| 1. |
- Jesberger, M., et al.
(författare)
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Hyperbranched polymers as scaffolds for multifunctional reversible addition-fragmentation chain-transfer agents : A route to polystyrene-core-polyesters and polystyrene-block-poly(butyl acrylate)-core-polyesters
- 2003
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 41:23, s. 3847-3861
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Tidskriftsartikel (refereegranskat)abstract
- Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition-fragmentation chain-transfer (RAFT) agents. The polyester-core-based RAFT agents were subsequently employed to synthesize star polymers of n-butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free-radical process. Although the polyester-core-based RAFT agent mediated polymerization of n-butyl acrylate displayed a linear evolution of the number-average molecular weight (M.) up to high monomer conversions (>70%) and molecular weights [M-n > 140,000 g mol(-1), linear poly(methyl methacrylate) equivalents)], the corresponding styrene-based system reached a maximum molecular weight at low conversions (approximate to30%, M-n = 45,500 g mol(-1), linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n-butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene-based star polymers were successfully cast into highly regular honeycomb-structured microarrays.
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| 2. |
- Hao, X. J., et al.
(författare)
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Dendrimers as scaffolds for multifunctional reversible addition-fragmentation chain transfer agents : Syntheses and polymerization
- 2004
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 42:23, s. 5877-5890
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of novel first- and second-generation true dendritic reversible addition-fragmentation chain transfer (RAFT) agents carrying 6 or 12 pendant 3-benzylsulfanylthiocarbonylsulfanylpropionic acid RAFT end groups with Z-group architecture based on 1,1,1-hydroxyphenyl ethane and trimethylolpropane cores are described in detail. The multifunctional dendritic RAFT agents have been used to prepare star polymers of poly(butyl acrylate) (PBA) and polystyrene (PS) of narrow polydispersities (1.4 < polydispersity index < 1.1 for PBA and 1.5 < polydispersity index < 1.3 for PS) via bulk free-radical polymerization at 60 degreesC. The novel dendrimer-based multifunctional RAFT agents effect an efficient living polymerization process, as evidenced by the linear evolution of the number-average molecular weight (M.) with the monomer-polymer conversion, yielding star polymers with molecular weights of up to M-n = 160,000 g mol(-1) for PBA (based on a linear PBA calibration) and up to M. = 70,000 g mol(-1) for PS (based on a linear PS calibration). A structural change in the chemical nature of the dendritic core (i.e., 1,1,1-hydroxyphenyl ethane vs trimethylolpropane) has no influence on the observed molecular weight distributions. The star-shaped structure of the generated polymers has been confirmed through the cleavage of the pendant arms off the core of the star-shaped polymeric materials.
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