Preparation of Multicomponent Biocomposites and Characterization of Their Physicochemical and Mechanical Properties

Abstract

This work focused on a mutual comparison and characterization of the physicochemical properties of three-component polymer composites. Binary polyaniline–chitosan (PANI–CHT) composites were synthesized by in situ polymerization of PANI onto CHT. Ternary composites were prepared by blending with a third component, polyvinyl alcohol (PVA). Composites with variable PANI:CHT (25:75, 50:50 and 75:25) weight ratios were prepared whilst fixing the composition of PVA. The structure and physicochemical properties of the composites were evaluated using thermal analysis (thermogravimetric analysis (TGA), differential scanning calorimetry (DSC)) and spectroscopic methods (infrared (IR), nuclear magnetic resonance (NMR)). The equilibrium and dynamic adsorption properties of composites were evaluated by solvent swelling in water, water vapour adsorption and dye adsorption isotherms. The electrical conductivity was estimated using current–voltage curves. The mechanical properties of the samples were evaluated using dynamic mechanical analysis (DMA) and correlated with the structural parameters of the composites. The adsorption and swelling properties paralleled the change in the electrical and mechanical properties of the materials. In most cases, samples with higher content of chitosan exhibit higher adsorption and mechanical properties, and lower conductivity. Acid-doped samples showed much higher adsorption, swelling, and electrical conductivity than their undoped analogues.

Binary Pectin-Chitosan Composites for the Uptake of Lanthanum and Yttrium Species in Aqueous Media

“…The smaller particle size of the PC 51 S composite may be due to the formation of the amide linkage between pectin and chitosan polymers [ 13 ]. As the concentration of the chitosan increased, the particle size of composites increased because the swelling behavior of chitosan and water molecules can be absorbed to increase the size of composites [ 30 , 31 ]. The chitosan particle (d = 723 nm) has the smallest diameter when compared to the composites, which concur with estimates from another study [ 24 ].…”

Polyaniline/Biopolymer Composite Systems for Humidity Sensor Applications: A Review

“…The value of water vapor adsorption is proportional to the environmental RH [ 77 ]. Hereafter, an increase in RH implicitly assumes an increase in the extent of adsorption, where there are two types of humidity-sensing (resistive and capacitive) devices, as outlined in Table 1 .…”

“…Since the conductivity of PANI depends strongly on its oxidation state, synthesis is often directed at the preparation of conductive emeraldine salt (PANI-ES) forms. Salt formation is aided by the use of dopants such as HCl or acetic acid, where some studies report the use of an intermediary neutralization step with NaOH (leading to a de-doped emeraldine base (PANI-EB) form), with subsequent re-doping upon the addition of an acid to obtain conductive PANI-ES [ 77 , 85 , 86 ]. Polymerization is carried out in the presence of an ammonium persulfate (APS) initiator.…”

“…Although numerous papers reported comparable synthetic procedures, the structural features of PANI/CHT composites are variable. The bonding interactions between PANI and CHT have been described in the literature [ 77 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 ], which include noncovalent (hydrogen bonding) interactions shown in Figure 6 a, along with covalent grafting of chitosan units onto PANI via covalent bonding (cf. Figure 6 b).…”

“…Previous reports [ 85 , 89 ] for PANI/CHT composites indicate that such materials possess higher crystallinity with respect to pristine PANI but are lower than that of pure CHT. The electrical conductivity values of PANI/CHT samples have been reported in the range of 10 −6 to 10 −3 S/cm [ 77 , 84 , 87 ]. The water vapor adsorption by PANI/CHT composites shows an increase as the RH levels rise, resulting in greater electrical conductivity.…”