Preparation of alkylated graphene oxide layers for polymer composites

Graphene oxide has the same two-dimensional sp2 carbon nanostructure of graphene but it is characterized by the presence of hydroxyl and epoxy functional groups on the sheet surface, moreover carbonyl groups are present as carboxylic acid along the sheet edge and also as organic carbonyl defects within the sheets1,2. Graphene oxide is attracting a great research interest as the most common preparation method of graphene starts from the oxidation and exfoliation of graphite to graphene oxide (GO)3-5: afterwards it can be reduced to graphene through thermal or chemical methods. Moreover the functional groups in the GO structure give to this material hydrophilic properties allowing the easy preparation of stable and homogeneous GO dispersion in water6: wet-chemistry approaches are the most desirable methods for the large scale integration of reduced GO for the production of GO-based polymeric nanocomposites. The possibility to use soluble alkylated reduced GO nanosheets as fillers in polymeric nanocomposites films7,8 was investigated. For this approach the critical issue in terms of physical properties and film uniformity is the aggregation of the reduced GO sheets after the dispersant evaporation. The formation of aggregates of GO layers after the filler mixing with the polymer matrix can produce a worsening of the material properties: in the case of the development of transparent electrodes for applications in the area of optoelectronics it could result in the reduction of the optical transparency and conductivity of the graphene/polymer composites. Along this line, the current interest is designing new soluble polymer-modified reduced graphene oxide materials that can be directly used to fabricate graphene-based molecular photoresponsive devices.