Abstract
Block copolymers posses inherently the ability of form a variety of phase-separated microdomain structures. The lengths of block segments and the selectivity of the solvent are primary factors affecting the resultant morphology. This paper investigated the effect of casting solvents on the morphologies and electrical actuation of poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) (PMMA-PnBA-PMMA) triblock copolymer films comprising PMMA hard segment and PnBA soft segment. Transmission electron microscopy and confocal laser scanning microscopy observation revealed that PMMA and PnBA segments were assembled into various micro- and nano-sized phase structures where either of them formed continuous phase. This implies that continous phase could be inversed by used casting solvents. Solvent-dependent phase morphologies had a significant effect on the electrical actuation results. Increase of the PnBA contents and the continuous phases of PnBA soft segments improved both of electrical actuation and dielectric constant, indicating that solvent-induced phase separation modulates the electrical actuation of dielectric films. The significance of the role of solvent selectivity and the major continuous phase of the polymer in defining the morphology and electrical actuation of the self-assembled block copolymer structure are discussed.
Highlights
Dielectric elastomer actuators (DEAs) behave as actuators by changing their shape in response to electrical stimulation
This paper investigated the effect of casting solvents on the morphologies and electrical actuation of poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) (PMMA-PnBA-PMMA) triblock copolymer films comprising PMMA hard segment and PnBA soft segment
Transmission electron microscopy and confocal laser scanning microscopy observation revealed that PMMA and PnBA segments were assembled into various micro- and nano-sized phase structures where either of them formed continuous phase
Summary
Dielectric elastomer actuators (DEAs) behave as actuators by changing their shape in response to electrical stimulation. When an appropriate voltage is applied to a DEA, the very soft nature of both the dielectric elastomer and its electrodes allows for significant coupling of the mechanical properties of the system with the electrostatic interactions arising between the induced polarization charges and the supplied surface free charges. This actuation mechanism is the so-called ‘Maxwell stress’, as depicted in Scheme 1. Electrostatic attraction between the oppositely charged compliant electrodes applied to opposing surfaces of the D-EAP generates a normal Maxwell stress upon actuation and compresses the film in the transverse (z) direction. To clarify the relation between phase morphologies and physical properties, the phase structures of films were observed by transmission electron microscopy (TEM) and confocal laser scanning microscopy to find the morphologies both of micro- and nanosize
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