Critical Exponents of Gelation and Conductivity in Polyacrylamide Gels Doped by Multiwalled Carbon Nanotubes

Abstract

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 obeyed the percolation result. The critical exponent r of AC electrical conductivity for the composite PAM-MWNT gel was also measured and found to be about 2.0, which agrees with a random resistor network. (C) Koninklijke Brill NV, Leiden, 201

The Graphene Oxide Effect on the Optical Properties of Nipa-Go Composites

“…During the gelation process, the wavelengths behave to increase to the 427 nm-peak, and decrease to the 512 nm-peak, and also the short wavelength at 380 nm shifting through 427 nm which gives the information about the interaction between the monomer, GO and pyranine as defined in the previous studies (14)(15)(16)(17)19). Because pyranine is a fluorescent probe and its photophysical properties are well characterized and can be bound to polymeric structure because of having three functional groups (20).…”

Monitoring the gelation of polyacrylamide–sodium alginate composite by fluorescence technique

“…However, classical results were produced at high carrageenan content (42.0%). On the other hand, PAAm-PNIPA and PAAm-MWNT composites show that the gel fraction exponent obeyed the percolation result [21,22]. In this study, the critical exponents of AAm-SA composite gels were investigated for various SA contents and it was observed that the gel fraction exponent and agree best with the percolation theory for (50.25% (w/v)) SA contents.…”

“…By adding a luminescent dye as a probe, it is possible to measure some physical parameters of the polymerizing system, such as polarity [15,16], physical aging [17], mobility [18], and viscosity [19]. Recent studies in our laboratory, using pyranine as an intrinsic fluoroprobe, showed that the universality of composite gels could be described by classical and percolation exponents during the solgel phase transition in PAAm-kappa()-carrageenan [20], PAAm-PNIPA [21], and PAAm-multiwalled carbon nanotube composites (MWNTs) [22]. In composite hydrogels, it is found that the critical exponents did not follow the features of the same universality class, where the most important factor is the monomer content in which the exponents drastically differ from percolation to the classical values.…”

“…showed that the produced critical exponents follow the features of different universality classes for AAm [39], PAAm-kappa()-carrageenan [20], PAAm-PNIPA [21], and PAAmMWNTs [22] composite gels. In AAm hydrogels, it was shown that the critical exponents agree best with the percolation results for high AAm contents above 1 M, but they cross over from percolation to classical (mean-field or Flory-Stockmayer) values when the AAm content goes from 2 M to lower values down to 1 M, and present classical values below 1 M. Further down, below 0.5 M, however, no gelation was observed [39].…”

Drying of polyacrylamide-multiwalled carbon nanotube (MWNT) composites with various MWNTs contents: a fluorescence study

“…The solution was stirred (200 rpm) for 15 min to achieve a homogenous solution. All samples were deoxygenated by bubbling nitrogen for 10 min just before the polymerization process [19] ; each pre-composite gel solution of 5 ml was poured into a cylindrical glass tube and injector for the drying experiment. Before drying was started, composites were cut into discs with a diameter of 10 mm and a thickness of 4 mm from the injector.…”