ABSTRACT
Surfactants are frequently employed in the fabrication of polymer/graphene-based nanocomposites via emulsion techniques. However, the impact of surfactants on the electrical and mechanical properties of such nanocomposite films remains to be explored. We have systematically studied the impact of two anionic surfactants [sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS)] on intrinsic properties of the nanocomposite films comprising reduced graphene oxide in a matrix of poly(styrene-stat-n-butyl acrylate). Using these ambient temperature film-forming systems, we fabricated films with different concentrations of the surfactants (1-7 wt %, relative to the organic phase). Significant differences in film properties were observed both as a function of amount and type of surfactant. Thermally reduced films exhibited concentration-dependent increases in surface roughness, electrical conductivity, and mechanical properties with increasing SDS content. When compared with SDBS, SDS films exhibited an order of magnitude higher electrical conductivity values at every concentration (highest value of â¼4.4 S m-1 for 7 wt % SDS) and superior mechanical properties at higher surfactant concentrations. The present results illustrate how the simple inclusion of a benzene ring in the SDS structure (as in SDBS) can cause a significant change in the electrical and mechanical properties of the nanocomposite. Overall, the present results demonstrate how nanocomposite properties can be judiciously manipulated by altering the concentration and/or type of surfactant.
ABSTRACT
Poly(n-butyl methacrylate) (PnBMA)/reduced graphene oxide (rGO) nanocomposite films are prepared using two different routes. The first route involves preparation of PnBMA nanoparticles containing homogeneously dispersed rGO nanosheets by miniemulsion polymerization using a block copolymer of ionic liquid (IL) monomer and nBMA. The IL units act as adsorption sites for rGO whereas BMA units provide solubility in the BMA monomer droplets. Nanocomposite films obtained from miniemulsion polymerization exhibit higher tensile modulus in comparison with the films prepared by mixing a PnBMA emulsion and aqueous graphene oxide (GO) dispersion. The second route involves preparation of PnBMA particles armored with rGO nanosheets via miniemulsion polymerization using the same poly(ionic liquid) (PIL) block copolymer. An anionic exchange reaction is conducted to obtain more hydrophilic PIL units in the block copolymer, thus providing adsorption sites of GO nanosheets at the interface of the polymer particles. Subsequent chemical reduction of GO to rGO using hydrazine monohydrate results in formation of a PnBMA/rGO nanocomposite. The resulting nanocomposite film exhibits electrical conductivity (2.0 × 10-3 S m-1).
Subject(s)
Ionic Liquids , Nanocomposites , Graphite , Methacrylates , Polymerization , PolymersABSTRACT
Electrically conductive polymer/rGO (reduced graphene oxide) films based on styrene and n-butyl acrylate are prepared by a variety of aqueous latex based routes involving ambient temperature film formation. Techniques based on miniemulsion polymerization using GO as surfactant and "physical mixing" approaches (i.e., mixing an aqueous polymer latex with an aqueous GO dispersion) are employed, followed by heat treatment of the films to convert GO to rGO. The distribution of GO sheets and the electrical conductivity depend strongly on the preparation method, with electrical conductivities in the range 9 × 10-4 to 3.4 × 102 S/m. Higher electrical conductivities are obtained using physical mixing compared to miniemulsion polymerization, which is attributed to the former providing a higher level of self-alignment of rGO into larger linear domains. The present results illustrate how the distribution of GO sheets within these hybrid materials can to some extent be controlled by judicious choice of preparation method, thereby providing an attractive means of nanoengineering for specific potential applications.
ABSTRACT
We have developed a facile and industrially scalable method to synthesize colloidally stable polymer nanoparticles decorated with graphene oxide (GO) sheets via miniemulsion polymerization, which in turn enables the preparation of electrically conductive films using a simple dropcasting method at ambient temperature. The resulting nanocomposite films exhibited high electrical conductivity with a wide range of potential applications as conductive coatings.
