Synthesis of polypyrrole/polythiophene copolymers in supercritical carbon dioxide

Conductivity and dielectric analysis of nanocolloidal polypyrrole particles functionalized with higher weight percentage of poly(styrene sulfonate) using the dispersion polymerization method

Nanocolloidal polypyrrole/poly(styrene sulfonate) PPy:PSS composites were prepared by dispersion polymerization of pyrrole with 0.5 wt%, 1 wt%, 2.5 wt%, 5 wt%, 10 wt% and 15 wt% of PSS. Higher doping level of PPy was confirmed with increased S/N value of elemental analysis. Morphological variations of PPy composite matrix based on PSS were analyzed in which spherical shaped PPy particles of 20–40 nm were obtained for 1:1 wt% of PPy:PSS. Presence of higher concentration of PSS within the PPy matrix substantially improved its thermal stability. Dielectric properties were investigated using complex impedance analyzer as a function of frequency (50 Hz–5 MHz) and temperature between 30°C and 120°C. PPy, with improved dispersion, showed higher dielectric constant values up to 15 wt% of anionic polyelectrolyte PSS and the dielectric loss varied between 4.7 and 7.9 for different wt% of PSS. AC conductivity (σac) enhanced up to 1:1 wt% of PPy:PSS composite, which is found to be the optimum wt% in this study. DC conductivity was found to decrease after 1:1 wt% of PPy:PSS composite, which is due to excess oxidation, leading to reduced π conjugation of PPy chains. Higher dielectric constant values of composite, with relatively low dielectric loss values, indicate their potential usage in the electric and electronic industry.

Preparation of high-strength microporous phenolic open-cell foams with physical foaming method

A series of high-strength and highly microporous phenolic open-cell foams modified by different epoxy resins were fabricated using physical foaming method. The new compound emulsifiers consisting of anionic and nonionic surfactants were physical blended at high speed with modified resols, foaming agent, and mixed acid curing agent. The modified synthesis of epoxy-modified phenol-formaldehyde (PF) resin was conducted via the etherification mechanism. In order to verify the occurrence of etherification mechanism by co-reaction between resole methylol, hydroxyl group, and ring-opening epoxy group and to characterize the structure successfully, Fourier transform infrared spectroscopy, carbon-13 (13C) and proton nuclear magnetic resonance (1H NMR) had been used to characterize the structure successfully. The phase of resols and curing behavior were characterized. Fabricated foams were characterized for cellular, water absorption, apparent density, and mechanical and thermal properties. The results show epoxy modified resol demonstrated single uniform phase. The open-cell micropore structure revealed by scanning electron microscopy (SEM) demonstrates that smaller and more homogeneous cells existed with increasing dosage of epoxy. When the content of epoxy increased from 0 wt% to 10 wt%, the thermal conductivity, water absorption, and porosity of PF gradually increased. The highest open-cell porosity reached up to 90.959%. The differential scanning calorimetry and gel time data demonstrated that modified resols exhibited less gel time and lower endothermic and curing exothermic heat. Anionic surfactant, sodium dodecyl sulfonate, which was better compatible with resol, promoted the formation of open cells and produced good homogeneous and moderate micropores. In addition, the high-strength open-cell PF possessed excellent filterable and separation performance and absorbency. The porous micropore structure controlled by the content of epoxy resin and the ratio of sodium dodecyl sulfate /Tween80 greatly improved the mechanical strengths of PF.