| 1. |
- Carlmark, Anna, et al.
(författare)
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Atom transfer radical polymerization from cellulose fibers at ambient temperature
- 2002
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Ingår i: Journal of the American Chemical Society. - WASHINGTON, DC : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 124:6, s. 900-901
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose fibers have been successfully grafted with poly(methyl acrylate) using atom transfer radical polymerization, mediated by Me6-TREN and Cu(I)Br at ambient temperature. The initially hydrophilic cellulose was first modified by reacting the hydrozyl groups with 2-bromoisobutyryl bromide whereupon methyl acrylate was grafted from the surface. The resulting polymer-grafted papers were extremely hydrophobic, θa = 133°. FT-IR analysis indicates that the amount of grafted polymer can be controlled by adding sacrificial initiator to the polymerizing system. Size exclusion chromatography of the bulk polymer revealed narrow polydispersities and a molecular weight corresponding to the ratio [M]:[I].
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| 2. |
- Carlmark, Anna, et al.
(författare)
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ATRP grafting from cellulose fibers to create block-copolymer grafts
- 2003
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 4:6, s. 1740-1745
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose fibers, in the form of a conventional filter paper, have been modified by reacting the hydroxyl groups on the fiber surface with 2-bromoisobutyryl bromide, followed by grafting using ATRP conditions. The papers were first grafted with methyl acrylate (MA), rendering the paper very hydrophobic as reported in an earlier work. The papers were analyzed by gravimetry, FT-IR, ESCA, and AFM. To verify that the polymerization from the surface was living, a second layer of another, hydrophilic, polymer, 2-hydroxyethyl methacrylate (HEMA), was grafted upon the PMA layer, creating a block-copolymer graft from the fibers. After the layer of PHEMA had been attached, contact angle measurements were no longer possible, because of the absorbing nature of PHEMA-grafted layer. This indicates that a copolymer had indeed been formed on the surface. FT-IR showed a large increase in carbonyl content after the PHEMA-grafting, which further proves that a layer of PHEMA was attached to the PMA layer. This goes to show that the hydrophilic/ hydrophobic behavior of a cellulose surface can be tailored by the use of living/controlled radical polymerization methods such as ATRP.
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| 3. |
- Carlmark, Anna, et al.
(författare)
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ATRP of dendronized aliphatic macromonomers of generation one, two, and three
- 2004
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 37:20, s. 7491-7496
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Tidskriftsartikel (refereegranskat)abstract
- Atom transfer radical polymerization (ATRP) of dendritic, aliphatic macromonomers has been investigated. The macromonomers were based on acrylate functionalized 2,2-bis(methylol)propionic acid (bis-MPA) dendrons, with a flexible spacer of 10 carbons incorporated in the structure in between the polymerizable group and the dendritic wedge. Dendronized polymers of generation one, two, and three were successfully synthesized by ATRP. The polymerizations proceeded until over 80% conversion was reached, while maintaining control over polydispersity index (PDI). Plots of ln([M](0)/[M]) vs time for the polymerization of all three macromonomers showed a linear dependence, indicating that the number of propagating radicals in the reaction solution was constant throughout the reaction, when ethyl 2-bromopropionate (EBrP) was used as an initiator (i.e., radical termination was negligible). All of the resulting polymers had low PDI values and molecular weight close to the theoretical ones. The products were analyzed by H-1 and C-13 NMR spectroscopies, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF).
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| 4. |
- Carlmark, Anna E, et al.
(författare)
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Atom transfer radical polymerization of methyl acrylate from a multifunctional initiator at ambient temperature
- 2002
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Ingår i: Polymer. - OXFORD, ENGLAND : ELSEVIER SCI LTD. - 0032-3861 .- 1873-2291. ; 43:15, s. 4237-4242
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Tidskriftsartikel (refereegranskat)abstract
- A multifunctional initiator for ATRP has been synthesized by reacting a hyperbranched polyether, based on 3-ethyl-3-(hydroxymethyl)oxetane, with 2-bromo-isobutyrylbromide. The macroinitiator contained approximately 25 initiating sites per molecule. It was used for the atom transfer radical polymerization of methyl acrylate mediated by Cu(I)Br and tris(2-(dimethylamino)ethyl)amine (Me-6-TREN) in ethyl acetate at room temperature. This yielded a co-polymer with a dendritic-linear architecture. The large number of growing chains from each macromolecule increases the probability of inter-and intramolecular reactions. In order to control these kinds of polymerizing systems and prevent them from forming a gel, the concentration of propagating radicals must be kept low. The polymerizations under these conditions were well controlled. When a ratio of initiating sites-to-catalyst of 1:0.05 was used, the polymers from all of the reactions had a low polydispersity, ranging from 1.1 to 1.4. None of the polymerizations under these conditions gave gelation. Monomer conversions as high as 65% were reached while maintaining control over the polymerization. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 5. |
- Claesson, Hans, et al.
(författare)
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Rheological behaviour during UV-curing of a star-branched polyester
- 2002
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Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 44:1, s. 63-67
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Tidskriftsartikel (refereegranskat)abstract
- Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.
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| 6. |
- Claesson, Hans, et al.
(författare)
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Semi-crystalline thermoset resins : tailoring rheological properties in melt using comb structures with crystalline grafts
- 2004
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Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 49:1, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, bis-MPA in bulk at 155 degreesC. Functionalization with bis-MPA was monitored using FT-IR, FT-Raman and SEC. The reaction was complete in 30 min. Grafts of poly(epsilon-caprolactone) were then grown from the hydroxyl functional resin and end capped with methacrylate groups. The polymerization Of epsilon-caprolactone, performed in bulk at 110 degreesC using Sn(Oct)(2), was characterized using H-1 NMR and SEC. The obtained molecular weights agreed well with theoretical values. The final end capping was performed using methacrylic anhydride, and monitored with SEC and H-1 NMR, which indicated full substitution. Two combs were synthesized with different arm lengths, DP 10 and 20, and the obtained M-W were close to calculated values. The complex viscosity was measured from low to high temperature for the crystalline resins, the amorphous resin and blends thereof. Rheological data show a rapid decrease in viscosity within a temperature change of 10-15 degreesC for the crystalline resins while the amorphous resin exhibited a slow softening. The blends exhibited a behavior in-between that of the crystalline and the amorphous resin. Films were prepared from the pure resins and the blends. The films were cured using UV irradiation. The comb architecture of these resins has advantages such as crystallinity, high molecular weight and low viscosity, facilitating leveling and resulting in smooth films. The final film properties varied with the ratio of crystalline to amorphous resin, where increase in the amount of crystalline resin correlated with increased the flexibility.
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| 7. |
- Claesson, Hans, et al.
(författare)
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Synthesis and characterisation of star branched polyesters with dendritic cores and the effect of structural variations on zero shear rate viscosity
- 2002
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:12, s. 3511-3518
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Tidskriftsartikel (refereegranskat)abstract
- A series of branched polyesters consisting of poly(epsilon-caprolactone) (PCL) (degree of polymerisation: 5-200) initiated from hydroxy-functional cores and end-capped with methylmethacrylate have been prepared. The cores were third-generation hyperbranched polyester, Boltorn, with approximately 32 hydroxyl groups, a third-generation dendrimer with 24 hydroxyl groups and a third-generation dendron with eight hydroxyl groups. Finally, a linear PCL was synthesised as a reference material. All initiators were based on 2,2-bis(methylol) propionic acid (bis-MPA). C-13 NMR spectra of the polymers showed that those with shorter arms contained unreacted hydroxyl groups on the core. Rheological measurements of zero shear rate viscosity, eta(0), showed that the branched polyesters had a considerably lower eta(0) than linear polyester with similar molecular weight. The low melt viscosity and the crystallity produced a theological behaviour suitable for the film formation process for powder coatings. Measurements of mechanical properties of cured films showed that those with low arm molecular weight, M-a, were amorphous while those of high M-a were crystalline.
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| 8. |
- Coullerez, G., et al.
(författare)
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Insights into ToF-SIMS analysis of dendritic macromolecules : cationization and PCA to probe their molecular weight on surfaces
- 2003
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 203, s. 620-624
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Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is utilized to study dendrons, dendrimers and hyperbranched derivatives prepared from the 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) or the 3-ethyl-3-(hydroxymethyl)oxetane (TMPO). We show that the cationization experiments of the intact molecules with alkali or metal ions such as Na+, Cu+ or Ag+ allow to detect whole molecular species up to 3000 Da (low generation). It allows to probe directly their molecular TM weight and end-functionality. However, when the molecule lift-off fails for series of hyperbranched polyesters Boltorn(TM), the fingerprint part of the SIMS spectra (m/z < 300 Da) is instead used. The low-mass fragments are mainly assigned to the bis-MP repeating unit. Ions due to the core molecule are also distinguished. Data treatment is combined with the principal component analysis (PCA) multivariate statistical method to highlight the main differences between the spectra. Only one principal component (PC1) is needed to describe most of the variance between the samples taking into account the generation effect. PC1 plotted as a function of the molecular weight gives a calibration curve. Normalization of the data set by ion intensities from the core molecule allows the linearization of the SIMS intensities vs. the molecular weight.
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| 9. |
- Coullerez, G., et al.
(författare)
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ToF-SIMS for the characterization of hyperbranched aliphatic polyesters : probing their molecular weight on surfaces based on principal component analysis (PCA)
- 2003
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Ingår i: Surface and Interface Analysis. - : Wiley. - 0142-2421 .- 1096-9918. ; 35:8, s. 693-708
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Tidskriftsartikel (refereegranskat)abstract
- A series of 2,2-bis(hydroxymethyl)propionic acid (Bis-MPA) hyperbranched aliphatic polyesters with different molecular weights (generations) is analysed for the first time by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The main negative and positive low-mass fragments are identified in the fingerprint part of the spectra (m/z < 400) and are principally assigned to fragmentation of the Bis-MPA repeating units. In addition, it is shown that the fragmentation pattern is highly affected by the functional end-groups. This is illustrated for a phthalic acid end-capped hyperbranched polymer and for an acetonide-terminated dendrimer analog. Also, typical fragments assigned to the ethoxylated pentaerythritol core molecule are detected. These ions show decreasing intensities with increasing molecular weight. This intensity dependency on the generation is used to calibrate the molecular weight of hyperbranched polyesters on the surface. To obtain quantitative information, a principal component analysis WCA) multivariate statistical method is applied to the ToF-SIMS data. The influence of different normalization procedures prior to PCA calculation is tested, e.g. normalization to the total intensity, to the intensities of ions assigned to the Bis-MPA repeating unit or to intensities of fragments due to the core molecule. It is shown that only one principal component (PC1) is needed to describe most of the variance between the samples. In addition, PC1 takes into account the generation effect. However, different relationships between the PC1 scores and the hyperbranched mass average molecular weights are observed depending on the normalization procedure used. Normalization of data set ion intensities by ion intensities from the core molecule allows linearization of the SIMS intensities versus the molecular weight and allows the hyperbranched polymers to be discriminated up to the highest generations. In addition, PCA applied to ToF-SIMS data provides an extended interpretation of the spectra leading to further identification of the correlated mass peaks, such as those of the Bis-MPA repeating unit (terminal, dendritic and linear) and those of the core molecule. Finally, the work presented demonstrates the extreme potential of the static ToF-SIMS and PCA techniques in the analysis of dendritic molecules on solid surfaces.
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| 10. |
- Coullerez, Geraldine, et al.
(författare)
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Understanding copper-based atom-transfer radical polymerization in aqueous media
- 2004
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 108:35, s. 7129-7131
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the mechanism of copper(I)-mediated living atom-transfer radical polymerization (ATRP) in aqueous media. It is shown that the ATRP apparent rate constant for polymerization of methoxycapped oligo(ethylene glycol) methacrylate (OEGMA) in water (k(P)(app)) at room temperature correlates with the redox potential (E-1/2) of the copper complexes. The results are discussed along with previously published results on the kinetics for bulk polymerization of methyl acrylate at 60 degreesC with the redox potentials measured in MeCN. The faster ATRP kinetics in water can mainly be attributed to a higher equilibrium concentration of propagating radicals [W] and to solvent effects on the rate of propagation k(p). It is shown that [R*] can be calculated from the redox properties of the alkyl halide and the copper complex. The values of [R*] in MeCN/bulk and in H2O were determined to be 8.2 x 10(-8) and 6.3 x 10(-5) M, respectively. The respective kp values are in good agreement with the literature values (3.6 x 10(3) M-1 s(-1) for OEGMA in water and 2.5 x 10(3) M-1 s(-1) for methyl acrylate in bulk).
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