Browsing by Subject "Critical phenomena"
Now showing items 1-6 of 6
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Critical Exponents of Gelation and Conductivity in Polyacrylamide Gels Doped by Multiwalled Carbon Nanotubes
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Publisher and Date:(Taylor & Francis Ltd, 2010)Polyacrylamide (PAM) doped by multiwalled carbon nanotube (MWNT) gels were prepared with different amounts of MWNTs varying in the range between 0.1 and 15 wt%. The PAM-MWNT composite gels were characterized by the steady state fluorescence technique (SSF). The alternative electrical conductivity (AC) of PAM-MWNT composite gels was measured by the dielectric spectroscopy technique. Observations around the gel point t(gel) for PAM-MWNTs composite gels showed that the gel fraction exponent beta ...
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Fractal dimension and phase transition of graphene oxide (GO) doped polyacrylamide
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Publisher and Date:(ELSEVIER SCI LTD, 2020)Graphene Oxide (GO)- Polyacrylamide composites prepared between 5 and 50 mu l GO were performed by Fluorescence Spectroscopy. The phase transition performed on the composites was measured by calculating the critical exponents, beta and gamma, respectively. In addition, fractal analysis of the composites was calculated by a fluorescence intensity of 427 nm. The geometrical distribution of GO in the composites was calculated based on the power law exponent values using scaling models. While the ...
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Gelation of PAAm-PVP composites: A fluorescence study
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Publisher and Date:(World Scientific, 2014)Hybrid hydrogels are a new class of composite materials. Polyacrylamide (PAAm) hydrogels are mainly produced by free radical crosslinking copolymerization (FCC) of AAm in the presence of N N'-methylene bis (acrylamide) (BIS) as the crosslinker. Pyranine doped PAAm-poly (N-vinyl pyrrolidone) (PVP) composite were prepared with different amounts of PVP varying in the range between 0.0015 and 0.1 gr. It was observed that pyranine molecules as a fluoroprobe bind to AAm and PVP chains upon the initiation ...
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Monitoring the gelation of polyacrylamide-sodium alginate composite by fluorescence technique
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Publisher and Date:(Taylor & Francis Ltd, 2012)Polyacrylamide (PAAm)-sodium alginate (SA) composite was prepared with different amounts of SA varying in the range between 0.06% and 2% (w/v). The PAAm-SA composite was characterized by the steady-state fluorescence technique. Pyranine was added as a fluoroprobe for monitoring the polymerization. It was observed that pyranine molecules bind to AAm and SA chains upon the initiation of the polymerization. Thus the fluorescence spectra of the bonded pyranines shift to the shorter wavelengths. ...
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Phase Transitions in Pure and Hybrid Hydrogels: A Fluorescence Study
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Publisher and Date:(Wiley, 2009)Recent observations on phase transitions around the critical point showed that the critical exponents differed drastically from percolation results and classical results for pure hydrogel systems depending on monomer concentration. in addition to pure hydrogels the sol-gel phase transition during radical crosslinking copolymerization of acrylamide (AAm) and N-isopropylacrylamide (NIPA) hybrid was studied by using the steady state fluorescence (SSF) technique. NN'-methylenebis(acrylamide) (BIS) and ...
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Steady state fluorescence technique for studying phase transitions in PAAm-PNIPA mixture
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Publisher and Date:(Taylor & Francis, 2009)The steady state fluorescence (SSF) technique was used to study the sol-gel phase transition during free radical crosslinking copolymerisation of various amounts of acrylamide (AAm) and N-isopropylacrylamide (NIPA) mixtures. NN'-methylenebis (acrylamide) (BIS) and ammonium persulfate (APS) were used as crosslinker and an initiator respectively. Pyranine (8-hydroxypyrene-1 3 6-trisulfonic acid trisodium salt HPTS) was added as a fluoroprobe for monitoring the polymerisation. It was observed that ...
