Well-defined stimuli-responsive alkali-soluble poly(methacrylic acid)-block-[60]fullerene
(PMAA-b-C60) was synthesized via atom transfer radical polymerization (ATRP), and its aggregation
behavior in aqueous solution was examined using potentiometric and conductometric titrations, static
and dynamic light scattering, and transmission electron microscopic (TEM) techniques. PMAA-b-C60 shows
pH-responsive and water-soluble properties at high pH. In dilute solution, the micelles and large secondary
aggregates, which are independent of polymer concentration, coexist in solution. The R
h of micelles
increases from 6 to 10 nm with increasing degree of neutralization and remains constant at 10 nm with
the addition of salt. However, the R
h of large aggregates increases from 91 to 153 nm with increasing
degree of neutralization and decreases from 153 to 105 nm with increasing NaCl concentration. TEM
studies revealed that the large aggregates comprise of individual micelles and possess microstructure
similar to large compound micelles (LCM).
Well-defined water-soluble pH-responsive [60]fullerene (C60) containing poly(methacrylic acid) (PMAA-b-C60) was synthesized using the atom transfer radical polymerization technique. By varying pH and salt concentration, different types of fractal patterns at nano- to microscopic dimensions were observed for negatively charged PMAA-b-C60, while such structure was not observed for positively charged poly(2-dimethylaminoethyl methacrylate)-b-C60. We demonstrated that negatively charged fullerene containing polymeric systems can serve as excellent nanotemplates for the controlled growth of inorganic crystals at the nano- to micrometer length scale, and the possible mechanism was proposed.
Received February 18, 2005 We report the fabrication of phase-shifted long-period fiber gratings by use of a CO2 laser with a surface deformation technique and a point-by-point method. Due to periodicities that are structurally induced by a heat source and refractive-index modulation caused by a perturbational photoelastic effect, the results of thermal testing show a grating temperature coefficient of 28 pm/ degrees C at a range from 22 to 180 degrees C, indicating that the band rejections of the grating that is formed remain unchanged in their resonant strengths even at temperatures up to the fictive point of fiberglass. It is found for what is believed to be the first time that such a grating possesses an anomalous strain behavior of resonance with -1.52 x 10(-4) dB/muepsilon for the right notch and 7.05 x 10(-5) dB/muepsilon for the left notch.
We demonstrate what is believed to be the first fabrication of a wide-passband, temperature-insensitive, and compact spectral filter based on a pi-phase-shifted long-period grating in an endless single-mode photonic crystal fiber. By introducing a pi-phase shift in the middle of a 12-period long-period grating, two symmetrical rejection bands at wavelengths of 1252.65 and 1418.7 nm are obtained with isolation higher than 18 dB and a passband bandwidth of 84.15 nm. The pi-phase-shifted long-period gratings are inscribed by the relaxation of mechanical stress with the focused pulses of a CO2 laser and a point-by-point technique without geometric deformation. The length of the spectral filter is approximately 6.6 mm with a sensitivity of 8 pm/ degrees C at a medium temperature range of 23-190 degrees C.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.