| 1. |
- Aziz, Shazed, et al.
(författare)
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Effect of anisotropic thermal expansion on the torsional actuation of twist oriented polymer fibres
- 2017
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Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 129, s. 127-134
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Tidskriftsartikel (refereegranskat)abstract
- Torsional actuation of twisted polymer fibres is the basis for high performance tensile actuation when these fibres are formed into coils. The thermally-induced torsional actuation of twisted polyamide-6 fibres can be predicted by a single helix approximation when the measured diameter and length direction thermal expansion coefficients are known. The single helix model illustrates the sensitivity of the magnitude of torsional actuation to the volume expansion anisotropy for a given volume change. The applicability of the model has been further assessed by investigating three polymer fibres that display different thermal expansion anisotropies. Commercially available polyethylene, polypropylene and polyamide-6 fibres were twisted to the maximum extent without coiling and then heat treated to fix the twisted structure. Heating the twisted fibres between 26 and 62 °C resulted in a partial untwist which was reversed during cooling. The single-helix model of the twisted fibres was used to accurately predict the torsional stroke based on the measured fibre length and diameter change during heating. Comparative torsional stroke of twisted polyamide-6, polyethylene and polypropylene was explained in terms of materials thermo-physical properties. Generated blocked torques was also correctly predicted by the single-helix model when combined with the measured fibre torsional stiffness. Variances between torsional stiffnesses were found to be dependent of different anisotropic thermal properties of tested fibres.
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| 2. |
- Bergfelt, Andreas, et al.
(författare)
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d8-poly(methyl methacrylate)-poly[(oligo ethylene glycol) methyl ether methacrylate] tri-block-copolymer electrolytes : Morphology, conductivity and battery performance
- 2017
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 131, s. 234-242
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Tidskriftsartikel (refereegranskat)abstract
- A series of deuterated tri-block copolymers with the general structure d(8)-PMMA-POEGMA-d(8)-PMMA, with variation in d(8)-PMMA chain length, were synthesized using sequential controlled radical polymerization (ATRP). Solid polymer electrolytes (SPEs) were produced by blending tri-block copolymers and lithium bis(trifluoro methylsulfonate) (LiTFSI). Small-angle neutron scattering (SANS) was used to study the bulk morphology of the deuterated tri-block copolymer electrolyte series at 25 degrees C, 60 degrees C and 95 degrees C. The lack of a second T-g in DSC analysis together with modelling with the random phase approximation model (RPA) confirmed that the electrolytes are in the mixed state, with negative Flory-Huggins interaction parameters. AC impedance spectroscopy was used to study the ionic conductivity of the SPE series in the temperature interval 30 degrees C-90 degrees C, and a battery device was constructed to evaluate a 25 wt% d(8)-PMMA electrolyte. The Li | SPE | LiFePO4 cell cycled at 60 degrees C, giving a discharge capacity of 120 mAh g(-1), while cyclic voltammetry showed that the SPE was stable at 60 degrees C.
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| 3. |
- Boujemaoui, Assya, et al.
(författare)
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SI-RAFT/MADIX polymerization of vinyl acetate on cellulose nanocrystals for nanocomposite applications
- 2016
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Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 99, s. 240-249
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, poly(vinyl acetate) grafted cellulose nanocrystals (CNC-g-PVAc) were prepared via surface initiated reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthates (SI-RAFT/MADIX) polymerization. Successful grafting of PVAc from CNC was confirmed by FT-IR and TGA analysis. PVAc nanocomposites reinforced with CNC-g-PVAc, as well as pristine CNC for comparison, of different weight percentages (0.5, 1, 3 and 5 wt%) of CNC were prepared via solvent casting. The PVAc reinforced with CNC-g-PVAc resulted in higher transparency and improved mechanical properties compared with unmodified CNC nanocomposites. The addition of 5 wt% CNC-g-PVAc increased the modulus of neat PVAc with as much as 154%. The proposed SI-RAFT/MADIX on CNC could be applied to wide range of monomers, and it is believed to be an efficient and robust method for CNC functionalization, thus expanding the potential applicability of CNC.
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| 4. |
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| 5. |
- Chang, B., et al.
(författare)
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Microstructure characterization in a single isotactic polypropylene spherulite by synchrotron microfocus wide angle X-ray scattering
- 2018
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Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 142, s. 387-393
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Tidskriftsartikel (refereegranskat)abstract
- Position-resolved microstructure in a single spherulite of iPP is quantitatively studied by synchrotron microfocus wide angle X-ray scattering. The results show that the normal of mother lamellae in a spherulite is aligned mainly perpendicular to the radius, and the subsidiary daughter lamellae are inclined 80.75° with respect to that of the dominant mother lamellae. The crystallinity in the spherulite is in the range of 46%–56%, which is rarely influenced by the crystallization temperature. The ratio between the daughter lamellae and the mother lamellae is 0.18 when iPP crystallizes at 138 °C and it decreases to 0.11 as the crystallization temperature is decreased to 130 °C. The b-axis and c-axis in the mother lamellae tend to orient perpendicular to the radius direction, and the a-axis prefers to align in the radius direction.
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| 6. |
- Crassous, Jerome, et al.
(författare)
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Design of block copolymer micelles via crystallization
- 2015
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 62, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- This Feature Article provides an overview of the progress made over the last few years in the design of diblock copolymer micelles based on crystallization-driven self-assembly (CDSA) towards the development of novel and fascinating morphologies with crystalline-cores. Here, we describe the different approaches employed in order to engineer a large variety of semicrystalline micellar architectures. We highlight kinetic strategies that have been employed to direct morphological transitions, which can then be further tuned thus increasing the range of possible micellar structures. We then emphasize the development of complex hybrid assemblies generated by taking advantage of the self-assembly process of crystalline-corona di-BCP micelles with colloidal particles. Each section introduces and emphasizes the potential applications of this class of nanomaterials. (C) 2015 Elsevier Ltd. All rights reserved.
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| 7. |
- Diaz, M., et al.
(författare)
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Thermophysical characterization of a reversible dynamic polymer network based on kinetics and equilibrium of an amorphous furan-maleimide Diels-Alder cycloaddition
- 2017
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 120, s. 176-188
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium and kinetics of the furan-maleimide Diels-Alder (DA) reaction for the formation of a reversible network were studied by calorimetry between 25 °C and 90 °C using an amorphous bismaleimide eliminating solvent use. The relationship between the equilibrium conversion xeq with temperature and the effect of dilution were simulated. The glass transition-conversion relationship of the reversible network was established. The thermophysical properties of the reversible network were linked to the kinetics and equilibrium of the DA system, and studied by dynamic mechanical analysis (DMA), dielectric analysis (DEA) and rheometry. Below Tg the reversible network behaves like an irreversible network; however, above Tg, a decrease in the rubber tensile storage modulus was observed due to a reduction of cross-link density caused by the retro DA reaction. DEA revealed that above Tg, an interface is formed between released bismaleimide molecules and the remaining network. The rheological behavior is related to xeq and the lifetime of the reversible covalent bonds. When xeq is higher than the gelation conversion xgel (below 90 °C), the system gels at constant xgel. An elastic strengthening effect is observed in a transition region between 90 °C and 115 °C. Above 115 °C the system is reaching a viscous melt behavior. These observations are important for the application of this network as a self-healing material and as a recyclable elastomer or thermoset.
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| 8. |
- Engqvist, Jonas, et al.
(författare)
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Measurement of multi-scale deformation of polycarbonate using X-ray scattering with in-situ loading and digital image correlation
- 2016
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 82, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- Deformation of amorphous, glassy polycarbonate (PC) is characterised over a wide range of length-scales using spatially-resolved wide angle X-ray scattering (WAXS) with simultaneous digital image correlation and in-situ uni-axial loading. Novel observations are presented on the correlation of the evolution of the molecular structure linked to the relevant local macroscopic measures of strain as the sample deforms. This provides new insights into the mechanisms of deformation in amorphous, glassy polymers. Strains and evolving anisotropy are observed, and quantified, at different length scales identified from the WAXS measurements connected to inter- and intramolecular structures. The intermolecular structures show permanent deformations in the form of unrecoverable stretches and reorientations, whilst intramolecular structures how recoverable strains and unrecoverable reorientations. Such insights pave the way for development of enhanced constitutive models for amorphous glassy polymers with a correct micro-mechanical basis and calibrated evolution of anisotropy.
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| 9. |
- Gedde, Ulf W, et al.
(författare)
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Richard Hays Boyd in memorial
- 2017
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Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 118, s. 305-306
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Hassanzadeh, Salman, et al.
(författare)
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A proof-of-concept for folate-conjugated and quercetin-anchored pluronic mixed micelles as molecularly modulated polymeric carriers for doxorubicin
- 2015
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 74, s. 193-204
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Tidskriftsartikel (refereegranskat)abstract
- Pluronic, F127 (PEG-PPO-PEG, Mn = 12,500 g/mol) and reverse pluronic, 10R5 (PPO-PEG-PPO, Mn = 2000 g/mol) were molecularly modulated to reach multifunctional mixed micelle systems aiming to overcome some of the inherent weaknesses of pluronic based drug delivery systems. Targeting function was introduced by covalent attachment of folic acid to F127 (F127-FA), while quercetin was anchored to 10R5 (P-Q). The successful syntheses were evidenced by H-1 NMR, FTIR, DSC and UV-Vis. The proof-of-concept for the mixed micelles prepared from the drug anchored pluronics was demonstrated through reduced CMCs, slower release rates and increased Doxorubicin (DOX) encapsulation capacity from similar to 19% to similar to 43%. Quercetin therefore boosted the interactions of DOX with the hydrophobic core of the micelles. This was further evidenced by colloidal probe AFM which demonstrated almost doubled adhesion forces between the DOX coated probe and the quercetin modified pluronic as compared to the plain pluronic. The pre-biological essay of the DOX-modulated mixed micelle demonstrates promising properties. In addition quercetin has previously been proposed as combinatory drug to DOX enhancing its therapeutic function and reducing the side effects to normal cells.
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