| 1. |
- Atlas, Salima, et al.
(författare)
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Radical copolymerization of acrylonitrile with 2,2,2-trifluoroethyl acrylate for dielectric materials : Structure and characterization
- 2013
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 51:18, s. 3856-3866
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Forskningsöversikt (refereegranskat)abstract
- Radical copolymerization based on acrylonitrile (AN) and 2,2,2-Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN-co-ATRIF) copolymers were characterized by 1 H, 13 C, and 19 F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by 1 H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 degrees C from initial [AN](0)/[ATRIF](0) molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer-polymer copolymerization curve, the Fineman-Ross and Kelen-Tudos laws enabled to assess the reactivity ratios (r(AN) = r(1) = 1.25 +/- 0.04 and r(ATRIF) = r(2) = 0.93 +/- 0.05 at 70 degrees C) while the revised patterns scheme led to r(12) = r(AN) = 1.03, and r(21) = r(ATRIF) = 0.78 at 70 degrees C. In all cases, rAN x rATRIF product was close to unity, which indicates that poly(AN-co-ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN-ATRIF, AN-AN, and ATRIF-ATRIF dyads. The Q and e values for ATRIF were also assessed (Q(2) = 0.62 and e(2) = 0.93). The glass transition temperature values, Tg, of these copolymers increased from 17 to 61 degrees C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN-co-ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer.
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| 2. |
- Carlborg, Carl Fredrik, et al.
(författare)
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Functional Off-Stoichiometry Thiol-ene-epoxy Thermosets Featuring Temporally Controlled Curing Stages via an UV/UV Dual Cure Process
- 2014
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Ingår i: Journal of Polymer Science Part A. - : John Wiley & Sons. - 0887-624X .- 1099-0518. ; 52:18, s. 2604-2615
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Tidskriftsartikel (refereegranskat)abstract
- We present a facile two-stage UV/UV activation method for the polymerization of off-stoichiometry thiol-ene-epoxy, OSTE+, networks. We show that the handling and processing of these epoxy-based resins is made easier by introducing a material with a controlled curing technique based on two steps, where the first step offers excellent processing capabilities, and the second step yields a polymer with suitable end-properties. We investigate the sequential thiol-ene and thiol-epoxy reactions during these steps by studying the mechanical properties, functional group conversion, water absorption, hydrolytic stability, and thermal stability in several different thiol-ene-epoxy formulations. Finally, we conclude that the curing stages can be separated for up to 24 h, which is promising for the usefulness of this technique in industrial applications.
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| 3. |
- Claudino, Mauro, et al.
(författare)
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Photoinduced thiol-ene cross-linking of globalide/ε-caprolactone copolymers : curing performance and resulting thermoset properties
- 2012
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 50:1, s. 16-24
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand for bioderived polymers led us to investigate the potential use of the macrolactone globalide in thermoset synthesis via the photoinduced thiolene reaction. A series of six lipase-catalyzed poly(globalide-caprolactone) copolyesters bearing internal main-chain unsaturations ranging from 10 to 50 and 100 mol % were successfully crosslinked in the melt with equal amounts of thiol groups from trimethylolpropane-trimercapto propionate affording fully transparent amorphous elastomeric materials with different thermal and viscoelastic properties. Three major conclusions can be drawn from this study: (i) high thiol-ene conversions (> 80%) were easily attained for all cases, while maintaining the cure behavior, and irrespective of functionality at reasonable reaction rates; (ii) parallel chain-growth homopropagation of the ene monomer is insignificant when compared with the main thiolene coupling route; and (iii) high ene-density copolymers result in much lower extracted sol fractions and high T(g) values as a result of a more dense and homogeneous crosslinked network. The thiol-ene system evaluated in this contribution serve as model example for the sustainable use of naturally occurring 1,2-disubstituted alkenes in making semisynthetic polymeric materials in high conversions with a range of properties.
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| 4. |
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| 5. |
- Dax, Daniel, et al.
(författare)
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Synthesis of SET-LRP-Induced Galactoglucomannan-Diblock Copolymers
- 2013
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 51:23, s. 5100-5110
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Tidskriftsartikel (refereegranskat)abstract
- Polysaccharides are biorenewable and biodegradable starting materials for the development of functional materials. The synthesis of a monofunctional macroinitiator for single electron transfer-living radical polymerization was successfully developed from a wood polysaccharide-O-acetyl galactoglucomannan (GGM) using a beforehand synthesized amino-functional -bromoisobutyryl derivative applying reductive amination. The GGM macroinitiator was employed to initiate a controlled radical polymerization of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MeDMA), methyl methacrylate (MMA), and N-isopropylacrylamide (NIPAM) using Cu-0/Me-6-Tren as a catalyst. The either charged or amphiphilic GGM-b-copolymers with different chain lengths of the synthetic block were successfully synthesized without prior hydrophobization of the GGM chain and dimethyl sulfoxide (DMSO) or DMSO/water mixtures were used as solvents. This novel synthetic approach may find untapped potentials particularly for the development of polysaccharide-based amphiphilic additives for cosmetics or paints and for the design of novel temperature or pH responsive polymers with such potential applications as in drug delivery systems or in biocomposites.
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| 6. |
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| 7. |
- Edlund, Ulrica, 1972-, et al.
(författare)
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Macroinitiator Halide Effects in Galactoglucomannan-Mediated Single Electron Transfer-Living Radical Polymerization
- 2011
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 49:19, s. 4139-4145
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Tidskriftsartikel (refereegranskat)abstract
- Chloro (Cl)- and bromo (Br)-functionalized macroinitiators were successfully prepared from the softwood hemicellulose O-acetylated galactoglucomannan (AcGGM) and then explored and evaluated with respect to their ability and efficiency of initiating single electron transfer-living radical polymerization (SET-LRP). Both halogenated species effectively initiate SET-LRP of an acrylate and a methacrylate monomer, respectively, yielding brushlike AcGGM graft copolymers, where the molecular weights are accurately controlled via the monomer:macroinitiator ratio and polymerization time over a broad range: from oligomeric to ultrahigh. The nature of the halogen does not influence the kinetics of polymerization strongly, however, for acrylate graft polymerization, AcGGM-Cl gives a somewhat higher rate constant of propagation, while methacrylate grafting proceeds slightly faster when the initiating species is AcGGM-Br. For both monomers, the macroinitiator efficiency is superior in the case of AcGGM-Br.
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| 8. |
- Edlund, Ulrica, et al.
(författare)
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SET-LRP Goes "Green" : Various Hemicellulose Initiating Systems Under Non-Inert Conditions
- 2012
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 50:13, s. 2650-2658
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Tidskriftsartikel (refereegranskat)abstract
- Robust and versatile controlled radical polymerization, also in air, was achieved via single electron transfer living radical polymerization (SET-LRP) initiated by purposely designed hemicellulose-derived macroinitiators. The efficiency of the substitution reaction, converting the polysaccharides into bromo-multifunctionalized initiators, as well as the rate of subsequent induced polymerizations of methyl acrylate were controlled by the hemicellulose repeating unit structure, branching pattern, and molecular weight. Macroinitiators with mannan-based backbones induce SET-LRP with somewhat higher apparent rate constants than xylan-derived analogues, increasing by a factor two to three when raising the reaction temperature from 25 to 40 degrees C. The presence of lignin in a non-purified xylan fraction did not impair its viability as a macroinitiator. Hemicellulose-initiated SET-LRP was feasible in air, proceeding with comparable or somewhat higher apparent rate constants than when conducted under deoxygenated conditions.
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| 9. |
- Eriksson, Magnus, et al.
(författare)
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One-Pot Enzymatic Route to Tetraallyl Ether Functional Oligoesters : Synthesis, UV Curing, and Characterization
- 2010
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 48:23, s. 5289-5297
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Tidskriftsartikel (refereegranskat)abstract
- An enzymatic one-pot route in bulk was used to synthesize tetraallyl ether (tAE) functional oligomers based on divinyl adipate, 1,4-butanediol and trimethylolpropane diallyl ether. By using lipase B from Candida antarctica as catalyst and varying the stoichiometric ratio of monomers, it was possible to reach targeted molecular weights (from 1300 to 3300 g mol(-1)) of allyl-ether functional polyesters. The enzyme catalyzed reaction reached completion (>98% conversion based on all monomers) within 24 h at 60 degrees C, under reduced pressure (72 mbar) resulting in similar to 90% yield after filtration. The tAE-functional oligoesters were photopolymerized, without any purification other than removal of the enzyme by filtration, with thiol functional monomers (dithiol, tetrathiol) in a 1: 1 ratio thiol-ene reaction. The photo-initiator, 2,2-dimethoxy-2-phenylacetophenone, was used to improve the rate of reaction under UV light. High conversions (96-99% within detection limits) were found for all thiol-ene films as determined by FT-Raman spectroscopy. The tAE-functional oligoesters were characterized by NMR, MALDI, and SEC. The UV-cured homopolymerized films and the thiol-ene films properties were characterized utilizing DSC and DMTA.
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| 10. |
- Ghirardello, Mattia, et al.
(författare)
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Thiol-Ene and Thiol-Yne-Based Synthesis of Glycodendrimers as Nanomolar Inhibitors of Wheat Germ Agglutinin
- 2014
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 52:17, s. 2422-2433
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Tidskriftsartikel (refereegranskat)abstract
- Alkene and alkyne functional polyester-based dendrimers of generation 1 to 4 have been prepared and reacted under free-radical conditions with 2-acetamido-2-deoxy-1-thio--D-glucose (GlcNAc-SH). As the alkene-dendrimers underwent the addition of one thiyl radical per ene group whereas each yne group of alkyne-dendrimers was saturated by two thiyl radicals, a collection of glycodendrimers with glycan density ranging from six to ninety-six GlcNAc per dendrimer was obtained. The recognition properties of the prepared glycodendrimers toward the wheat germ agglutinin (WGA) were evaluated by enzyme-linked lectin assay (ELLA). The eight glycodendrimers were excellent ligands showing IC50 values in the nanomolar range and relative potencies per sugar unit up to 2.27 e(6) when compared to monosaccharidic GlcNAc used as monovalent reference.
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