| 1. |
- Ajjan, Fátima, et al.
(författare)
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Innovative polyelectrolytes/poly(ionic liquid)s for energy and the environment
- 2017
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Ingår i: Polymer international. - : WILEY. - 0959-8103 .- 1097-0126. ; 66:8, s. 1119-1128
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Forskningsöversikt (refereegranskat)abstract
- This paper presents the work carried out within the European project RENAISSANCE-ITN, which was dedicated to the development of innovative polyelectrolytes for energy and environmental applications. Within the project different types of innovative polyelectrolytes were synthesized such as poly(ionic liquid)s coming from renewable or natural ions, thiazolium cations, catechol functionalities or from a new generation of cheap deep eutectic monomers. Further, macromolecular architectures such as new poly(ionic liquid) block copolymers and new (semi)conducting polymer/polyelectrolyte complexes were also developed. As the final goal, the application of these innovative polymers in energy and the environment was investigated. Important advances in energy storage technologies included the development of new carbonaceous materials, new lignin/conducting polymer biopolymer electrodes, new iongels and single-ion conducting polymer electrolytes for supercapacitors and batteries and new poly(ionic liquid) binders for batteries. On the other hand, the use of innovative polyelectrolytes in sustainable environmental technologies led to the development of new liquid and dry water, new materials for water cleaning technologies such as flocculants, oil absorbers, new recyclable organocatalyst platforms and new multifunctional polymer coatings with antifouling and antimicrobial properties. All in all this paper demonstrates the potential of poly(ionic liquid)s for high-value applications in energy and enviromental areas. (c) 2017 Society of Chemical Industry
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| 2. |
- Amanizadeh, Farhad, et al.
(författare)
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Starve fed emulsion copolymerization of vinyl acetate and 1-hexene at ambient pressure
- 2014
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Ingår i: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 63:10, s. 1850-1855
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Tidskriftsartikel (refereegranskat)abstract
- A novel emulsion copolymer of vinyl acetate (VAc) and 1-hexene was synthesized at ambient pressure. The feeding technique, initiation system and reaction time of the copolymerization were optimized based on molecular characteristics such as the weight contribution of 1-hexene in the copolymer chains and glass transition temperature (T-g) as well as on bulk properties like minimum film-formation temperature (MFFT) and solid content. According to nuclear magnetic resonance spectroscopy and differential scanning calorimetry results, the combination of starve feeding and redox initiation, within a reaction time of 4h, effectively led to the copolymerization at ambient pressure between highly reactive polar VAc monomers and non-polar 1-hexene monomers of low reactivity. The copolymer showed a lower T-g and MFFT, and a reasonable solid content compared to the poly(vinyl acetate) (PVAc) homopolymer. The consumption rate, hydrolysis of acetate groups and chain transfer reactions during the polymerization were followed using infrared spectroscopy. Based on the results, the undesirable reactions between the VAc blocks were hindered by the neighbouring 1-hexene molecules. Tensile testing revealed an improvement in the toughness and elongation at break of VAc-1-hexene films compared to PVAc films.
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| 3. |
- Camacho, W., et al.
(författare)
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Near infrared (NIR) spectroscopy compared with thermogravimetric analysis as a tool for on-line prediction of water diffusion in polyamide 6,6
- 2002
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Ingår i: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 51:12, s. 1366-1370
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Tidskriftsartikel (refereegranskat)abstract
- NIR spectroscopy in the transmission mode and thermogravimetric analysis were used to predict diffusion of water into polyamide 6,6 samples immersed in water at 40, 60, 75 and 90degreesC for different periods of time. The sorption curves between 40 and 75 were sigmoidal indicating that the surface concentration was time dependent. The sorption curves were readily fitted by the use of a time-dependent surface concentration and a water-concentration-dependent diffusivity. The zero-concentration water diffusivity decreased non-linearly and the activation energy of diffusion increased from 24 to 58 kJ mol(-1), with decreasing temperature. The surface concentration relaxation time decreased rapidly. The sorption of water in thick polyamide samples was readily characterized by FT-NIR spectroscopy. The accuracy and feasibility of this method was similar to conventional thermogravimetric methods. The greatest advantage of FT-NIR, however, is the possibility of detecting and monitoring the moisture concentration on-line and in a non-destructive way.
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| 4. |
- de Melo, J. Sergio Seixas, et al.
(författare)
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Fluorescence studies on the interaction between pyrene-labelled poly(acrylic acid) and cyclodextrins
- 2007
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Ingår i: Polymer International. - : Wiley. - 0959-8103 .- 1097-0126. ; 56:7, s. 882-899
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Tidskriftsartikel (refereegranskat)abstract
- The interactions, in aqueous media, between a pyrene-labelled polyelectrolyte poly(acrylic acid) (PAAMePy) with two different degrees of labelling and beta- and gamma-cyclodextrins (beta- and gamma-CD) were studied using absorption and fluorescence (steady-state and time-resolved) techniques. In addition to qualitative and quantitative parameters obtained from absorption and steady-state fluorescence spectra, time-resolved fluorescence data are presented, allowing additional important observations regarding the nature of the interactions. From the overall data it was possible to conclude that in the case of interaction with gamma-CD the efficient encapsulation of two pyrene units into the cavity of the cyclodextrin molecule leads to a decrease in the number of available free monomers and an increase in the number of preformed ground-state dimers (GSDs) of pyrene. It was also shown that contrary to the situation in water, where only intramolecular interactions are present, the addition of gamma-CD leads to new interpolymeric interactions. The absence of significant changes is noted when the interactions of PAAMePy polymers take place with beta-CD. The excimer-to-monomer fluorescence intensity ratio (I-E/I-M) was found to increase with the added amount of gamma-CD but not with beta-CD. This increase is justified on the basis of the increase of the GSD contribution. The photophysical behaviour was found to be dependent on the pH of the media, but with the absence of relevant interactions between CD and PAAMePy polymer at alkaline values. (C) 2007 Society of Chemical Industry.
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| 5. |
- Detta, Nicola, et al.
(författare)
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Melt electrospinning of polycaprolactone and its blends with poly(ethylene glycol)
- 2010
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Ingår i: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 59:11, s. 1558-1562
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Tidskriftsartikel (refereegranskat)abstract
- Melt electrospinning is one aspect of electrospinning with relatively little published literature, although the technique avoids solvent accumulation and/or toxicity which is favoured in certain applications In the study reported, we melt-electrospun blends of poly(epsilon-caprolactone) (PCL) and an amphiphilic diblock copolymer consisting of poly(ethylene glycol) and PCL segments (PEG-block PCL) A custom-made electrospinning apparatus was built and various combinations of instrument parameters such as voltage and polymer feeding rate were investigated Pure PEG-block-PCL copolymer melt electrospinning did not result in consistent and uniform fibres due to the low molecular weight, while blends of PCL and PEG-block-PCL, for some parameter combinations and certain weight ratios of the two components, were able to produce continuous fibres significantly thinner (average diameter of ca 2 mu m) compared to pure PCL The PCL fibres obtained had average diameters ranging from 6 to 33 mu m and meshes were uniform for the lowest voltage employed while mesh uniformity decreased when the voltage was increased This approach shows that PCL and blends of PEG block-PCL and PCL can be readily processed by melt electrospinning to obtain fibrous meshes with varied average diameters and morphologies that are of interest for tissue engineering purposes.
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| 6. |
- El Ghaoui, Hanane, et al.
(författare)
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Bismuth complex catalysts for the in situ preparation of polycaprolactone/silicate bionanocomposites
- 2014
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Ingår i: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 63:4, s. 709-717
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Tidskriftsartikel (refereegranskat)abstract
- Solvent-free, bismuth-catalysed in situ polymerization of caprolactone in the presence of layered silicates enables the formulation of a series of polycaprolactone/silicate bionanocomposites. Three organophilic montmorillonites obtained by cationic exchange reaction with tetrabutylammonium iodide, benzyltriethylammonium chloride and vinylbenzyltriphenylphosphonium chloride salts, respectively, were used as reinforcing reagents for these materials. The effects of clay and bismuth catalyst type (bismuth(III) acetate and triphenylbismuth) are discussed on the basis of composite morphologies and molecular weights of resulting polymers.
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| 7. |
- Gabilondo, Nagore, et al.
(författare)
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Property tailoring of phenol-formaldehyde matrices by control of reactant molar ratio and thermoplastic modification
- 2011
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Ingår i: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 60:5, s. 851-858
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Tidskriftsartikel (refereegranskat)abstract
- High modulus, strength and thermal stability make phenol-formaldehyde resins (PFRs) interesting as matrices for nanocomposites. Four PFR matrices synthesized with different formaldehyde (F) to phenol (P) molar ratios were investigated, as well as the influence of thermoplastic modification on their mechanical properties. The effectiveness of a specific curing cycle for obtaining macrovoid- and microvoid-free specimens by controlling the thickness of samples is demonstrated. Fourier transform infrared spectroscopy results reveal that F content increases the presence of oxidized linkages as benzophenones and fully substituted aromatic structures. PFR matrices with highest F content present the highest values of main transition temperature and flexural modulus up to an F/P ratio of 1.8, revealing the achievement of a densely crosslinked and rigid structure. A selected PFR matrix was modified with 5, 10 and 15 wt% of two poly(vinyl butyral) (PVB) thermoplastics of differing molecular weight. Phase separation occurs before gelation in all cases leading to different morphologies, observed using atomic force microscopy and optical microscopy, depending on PVB content: PVB-rich particles in PFR-richmatrix for 5 wt% and co-continuous dual morphology for 10 and 15 wt% for both PVBs. Strength improvement is achieved for PFR matrices modified with 5 wt% of PVB associated with a tailored particulate morphology with a particle size of around 1.2 mu m. Finally, 5 and 10 wt% PVB-modified PFR materials exhibit a very high thermal stability with degradation temperatures very close to those for neat PFR matrix.
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| 8. |
- Gamiz Gonzalez, Maria Amparo, et al.
(författare)
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Synthesis of highly swellable hydrogels of water-soluble carboxymethyl chitosan and poly(ethylene glycol)
- 2017
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Ingår i: Polymer international. - : WILEY. - 0959-8103 .- 1097-0126. ; 66:11, s. 1624-1632
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Tidskriftsartikel (refereegranskat)abstract
- Highly swellable hydrogels were produced by crosslinking of high molecular weight carboxymethylated chitosan (CmCHT) with poly(ethylene glycol) (PEG) oligomers. The hydrogel swelling capacity could be controlled via the crosslinking density and ranged from 900% to 5600%. The hydrogels showed good homogeneity with a high interconnected porosity in the swollen state and with nanodomains rich in CmCHT and others rich in PEG diglycidyl ether. Oscillatory frequency sweep analysis showed a storage modulus of 27kPa for the hydrogel with the highest crosslinking density, which together with the exhibited enzyme degradability with lysozyme at 59days indicate that these hydrogels have potential use in delivery systems or soft tissue regeneration.
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| 9. |
- Gedefaw, Desta Antenehe, 1971, et al.
(författare)
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Conjugated polymers with polar side chains in bulk heterojunction solar cell devices
- 2014
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Ingår i: Polymer International. - : Wiley. - 1097-0126 .- 0959-8103. ; 63:1, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- Two polymers with polar side chains, namely poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5',8'-di-2-thienyl-(2',3'-bis(3''-(2-(2-methoxyethoxy)ethoxy)phenyl)quinoxaline))] (P1) and poly[2,7-(9,9-bis(2-(2-methoxyethoxy)ethyl)fluorene)-alt-5,5-(5',8'-di-2-thienyl-(2',3'-bis(3''-(2-(2-methoxyethoxy)-ethoxy)phenyl)quinoxaline))] (P2), were synthesized for solar cell application. A series of bulk heterojunction solar cells were systematically fabricated and characterized by varying the electron-acceptor materials, processing solvents and thickness of the active layer. The results show that P1, with a higher molecular weight and good film-forming properties, performed better. The best device showed an open circuit voltage of 0.87 V, a short circuit current of 6.81 mA cm(-2) and a power conversion efficiency of 2.74% with 1:4 polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM[70]) mixture using o-dichlorobenzene (o-DCB) as processing solvent. P2 on the other hand showed a poorer performance with chlorobenzene as processing solvent, but a much improved performance was obtained using o-DCB instead. Thus, an open circuit voltage of 0.80 V, short circuit current of 6.21 mA cm(-2) and an overall power conversion efficiency of 2.22% were recorded for a polymer:PCBM[70] mixing ratio of 1:4. This is presumably due to the improvement of the morphology of the active layer using o-DCB as processing solvent. (c) 2013 Society of Chemical Industry
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| 10. |
- Hobzova, R., et al.
(författare)
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Methacrylate hydrogels reinforced with bacterial cellulose
- 2012
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Ingår i: Polymer International. - : Wiley. - 1097-0126 .- 0959-8103. ; 61:7, s. 1193-1201
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Tidskriftsartikel (refereegranskat)abstract
- Composite hydrogels consisting of nanofibrous bacterial cellulose (BC) embedded in a biocompatible polymeric matrix of various methacrylates were synthesized by UV polymerization using the ever-wet technique. The effect of monomer(s) type and ratio, system dilution at polymerization, monomer(s) hydrophilicity, crosslink density and cellulose/hydrogel ratio was investigated. The effect of BC reinforcement on equilibrium swelling depends on whether the neat gel swells more when brought into contact with water. The major improvement achieved by introduction of 1%2% BC concerns mechanical properties. Compared with neat gels, the storage shear modulus G' increased by a factor 10-20, and the loss part G? also rose significantly. The compression modulus ranged from 2 to 5.5 MPa for composites swollen to equilibrium (20-70 wt% water). The BC-hydrogel composites are considered for application in the tissue engineering area.
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