Prikaz stereokemijskih istraživanja kiralnih malih organskih molekula i optički aktivnih polimera otkriva akademika Dragutina Fleša kao utemeljitelja ovih područja organske kemije u Hrvatskoj. ...Izdvojeno su prikazani najznačajniji znanstveni rezultati sinteze kiralnih β-aminokiselina i njihovih analoga, korelacija apsolutne konfiguracije u biološki značajnim strukturama kao što su efedrin i antibiotik kloramfenikol. Kronološki su slijedila istraživanja na području optički aktivnih polimera pripravljenih iz kiralnih derivata cisteina preko reaktivnih β-tiolaktona te iz mono- i disupstituiranih butadiena i vinil-alkil etera.
Cilj je ovoga istraživanja bio utvrditi in vivo toksičnost i raspodjelu jednokratne i višekratnih doza polimernih nanočestica L-glutaminske kiseline-g-p(HEMA) u funkciji isporuke lijekova. ...Jednokratna oralna doza nije prouzročila smrtnost, a akutni LD50 iznosio je >2,000 mg/kg tjelesne težine. Višekratne oralne dnevne doze od 25 mg, 50 mg i 100 mg/kg tjelesne težine, davane 28 dana, nisu dovele do značajnih razlika u ukupnoj tjelesnoj i relativnoj težini organa u usporedbi s kontrolnom skupinom. Ove rezultate potvrđuju biokemijski i histološki nalazi. Izloženost nanočesticama nije uzrokovala statistički značajne razlike u broju mikronukleusa u stanicama koštane srži miševa u odnosu na kontrolu. Raspodjela nanočestica u tijelu mijenjala se s vremenom, a nanočestice bi doprle u organe, pa i u koštanu srž, unutar prvih šest sati od primitka doze, što je utvrđeno ex vivo snimkama dobivenim pomoću sustava IVIS® Spectrum. Naši rezultati upućuju na to da su polimerne nanočestice L-glutaminske kiseline-g-p(HEMA) biokompatibilne i imaju potencijala za primjenu kao sustav isporuke lijekova.
Molecular Gels Weiss, Richard G; Terech, Pierre
2005, 2005-12-12
eBook
"Molecular Gels: Materials with Self-Assembled Fibrillar Networks" is a comprehensive treatise on gelators, especially low molecular-mass gelators and the properties of their gels. The structures and ...modes of formation of the self-assembled fibrillar networks (SAFINs) that immobilize the liquid components of the gels are discussed experimentally and theoretically. The spectroscopic, rheological, and structural features of the different classes of low molecular-mass gelators are also presented. Many examples of the application of the principal analytical techniques for investigation of molecular gels (including SANS, SAXS, WAXS, UV-vis absorption, fluorescence and CD spectroscopies, scanning electron, transmission electron and optical microscopies, and molecular modeling) are presented didactically and in-depth, as are several of the theories of the stages of aggregation of individual low molecular-mass gelator molecules leading to SAFINs. Several actual and potential applications of molecular gels in disparate fields (from silicate replication of nanostructures to art conservation) are described. Special emphasis is placed on perspectives for future developments.
This book is an invaluable resource for researchers and practitioners either already researching self-assembly and soft matter or new to the area. Those who will find the book useful include chemists, engineers, spectroscopists, physicists, biologists, theoreticians, and materials scientists.
Gospodarenje otpadnom plastikom Budiša, Mirko; Ptiček Siročić, Anita
Kemija u industriji; časopis kemičara i tehnologa Jugoslavije,
09/2022, Letnik:
71, Številka:
9-10
Journal Article
Recenzirano
Odprti dostop
U zadnjih pedesetak godina zabilježen je značajan rast količina plastičnog otpada koji nekontroliranim odbacivanjem postaje sve veći problem za okoliš i sa značajnim posljedicama na živuće ...ekosustave. Plastika je važan i sveprisutan materijal u gospodarstvu i svakodnevnom životu i godišnje u zemljama Europske unije nastaje blizu 26 milijuna tona plastičnog otpada. Oko 30% tog otpada se reciklira, znatan dio se energetski oporabljuje, a dio se još uvijek odlaže i na odlagališta otpada. Recikliranjem plastičnog otpada čuvaju se prirodne sirovine kao što su nafta i zemni plin koje se upotrebljavaju za proizvodnju plastičnih materijala te se smanjuju emisije u okoliš i potrošnja energije. Planom za resursno učinkovitu Europu, plastični otpad prepoznat je kao važna sirovina za proizvodnju novih proizvoda i jedna je od ključnih sirovina u prelasku na kružno gospodarstvo. U ovom je radu dan prikaz općih mogućnosti recikliranja tj. oporabe plastičnog otpada. Na temelju indikativnih rezultata ispitivanja sastava odvojeno prikupljenog plastičnog otpada u Zagrebu dana je procjena mogućnosti njegove reciklaže. U Republici Hrvatskoj plastični otpad velik je problem budući da se adekvatno ne sortira. Zbog toga je značajno financijsko opterećenje komunalnim društvima koja njime gospodare u sklopu javne usluge prikupljanja komunalnog otpada.
The aim of this safety study in mice was to determine
toxicity and biodistribution potential of a single and multiple doses of L-glutamic acid-g-p(HEMA) polymeric nanoparticles as a drug delivery ...system. The single dose did not cause any lethal effect, and its acute oral LD
was >2.000 mg/kg body weight (bw). Multiple doses (25, 50, or 100 mg/kg bw) given over 28 days resulted in no significant differences in body and relative organ weights compared to control. These results are supported by biochemical and histological findings. Moreover, nanoparticle exposure did not result in statistically significant differences in micronucleus counts in bone marrow cells compared to control. Nanoparticle distribution was time-dependent, and they reached the organs and even bone marrow by hour 6, as established by
imaging with the IVIS
spectrum imaging system. In conclusion, L-glutamic acid-g-p(HEMA) polymeric nanoparticles appear biocompatible and have a potential use as a drug delivery system.
The latest research is about ProsopisJuliflora’s mining and characterization officers. The fibres were cut, chemically treated using sodium and hydrochloric acid (alkali) solutions. Chemically ...modified and non-modified fibres have been analysed for their thermal, chemical, crystalline, electrical, morphological and tensile characteristics. The findings showed that a cellulose content was increased by 59.8 % with a reduction of amorphous content and humidity by chemical treatment with alkali. However, due to its acid-plus attacks whose values were lower than untreated, the treatment for hydrochloric acid reduced cellulosis material. There were four hundred and seventeen nm of crystalline fibre of alkaline therapy, less than one 68.01 nm. Thus the ProsopisJuliflora can be suggested for lightweight polymer applications as a possible reinforcement.
One of the main disadvantages of the use of synthetic or semi-synthetic polymeric materials is their degradation and aging. The purpose of this study was to use artificial neural networks (ANN) and ...multiple linear regressions (MLR) to predict the carbonyl, hydroxyl, and polyene indices (
I
CO,
I
OH, and
I
OP), and viscosity average molecular weight (
M
V) of poly(vinyl chloride), polystyrene, and poly(methyl methacrylate). These physicochemical properties are considered fundamental during the study of photostabilization of polymers. From the five repeating units of monomers, the structure of the polymer studied is shown. Quantitative structure-property relationship (QSPR) models obtained by using relevant descriptors showed good predictability. Internal validation {
R
2, RMSE, and
Q
2LOO}, external validation {
R
2, RMSE,
Q
2pred,
r
m2, Δ
r
m2,
k
, and
k
’}, and applicability domain were used to validate these models. The comparison of the results shows that the ANN models are more efficient than those of the MLR models. Accordingly, the QSPR model developed in this study provides excellent predictions, and can be used to predict
I
CO,
I
OH,
I
OP, and
M
V of polymers, particularly for those that have not been tested.
Jedan od glavnih nedostataka upotrebe sintetičkih ili polusintetičkih polimernih materijala je njihova razgradnja i starenje. Svrha ove studije je primjena umjetnih neuronskih mreža (ANN) i višestrukih linearnih regresija (MLR) za predviđanje karbonilnih, hidroksilnih i polienskih indeksa (
I
CO,
I
OH i
I
OP) i prosječne molekulske mase viskoznosti (
M
V) poli(vinil-klorida), polistirena i poli(metil metakrilata). Ta fizikalno-kemijska svojstva smatraju se važnim tijekom proučavanja fotostabilizacije polimera. Iz pet ponavljajućih jedinica monomera prikazana je struktura ispitivanog polimera. Kvantitativni modeli odnosa strukture-svojstava (QSPR) dobiveni primjenom relevantnih deskriptora pokazali su dobru predvidljivost. Za potvrdu tih modela provedene su: interna provjera {
R
2, RMSE i
Q
2LOO}, vanjska provjera {
R
2, RMSE,
Q
2pred,
r
m2, Δ
r
m2,
k
i
k
’} i domena primjenjivosti. Usporedba rezultata pokazuje da su modeli ANN učinkovitiji od modela MLR. Prema tome, model QSPR razvijen u ovoj studiji pruža izvrsna predviđanja i može se primjenjivati za predviđanje
I
CO,
I
OH,
I
OP i
M
V polimera, posebno za one koji nisu testirani.
Recikliranje otpadne gume devulkanizacijom Ptiček Siročić, Anita; Florijanić, Franjo; Šokman, Maja ...
Kemija u industriji,
06/2019, Letnik:
68, Številka:
5-6
Journal Article, Paper
Recenzirano
Odprti dostop
Posljednjih nekoliko desetljeća polimeri i polimerni materijali postali su neizostavni dio različitih grana industrije i svakodnevnog života. Zbog vrlo raširene upotrebe elastomera nastaju velike ...količine gumenog otpada, što je opterećenje za okoliš te zahtijeva posebne mjere zbrinjavanja kako bi se smanjio njihov negativan utjecaj na okoliš. Uzorci polimernih mješavina na bazi prirodnog (NR) i stiren-butadienskog kaučuka (SBR) pripremljeni su u dvije serije s ciljem ispitivanja mehaničkih (prekidna čvrstoća, prekidno istezanje, ispitivanje čvrstoće na zarez) i reoloških svojstava te krajnje upotrebe u proizvodnji gumenih pružnih prijelaza. Prva serija uzoraka pripremljena je s gumenim prahom, a u drugu seriju umiješan je devulkanizirani gumeni prah. Uzorci su miješani na laboratorijskom mikseru te homogenizirani na laboratorijskom dvovaljku, a proces prešanja proveden je na hidrauličkoj preši. Dobiveni rezultati ispitivanja mehaničkih i reoloških svojstava pokazali su da je za NR/SBR polimernu mješavinu koja bi se upotrebljavala za pružne prijelaze znatno bolja opcija dodatak gumenog praha koji je dodatno devulkaniziran.
Environmental protection requires constant improvement of quality and the environmental management system in accordance with the international standards and laws in order to reduce human impact on the environment and responsibly manage natural resources. Environmentally acceptable recycling of waste tires and other rubber products is one of the biggest ecological challenges today. Landfilling or dumping of tires causes serious long-term pollution. The lack of alternatives for tire recycling increases their disposal in landfills. Recycling is currently the most effective way to improve the sustainability of the environment. The purpose of this work was to determine the optimal composition of the rubber blend to be used for rubber track crossings production, and to examine the ratio of individual components,
i.e.
, milled recycled tires, and milled and devulcanized tires in order to determine which option is more environmentally friendly and financially viable. In the first series of samples, recycled rubber powder (milled recycled tires) was mixed with a polymer blend of natural rubber and styrene-butadiene rubber, while the second series was milled and the devulcanized tires mixed with natural rubber and styrene-butadiene rubber. Rheological and mechanical properties of all the samples were measured according to appropriate standards. The results showed that an increase in the ratio of rubber powder increased the values of minimal rotation resistance and proportionally reduced the maximum rotation resistance. Minor deviations in the values of the vulcanization rate indicated that various ratios of added rubber powder had no significant effect on the rate of vulcanization of individual samples. The results of the viscosity measurement indicated a proportional increase in the values of initial rotation resistance with the increase in the ratio of added rubber dust compared to the samples prepared with milled and devulcanized rubber, whereby a proportional decrease in value was apparent. From the results of mechanical properties, observed was a reduction in tensile strength and elongation at break values for both series of tested samples. The same behaviour was also observed for the tear strength values. With the addition of different filler ratios, the hardness value for both series of prepared samples had reduced, while the values of the rebound elasticity differed slightly. Significant reduction in hardness value was evident for the samples prepared with the milled and devulcanized rubber powder, which could be attributed to the use of a softener during devulcanization of the material. It can be concluded that NR/SBR polymer blends can be mixed with various recycled rubber materials whereby the devulcanization process enables better mechanical and rheological properties, thus, used rubber tires can be effectively removed from the environment.
Up-to-date, comprehensive coverage on radiation-processed polymer materials and their applicationsOffering a unique perspective of the industrial and commercial applications of the radiation ...processing of polymers, this insightful reference examines the fundamental scientific principles and cutting-edge developments advancing this diverse field. Through a variety of case studies, detailed examples, and economic feasibility analysis, Radiation Processing of Polymer Materials and Its Industrial Applicationssystematically explains the commercially viable ways to process and use radiation-processed polymeric materials in industrial products. In addition, this one-of-kind text:Covers important chemistry and processing fundamentals, while emphasizing their translation into practical applications of radiation-processed polymersIncorporates new applications in nanotechnology, biomaterials, and recyclingSystematically discusses new developments in the field and summarizes past achievementsBy helping readers—from students to scientists, engineers, technicians, and sales and marketing professionals—understand and solve problems associated with radiation processing of polymers, Radiation Processing of Polymer Materials and Its Industrial Applicationsserves as an essential reference and fills an important gap in the literature.
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