Methylcellulose attains the water‐solubility by reducing the strong hydrogen‐bonding. The reduction of the hydrogen bonding is achieved by partially substituting hydrophobic methoxy group for hydroxy group in cellulose. However, the substitution gives double‐bladed property to the aqueous methylcellulose, namely, excessive substitution makes again methylcellulose insoluble in water. Therefore, the water‐solubility of methylcellulose is strongly affected by the degree of substitution and moreover the distribution of the substituents. In this study, however, for a commercially available methylcellulose we have modified the cloud point by the addition of various organic salts. Sodium styrene sulfonate (NaSS) showed a strong salting‐in effect, whereas the polymeric NaSS, i.e., sodium polystyrene sulfonate (NaPSS), showed oppositely a salting‐out effect.

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A drug‐eluting fully bioabsorbable stent which is made of poly(L‐lactic acid) (PLLA) and coated with a drug using PLLA as coating substrate was developed. Drug release behavior from the stent was evaluated in vitro in terms of different molecular weights of substrate PLLA and different coating methods. Four different types of coating method including, PLLA spray coating on the PLLA stent followed by immersion in the drug solution (type 1), spray coating of PLLA/drug mixture (type 2), spray coating of PLLA/drug mixture followed by the heating process (type 3), and spray coating of PLLA/drug mixture followed by immersion in the drug solution (type 4), were employed. The inner and surface structures of the spray coated layer varied depending on the molecular weights of PLLA and/or the drug coating methods, and consequently led to the change in the amount of drug contained as well as the drug releasing behavior. Spraying a pure PLLA onto stent created a dense PLLA coating layer, which prevented the invasion of the drug deep in the layer, and the drug was just only adhered to the pure PLLA surface, resulted in the significant reduction of drug content on the stent surface. On the contrary, the spray coating of PLLA/drug mixture provided a porous layer, which allowed for the drug to invade deep into the layer and resulted in increase of drug content. Porosity and the size of the pore tended to decrease with increasing PLLA molecular weight, and drug release rate also decreased accordingly. Additional heat process facilitated PLLA crystallization, leading to significant reduction of the drug release rate.

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The laser drawing phenomena of syndiotactic polystyrene fiber was analyzed through a numerical simulation of fiber temperature profiles, and the structure and properties of laser‐drawn fibers were compared with the results of contact heater‐drawn fibers. The low oriented and amorphous as‐spun fibers could be drawn steadily up to 5.0 times by laser‐drawing with increasing laser power with the increase of draw ratio, while it could not be drawn over 4.4 times by heater‐drawing. The fiber drawn over 4.4 times by laser‐drawing showed saturating phenomena in birefringence, initial modulus, and elongation at break, while fiber strength solely continues to increase with draw ratio. As the results, higher maximum strength 400　MPa of laser‐drawn fiber than 374　MPa of heater‐drawn fiber, as well as higher toughness were obtained. In addition, laser‐drawn fiber showed larger d‐spacing along the lateral directions, larger crystallite size along the (002) direction, and higher melting temperature.

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