Insights into the Effect of Polymer Functionalization of Multiwalled Carbon Nanotubes in the Design of Flexible Strain Sensor

Abstract In the background of designing a polymer nanocomposite based flexible strain sensors, homogenized dispersion of nanofillers remain challenging due to the trade-off between upholding of inherent characteristics of nanofillers and stable dispersion of nanofillers in the polymer matrix. This study provides an approach of balancing the stable dispersion of nanofillers and maintain the inherent characteristics of nanofibers by the method of polymer functionalization. Herein, two oppositely charged polymers polystyrene sulfonate sodium salt (PSS) and poly-diallyl-dimethyl-ammonium chloride (PDDA) are used separately to functionalize the multiwalled carbon nanotubes (CNT) and it dispersed in poly (vinylidene difluoride) (PVDF) polymer matrix to get flexible nanocomposite strain sensor to investigate both electrical conductivity and the gauge factor. PSS functionalized CNT (PSS-CNT) shows better dispersion than the PDDA-CNT in PVDF matrix. Besides, the electrical conductivity of PVDF/PSS-CNT (0.44 ± 0.02 Scm-1) is about 28 times higher than the PVDF/PDDA-CNT, and the gauge factor of PVDF/PSS-CNT (9.8 ± 0.3) is 2-fold higher than the PVDF/PDDA-CNT. The stable dispersion of PSS-CNT is due to the repulsive nature existing between the individual CNTs caused by the attachment of charged polymer functional groups as same as intrinsic functional groups of the pristine CNT. This work signifies the role of synergy between the charged particles in the functional groups and charged nature of the filler influencing the performance of flexible strain sensors. The detailed investigation using various techniques reveals significance of selection of suitable polymers for functionalization by showing its influence in the context of designing the high-performance flexible strain sensor.