Influence of biopolymer loading on the physiochemical and electrochemical properties of inherently conducting polymer biomaterials

• We examine the influence of dextran sulphate bioloading in polypyrrole biomaterials.
• We employ QCM-D to characterise electrochemically polymerised PPy biomaterials.
• Increasing DS bioloading in PPy films increases film modulus and electroactivity.
• Higher DS loading reduces polymer thickness, mass and surface roughness.
• Decreasing DS bioloading increases PPy–DS electrochemical actuation during CV.

The physicochemical and electrochemical properties of polypyrrole (PPy) doped with the biological dopant dextran sulphate (DS) were shown to be significantly altered as a function of varying the salt concentration (0.2, 2 or 20 mg/ml) in the polymerisation electrolyte. Films grown in the presence of 0.2 mg/ml DS generated the highest potential during galvanostatic growth, with the potential decreasing with each subsequent increase in DS concentration. The electroactivity of the polymers was similar for all three DS concentrations, with the 20 mg/ml film drawing slightly more current upon reduction in PBS. Increasing the DS concentration reduced film interfacial roughness and increased polymer hydrophilicity. Polymer mass and thickness was larger for DS films grown from 0.2 mg/ml and 2 mg/ml DS electrolyte solutions, compared to the 20 mg/ml films. The latter also demonstrated a much higher shear modulus than the 2 mg/ml and 0.2 mg/ml films, respectively. The changes in the polymer physicochemical properties were associated with an increase in polymer densification with increasing DS loading, correlating with a likely higher conjugation generated during polymerisation at a potential closer to the ideal oxidation potential of pyrrole. Herein we describe a facile approach through which polymer properties may be varied significantly by varying the dopant concentration in the electrolyte, providing the ability to tune polymer properties for enhanced functionality while preserving fundamental polymer chemistry.