High strain electromechanical actuators based on electrodeposited polypyrrole doped with di-(2-ethylhexyl)sulfosuccinate

The low-voltageelectromechanicalactuationofpolypyrrole(PPy)dopedwithdi-(2-ethylhexyl)

sulfosuccinate (DEHS)hasbeeninvestigated.ThePPy-DEHShasbeenpreparedbothchemically(cast

as filmsfromsolution)andbymoreconventionalelectrochemicalpolymerization.Verylargestrainsof

∼30% wereobtainedduringslow-scanredoxcyclingoftheelectrochemicallypreparedPPy-DEHSfilms.

In constrast,PPy-DEHSfilmscastfromsolutionsofthechemicallypolymerizedpolymergaveactuation

strains of ∼2.5%. Thepolymerizationmethodwasalsofoundtohaveasignificanteffectonthestructure,

conductivity andmechanicalpropertiesofthePPy-DEHSmaterials.Theconductivityoftheelectrochem-

ically polymerizedPPy-DEHSwas75Scm−1, considerablyhigherthanthatfoundforthechemically

derived polymer(7Scm−1). ThestructureofthePPy-DEHSwasfurtherelucidatedfromUV–vis,Raman

and FT-IRspectralstudieswhichindicatedthattheconjugationlengthofthePPycouldbeincreased

significantly byvaryingthepolymerizationmethod.FilmsobtainedbycastingchemicallypreparedPPy-

DEHS showedhighermodulus(2.3GPa)thanelectropolymerizedPPy-DEHS(0.6GPa),butweremore

brittle. Bothmaterialswereelectroactiveinacetonitrile/waterelectrolyte.Thehigheractuationstrain

observed intheelectrochemicallypreparedfilmswasattributedtoamoreopenmolecularstructure(as

indicated bythelowermodulus)allowingforeasieriondiffusionandahigherconductivityallowing

easier chargetransfer.