A simple process for fast fabrication of thin films with biomimetic morphological structures from a group of linear homopolymers is developed. Natural evaporation of tetrahydrofuran, chloroform, and hexane-dichloromethane solutions of poly(phenylacetylene)s that contain amino acid and ethylene glycol moieties under ambient conditions instantly produces three-dimensional porous films with structural patterns reminiscent of honeycombs and radiolarian shells. Morphological analysis by optical and electronic microscopy suggests that vesicles of the amphiphilic polymers serve as building blocks in the self-organization to the biomimetic structures.
Because of its slowly crystallizing nature, poly(ethylene terephthalate) (PET) can be supercooled into an amorphous glass by rapid quenching. Upon reheating between T g and T m , the amorphous PET are subjected to two competing processes: rubber softening and crystallization. Fusion bonding of two such crystallizable amorphous polymer sheets in this processing temperature window is thus a complex process, different from fusion of purely amorphous polymer above T g or semicrystalline polymer above T m . In this study, the interfacial morphological development during fusion bonding of supercooled PET in the temperature window between T g and T m was studied. A unique double-zone interfacial morphology was observed at the bond. Transcrystals were found to nucleate at the interface and grow inward toward the bulk and appeared to induce nucleation in the bulk to form a second interfacial region. The size and morphology of the two zones were found to be significantly affected by the fusion bonding conditions, particularly the fusion temperature. The fusion bonding strength determined by the peeling test was found to be significantly affected by the state of crystallization and the morphological development at the bonding interface. Based on the interfacial morphology observed and the bonding strength measured, a fusion bonding mechanism of crystallizable amorphous polymer was proposed.
At present, the application of carbon isotope is becoming more and more extensive, especially in the field of medical testing, and the demand for 13C in high abundance is fast increasing. Using carbon tetrafluoride (CF4) as separation medium, study on centrifugal separation of carbon isotopes was carried out. Single-centrifuge experiments were done based on modified domestic gas centrifuges. As a result, the separation factor and single-centrifuge separative power under different working conditions were obtained. Based on the results of single-centrifuge separation experiments, cascade calculation of the enrichment of 13C isotope was conducted by ideal cascade. According to calculation results, through two cascade separations, 13C isotope could be enriched from 30% to above 99% in abundance. The study laid a good basement for production of 13C isotope in high abundance.
We report here that well-aligned carbon nanotubes with open tips can be directly obtained by introducing carbon dioxide during the chemical vapor deposition process. In-situ oxidation of carbon nanotubes by carbon dioxide results in the strip off of nanotube tips, however, without damaging the nanotube alignment. Such oxidation of aligned nanotube arrays, whose tips are all on the array surface, is more efficient than the oxidation of disordered nanotubes. Aligned carbon nanotube arrays with open tips have potential applications in field emission, filter membrane, and energy storage.
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