Structural characterization and DC conductivity of honeycomb-patterned poly(ε-caprolactone)/gold nanoparticle-reduced graphite oxide composite films
Graphical abstract
Highlights
► Biocompatible poly(ε-caprolactone) composites were synthesized by Au nanoparticles dispersed on RGO. ► Honeycomb-patterned thin films were fabricated by casting the composite solution under humid conditions. ► The variance of conductivity and pattern structure of the composite films were studied.
Introduction
In the past two decades, aliphatic polyesters such as poly(ε-caprolactone) (PCL) poly((R)-3-hydroxybutyrate), and poly(l-lactide) have been intensively studied because of their hydrolyzability in the human body and under natural circumstances [1], [2]. PCL attracts great interest due to its low cost, sustained biodegradability, and availability at a low molecular weight [3]. Due to its hydrolyzability in the human body, PCL has been considered in a wide range of possible applications, such as biodegradable packaging materials, implantable biomaterials, and microparticles for drug delivery [4].
The preparation of nanostructure PCL composites using reinforcement materials, such as starch, clay, and carbon nanotubes, has recently attracted significant attention due to their excellent physical, mechanical, and electrical properties, including high conductivity, catalytic activity, gas sensitivity, and optoelectronic properties [5]. Gold nanoparticles (GNPs) have been widely studied as a component of polymer composites because of their unique size-related electronic and optical properties [6]. GNPs dispersed into polymeric networks are currently used in sensors, catalytic purposes, conductive inks, and electron or energy storage [7]. Graphene and its derivatives have also attracted considerable attention in recent years because of their unique physical properties [8].
In the present study, we incorporated different weight percentages (wt%) of GNPs dispersed on reduced graphite oxide (RGO), hereafter denoted as GNP-RGO, during the ring opening polymerization of ε-caprolactone to obtain a conductive PCL polymer composite. The synthesized PCL-GNP-RGO composites were characterized by Fourier transform infrared (FTIR) and UV–vis spectroscopic methods. Honeycomb-patterned polymer films were produced by the assistance of water droplets in a volatile solvent under humid conditions. The dependence of the room-temperature DC conductivity and pattern structure of the films on the GNP-RGO concentration were studied.
Section snippets
Experimental
Materials: Sodium borohydride (NaBH4) and gold (III) chloride trihydrate (HAuCl4·3H2O, 99.0%) were purchased from TCI Fine Chemicals. Graphite (<20 μm), ε-caprolactone, stannous octoate (Sn(Oct)2), and other reagents were purchased from Sigma–Aldrich and used as received.
Preparation of GNP-RGO: RGO was prepared via the chemical reduction of GO by NaBH4. GO was prepared from purified natural graphite according to a modified Hummers method [9], [10]. Exactly 0.3 g of GO was dispersed in 50 mL of DI
Results and discussion
Characterization of the synthesized composites: Fig. 2(a) shows the FTIR spectra of PCL, GNP-RGO, PCL-GRG-5, and PCL-GRG-10 composites. PCL peaks located at 2942 and 2862 cm−1 can be assigned to the stretching and bending vibration of CH2, whereas the peak at 1723 cm−1 is due to the vibration of the CO bonds of neat PCL polymer [14]. GNP-RGO shows peaks that correspond to both RGO and GNP particles. GNP-RGO shows peaks at 3468, 2923, 2855, and 1655 cm−1 that correspond to OH, CH, and CC of
Conclusion
New polymer composites with a biocompatible polymer containing PCL with different wt% of highly conductive GNP-RGO nanoparticles were prepared. Honeycomb-patterned films were obtained with the assistance of water droplets under humid conditions. The dependence of the room-temperature DC conductivity and honeycomb structures of the films on the GNP-RGO concentration were determined. The conductivity of the composite film increased to ∼0.0956 S/cm after incorporating 10 wt% of GNP-RGO into PCL,
Acknowledgment
This research was supported by the National Research Foundation of Korea (2011–0025853).
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