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. 2020 Jul 23;10(46):27585-27597.
doi: 10.1039/d0ra04649c. eCollection 2020 Jul 21.

Formation of dialysis-free Kombucha-based bacterial nanocellulose embedded in a polypyrrole/PVA composite for bulk conductivity measurements

Nadia Nirmal  1 , Michael N Pillay  1 , Marco Mariola  1 , Francesco Petruccione  1 , Werner E van Zyl  1
Affiliations

Formation of dialysis-free Kombucha-based bacterial nanocellulose embedded in a polypyrrole/PVA composite for bulk conductivity measurements

Nadia Nirmal et al. RSC Adv. .

Abstract

The preparation of dialysis-free bacterial nanocrystalline cellulose (BNCC) combined with a suitable polymer to form a robust conducting material remains a challenge. In this work, we developed a polypyrrole@BNCC/PVA nanocomposite that avoids the time-consuming dialysis step and which exhibits bulk electrical conductivity. The nanocellulose (NC) was derived from bacterial cellulose (BC) that was grown from a symbiotic colony of bacteria and yeast (SCOBY) starting from Kombucha tea, and then subjected to sulfuric acid hydrolysis that led to isolable bacterial nanocrystalline cellulose (BNCC) product and subsequently utilized as a stabilizer and support. Pyrrole monomer was reacted with FeCl3·6H2O as a polymerization initiator to form polypyrrole (PPy) and combined with BNCC it produced PPy@BNCC nanocomposite. We found PPy to BNCC in a 1 : 1 ratio provided the best suspension of the components and formed a well dispersed homogeneous network. The PPy@BNCC nanocomposite was then suspended in polyvinyl alcohol (PVA), that facilitated the construction of a continuous PPy@BNCC/PVA conductive network in the matrix. We designed an in-house electrical measurement apparatus and developed a method that recorded bulk resistance. The results obtained from the measurements of the electrical properties of the PPy@BNCC/PVA composite prepared dialysis-free were then compared with (i) a dialyzed sample of similar composition, and (ii) a traditional four-point probe measurement. The PPy@BNCC/PVA dialysis-free sample showed a higher conductivity compared to the dialyzed composite at 4.27 × 10-1 and 3.41 × 10-1 S m-1, respectively, and both values closely matched the traditional four-point probe measurement.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Schematic representation of the dialysis-free synthetic methodology used.
Fig. 1
Fig. 1. (a) Bacterial cellulose film formed in growth medium after 2 weeks of growth, (b) TEM image of isolated bacterial cellulose.
Fig. 2
Fig. 2. TEM images of negatively stained BNCC crystalline needles prepared by the dialysis-free method.
Fig. 3
Fig. 3. FT-IR spectrum of the BNCC sample prepared by the dialysis-free method.
Fig. 4
Fig. 4. Raman spectrum of BNCC from the dialysis-free method.
Fig. 5
Fig. 5. TEM images of PPy@BNCC prepared by dialysis-free method.
Fig. 6
Fig. 6. Digital pictures of varying ratios of PPy : BNCC (L–R): (a) 0 : 1; (b) 1 : 2; (c) 1 : 1; (d) 2 : 1 and (e) 1 : 0, when left for 30 minutes.
Fig. 7
Fig. 7. SEM image of (a) PPy in PVA, (b) and (c) dialysis-free method of PPy@BNCC/PVA.
Fig. 8
Fig. 8. Linear relationship based on Ohm's law showing the change in current as voltage was applied for dialysis-free vs. dialyzed samples.
See this image and copyright information in PMC

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