PET-based biodegradable fibers were obtained using two-step process; (1) melt spinning at several winding speeds, and (2) hot-drawing at various drawing rates. Two kinds of polymers were used in this study and the fibers from them were characterized by several analyzing techniques such as tensile test, X-ray diffraction, scanning electron microscope, etc. At fixed extrusion rate, the mechanical properties of as-spun fibers were dependent on the winding speed. The higher winding speed resulted in the higher modulus and strength, and the lower elongation at break. At fixed drawing temperatures of rollers, the mechanical properties of the drawn fibers were also strongly dependent on the drawing rates. The drawn fibers showed the increased orientation upto 94% and breaking strengths of 4.2~4.8 g/d.

Transdermal drug delivery system has various merits compared to oral drug delivery system. Polyurethane nonwovens have been attracted as backing materials for patch and wound dressing, as they have superior stretchability and breathablility to films. The previous works on thermoplastic polyurethane nonwovens were mainly focused on the effects of meltblow processing parameters rather than pore, through which the infection can be occurred. It is critical to reduce the pore size without sacrificing the air permeability. In this study, we developed polyurethane composite nonwovens by combining the meltblowing and electrospinning processes. The composite nonwoven showed less than $3{\mu}m$ of mean pore diameter with maintaining the air permeability. The load-elongation curve showed excellent adhesion between the meltblown and the electrospun layers even at large elongation. The excellent pore properties and stretchability of the composite nonwoven can be very useful for patch backing materials.

Nanocomposite films of poly(ethylene terephthalate)(PET) and nano titania($TiO_2$) were prepared by melt compounding with a twin-screw extruder followed by hot pressing for the purpose of investigating antibacterial activity. FE-SEM, EDS and XRD measurements confirmed that nano $TiO_2$ was successfully dispersed at the level of individual particles in the PET matrix. Silver was introduced through photocatalytic reduction by nano $TiO_2$ under UV (254 nm) irradiation to the nanocomposite films after being immersed in aqueous solution $AgNO_3$ (100 ppm Ag ion). Even at 1 wt% of $TiO_2$ content, the nanocomposite with silver photodeposition exhibited strong antimicrobial activity against Klebsiella pneumoniae and Staphylococcus aureus in measurement by shaking flask method.

Two kinds of semi-aromatic polyamide terpolymers based on the isomorphic replacement copolymer system of poly(hexamethylene adipamide-co-hexamethylene terephthalamide) (PA 66/6T), that is, poly(hexamethylene adipamide-co-hexamethylene terephthalamide-co-hexamethylene sebacamide) (PA 66/6T/610) and poly(hexamethylene adipamide-co-hexamethylene terephthalamide-co-hexamethylene isophthalamide) (PA 66/6T/6I), were synthesized by melt polycondensation in order to study the effect of comonomer structure on the properties of terpolyamides. Although the incorporation of the 610 or 6I in the PA terpolymers led to overall depression in the thermal properties of terpolymers, PA 66/6T/610 exhibited noticeably higher thermal properties such as melting point ($T_m$), heat of fusion (${\Delta}H_m$), and tensile mechanical performances as well as lower water absorption than those of PA 66/6T/6I. The lower water absorption might be originated from the enhanced chain mobility and the lower density of amide bond owing to the long aliphatic chain of the sebacic acid. On the other hand, the glass transition temperatures ($T_g$) of PA 66/6T/6I copolymers increased with the increment of the 6I content, which was resulted from the reduced chain mobility due to the rigid aromatic structure of the comonomer.

The poled PVDF film sensor with thin silver electrode on both surfaces was coated with conductive carbon paste followed by silicon elastomer/carbon black mixture coating. This process gave it EMI shielding as well as enhanced toughness. The physiological sensing belt(PSB) for respiration monitoring was made by embedding the silicone rubber/carbon black/conductive carbon layer coated PVDF film between elastic textile bands. The sport bra having PSB could be well applied to respiration monitoring for the woman wearing it with very low motion artifact even during walking and running.

Polymers containing POSS(polyhedral oligomeric silsesquioxane) nanostructures show improved properties such as thermal stability, mechanical properties and oxidation resistance. Polyacrylonitrile(PAN) is one of the most widely used precursors for carbon fibers. However, PAN homopolymer has poor chemical, mechanical and thermal properties. A certain amount of suitable acidic comonomers is incorporated into PAN during polymerization for enhancing the solubility, the spinnability and especially, the thermo-oxidative stabilization. Among the acidic comonomers, IA(itaconic acid) is the preferably and the most widely used one because of the presence of two carboxyl group, which provides more opportunities for the carboxyl groups to interact with the nitrile groups during stabilization. In this work, we used Octa amic acid POSS having two carboxyl groups, to improve the properties of PAN copolymer. We investigated the effect of POSS addition during polymerization on the thermal properties of PAN copolymer. P(AN-IA)/POSS was prepared in dimethylsulfoxide (DMSO) by solution polymerization. Thin films of P(AN-IA)/POSS were prepared by spin coater using solution cast technique. The films were stabilized at different temperatures for various holding time. The structural evolution and the thermal properties of P(AN-IA)/POSS were studied by Fourier transform infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). From those results, the cyclization of nitrile groups was found to be initiated at lower temperature with increasing POSS contents and stabilization proceeded at more moderate pace in P(AN-IA)/POSS than PAN.

To develop shape memory foam for the insole of footwear, two types of hydrogenated styrene-butadiene random copolymer(HSBR) and ethylene vinyl acetate(EVA) foams were produced, and the effects of content of crosslinking agent on both physical and shape memory properties have been studied. Expansion ratio and permanent deformation of the foams decreased with increasing content of crosslinking agent. The result showed that tear strength and resilience of the foams are independent of the amount of crosslinking agent, but rely heavily on the type of resin within the experimental range. Increasing sulfur ratio of the crosslinking agent increased the shape recovery ratio of the foam, but decreased the shape retention characteristics under compression.

Pedometer, tri-axial accelerometer, and measuring system of $CO_2$ generated during metabolism have mainly been used to measure the quantity of motion and inhaling capacity while walking or running. However, these sensors are heavy, expensive, and uncomfortable to wear and difficult to check the work-out condition. In an attempt to overcome these limitations, a soft, flexible, and lightweight piezoelectric polymer-based sensor has been prepared. The PVDF film sensor with thin silver-paste layers in both sides was coated with silicon rubber to amplify stress by the external power such as tension and pressure. Thus, movement of thigh muscles was monitored and physical activity was predicted during walking and running, with an elastic belt embedded with the prepared PVDF film sensor, which was named as a physiological sensing belt (PSB), strapped on the thigh.

The purpose of this study is to improve interfacial adhesion strength of carbon fiber reinforced hybrid composites by physical and chemical treatment. Ultrasonic irradiation was used as physical and chemical treatment relatively. The morphologies of fracture-section and surface of carbon fiber fabric/CNT reinforced hybrid composites were observed by SEM. The morphologies of specimens treated with ultrasonic showed rougher and more compact surfaces than those of untreated specimens. The specimens treated with ultrasonic showed higher impact strength compared with untreated specimens. This result showed ultrasonic irradiation is one of the effective method to improve interfacial adhesion strength between carbon fiber and matrix.

Solution-processed small molecular semiconductors (soluble acenes) serve as ideal active materials for high-performance, printed organic thin-film transistors (OTFTs). However, device stability of soluble acene TFTs has not been intensively studied. Here, we showed that device stability of soluble acene TFTs can be significantly enhanced by the use of polymer/inorganic hybrid gate-dielectrics. Triethylsilylethynyl-anthradithiophene (TES-ADT) TFTs fabricated on polystyrene (PS)/$Al_2O_3$ hybrid gate dielectrics exhibited high performance such as high field-effect mobility ($0.6cm^2/Vs$) and on-off current ratio ($10^6$). In addition, transfer characteristic of the TFTs did not shift under the prolonged gate-bias (8000s). This outstanding device stability is due to the device structure which consists of highly crystalline TES-ADT crystals and trap-free PS/$Al_2O_3$ dielectric.