Photocured conductive PANI/acrylate composites for digital light processing. Influence of HDODA crosslinker in rheological and physicochemical properties

Abstract

The design of novel photocurable conductive acrylic composites demands thorough research to find appropriate balance between the relative concentrations of monofunctional/ multifunctional monomers, photoinitiators and conductive filler, besides adjusting polymerization conditions. Likewise, when an intrinsically conductive polymer such as polyaniline (PANI) is selected as conductive filler, the homogeneous distribution of its nano metric aggregates is essential to prevent heterogeneous curing due to its strong UV absorption. In this work, the influence of PANI-HCl on the physical properties of acrylic composites based on Ethyleneglycolphenylether acrylate (EGPEA) and Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), photoinitiator, was examined in the frame-work of the percolation model. Rheological testing combined with Scanning Electron Microscopy (SEM) were used for efficient control of the filler dispersion in order to better understand the electrical con ductivity-structure behaviour. Infrared Spectroscopy probed the degree of monomer conversion and the filler interaction with the polymer matrix, whereas the thermal properties were evaluated with the aim of establishing the maximum working temperatures. Above the percolation threshold, the formulation with 4.8 wt% PANI was selected as the most suitable composition achieving maximum conductivity (10-3 S cm−1 ) at the lowest PANI content. The problem of excessive aggregation of PANI clusters was tackled by the addition of a 15 wt% of the reactive diluent 1,6-hexanediol diacrylate (HDODA) to the previous formulation. The outcomes were improved dispersion and better integration of PANI nanorods within the acrylic matrix plus a smoother film surface, while retaining high electrical conductivity. The viscosity of the selected prepolymer formulations and penetration depth of UV photons gave encouraging results for the use of the developed compositions as anticorrosion coatings, digital light processing (DLP) or piezoelectric sensors. The high critical cure dosages obtained will be easily overcome by adjusting the type and/or amount of photoinitiator.