, the observed R-h-M-n relationships indicate a stronger dependence of R-h on M-n for poly(butyl acrylate) stars than for the corresponding styrene polymers. R-h increases significantly when the macro-star-RAFT agent is chain extended with either styrene or n-butyl acrylate.
Place, publisher, year, edition, pages
2005. Vol. 58, no 6, 483-491 p.
free-radical polymerization, gpc-distribution coefficients, dendritic macromolecules, molecular architecture, living polymerization, methyl-methacrylate, spherical pores, graft polymers, ab-initio, styrene
IdentifiersURN: urn:nbn:se:kth:diva-14834DOI: 10.1071/CH05036ISI: 000229784500014ScopusID: 2-s2.0-22744444429OAI: oai:DiVA.org:kth-14834DiVA: diva2:332875
QC 201005252010-08-052010-08-052010-10-25Bibliographically approved