دانلود رایگان مقاله نظارت بر دینامیک مولکولی کامپوزیت سلولز باکتریایی با اکسید گرافن

ABSTRACT

Broadband Dielectric Relaxation Spectroscopy was performed to study the molecular dynamics of dried Bacterial Cellulose/Carboxymethyl Cellulose-Graphene Oxide (BC/CMC-GO) composites as a function of the concentration of CMC in the culture media. At low temperature the dielectric spectra are dominated by a dipolar process labelled as a -relaxation, whereas electrode polarization and the contribution of dc-conductivity dominate the spectra at high temperatures and low frequency. The CMC concentration affects the morphological structure of cellulose and subsequently alters its physical properties. X-ray diffractometry measurements show that increasing the concentration of CMC promotes a decrease of the I/I ratio. This structural change in BC, that involves a variation in inter- and intramolecular interactions (hydrogen-bonding interactions), affects steeply their molecular dynamics. So, an increase of CMC concentration produces a significantly decrease of the -relaxation strength and an increase of the dc-conductivity.

Conclusions

This work presents a combined analysis of the structure and properties of cellulose bacterial composites reinforced by graphene oxide. As a result, the crucial role of CMC addition to induce substantial structural changes in Cellulose is evidenced. The fraction of the two allomorphs of I structure (I/I) is greatly decreased with increasing concentrations of CMC sodium salt (CMC) in the incubation medium. The crystalline size and crystallinity sample index decrease with an increasing concentration of CMC. The sample CrI values, estimated from the ratio of the area of the crystalline peaks to the total area, experiences a reduction of a 13% with respect BC alone. These changes in the sample’s CrI value and morphology are in good agreement with the results obtained from SEM and AFM. The proportion of both phases and how they are distributed in the microfibrils determines electrical behavior and therefore, their potential applications. As expected, the presence of GO produces a rise in the conductivity of the BC composites. Additionally, this increase is higher with increasing the CMC content. The dynamic mobility is dramatically affected by the number of hydroxyl groups and their ability to make hydrogen bonds between cellulose chains. Both the -relaxation and conductivity process are thermally activated processes, and both are steeply dependent on the CMC concentration. Given the results obtained, we believe that the composites described herein could find various applications in portable and bendable electronics. According to our results the sample with a 3% of CMC has the higher conductivity, but it would be appropriate to perform a future study of samples with higher GO and CMC contents, in order to find the composition that optimizes the electric properties.