Crosslinking of Electrospun Fibres from Unsaturated Polyesters by Bis-Triazolinediones (TAD) (original) (raw)
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European Polymer Journal, 2019
Poly(2-ethyl-2-oxazoline)s (PEtOx) have received substantial attention for various potential biomedical applications, yet they have not been explored as scaffold materials to any extensive degree. A major challenge to open up future applications is to overcome the poor water stability of these materials. We here propose a universal crosslinking strategy for these materials based on a partial acidic hydrolysis of PEtOx to poly[(2-ethyl-2-oxazoline)-co-(ethylenimine)] (PEtOx-EI) followed by exposure to glutaraldehyde vapour to create water-stable scaffolds. To demonstrate the utility of this approach two different fabrication techniques were used to make 2and 3-dimensional structures, namely solution electrospinning and fused deposition modelling (FDM). Because the partial hydrolysis results in increased hydrophilicity, the crosslinking conditions for the fine PEtOx-EI nanofibers were carefully tuned to enable crosslinking of the nanofibers prior to a loss of the nanofibrous morphology. Conversely, for the thicker FDM printed PEtOx-EI structures the crosslinking conditions are more tolerant. Crosslinking with glutaraldehyde vapour provided water-stability to both 2D and 3D constructs, which is an important asset for biomedical applications.
In Situ Cross-Linking of Electrospun Poly(vinyl alcohol) Nanofibers
Macromolecules, 2009
We examine single step reactive electrospinning of poly(vinyl alcohol) (PVA) and a chemical cross-linking agent, glutaraldehyde (GA), with hydrochloric acid (HCl) as a catalyst to generate water insoluble PVA nanofibers. Such an approach using a conventional setup with no modification enables the fibers to cross-link during the electrospinning process, thereby eliminating the need for post-treatment. Significant changes in the rheological properties occur during in situ cross-linking, which we correlate with electrospinnability. In particular, we associate changes in dynamic rheological properties to changes in fiber morphology for two regions: (1) below the critical concentration to electrospin PVA only and (2) above the critical concentration to electrospin PVA only. In region 1 fiber morphology changes from beaded fibers to uniform fibers to flat fibers, and in region 2 fiber morphology changes from uniform fibers to flat fibers. Electrospinning windows to generate uniform fibers for both regions are determined and can be manipulated by changing the molar ratio of GA to PVA and the volume ratio of HCl to GA. The electrospun fibrous material generated can be rendered insoluble in water, and the uniform fiber morphology can be maintained after soaking in water overnight. The reactive electrospinning process also lowers the critical PVA concentration required for successful electrospinning of the system.
Organic and Inorganic PCL-Based Electrospun Fibers
Polymers
In this work, different nanocomposite electrospun fiber mats were obtained based on poly(e-caprolactone) (PCL) and reinforced with both organic and inorganic nanoparticles. In particular, on one side, cellulose nanocrystals (CNC) were synthesized and functionalized by “grafting from” reaction, using their superficial OH– group to graft PCL chains. On the other side, commercial chitosan, graphene as organic, while silver, hydroxyapatite, and fumed silica nanoparticles were used as inorganic reinforcements. All the nanoparticles were added at 1 wt% with respect to the PCL polymeric matrix in order to compare the different behavior of the woven no-woven nanocomposite electrospun fibers with a fixed amount of both organic and inorganic nanoparticles. From the thermal point of view, no difference was found between the effect of the addition of organic or inorganic nanoparticles, with no significant variation in the Tg (glass transition temperature), Tm (melting temperature), and the degr...
In situ cross-linking of electrospun poly (vinyl alcohol) nanofibers
2009
We examine single step reactive electrospinning of poly(vinyl alcohol) (PVA) and a chemical cross-linking agent, glutaraldehyde (GA), with hydrochloric acid (HCl) as a catalyst to generate water insoluble PVA nanofibers. Such an approach using a conventional setup with no modification enables the fibers to cross-link during the electrospinning process, thereby eliminating the need for post-treatment. Significant changes in the rheological properties occur during in situ cross-linking, which we correlate with electrospinnability. In particular, we associate changes in dynamic rheological properties to changes in fiber morphology for two regions: (1) below the critical concentration to electrospin PVA only and (2) above the critical concentration to electrospin PVA only. In region 1 fiber morphology changes from beaded fibers to uniform fibers to flat fibers, and in region 2 fiber morphology changes from uniform fibers to flat fibers. Electrospinning windows to generate uniform fibers for both regions are determined and can be manipulated by changing the molar ratio of GA to PVA and the volume ratio of HCl to GA. The electrospun fibrous material generated can be rendered insoluble in water, and the uniform fiber morphology can be maintained after soaking in water overnight. The reactive electrospinning process also lowers the critical PVA concentration required for successful electrospinning of the system.
Development of Novel Electrospun Fibers Based on Cyclic Olefin Polymer
Nanomaterials
For the first time, a systematic study to investigate the electrospinnability of cyclic olefin polymer (COP) was performed. Different solvents and mixtures were tested together with different electrospinning parameters and post-treatment types to prepare bead-free fibers without defects. These were successfully obtained using a chloroform/chlorobenzene (40/60 wt.%) solvent mixture with a 15 wt.% COP polymer, a 1 mL/h polymer solution flow rate, a 15 cm distance between the needle and collector, and a 12 kV electric voltage. COP fibers were in the micron range and the hot-press post-treatment (5 MPa, 5 min and 120 °C) induced an integrated fibrous structure along with more junctions between fibers, reducing the mean and maximum inter-fiber space. When the temperature of the press post-treatment was increased (from 25 °C to 120 °C), better strength and less elongation at break of COP fibers were achieved. However, when applying a temperature above the COP glass temperature (Tg = 138 °...
Cross‐Linking of Polyesters Based on Fatty Acids
European Journal of Lipid Science and Technology
This paper aimed at obtaining cross-linked polymeric materials of biomass origin. For this purpose one-pot polyesterification of methyl ricinoleate and methyl 12-hydroxystearate using titanium isopropoxide as a catalyst has been performed leading to polyesters known as estolides. The obtained estolides were successfully cross-linked using dicumyl peroxide or a sulfur vulcanization system. The so-formed bio-based elastomers appeared to exhibit promising properties. The latter were analyzed by mechanical tensile tests and thermal techniques (TGA, DSC, DMA) and showed high thermal stability (T5% = 205-318 °C) and tailored physico-mechanical properties (low glass transition temperature in the range from-69 to-54 °C) and good tensile strength (0.11-0.40 MPa). Networks prepared from high molecular weight estolides appear to be promising bio-based elastomers. Practical applications The vegetable oil-based estolides described in this contribution, are new fully bio-based precursors for further elastomers synthesis. The resulting estolide networks (obtained by peroxide or sulfur cross-linking) exhibit tailored thermo-mechanical properties.
European Polymer Journal, 2008
For the first time preparation of electrospun poly(e-caprolactone) (PCL) based nanofibers possessing surface enriched in tertiary amino groups is shown. For that purpose the pair PCL and poly(e-caprolactone)-b-poly[(2-dimethylamino)ethyl methacrylate] (PCL-b-PDMAEMA) diblock copolymers was used. PCL-b-PDMAEMA copolymers were synthesized using a combination of ring-opening polymerization and atom transfer radical polymerization (ATRP). Nanofibers with mean diameters ranging from 400 to 800 nm were obtained. Their morphology was evaluated by scanning electron (SEM) and atomic force microscopy (AFM). It was found that the morphology of the fibers depended on the weight ratio between the partners and the length of the PDMAEMA-block in the copolymers. The enrichment of the fiber surface in tertiary amino groups was studied by X-ray photoelectron spectroscopy (XPS). Increasing the copolymer content and the length of the PDMAEMA-block led to increase of the amount of tertiary amino groups on the fiber surface. The AFM analyses of the mechanical properties of the fiber surface showed that increasing the copolymer content led to decrease of the surface stiffness. The increase of the copolymer content led also to decrease of the melting temperature and the crystallinity degree in respect to PCL from the (co)polymer as determined by differential scanning calorimetry.
Polymers
New bio-based polymers capable of either outperforming fossil-based alternatives or possessing new properties and functionalities are of relevant interest in the framework of the circular economy. In this work, a novel bio-based polycarvone acrylate di-epoxide (PCADE) was used as an additive in a one-step straightforward electrospinning process to endow the fibres with functionalisable epoxy groups at their surface. To demonstrate the feasibility of the approach, poly(vinylidene fluoride) (PVDF) fibres loaded with different amounts of PCADE were prepared. A thorough characterisation by TGA, DSC, DMTA and XPS showed that the two polymers are immiscible and that PCADE preferentially segregates at the fibre surface, thus developing a very simple one-step approach to the preparation of ready-to-use surface functionalisable fibres. We demonstrated this by exploiting the epoxy groups at the PVDF fibre surface in two very different applications, namely in epoxy-based carbon fibre reinforce...
Silane crosslinking of electrospun poly (lactic acid)/nanocrystalline cellulose bionanocomposite
Materials Science and Engineering: C, 2016
Biodegradable nanofibrous mats fabricated by electrospinning are commonly used in tissue engineering, however, lack of essential mechanical properties of such nanofibers is a challenging issue. In this work, vinyltrimethoxysilane (VTMS) was grafted onto poly (lactic acid) (PLA) and the silane grafted PLA was subsequently applied in electrospinning process. Electrospun nanofibrous mats based on PLA/nanocrystalline cellulose (NCC) and PLA-gsilane/NCC nanocomposites were fabricated and immersed in hot water (70 °C) for crosslinking of silane grafted PLA. It was found that introducing NCC to the samples cause to reduction in fiber diameter and the other hand the silane crosslinking of PLA increase the mean fiber diameter. DSC thermograms also revealed that silane grafting caused a reduction in mobility of polymer segments, and consequently reduction of crystallinity. On the contrary, the NCC in the PLA-g-silane samples effectively influenced the crystal nucleation, while in the PLA nanofibers the nucleation was lower. The impact of NCC on tensile strength enhancement of samples was notable. The results suggested that the chemical crosslinking remarkably improves the mechanical properties of PLA nanofibers. Furthermore, biocompatibility of such modified nanofibers was also evaluated through cytotoxicity results, therefore the modified PLA nanocomposite can be considered as a practical candidate for hard tissue engineering applications.