| 1. |
- Andronova, Natalia, et al.
(author)
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Potential tissue implants from the networks based on 1,5-dioxepan-2-one and epsilon-caprolactone
- 2005
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In: Polymer journal. - : Elsevier BV. - 0032-3896 .- 1349-0540. ; 46:18, s. 6746-6755
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Journal article (peer-reviewed)abstract
- The synthesis and characterization of degradable polymeric networks for biomedical applications was performed. Cross-linked films of poly(epsilon-caprolactone) (PCL) and poly(1,5-dioxepan-2-one) (PDXO) having various mole fractions of monomers and different cross-link densities were successfully prepared using 2,2'-bis-(epsilon-caprolactone-4-yl) propane (BCP) as cross-linking agent. Reaction parameters were carefully examined to optimise, the film-formin.,, conditions. Networks obtained were elastomeric materials. easy to cast and remove from the mould. Effect of CL content and cross-link density on the final properties of the polymer network was evaluated. High CL content or degree of cross-linking led to increase in Young's modulus and decrease in elongation at break. An increase in crystalline domains in films having a higher CL content was observed by optical microscopy. A greater thermal stability was observed in films having a high CL content. The hydrophilicity of the materials could be tailored by changing the CL content. The surface of the films became rougher with higher CL content.
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| 2. |
- Alla, Abdelilah, et al.
(author)
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Acylated and hydroxylated polyamides derived from L-tartaric acid
- 2005
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In: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 46:9, s. 2854-2861
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Journal article (peer-reviewed)abstract
- A series of polyamides 6,4 were prepared from 1,6-hexanediamine and active esters of 2,3-di-O-acylated l-tartaric acid by polycondensation in solution. Both O-alkoyl and O-benzoyl esters were used as hydroxyl protecting groups. The resulting acylated polytartaramides were found to be semicrystalline polymers with Tm between 100 and 200°C and Tg slightly above 100°C. Controlled hydrolysis of the ester side group led to the preparation of poly(hexamethylene l-tartaramide)s with different content in free hydroxyl groups. These polyamides continue being crystalline but their properties largely differ from those displayed by their parent acylated polymers.
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| 3. |
- Andersson, L. H. U., et al.
(author)
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The effect of different structure parameters on the crosslinking behaviour and network performance of LDPE
- 2006
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In: Polymer. - : Elsevier BV. - 0032-3861. ; 47:1, s. 200-210
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Journal article (peer-reviewed)abstract
- In the present study, we investigate the crosslinking behaviour of 6 ordinary low density polyethylenes, and the effect of relatively modest changes in the polyethylene structure on the properties of the resulting network. The observed variations in gel formation are mainly explained by differences in molecular weight, where both M̄n and M̄w affect the results. The presence of long chain branches (LCB) present on the polymer main chain is shown to have a significant effect on the network quality. The occurrence of LCB affects the ability in making effective entanglements, a behaviour which is largely dependent on the length of the branches. At high LCB frequencies, the long chain branches are relatively short and therefore more prone to disentangle. The frequency and the amount of LCB, together with the molecular weight, have a large impact on the coil size. The coil size is believed to be an important parameter for the crosslinking behaviour, as a large coil size facilitates interconnections between adjacent polymer coils. In addition, LCB increases the probability of creating intramolecular crosslinks. However, this study shows that a very high amount of LCB is needed in order to obtain any significant effect on the network quality originating from intramolecular crosslinks. © 2005 Elsevier Ltd. All rights reserved.
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| 4. |
- Colombini, Didier, et al.
(author)
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The effect of the polymerization route on the amount of interphase in structured latex particles and their corresponding films
- 2005
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In: Polymer. - : Elsevier BV. - 0032-3861. ; 46:4, s. 1295-1308
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Journal article (peer-reviewed)abstract
- Three series of hard/soft styrene-acrylic latex based systems with equivalent compositions were prepared either by blending of homopolymer latexes or by preparing structured latex particles having core shell (CS) or inverted core shell (ICS) morphologies. Transmission electron microscopy (TEM) was used to investigate the particle morphologies, which were correlated to the calculated fractional radical penetration for the propagating species during the reactions. The thermo-mechanical properties as well as the morphology of the resulting latex films were analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and TEM. The viscoelastic properties of the interphase between the first and second-stage polymers formed in the structured hard/soft latex films, as well as its qualitative amount and also the film morphologies were found to depend on the interplay between thermodynamic and kinetic parameters during the synthesis of the samples. (C) 2004 Elsevier Ltd. All rights reserved.
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| 5. |
- Courtois, Julien, et al.
(author)
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Novel monolithic materials using poly(ethylene glycol) as porogen for protein separation
- 2006
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In: Polymer. - Guildford, Surrey : Butterworth. - 0032-3861 .- 1873-2291. ; 47:8, s. 2603-2611
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Journal article (peer-reviewed)abstract
- Several recipes are described for the preparation of porous polymeric monoliths in the capillary format, using poly(ethylene glycol) (PEG) as porogen as well as constituent in the monomer mixture. Acrylic or methacrylic monomers with a variety of terminal groups, with and without ethylene glycol links of differing lengths in the side chains, have been used in combination with triethylene glycol dimethacrylate (TEGDMA) and trimethylol-propane trimethacrylate (TRIM) as cross-linkers. PEGs of 4–20 kDa molecular weight dissolved in 2-methoxy-ethanol were used as porogens to yield large, biocompatible pores. A number of common solvents have been used as co-porogens for the PEGs, and the surface areas, median pore diameters, and back pressures of the resulting monoliths have been correlated with a number of molecular descriptors by means of chemometrics to describe the results. Photopolymerizations induced by either continuous or pulsed UV light were furthermore compared. Pore size distribution and surface area characterization have been assessed by nitrogen adsorption–desorption and mercury intrusion porosimetry, and scanning electron microscopy (SEM) was used to evaluate the differences in macroporous morphology obtained with the different porogen solutions. Mixtures selected from screening syntheses carried out in vials have been implemented in 100 μm fused silica capillaries and the back pressures measured and cross-validated with the pore information. Some of these capillary columns were finally tested for the separation of proteins using micro-HPLC.
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| 6. |
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| 7. |
- Edgecombe, Samuel, et al.
(author)
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Monte Carlo simulation of two interpenetrating polymer networks: Structure, swelling, and mechanical properties
- 2008
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In: Polymer. - : Elsevier BV. - 0032-3861. ; 49:7, s. 1981-1992
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Journal article (peer-reviewed)abstract
- The swelling and mechanical properties of various interpenetrating polymer networks (IPNs) were studied. Six networks made from permutations of a moderately crosslinked polyelectrolyte network (ref), a moderately crosslinked neutral polymer network (net1), and a highly crosslinked polyelectrolyte network (net2) were first swollen in water and structural properties such as end-to-end chain lengths and radial distribution functions were compared with the component networks' equilibrium properties. The swelling of composite IPNs was discussed in terms of a balance between the osmotic pressure due to mobile counterions and the restoring force of the network chains, which act in parallel to counteract the osmotic swelling. For the ref-net2 system, the strong stretching of net2 chains increases the network restoring force and the further swelling due to the counterions is suppressed. The swollen networks were then uniaxially stretched, and equilibrium stress-strain plots were obtained up to high extension ratios. The equilibrium volume decreased upon uniaxial extension, and the elastic moduli of IPNs of the A-A type were slightly greater than that of their respective single networks.
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| 8. |
- Gasslander, Ulla, et al.
(author)
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Polymer-water partition coefficients of extended range measured by using organic modifiers in the aqueous phase
- 2007
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In: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 48:26, s. 7523-7530
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Journal article (peer-reviewed)abstract
- A procedure for estimating equilibrium polymer-water partition coefficients over a broad range of solute hydrophobicity is presented and evaluated. The coefficients were calculated from the concentration change in the liquid phase and hydro-organic mixtures of varying proportions were used to extend the range. Three hydrophobic polymers (PP, PE, and EBA), two types of solvent (acetonitrile and alcohols) and 12 model solutes were used. The estimated polymer-water partition coefficients, log K-pw, ranged from -0.5 to 8.5. The coefficients correlated to other partitioning systems such as the calculated log Poctanol-water up to similar to 14 and the retention factor (log k(w)) in reversed-phase liquid chromatography.
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| 9. |
- Gelin, Kristina, et al.
(author)
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Characterization of water in bacterial cellulose using dielectric spectroscopy and electron microscopy
- 2007
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In: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 48:26, s. 7623-7631
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Journal article (peer-reviewed)abstract
- It is shown that only 10% of the 99 wt% water present in bacterial cellulose (BC) gels, produced by Acetobacter xylinum, behave like free bulk water; the majority of the water molecules in the gels is more or less tightly bound to the cellulose. The magnitude of the diffusion coefficients of ions transported in the water phase of the BC gels as well as the information contained in freeze fracture transmission electron microscopic images of the gel structures indicates that the bulk-like water is confined in “lakes” rather than forming a continuous phase throughout the gel. Water desorption isotherms suggest that these “lakes” decrease in size with increasing oxygen concentration used during the biosynthesis process of the gels.
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| 10. |
- Johansson, Erik, et al.
(author)
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Molecular simulation of the effect of ionic impurities and external electric fields on rod-like water clusters in polyethylene
- 2008
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In: Polymer. - : Elsevier Ltd. - 0032-3861 .- 1873-2291. ; 49:24, s. 5357-5362
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Journal article (peer-reviewed)abstract
- Monte Carlo methods have been combined with end-bridging methods to study the solubility and structure of water in polyethylene, where the polyethylene contains a pair of oppositely charged ionic impurities. The water in the polymer is in equilibrium with pure liquid water. Both the polymer and pure water phases are exposed to an external electric field. The ions dramatically increase the solubility of water in polyethylene and induce the formation of a stable, rod-like water cluster between the ions. The solubility, the hydrogen-bond ordering of the water molecules in the cluster and the size of the cluster increase in the presence of an external field that enhances the local electric field between the ions. When the direction of the external field is reversed, and when it has the same magnitude as the local ionic field, the rod-like structure is broken up and a smaller cluster forms around each ion. (C) 2008 Elsevier Ltd. All rights reserved.
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