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A novel approach to simultaneously improve the physical mechanical properties and tune the biodegradation of polycaprolactone (PCL)-based composites is presented. The viability of electrospun fibers as fillers for polymer nanocomposites is shown. Nylon was chosen as the reinforcing material, whereas polyvinylpirrolidone (PVP) was selected to calibrate the biodegradation rate. Nylon fibers were effective reinforcing fillers for the PCL matrix, also in co-presence with PVP fibers. PVP fibers were, on the other hand, critical in shaping the biodegradation behavior, because they were able to create channels by which water can easily penetrate within the bulk of the material. The cooperative effect of nylon and PVP fibers allowed to obtain composites able to degrade more quickly than the matrix or than the samples containing either of the two fibers, while retaining a remarkable dimensional stability even after 20% of the total mass had degraded.

We demonstrate for the first time herein that the successive electrospinning can change the fiber morphology in the electrospun mat of the polymer at the same electrospinning parameters. Two types of fibers (nano and sub-nano size) arranged in a spider-net like structure were obtained from the single polymer nylon-6 by electrospinning. FE-SEM images of the mats at different applied voltage showed that this network consisted of thin nanofibers with diameters of about 8–29 nm and thick nanofibers with diameters of about 80–292 nm, arranged in a spider-net like structure. The successive electrospinning sufficiently decreased the diameter of the main nanofibers and hardly change the diameter of the thinner fibers. The study of FT-IR spectra and the conductivity of the different mats in acidic solution showed that the formations of spider-net structure were due to the formation of stronger hydrogen bonds between ionized oligomer/monomer and polymer molecules. The possible mechanism of hydrogen bonds formation during electrospinning was proposed. These spider-net structures with high aspect ratio were responsible to increase the mechanical strength of nylon-6 mat.

A methoxy poly(ethylene glycol) (MPEG) oligomer with a viscous nylon-6 supporting solution was fabricated and polymerized simultaneously to form a nanofiber network structure via electrospinning. This network consisted of thin MPEG nanofibers and thick nylon-6 nanofibers, which were arranged in a spider-web like structure. These two different nanofibers were separated from the electrospun mat by extraction of MPEG using water. This result showed that the hybrid nanocomposite mat consisted of two different interconnecting polymeric nanofibers. We propose that this interconnection is due to the formation of hydrogen bonds between MPEG and nylon-6 molecules. This spider-web structure formed by electrospinning was responsible for increasing the mechanical strength and the wetability of nylon-6 mat in the presence of small amounts of MPEG.

A novel biodegradable graft copolymer, dextran-g-poly(1,4-dioxan-2-one) (PODEX), was synthesized through the ring-opening polymerization (ROP) of 1,4-dioxan-2-one (PDO) onto a dextran backbone. Initially, dextran was silylated with 1,1,1,3,3,3-hexamethyldisilazane. The grafting from pathway was conducted with various (30–70) PDO/OH feed ratios to obtain PODEX copolymers with a various PPDO graft structures. Graft copolymers were characterized by FT-IR, 1 H and 13 C NMR, DSC, TGA, and WAXD. Molecular weights of the PODEX copolymers ( M W : 94,700–117, 300 Da), glass transition temperature (−29 to −17 °C), melting temperature (82–100 °C), and crystallinity (32–40%) were increased with the content of PPDO. AFM observations revealed that polymeric micelles were spherical and uniform in morphology with around 30–58 nm diameter. Critical micelle concentration (CMC) of self-assembled system was significantly decreased from 3.2 to 1.09 mg/L with the increment of PPDO.

Acrylic acid monomer in a viscous supporting nylon solution was polymerized and fabricated simultaneously via an electrospinning process. This novel polymerization method defines the fiber morphology as a network of interconnected mats. This network consists of smaller poly(acrylic acid) (PAA) fibers, approximately 19 nm in diameter, and larger nylon 6 fibers, approximately 75 nm in diameter. These two different fibers are separated by extraction of PAA from the fibrous mat in water and differentiation of field-emission scanning electron microscopy (FESEM) images of the same mat using before and after extraction of PAA. The structure of the extracted PAA was confirmed by 1H NMR and Fourier transform infrared (FT-IR) analysis. The observed modification to conventional electrospun mats is due to the presence of an extra phase-separated PAA produced by the electrospinning polymerization process. Finally, fiber morphologies and hybrid property were characterized via FT-IR, FESEM, thermogravimetric analysis, and X-ray diffraction. Similarly extracted samples and synthesis PAA were characterized in FT-IR and 1H NMR spectroscopy.

Brush copolymers composed of methoxy poly(ethylene glycol) (MPEG) and poly(e-caprolactone) (PCL) have been synthesized by the ring-opening polymerization of e-caprolactone initiated by hydroxyl function of thermally esterified MPEG-citrate in presence of stannous octoate. Citric acid (CA) acts as spacer between brush-like MPEG and the long chain of PCL. Existence of hydrophobic domains as cores of the micelles were characterized by 1H NMR spectroscopy and further confirmed with fluorescence technique using pyrene as a probe. Critical micelle concentration (CMC) of the synthesized copolymer decreased from 0.019 to 0.0031 mg/mL on increasing the fraction of PCL. Along with the physicochemical study, the brush copolymers were explored for the preparation of nanoparticles by nanoprecipitation technique. The morphology and geometry of micelles were investigated by using DLS, AFM, and TEM. Hydrodyanamic dimensions of micelles were around 118 and 178 nm with the core size of 8–10 nm, which further aggregated to form secondary micelle of 60–90 nm. Such assembled polymeric micelles with its flexible dendritic MPEG corona could hold a promise for the immobilization (encapsulation) of hydrophobic drugs and subsequently promote sustained release so that it can be a good vehicle for anti-cancer drug deliverance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The main objective of the present work was to fabricate poly(ϵ-caprolactone) grafted dextran (PGD) electrospun matrix (matrix) and to investigate the scaffold potential in tissue engineering application. In this work, at first we synthesized PGD polymer via ring opening polymerization (ROP), and with predetermined electrospinning conditions, nanofibrous matrix with high molecular weight PGD (PGD-50, Mw = 45,500) has been successfully fabricated for the first time. Mouse osteoblast like cells, MC3T3 was used to test biocompatibility, assays of cell adhesion, survival, and effects on cell morphology of the matrix. The data demonstrate that PGD-50 matrix represent a suitable substrate for supporting cell proliferation, process outgrowth and migration and as such would be a good material for artificial extra cellular matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Poly(lactide) (PLA) composites filled with electrospun nylon 6 fibers were prepared. This allowed us to simultaneously improve the mechanical properties and tune the degradation of the PLA matrix. The interfacial adhesion between the PLA matrix and the nylon fibers was good. The major effect of electrospun fibers on the matrix was that of modifying the semicrystalline framework, thickening the polymer lamellae. This allowed an increase in the mechanical properties of the material, and on the other hand to modify its degradation behavior. The modulus of the composites was increased up to 3-fold with respect to neat PLA. The peculiar morphology of matrix–filler interaction moreover slowed down the degradation rate of the material and improved the dimensional stability of the specimens during the degradation process. This shows the potential of electrospun fibers as a way to tune the durability of PLA-based products, widening the range of application of this promising material.

In this study, electrospun nylon-6 spider-net like nanofiber mats containing TiO(2) nanoparticles (TiO(2) NPs) were successfully prepared. The nanofiber mats containing TiO(2) NPs were characterized by SEM, FE-SEM, TEM, XRD, TGA and EDX analyses. The results revealed that fibers in two distinct sizes (nano and subnano scale) were obtained with the addition of a small amount of TiO(2) NPs. In low TiO(2) content nanocomposite mats, these nanofiber weaves were found uniformly loaded with TiO(2) NPs on their wall. The presence of a small amount of TiO(2) NPs in nylon-6 solution was found to improve the hydrophilicity (antifouling effect), mechanical strength, antimicrobial and UV protecting ability of electrospun mats. The resultant nylon-6/TiO(2) antimicrobial spider-net like composite mat with antifouling effect may be a potential candidate for future water filter applications, and its improved mechanical strength and UV blocking ability will also make it a potential candidate for protective clothing.

Electrospun fibres are very rarely used as reinforcing agents in polymer-based composites. A fabrication approach is presented that allows to easily prepare composites based on polycaprolactone (PCL) filled with nylon 6 electrospun fibres by compression moulding. At very low filler contents (3%), the obtained composites exhibited improved stiffness with a simultaneous increase in ductility, differently from what is usually found in PCL nanocomposites with a variety of fillers, in which increases in modulus happen at the expense of elongation at break. The presence of fibres with a very small diameter, typical of the products of electrospinning, favoured a good interfacial adhesion between matrix and filler. Being of a similar order of magnitude than polymer lamellae, electrospun fibres can be used to shape the morphology of lamellar stacks, and therefore the final properties of the composites.

A chemically-etched titanium surface was modified by electrospinning a sol-gel-derived hydroxyapatite (HAp) that was subjected to calcination within the temperature range of 200-1400 degrees C in the normative atmospheric condition. After heat treatment, crystal structures of the filmed titanium oxide and HAp on the titanium's surface were identified using wide-angle X-ray diffraction. A highly porous layer of HAp was found to have formed on the oxidized titanium surfaces. The surfaces of three different samples; (1) electrospun HAp, (2) HAp calcined at 600 degrees C, and (3) HAp calcined at 800 degrees C, were investigated for their ability to foster promotion, proliferation, and differentiation of human osteoblasts (HOB) (in the 9th passage) in vitro up to 6 days. Among the three samples, cells cultured on the HAp calcined at 800 degrees C titanium surfaces displayed the best results with regard to adhesion, growth, and proliferation of HOB. This novel method for fabrication of titanium substrates would provide a promising improvement for titanium-based medical devices over the current standards, which lack such substrates. These titanium substrates explicitly provide enhanced HOB proliferation in terms of both desired surface properties and their produced bulk quantity.

A novel particulate nanofibrous hydroxyapatite (HA), which mimics the bone matrix, is presented as a surface functional material to modify silicon wafers by the electrospinning method. The HA precursors were treated with viscous polymer solution, and then electrospun under controlled conditions. After successive calcinations, the powder X-ray diffraction patterns of the samples revealed reflection toward the (300) HA plane that is linear with temperature. This prominent reflection suggests the crystallographic purity of the HA. Biocompatibility, cell proliferation, and microstructure were examined using AFM and FE-SEM. Morphology showed cell spreading and penetration instead of cell aggregation. The surface roughness as well as adhesion force was calculated using contact mode AFM. The results show that the composite matrix holds promise for use as a bone implant material.