Highly porous hydrogels based on functionalized glycidyl methacrylate (GMA) have been successfully prepared through the high internal phase oil-in-water emulsions. Pre-polymerization functionalization of GMA monomer, porous structure and water uptake of highly porous hydrogels were investigated. The primary amine groups of tris(2-aminoethyl)amine (TRIS) or 1,2-diaminoethane (EDA) were found to react in three distinct reactions with the GMA, giving a mixture of methacrylate and methaycrylamide as the major products with a small amount of the aza-Michael addition product, which were then polymerized. The water uptake and the specific surface area were found to be between 4-5 times higher than the corresponding values for the conventional GMA-based polyHIPE prepared from the water-in-oil HIPE. These results demonstrate a highly efficient pre-polymerization functionalization method for the preparation of GMA-based hydrogel polyHIPEs.
COBISS.SI-ID: 5948698
Superabsorbent, mechanically robust, high-porosity hydrogels based on poly(2-acrylamido-2-methyl-propansulfonic acid) (PAMPS) were successfully synthesized by templating within high internal phase emulsions (HIPEs). The more loosely crosslinked hydrogel polyHIPEs exhibited unusually high water uptakes, up to 338 g/g, when compared to a superabsorbent polymer (SAP) taken from a commercial diaper. All the hydrogel polyHIPEs exhibited artificial urine uptakes that were superior to that of the SAP taken from a commercial diaper. The more highly crosslinked polyHIPEs also exhibited extraordinary absorption of water-soluble contaminants: a hydrogel polyHIPEs with 3.1 mmol/g of highly accessible sulfonic acid groups exhibited a rapid adsorption of contaminants in water. The highly swollen hydrogel polyHIPE monoliths (cube of 1 cm3) do not fail at compressive strains of up to 60%, retaining water, and recovering their shapes upon the removal of stress.
COBISS.SI-ID: 5995802
A new process for the production of nanocellulose from selected cellulose-containing natural materials has been developed. The liquefaction reaction, using glycols and mild acid catalysis (methane sulphonic acid), was applied to four model materials, namely cotton linters, spruce wood, eucalyptus wood and Chinese silver grass. The process contains only four steps, i.e. the milling, glycolysis reaction, centrifugation and final rinsing with an organic solvent. The nanocrystalline cellulose recovery was between 56 and 75%. The crystallinity index was greater than that of the starting materials due to the liquefaction of lignin, hemicelluloses and amorphous cellulose. The final product was a stable, highly concentrated nanocrystalline cellulose suspension in the organic medium. The liquid residue obtained after liquefaction of the cotton linters contained significant quantities of levulinic acid and various sugar types.
COBISS.SI-ID: 38446853
Nanocrystalline cellulose (NCC) was isolated from microcrystalline cellulose by the polyol method in ethylene glycol. NCC was then modified with 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPADB) RAFT reagent to prepare the RAFT modified NCC. At optimal reaction conditions one CPADB molecule was bonded on average to every sixth β-glycoside ring. RAFT modified NCC was further used for grafting from reaction of methyl methacrylate (MMA) to produce the poly(methyl methacrylate) (PMMA) modified NCC. All three types of NCC, i.e. the unmodified NCC, RAFT modified NCC and PMMA modified NCC, were further used as the nanofillers in the preparation of PMMA/NCC composite plates by bulk polymerization of MMA. UV-VIS spectroscopy of PMMA/NCC composites showed enhanced visible light transparency when the RAFT modified NCC or PMMA modified NCC had been used as compared to the unmodified NCC. Mechanical properties measurements (tensile tests, dynamic mechanical analysis and Charpy impact resistance) showed that the modified NCC are the nanofillers with moderate potential in reinforcing the PMMA matrix, while the unmodified NCC caused detrimental effect on the mechanical properties of the PMMA/NCC composites.
COBISS.SI-ID: 5810714
The paper presents the first study of the ingestion and effects of textile fibers on a model freshwater zooplankton crustacean Daphnia magna. It has been shown that significant quantities of fibers are emitted into the environment during clothes washing making it a very relevant class of microplastics, especially in freshwater environments. Polyethylene terephthalate fibers used in the experiments were ground to simulate the effects of washing stress and weathering (approx. length: 60-1400 μm, width 30-530 μm, thickness 1-21 μm). Daphnia magna were subject to 48 h exposure to fibers followed by a 24 h of recovery in fiber-free medium and algae. The majority of ingested fibers by D. magna were approx. 300 μm in length, but also some very large twisted fibers around 1400 μm in length were found inside the gut. Exposure to fibers resulted in increased mortality of daphnids after 48 h in the case where daphnids were not pre-fed with algae prior to experiment, but no effect was found when daphnids were fed before the experiments. Regardless of the feeding regime, daphnids were not able to recover from fiber exposure after additional 24 h incubation period in a fiber free medium with algae. The study shows that Daphnia magna ingests textile fibers but is not able to excrete long fibers, which increase their mortality.
COBISS.SI-ID: 4088655