Abstract
The conductivity and high surface-to-volume ratio of carbon nanofibers (CNFs) composited with the medium-chain-length poly-3-hydroxyalkanoate (mcl-PHA) have attracted much attention as smart biomaterial. However, poor CNF dispersion leads to tactoid agglomerated composite with poor crystallite morphology resulting in inferior thermomechanical properties. We employed acoustic sonication to enhance the construction of exfoliated PHA/CNFs nanocomposites. The effects of CNF loading and the insonation variables (power intensity, frequency, and time) on the stability and microscopic morphology of the nanocomposites were studied. Sonication improved the dispersion of CNFs into the polymer matrix, thereby improving the physical morphology, crystallinity, and thermomechanical properties of the nanocomposites. For example, compositing the polymer with 10% w/w CNF resulted in 66% increase in crystallite size, 46% increase in micromolecular elastic strain, and 17% increase in lattice strain. Nevertheless, polymer degradation was observed following the ultrasound exposure. The constructed bionanocomposite could potentially be applied for organic electroconductive materials, biosensors and stimuli-responsive drug delivery devices.
Highlights
Increasing environmental pollution and degradation as a result of the utilization of petrochemical derived plastics have intensified the search for commercially viable biodegradable polymers [1]
Biodegradable medium-chain-length PHA with comonomeric composition of C4:0 to C10:0 and an average molecular weight (Mw) of 77.6 KDa was obtained from reported fermentation culture conditions [1], using Delftia tsuruhatensis Bet002 as a producer microorganism and oleic acid as a sole carbon and energy source
At higher carbon nanofibers (CNFs) loading (5%), tactoid aggregation morphology was observed in the composite prepared via solvent dispersion route (Figure 2(d))
Summary
Increasing environmental pollution and degradation as a result of the utilization of petrochemical derived plastics have intensified the search for commercially viable biodegradable polymers [1]. Among the biopolymers are the microbial produced polyhydroxyalkanoates (PHA), which have received much attention due to their biocompatibility, biodegradability, and diverse structural composition, imparting onto them physicomechanical properties close to those of polyvinyl chloride and polyethylene terephthalate [2] These combinations of excellent physicochemical properties led to the increasing commercial exploitation of PHA in different niche applications spanning from biomedical, packaging, automotive, infrastructure, and aerospace to military [3, 4]. Despite their promising commercial potentials, PHAs such as those with monomeric composition of 3-hydroxybutyric acid were reported to exhibit brittleness, low heat distortion temperature, poor gas-barrier properties, limited processing malleability, and ductility [5, 6]. While there have been reports on the fabrication of PHA/carbon nanoparticles composites [13, 14, 26,27,28,29], the combined effects as investigated in this study on the properties of PHA/CNFs nanocomposite have yet to be reported
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