Chemical and Electrochemical Synthesis of Contemporary Materials Based on Biopolymers and Metals

Abstract

New biopolymers’ materials, suitable for the adsorption of noble metal ions, were synthesized by chemical and electrochemical modification of biopolymers. Optimization of cellulose acrylate synthesis by reaction with sodium cellulosate and acryloyl chloride was carried out. Optimal conditions for conducting the synthesis reaction of cellulose acrylate were as follows: the molar ratio of cellulose/potassium-t-butoxide/acryloyl chloride was 1:3:10 and the optimal reaction time was 10 h. On the basis of elemental analysis with optimal conditions for conducting the reaction of cellulose acrylate, the percentage of substitution of glucose units in cellulose was Y = 80.7%, and the degree of substitution of cellulose acrylate of DS = 2.4 was determined. The grafting reaction of acrylate vinyl monomers onto cellulose in acetonitrile with azoisobutyronitrile initiator in a nitrogen atmosphere was performed, by mixing for 5 h at acetonitrile boiling temperature. Radical copolymerizations of synthesized cellulose acrylate and 4-vinylpyridine, 1-vinylimidazole, 1-vinyl-2-pyrrolidinone, 9-vinylcarbazole, cellulosepoly-4-vinylpyridine, cellulose-poly-1-vinylimidazole, cellulose-poly-1-vinyl-2-pyrrolidinone and cellulose-poly-9-vinylcarbazole were performed. Cellulose acrylate and cellulose grafted copolymers were confirmed by IR spectroscopy, based on elementary analysis and the characteristics of grafted copolymers of cellulose were determined. The mass share of grafted copolymers, X, the relationship of derivative parts/cellulose vinyl group, Z, and the degree of grafting copolymers of cellulose (mass%) were determined. The grafed copolymers of cellulose with 4-vinylpyridine and 1- vinylimidazole were reacted with methyl iodide and the corresponding 1 - methylpyridinium iodide and 3-methylimidazolium iodide copolymers of cellulose were obtained. Copolymers were transformed into new polymeric reagents, differing in anions (ClO4-, CF3COO-, NO3-, p-TsO-, BF4-, PF6-) by usage of different supporting electrolyte carrying the desired anions through the ion-exchange-electrochemical oxidation of the released iodide at a controlled anodic potential. The thermal stability of cellulose and some of its grafed copolymers with 4-vinyl pyridine in ionic form were studied in nitrogen atmosphere by non-isothermal thermogravimetry in the temperature interval 50-800°C at heating rate of 10°C/min and 80°C/min. Comparasion of the obtained thermogravimetric curves indicated the different thermal stability of cellulose, cellulose-4- vinylpyridine and its ionic derivates. The starting cellulose sample has had the highest thermal stability, while the copolymers in ionic form started to degrade at lower temperatures. There were also differences in the amount of carbonaceous residues at 550°C and 760°C. Grafted copolymers of cellulose were synthesized and tested for sorption of gold and palladium from acid aqueous solutions. The following grafted copolymers cellulose-poly-4-vinyl-pyridine, cellulose-1-methyl-poly-4-vinyl-pyridinium iodide and cellulose-1-methyl-poly-4-vinyl pyridinium three fluoroacetate were synthesized. Characteristcs of grafted cellulose copolymers such as: capacity, degree of sorption in the solution from the process for copper electrolysis were determined. The quantity of gold and palladium were determined by atomic apsorption spectrophotometry. The degree of sorption of all samples of grafted copolymers was more than 99 mass %, indicating that the sorption was good and took place in a period of one hour. Cellulosepoly-4-vinyl-pyridine showed the selectivity due to sepatarion of Au and Pd in regard to Cu and Fe. The capacities of cellulose copolymers for Au and Pd sorptions were determined. Grafted cellulose copolymers suitable for sorption of gold have potential to be used in cancer nanotechnology. Optimization of cellulose acrylate synthesis has been applied as a model for the synthesis of the grafted copolymers of lignin and tannin with vinyl monomers and it can be applied on lignocellulose, starch, chitin, chitosan, proteins and peptides. Synthesis and characterization of electroconductive composite materials prepared by the compression molding of mixtures of lignocellulose and electrochemically deposited copper powder under different pressures is presented. Investigation of the influence of particle size on conductivity and percolation threshold of obtained composites was carried out. Electrodeposited copper powder content was varied from 2.0-29.8 vol. %. Analyses of the most significant properties of individual components and prepared composites included structural and morphological analysis and measurements of hardness and electrical conductivity. The significant increase of the electrical conductivity could be observed as the copper powder content reached the percolationthreshold. The packaging effect and effective interpartical contact with smaller, highly porous, highly dendritic particles with large values of specific area lead to “movement” of percolation threshold towards lower filler content, which for the particles <45 μm and highest processing pressure of 27 MPa was 7.2% (v/v). In the investigated range of electrodeposited copper powder concentrations and applied pressures, the increase of the electrical conductivity of composites was as much as fourteen orders of magnitude. It was found that this transition occured at lower volume fractions for electrodeposited copper powder than stated in the literature which could be due to the filler with large specific area.