Macromolecular Research

New type of poly(N-vinylcarbazole) (PVK) polymer nanocomposites were prepared by a solid-state polymerization of N-vinylcarbazole in the presence of different concentration (wt%) of poly(3,4-ethylenedioxythiophene) (PEDOT). The prepared PVK/PEDOT nanocomposites were characterized by using Fourier transform infrared (FTIR) and UV-vis spectra. The transmission electron microscopy (TEM) and X-diffraction studies were performed to understand the surface morphology and nature of the polymer composites. The characterization and morphological studies suggest that there is a conjugation between PVK and PEDOT. Furthermore, the honeycomb-patterned films were obtained by dissolving the PVK/PEDOT nanocomposites into the chloroform solvent under humid conditions. The temperature-dependent DC electrical conductivity and room temperature photo-electrical conductivity of the honeycomb-patterned films were measured. Results showed that the incorporation of PEDOT in PVK polymer has greatly improved the electrical conductivity and photo-electrical behavior of the PVK/PEDOT nanocomposites.

We present simple, low-cost methods for the fabrication of polymeric waveguides that have large core sizes for use as optical interconnects. We have used both hot embossing and micro-contact printing techniques for the fabrication of multimode waveguides using the same materials. Rectangular and large-core (60 × 60 μm2) channels were readily prepared when using these methods. The dimensions of the embossed and printed channels were the same as those of the pattern on the original master. The polymeric waveguides that we fabricated with large core sizes exhibited a low propagation loss of 0.1 dB/cm at 850 nm, which indicates that hot embossing and micro-contact printing are suitable techniques for the fabrication of optical waveguides having large-core.

Mechanical stimuli should enhance cartilaginous tissue formation in elastic mechano-active poly(L-lactide-co-ɛ-caprolactone) (PLCL) scaffolds similar to what is observed in the body. The conditions for stem cell differentiation are also crucial for cartilage tissue engineering. Here, we investigate cartilaginous tissue formation of human adipose-tissue derived stem cells (hASCs)/hybrid scaffold constructs with fibrin gel and PLCL scaffolds. For this, hASCs were mixed with 1% or 5% fibrin gel and were subsequently seeded onto the PLCL scaffolds. Next, chondrogenesis was induced in vitro in the constructs with chondrogenic medium for 14 or 21 days to determine the optimal concentration of fibrin gel and pre-conditioning period. After pre-conditioning, the constructs were subcutaneously implanted in nude mice for up to 8 weeks. The constructs grown in 5% fibrin gel and induced for 21 days or 1% fibrin gel and induced for 14 days showed higher depositions of cartilage-specific extracellular matrix (ECM) components compare to the constructs in 5% fibrin gels that were induced for 14 days or 1% fibrin gels induced for 21 days. These results indicated that the constructs maintained in dense hydrogels need longer pre-conditioning periods for chondrogenesis. Consequently, the hybrid constructs in which chondrogenesis is appropriately induced in vitro could be used to engineer cartilage.

The side chain liquid crystal triblock copolymers (TBCs), which underwent phase transitions below their decomposition temperature, were prepared by copolymerization of poly(n-butyl acrylate) and a comonomer containing the mesogenic azobenzene group. The physical properties of TBCs in the distinctive transition temperature ranges were investigated in terms of the liquid crystal (LC) content in the copolymers. The phase transition temperatures traced optically, thermally and rheologically were well coincided one another and clearly exhibited the phase transition of smectic-nematic-isotropic with increasing temperature. In the smectic phase, increasing temperature made the liquid crystal system more elastic, but viscosity (η′) remained almost constant. In the nematic phase, increasing temperature abruptly decreased η′ andG′, ultimately leading to isotropic phase. Both smectic and nematic phases exhibited Bingham viscosity behavior but the former gave much greater yield stress at the same LC content.

In this study we prepared tissue-adhesive hemostatic glue and assessed hemostatic effects on hepatic bleeding animal model. Alginate was used as primary polymer for the fabrication of hemostatic glue, oxidized for the introduction of the tissue-adhesive Schiff base forming aldehyde and then encoded with mussel-inspired dopa. In addition, polyallylamine (PAA) was selected for as an intra-structuring polymer which ensures the gel strength and allows instantaneous glue formation on the bleeding spot. Primary glue (OA glue) was quickly formed within 5 to 10 seconds after the mixing oxidized alginate (OA) with PAA. The degree of oxidation and the mixing ratio of OA and PAA were precisely determined based on glue formation time and gel strength. And the extend of dopa conjugation on OA was determined by the tissue adhesion force and the elasticity of the glue (Dopa-OA glue). Especially, elasticity of Dopa-OA glue was significantly enhanced after introduction of dopa to OA. Functional assay of Dopa-OA glue on hepatic bleeding animal model showed much enhanced hemostatic action. Dopa-OA glue is expected to provide novel injectable tissue adhesives for the treatment of hemorrhage caused by clinical procedures or trauma.

Polypyrrole (PPy) was coated sequentially by chemical and electrochemical methods on a woven fabric, giving rise to a fabric having high electrical conductivity. We investigated the effects of the preparation conditions on the various properties of the resulting fabric. The PPy-coated fabric with optimum properties was obtained when it was prepared sequentially by chemical polymerization at the elevated temperature of 100 °C under a pressure of 0.9 kgf/cm2 and then electrochemical polymerization with a 3.06 mA/cm2 current density at 25 °C for 2 hrs with the separator plate. The surface resistivity of the resulting fabric was as low as 5Ω/□.The PPy-coated fabric prepared under the optimum conditions showed practically applicable heat generating property. When electrical power was supplied to the fabric using a commercial battery for a mobile phone (3.6 V, LGL1-AHM), the temperature of the fabric increased very quickly from room temperature to ca. 55 °C within 2 min and was maintained for ca. 80 min at that temperature. The heat generating property of the fabric was extremely stable, exhibiting similar behavior over 10 repeated cycles. Therefore, we suggest that the PPy-coated fabric in this study may be practically useful for many applications, including flexible, portable surface-heating elements for medical or other applications.

A simple strategy was developed based on polyelectrolyte/silver nanocomposite to obtain humidity-sensitive membranes. The major component of a humid membrane is the polyTEAMPS/silver nanocomposite obtained by thermal heating the mixture of a polyelectrolyte and silver isopropylcarbamate complex. Humidity sensors prepared from polyTEAMPS/silver (w/w=100/0 and 100/6) nanocomposites had an average impedance of 292, 8.83 and 0.86 kΩ, and 5,327, 140 and 0.93 kΩ at 30, 60 and 95% relative humidity (RH), respectively. Hysteresis, temperature dependence and response time were also measured. Activation energies and complex impedance spectroscopy of the various components of the polyelectrolyte/silver nanocomposite films were examined for the humiditysensing membrane.