Other natural polymer-based systems

The electrical properties of polymer electrolytes based on chitosan/PEO blends with LiTFSI salt were described by Idris et al. Conductivities between 10 and 10 S/cm were reported for samples based on swelling chitosan membranes and ammonium salts (NH4NO3 and NH4CF3SO3), which in water promote the protonation of chitosan amino groups, leading to protonic conductivity.  

Ionic conducting composites of chitosan, poly(aminopropyltriethoxysil ane), poly(ethylene oxide) (CHEpAPS/PEO) and a fixed amount of lithium salt were studied by Puentes et a/. The ternary composition Li (CHI)i(PEO)2(pAPS)i,2 reached a conductivity value of 1.7 x 10 S/cm at room temperature. It was also stated that this very transparent and good conducting structure was constituted essentially by lithium ion coordinated by APS residues intercalated in a layered CHI/PEO matrix. 

The ionic conductivity in the wet state of phosphorylated chitosan membranes prepared from the reaction of orthophosphoric acid and urea on the surface of chitosan membranes in AA -dimethylformamide was investigated by Wan et alP The authors observed that similarly to unmodified chitosan membranes phosphorylated chitosan membranes are hardly conductive in their dry states with conductivities between 10 and 10 S/cm. The entire conduction process occurs after the water incorporation increases the ionic conductivity values up to 10 and 10 S/cm depending on the phosphorus content in the sample. The best result of 1.2 x 10 S/cm was obtained with the sample containing 87.31 mg/m of phosphorus content. They also observed that the increase in the phosphorus content promotes a decrease in the crystallinity of phosphorylated chitosan membranes, an increase in the swelling index and not a significant loss of their tensile strength and thermal stability in comparison with the unmodified chitosan membranes. 

Another study published by Wan et reported on the di-o-butyryl-chitosan, prepared by reacting chitosan with butyric acid anhydride in the presence of perchloric acid as a catalyst. As in the previous study, the authors observed a decrease in the crystallinity of the samples due to the modification reaction and that the swelling indices of modified membranes were increased significantly in direct proportion to the degree of substitution. The thermogravimetric analysis indicated that the modified membranes exhibited a slightly increased thermal stability compared to the unmodified membrane. The ionic conductivity of di-o-butyrylchitosan membranes in the dry state exhibited ionic conductivities between 10 and 10 S/cm, which increased up to 10 S/cm for 25% of substitution after hydration. 

Chitosan/polyaniline (PANl) semi-interpenetrating network (semi-IPN) polymers were prepared and studied by Kim et The authors observed that the conductivity of the semi-lPNs increases from 10 to 10 S/cm with increasing PANI contents, adjusted to pH 1, forming a blended structure. They stated that the increase in the electrical conductivity caused by the interaction of the components also reflects the charge transfer and is associated with the acidic doping of PANl. 

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New natural polymers based on synthesis from renewable resources, improved recyclability based on retrosynthesis to reusable precursors, and molecular suicide switches to initiate biodegradation on demand are the exciting areas in polymer science. In the area of biomolecular materials, new materials for implants with improved durability and biocompatibility, light-harvesting materials based on biomimicry of photosynthetic systems, and biosensors for analysis and artificial enzymes for bioremediation will present the breakthrough opportunities. Finally, in the field of electronics and photonics, the new challenges are molecular switches, transistors, and other electronic components molecular photoad-dressable memory devices and ferroelectrics and ferromagnets based on nonmetals. 

The electron-transfer rate between large redox protein and electrode surface is usually prohibitively slow, which is the major barricade of the electrochemical system. The way to achieve efficient electrical communication between redox protein and electrode has been among the most challenging objects in the field of bioelectrochemistry. In summary, two ways have been proposed. One is based on the so-called electrochemical mediators, both natural enzyme substrates and products, and artificial redox mediators, mostly dye molecules and conducted polymers. The other approach is based on the direct electron transfer of protein. With its inherited simplicity in either theoretical calculations or practical applications, the latter has received far greater interest despite its limited applications at the present stage. 

In summary, I have discussed a semi-phenomenological elastic theory for ion clustering in ionomers. The theory is consistent with observed trends in perfluorinated ionomers. I have also demonstrated the percolatlve nature of ion transport in these ionomers and computed quantitatively their tensile modulus. Finally, I have discussed the Influence of morphology on ion selectivity in perfluorinated ionomer blends. In particular, I have pointed out that an universally preferred morphology beneficial to all blends does not exist the ideal morphology must be individually determined based on component properties. Most of the theories and conclusions here are very general and applicable to other composite polymer systems. 

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