ONE-STAGE ELECTROCHEMICAL SYNTHESIS OF A POLYMETHYLOLACRYLAMIDE/ULTRAFINE POLYTETRAFLUOROETHYLENE COMPOSITE

Abstract

A method for one-stage electrochemical synthesis of a composite consisting of two non-conductive polymers has been developed. Using the example of electropolymerization of acrylamide in the presence of particles of ultrafine polytetrafluoroethylene (UPTFE), it is shown that the electrochemical approach makes it possible to simplify the traditional multistage technologies for the formation of composite polymer materials by combining in one process the electropolymerization of acrylamide and the formation of a polymethylolacrylamide (PMAA) film on the cathode, the capture of UPTFE particles by a growing polymer matrix, and formation of a PMAA/UPTFE composite. This technology makes it possible to reduce the total time for creating a polymer/polymer composite to 5-10 minutes. A procedure for the preparation of stable aqueous dispersions of UPTFE has been developed. It has been established that the most effective stabilizers of UPTFE aqueous dispersion are sodium lauryl sulfate (LS) and siloxane-acrylate emulsion SE 13-36. The formation of the PMAA/UPTFE composite was confirmed by XRD, SEM, SAXS, and spectrophotometry. It was found that the composite includes both large (~1 μm) and nanosized (1–10) nm UPTFE particles. The color of the PMAA/UPTFE composite films changes from colorless and transparent, characteristic of PMAA, to milky white (color of UPTFE and SE 13-36). This reduces the light transmission of composite films, reaching the minimum value for PMAA/UPTFE/SE 13-36. The mass of the PMAA/UPTFE composite increases with increasing electropolymerization time, and the residual current, which characterizes the degree of electrode insulation, decreases in comparison with the PMAA coating. Modification of the film with ultrafine polytetrafluoroethylene leads to a decrease in the swelling of composite coatings by a factor of 1.26–2.60, depending on the nature and concentration of the additive. The maximum insulating effect and reduced swelling is achieved for the PMAA/UPTFE(LS) composite, which indicates the preferred use of UPTFE(LS) for the modification of PMAA. The thermal stability of the PMAA/UPTFE(LS) composite and matrix PMAA is almost identical.