1. Introduction Recently, electroactive polymers incorporated with aniline oligomers have attracted research attention because of their superior properties such as good sol- ubility, biodegradable properties and the ability to form films [1–5]. These synthetic strategies include post polymerization grafting of oligoanilines onto the polymer chain, polycondensation of reactive monomers containing oligoanilines to form poly- mers, and oxidative coupling polymerization to form oligoaniline segments during polymerization [6]. Chao and Wang synthesized a series of electroactive polymers which bear oligoaniline, phenylamine, and fluorene groups in their side chain [7–9]. The generated fluorescence showed a clear multiple stimuli-responsive behavior against redox species, pH, electricity, and pressure, contributed by the sen- sitive oligoaniline and phenylamine groups. Zagors- ka and co-workers prepared electroactive polymers combining the electrochromic properties of polythio- phenes and oligoanilines [10, 11]. Both the polythio- phene main chains and the oligoaniline side chains could be doped in various ways. Yeh and coworkers synthesized a series of electroac- tive polymers such as epoxy [12], polyimide [13, 14], polyurea [15], and polyamide [16] as anticorrosion coating materials. The mechanism for the enhanced corrosion protection ability of the electroactive poly- mer coatings could be attributed to the formation of passive metal oxide layers on the metal electrode surface, which was induced by the redox catalytic capabilities of the aniline oligomer [17, 18]. 71 Novel ascorbic acid sensor prepared from gold/aniline-pentamer-based electroactive polyamide composites M-H. Tsai 2 , S. H. Lu 1 , Y. H. Lai 1 , G-H. Lai 2 , G. V. Dizon 3 , T-I Yang 3 , Y-J. Lin 4 , Y. C. Chou 1* 1 Department of Applied Cosmetology, Hung Kuang University, 43302 Sha Lu, Taichung, Taiwan, R.O.C 2 Ph. D. Program, Graduate Institute of Precision Manufacturing, National Chin-Yi University of Technology, 41170 Taichung, Taiwan, R.O.C. 3 Department of Chemical Engineering, Chung Yuan Christian University, 32023 Chung Li, Taiwan, R.O.C. 4 Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, R.O.C. Received 16 June 2017; accepted in revised form 6 September 2017 Abstract. A novel gold/aniline-pentamer-based electroactive polyamide (Au/EPA) composites that can modify carbon paste electrodes (CPEs) for ascorbic acid (AA) sensing has been studied in detail in this article. Cyclic voltammetry studies indi- cated improved electrochemical properties of the Au/EPA composites, demonstrating the occurrence of efficient electron/ charge transfer between the Au and the EPA. Experimental tests shows that there is a linear relationship between the con- centration of added AA and the response current for the CPE modified with Au/EPA sensor to the concentration of AA in the range of 0.05–0.75 mM (R 2 = 0.996, n = 15). The detection limit and the sensitivity of the Au/EPA-CPE AA sensors were 2.75 μM at a signal to noise ratio (S/N) of 3, and 21.7 mA·mM –1 , respectively. Keywords: polymer composites, electroactive polymer, electrochemical sensing eXPRESS Polymer Letters Vol.12, No.1 (2018) 71–81 Available online at www.expresspolymlett.com https://doi.org/10.3144/expresspolymlett.2018.6 * Corresponding author, e-mail: jacs1@hk.edu.tw © BME-PT