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| 2. |
- 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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| 4. |
- Dam, Tine Vrist, et al.
(författare)
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Muscle Performance during the Menstrual Cycle Correlates with Psychological Well-Being, but Not Fluctuations in Sex Hormones
- 2022
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Ingår i: Medicine and Science in Sports and Exercise. - 0195-9131. ; 54, s. 1678-1689
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: We aimed to study variations in strength and power performance during the menstrual cycle (MC) in eumenorrheic young women and during the pill cycle in oral contraceptives (OC) users. Methods: Forty healthy, normal-weight women between 18 and 35 yr (n = 30 eumenorrheic women; n = 10 OC users) completed this prospective cohort study. Seven to nine times during the MC/pill-cycle, the participants completed a physical performance test series, a questionnaire about psychological well-being, blood sampling, and determination of body mass. The physical tests included isometric handgrip strength, elbow flexor strength, countermovement jump (CMJ) height, and a 10-s Wingate bike test. Results: No direct correlation was observed between the variations in sex hormones and physical performance parameters. However, positive correlations were observed between physical performance outcomes and self-reported motivation, perception of own physical performance level, pleasure level, and arousal level. CMJ was 6% lower in the late luteal phase (LL) compared with the midluteal phase (ML) (P = 0.04). Wingate peak power was 3% lower in early follicular (EF) compared with the ML (P = 0.04). Furthermore, Wingate average power was 2%-5% lower in LL compared with all other MC phases. In line with these observations, physical pain was higher in EF and LL, and the pleasure level was lower in EF compared with the other MC phases. In OC users, we observed no variation in performance and self-reported parameters between the placebo-pill phase and the OC-pill phase. Conclusions: Impairments in CMJ and Wingate performance were observed at the end and start of MC compared with other MC phases, which were associated with lower psychological well-being, but not the sex hormone fluctuations.
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| 5. |
- 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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| 6. |
- Hao, X. J., et al.
(författare)
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Dendrimers as scaffolds for reversible addition fragmentation chain transfer (RAFT) agents : A route to star-shaped block copolymers
- 2005
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Ingår i: Australian journal of chemistry (Print). - 0004-9425 .- 1445-0038. ; 58:6, s. 483-491
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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