M.Sc Thesis

M.Sc StudentRegueira Ramiro
SubjectHybrid Electrically Conducting Systems:
DepartmentDepartment of Polymer Engineering
Supervisors PROFESSOR EMERITUS Moshe Narkis
PROF. Gideon Grader
Full Thesis textFull thesis text - English Version


Graphene has drawn much attention in recent years. Graphene possesses remarkable properties i.e. mechanical properties, electrical and thermal conductivity, thus offering opportunities for development of new nanocomposites. Homogeneous dispersions of nanoparticles in polymers using conventional processing techniques is difficult since nanoparticles tend to agglomerate, thus efficient methods for agglomerate breakdown have been sought in recent years.

This work describes an in-situ inverse emulsion polymerization method of aniline in the presence of graphene nanoplatelets in organic solvents using ultrasonication.  In this dynamic inverse polymerization process the graphene nanoplatelets were coated with Polyaniline (PANI). Cryogenic transmission electron microscopy (Cryo-TEM) and High-resolution scanning electron microscopy (HR-SEM) showed that nanoplatelets are coated with PANI, leading to an improved dispersability, thus the PANI coating reduces the tendency of graphene nanoplatelets to re-agglomerate. The PANI/graphene dispersions were used for used for two main purposes: film forming and formation of nanocomposites powder. The films were produced by coating rods while the nanocomposites powder was prepared by a precipitation-filtration technique. The addition of nanoplatelets significantly lowers the electrical resistivity of the composite. The decrease was by four orders of magnitude for the dedoped PANI/graphene and two orders of magnitude for the doped PANI/graphene, as demonstrated by measurements conducted under loading. Cyclic electrical measurements under loading showed a distinct and reproducible dependence of the bulk resistivity vs. the pressure applied. This repetition is a key component for electromechanical sensors. To the author's best knowledge, this is the first publication on cyclic electrical measurements under pressure of PANI/graphene composites.