In order to describe the thermomechanical properties in shape memory polymer of polyurethane series, a thermomechanical constitutive model was developed by modifying a standard linear viscoelastic model. The model involved a slip element due to internal friction and took account of thermal expansion. In order to describe the variation in mechanical properties due to the glass transition, coefficients in the model were expressed by a single exponential function of temperature. Several kinds of thermomechanical tests were carried out. The proposed theory expressed well the thermomechanical properties of the material, such as shape fixity, shape recovery and recovery stress. The proposed model is useful for design of shape-memory polymer elements, in which the amount of recovery deformation, the tightening force and the working start and completion temperatures are specified.

A poly(tert-butyl acrylate)-block-poly(2-cinnamoylethyl methacrylate), PtBA-b-PCEMA, sample was synthesized and characterized. After annealing at 105 ( 2 °C, the PtBA block formed densely packed cylinders inside the PCEMA matrix. Thin films of the diblock were obtained by microtomy. After PCEMA photo-cross-linking, the tert-butyl groups of PtBA were hydrolyzed, leaving poly(acrylic acid) chains in the loosely packed nanometer-sized cylinders. The permeability of water across such films varied by several orders of magnitude, depending on the pH of the aqueous medium or the types of cations in it. The possibility of using such nanochannels as templates for making further nanostructures was tested by filling the nanochannels with CdS or Fe 2 O 3 nanoparticles.

The shape fixity and recovery in a film of shape memory polymer of polyurethane series were investigated by the thermomechanical cycling tests with loading at various temperatures. The results are summarized as follows: (1) Strain is recovered at temperatures in the vicinity of the glass transition temperature Tg for loading above Tg, but it is recovered at temperatures in the vicinity of the midpoint temperature of glass transition for loading below Tg. (2) The rate of strain fixity is 98% for loading above Tg, while it decreases with increasing cycles for loading below Tg. (3) The rate of strain recovery for loading above Tg is 98% except for the early cycles. (4) The thermomechanical properties of materials with different Tg are quite alike in spite of the difference in Tg.

The low-cycle fatigue of a TiNi shape memory alloy was investigated by the rotating-bending fatigue tests in air, in water and in silicone oil. (1) The influence of corrosion fatigue in water does not appear in the region of low-cycle fatigue. (2) The temperature rise measured through an infrared thermograph during the fatigue test in air is four times as large as that measured through a thermocouple. (3) The fatigue life at an elevated temperature in air coincides with the fatigue life at the same elevated temperature in water. (4) The shape memory processing temperature does not affect the fatigue life. (5) The fatigue equation is proposed to describe the fatigue life depending on strain amplitude, temperature and frequency. The fatigue life is estimated well by the proposed equation. [S0094-4289(00)01102-6]

In this work the effect of 2 quorum sensing inhibitors on different clinical isolates of Pseudomonas aeruginosa was examined and some of the isolates were found to be resistant the inhibitors. The results are potentially useful for the clinic and for treatment of P. aeruginosa infections. AbstractThe quorum-quenching compounds brominated furanone C-30 and 5-fluorouracil inhibit the pathogenicity of the Pseudomonas aeruginosa laboratory strains PA01 and PA14; however, there is no report studying the effectiveness of these compounds for clinical isolates. Therefore, the effect of both quorum quenchers on the production of pyocyanin, elastase and alkaline protease of eight clinical strains from children was evaluated. Although both compounds were in general effective for the attenuation of these factors, three strains resistant to C-30 were found. For 5-fluorouracil, PA01 and some clinical isolates showed resistance for at least one phenotype.