The use of p(4-VP) cryogel as template for in situ preparation of p(An), p(Py), and p(Th) conductive polymer and their potential sensor applications

Highlights

• P(4-VP)/conductive polymer interpenetrating cryogel composites as sensors.

• P(4-VP) semi-IPN conductive cryogel composite as sensor for HCl and NH₃ gas vapors.

• The cryogel-conductive polymer derived sensors for MB or MO dye solutions.

Abstract

Superporous poly(4-vinyl pyridine) (p(4VP)) cryogels were used as a template for the in situ synthesis of conductive polymer such as poly(aniline) (p(An)), poly(pyrrole) (p(Py)) and poly(thiophene) (p(Th)) via oxidative polymerization technique to obtain p(4-VP)/conductive composite semi-interpenetrating polymer networks (semi-IPN). The amount of in situ polymerized p(An), p(Py), and p(Th) within p(4-VP) cryogels were determined gravimetrically, and the highest amounts of conductive polymer was prepared for p(Th) in situ within p(4-VP) network with %39.3 ± 1.2 (wt%). The prepared p(4-VP)/p(An), p(4-VP)/p(Py), and p(4-VP)/p(Th) semi-IPN conductive cryogel composite systems were characterized by using Fourier Transform Infrared (FT-IR) spectrometer. The conductivities of p(4-VP) cryogels were increased from 1.75 × 10⁻⁹ ± 1.9 × 10⁻¹⁰ S cm⁻¹ to about 150 K, 65 K and 600 fold with the in situ synthesis of p(An), p(Py), and p(Th) respectively. Furthermore, the sensor applications of the prepared p(4-VP)/p(An), p(4-VP)/p(Py), and p(4-VP)/p(Th) semi-IPN conductive cryogel systems were tested for different gases such as HCl, NH₃ and against aqueous solutions of methyl orange (MO), methylene blue (MB) dyes.

Introduction

Conductive polymers as highly conjugated polymers provide unique electrical, electrochemical and optical properties due to their spatially extended Π-bondings [1]. Conductive polymers can operate at room temperature [2], [3], and possess low energy consumption, can be prepared readily, and generate fast and selective responses with high sensitivity to minor perturbs, and possesses chemical structural flexibility [4], [5], [6]. Due to their unique significant properties and advantages, conductive polymers have been widely used in the application of solar cells, optic and biomedical devices, biosensors, neural prostheses electrode application [7], [8], [9], [10], [11], [12], controlled drug delivery systems [13], [14], as well as microelectronic industry such as photovoltaic devices, electrochromic displays, light-emitting diodes and even in battery technology [15], [16], [17], [18]. Most commonly used conductive polymers represent a group of conjugated organic structures are poly(aniline) (p(An)), poly(pyrrolle) (p(Py)), poly(thiophene) (p(Th)), poly(p-phenylene vinylene) (p(Pv)) and poly(ethylene dioxythiophene) (p(EDOT)) with high electronic conductivities [1], [18], [19].

An interesting type of hydrogel named as cryogel with super and interconnected porosity, structural flexibility, higher mechanical strength and fast responsiveness in comparison to conventional hydrogels have attracted great interest by many researcher for various applications such as in situ metal nanoparticle preparation [20], in situ conductive polymer synthesis [21], [22], column filler material [23], cell scaffolds or tissue engineering [24], adsorbents for environmental applications [25], and bio-separation [26], and even in the design of bio-sensing devices [27], due to their superior modifiable physical, and chemical properties [28].

Composite materials from two or more constituents with significant different physical and chemical properties were also investigated by various researchers due to the value added properties of each component. Composite materials sometimes even offered new and more traits with advanced properties very different from each of the used constituents [28]. Interestingly, interpenetrations between the minimum of two polymers by crosslinking in presence or absence of mutual chemical interactions can be accomplished by just not interfering individual polymerizations as full interpenetrating network (IPN) but also preparing the second polymer in the presence of an already prepared polymeric networks as semi-interpenetrating polymer networks (semi-IPN) [29], [30].

In this study, we report the utilization of superporous p(4-VP) cryogels network as a template for in situ synthesis of conductive p(An), p(Py) and p(Th) polymers as p(4-VP)/p(An), p(4-VP)/p(Py), and p(4-VP)/p(Th) semi-IPN conductive composite cryogel systems. The amounts of the conductive polymers within p(4-VP) cryogels were determined gravimetrically. FT-IR spectrometer were used to confirm the formation of new conductive polymers within the pores of p(4-VP) cryogels. The conductivities of the bare p(4-VP) cryogels, p(4-VP)/p(An), p(4-VP)/p(Py), and p(4-VP)/p(Th) semi-IPN conductive cryogel composites systems were determined from I–V measurements. Moreover, the change in conductivities of p(4-VP)/p(An), p(4-VP)/p(Py), and p(4-VP)/p(Th) semi-IPN conductive cryogel systems upon 15 min exposure of HCl, NH₃ gas, and 10 s treatments of MO and MB dyes were determined to test their sensor applications.