Synthesis of Highly Conductive Poly(3-hexylthiophene) by Chemical Oxidative Polymerization Using Surfactant Templates.

Poly(3-hexylthiophene) (P3HT) was systematically synthesized by chemical oxidative polymerization in chloroform with ferric chloride (FeCl3) as the oxidizing agent and various surfactants of the shape templates. The effects of 3HT: FeCl3 mole ratios, polymerization times, and surfactant types and concentrations on the electrical conductivity, particle shape and size were systematically investigated. Furthermore, dodecylbenzenesulfonic acid (DBSA), p-toluenesulfonic acid (PTSA), sodium dodecyl sulfate (SDS), and sodium dioctyl sulfosuccinate (AOT) were utilized as the surfactant templates. The P3HT synthesized with DBSA at 6 CMC, where CMC stands for the Critical Micelle Concentration of surfactant, provided a higher electrical conductivity than those with PTSA, SDS and AOT. The highest electrical conductivity of P3HT using DBSA was 16.21 ± 1.55 S cm-1 in which the P3HT particle shape was spherical with an average size of 1530 ± 227 nm. The thermal analysis indicated that the P3HT synthesized with the surfactants yielded higher stability and char yields than that of P3HT without. The P3HT_DBSA electrical conductivity was further enhanced by de-doping and doping with HClO4. At the 10:1 doping mole ratio, the electrical conductivity of dP3HT_DBSA increased by one order of magnitude relative to P3HT_DBSA prior to the de-doping. The highest electrical conductivity of dP3HT_DBSA obtained was 172 ± 5.21 S cm-1 which is the highest value relative to previously reported.

Facile formation of agarose hydrogel and electromechanical responses as electro-responsive hydrogel materials in actuator applications.

The agarose hydrogels (AG HyGels) were fabricated by a solvent casting method at various agarose concentrations, resulting in the 3D hydrogel networks via the physical crosslinking from the hydrogen bonding. The actuator performances were investigated at various agarose contents and electric field strengths. For the electromechanical properties, the AG HyGel_12.0 %v/v possessed the highest storage modulus (G') and storage modulus relative response (ΔG'/G'0) of 4.48 × 106 Pa and 1.07, respectively under applied electric field strength of 800 V/mm due to the electrostriction effect. In the electro-induced bending measurement, the highest deflection distance was obtained from the AG HyGel_2.0 %v/v due to its initial lower rigidity. Relative to other bio-based hydrogels, the present AG HyGels are first demonstrated here as electroactive materials showing comparable magnitudes in the electroactive responses, but with the simple fabrication method without toxic ingredients required. Thus, the present AG HyGels are potential material candidates for soft actuator applications.

Influence of carrageenan molecular structures on electromechanical behaviours of poly(3-hexylthiophene)/carrageenan conductive hydrogels.

The κ, ι, and λ carrageenans were fabricated by solution casting as soft and electrically responsive actuators. The poly(3-hexylthiophene) (P3HT) was added as a dispersed phase to improve the electrical and electromechanical properties of the pristine carrageenan hydrogels. The electromechanical properties of the carrageenan hydrogels were investigated under the effects of electric field strength, carrageenan type namely κ, ι, and λ, operating temperature, and P3HT concentration. The electromechanical responses of the pristine carrageenans increased with increasing sulfated groups present; the λ-carragenan hydrogel provided the highest storage modulus sensitivity of 4.0 under applied electric field strength of 800 V/mm. With increasing temperature, the double-helical structure of the κ-carrageenan hydrogel changed into a random coil leading to the increase in the storage modulus response. On the other hand, the P3HT/κ-carrageenan hydrogel blend at 0.10%v/v P3HT provided the high storage modulus sensitivity of 2.20 at the electric field strength of 800 V/mm. The higher dielectrophoretic forces were due to the additional P3HT electronic polarization, but lower deflections relative to those of the pristine κ-carrageenan hydrogel. Both κ- and λ-carrageenans with the double helical structures are shown here as possible candidates to be fabricated as electroactive hydrogels for actuator or biomedical applications.

Softened and flexible biodegradable poly(lactic acid) and its electromechanical properties for actuator application.

Poly (lactic acid) (PLA) is a biodegradable polymer with high stiffness presenting a limitation for using in actuator applications. Adding a plasticizer is one way to solve this problem to enhance flexibility and improve electromechanical properties of pristine PLA. In this work, the PLA films were prepared via a simple solvent casting method. The influences of plasticizer type and electric field strength on electromechanical behavior of PLA films were investigated by the melt rheometer and bending measurement. For the PLA films filled with dibutyl phthalate (DBP), the storage modulus, G', immediately increased towards its steady state and rapidly recovered to its original value with and without electric field, respectively, which can be referred to a reversible system. On the other hand, the PLA film with Tween 20 processed the highest ∆G׳/G׳0 of 1.34 due to the available amount of polarized groups. In the bending measurement, the dielectrophoresis forces of plasticized PLA films were found to increase with increasing electric field where the deflections occurred towards anode side as the polarized groups generated negative charges. The DBP_PLA1.5D film exhibited the greatest bending and dielectrophoresis force. Thus, the biodegradable PLA along with DBP combine to have a great potential towards actuator application.