No abstract

A series of micro algea-based hydrogel composites were prepared from polyacrylamide and Spirulina (PAAm-sp). Free radical polymerization of acrylamide (AAm) in the presence of N,N-methylene bis-acrylamide (BAAm), as a crosslinker, and Spirulina microalgae in different loadings was conducted. Chromium metal adsorption capacity was determined with UV-VIS spectroscopy whereas mechanical performance of the resultant hydrogel composites was followed with uniaxial compression experiments. It has been found that efficiency can be tuned by Spiriluna composition in hydrogel. PAAm hydrogel composite having 0.5 % Spirulina had the maximum compression strength, good swelling in water as well as improved thermal stability due to the special and beneficial 'fishnet morphology" observed via scanning electron microscopy (SEM). The observed high performance of this composition is proved to be due to this morphology where all potential binding sites are under receptive position for metal adsorption. Spirulina by itself in water can remove only about 2 % of its weight of Cr +3 ion, however in the hydrogel structure this removal increases up to 200 % which makes this biotechnological approach superior in the metal removal from the water.

We report the synthesis of high-molecular-weight linear polyisobutylenes (PIBs) and PIB networks from low-molecularweight PIB by thiol-ene click chemistry. Thus, liquid allyl-telechelic PIB was reacted with small di-and tri-thiols, and the thiolated intermediates chain-extended by UV-or thermally induced free radical initiation to linear and crosslinked products. PIB networks were also prepared by crosslinking SH-telechelic PIB with a small triallyl compound. Linear products were characterized by 1 H NMR spectroscopy and GPC, and networks by FTIR spectroscopy, extractables, swelling, and permanent set. The effect of reaction conditions (nature of thiol chain extender, concentration of photo-and thermal initiators, UV radiation time, and reagent concentrations) on chain extension and crosslinking was investigated. Under well-defined conditions high-molecular-weight PIBs and tight PIB networks were prepared. Thiol-ene click chemistry provides novel thiolated PIB derivatives and is a useful strategy for the convenient preparation of high-molecular-weight rubbery PIBs and tight PIB networks from low-molecular-weight PIB precursors.

The synthesis of diblock copolymers of poly(N‐isopropylacrylamide) (PNIPAM) and poly(vinyl acetate) (PVAc) was performed by macromolecular design via interchange of xanthates (MADIX) process. Following the preparation of methyl (isopropoxycarbonothioyl) sulfanyl acetate (MIPCTSA) as chain transfer agent, it was reacted with vinyl acetate to obtain PVAc macro‐chain transfer agent. Then, block copolymerization was completed by successive addition of N‐isopropylacrylamide (NIPAM). 1H NMR spectroscopy confirmed the presence of both blocks in the copolymer structure, with the expected composition based on the feed ratio. Size Exclusion Chromatography (SEC) was used to investigate the relative values of molecular characteristics. Only 20% of PVAc was converted to block copolymer. The resultant block copolymer structures were further examined in terms of their morphologies as well as critical micelle concentration (CMC) by using ESEM and Fluorescence Excitation Spectroscopic techniques, respectively. Morphological characterization confirmed amphiphilic block copolymer formation with the existence of mainly ca. 100 nm well distributed micelles. The thermo responsive amphiphilic behavior of the block copolymer solutions were followed by Dynamic Light Scattering (DLS) technique.