Effect of low and high methoxyl citrus pectin on the properties of polypyrrole based electroactive hydrogels

• Low and high methoxyl citrus pectin were obtained through dialysis.
• Polypyrrole was synthetized in the presence of low and high methoxyl citrus pectin.
• The properties of polypyrrole/pectin hydrogels depend on the methoxyl content.
• Polypyrrole/citrus pectin hydrogels are electroactive.

Electroactive hydrogels were prepared using commercial citric pectin, either raw (PC) or purified through dialysis (dPC), and chemically synthesized polypyrrole (PPy). 1H NMR analyses showed that PC is a low methoxyl pectin (degree of methoxylation, DM = 46%) and dPC is a high methoxyl pectin (DM = 77%). The pyrrole polymerization was monitored through UV–vis spectroscopy and both samples were observed to be good stabilizers for PPy in aqueous medium. The dispersions were used to prepare the hydrogels h-PC-PPy and h-dPC-PPy. The hydrogel h-dPC-PPy has a higher swelling index (SI ≈ 25%) at pH 1.2 than the hydrogel h-PC-PPy (SI ≈ 7%). Contrastingly, at pH 6.8 both hydrogels lost their mechanical integrity. Raman spectroscopy revealed that PPy is more oxidized in h-PC-PPy. Nevertheless, both hydrogels are electroactive and therefore can be considered for applications in which the control of the degree of swelling is desired.

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