The synthesis structure and properties of segmented poly(urethane-urea-siloxanes)

Segmentirani poli(uretan-urea-siloksanski) kopolimeri (PUUS), na bazi 4,4'– metilendifenildiizocijanata (MDI) i etilendiamina (ED) kao komponeti tvrdog segmenta i α,ω–dihidroksipropil-poli(dimetilsiloksana) (PDMS, Мn = 1000 g mol-1) kao mekog segmenta, sintetisani su postupkom dvostepene poliadicije u rastvoru, uz kalaj-oktoat kao katalizator. Eksperimentalni uslovi za sintezu PUUS kopolimera su optimizovani variranjem temperature, odnosa korastvarača, koncentracije katalizatora, početne koncentracije monomera i vremena druge faze reakcije poliadicije. Za sintezu su korišćene dve različite smeše rastvarača: tetrahidrofuran/N,N-dimetilacetamid (THF/DMAc) i tetrahidrofuran/N-metilpirolidon (THF/NMP), pri konstantnom molarnom odnosu monomera (PDMS:MDI:ED=1:2:1). Pokazano je da polarnija THF/NMP smeša predstavlja bolju reakcionu sredinu za sintezu PUUS. Nađeno je da su optimalni reakcioni uslovi sledeći: temperatura 40 °C, koncentracija katalizatora 0,05 mol. % (u odnosu na PDMS), koncentracija monomera u reakcionoj smeši 25 mas. % i vreme druge faze reakcije 3 h, pri zapreminskom odnosu korastvarača THF/NMP=1:9. Serija PUUS kopolimera sa različitim sadržajem tvrdih segmenata sintetisana je pod optimalnim reakcionim uslovima, u THF/NMP smeši sa velikim udelom polarnog NMP rastvarača, što je omogućilo dobru rastvorljivost rastućih polimernih lanaca i dobijanje kopolimera relativno velike molarne mase. Molarni odnos PDMS-a, MDI-a i ED-a je variran od 1:2:1 do 1:6:5, što je odgovaralo promeni masenog udela tvrdih segmenata u kopolimerima od 36 do 64 mas. %. Struktura i sastav PUUS kopolimera su potvrđeni 1H NMR i FTIR spektroskopijom. Prosečna dužina sekvenci mekih i tvrdih segmenata, kao i raspodela sekvenci tvrdih segmenata u seriji PUUS kopolimera, dobijena je korišćenjem 13C NMR i dvodimenzionalne korelacione NMR spektroskopije. Kopolimeri sa manjim sadržajem tvrdih segmenata su imali nasumičnu raspodelu tvrdih i mekih segmenata duž kopolimernih lanaca, dok su se kopolimeri sa udelom tvrdih segmenata većim od 55 mas. % ponašali kao multiblok-kopolimeri. Detaljna analiza strukture je pokazala da se prosečna dužina sekvenci tvrdih urea segmenata povećavala od 2,2 do 4,9 sa povećanjem njihovog masenog udela od 38 do 65 mas. %. Na osnovu rezultata termičke i mehaničke analize, zatim analize rasipanja X-zraka na malim uglovima (SAXS), kao i FTIR analize vodoničnog vezivanja, utvrđeno je da sintetisani PUUS kopolimeri pokazuju mikrofazno razdvojenu strukturu i velike vrednosti zatezne čvrstoće. Globularne superstrukture, zapažene u filmovima uzoraka kopolimera pomoću skenirajuće elektronske mikroskopije (SEM) i mikroskopije atomskih sila (AFM), bile su posledica mikrostrukturne organizacije MDI–ED segmenata, zavisno od njihovog udela i dužine. Velike vrednosti početnih elastičnih modula i zatezne čvrstoće su bile posledica prisustva veoma jakih bidentatnih urea vodoničnih veza. PUUS kopolimeri su pokazali veliku otpornost na vodu, pri čemu se hidrofobnost i hrapavost njihove površine neznatno povećavala sa povećanjem masenog udela PDMS segmenta, što čini ove materijale pogodnim za potencijalnu biomedicinsku primenu...Segmented poly(urethane-urea-siloxane) copolymers (PUUS), based on 4,4′- methylenediphenyl diisocyanate (MDI) and ethylene diamine (ED) аs the hard segment components and α,ω-hydroxypropyl-poly(dimethylsiloxane) (PDMS, Mn= 1000 g mol-1) as the soft segment were prepared by a two-step polyaddition procedure in a solution in the presence of stannous octoate as a catalyst. The experimental conditions for the synthesis of PUUS copolymers were optimized by varying the temperature, the cosolvents ratio, the concentration of the catalyst, the initial monomer concentration and the time of the second step of the polyaddition reaction. Two different solvent mixtures: tetrahydrofuran/N,N-dimethylacetamide (THF/DMAc) and tetrahydrofuran/Nmethylpyrrolidone (THF/NMP) were used for the synthesis, at constant molar ratio of the monomers (PDMS:MDI:ED = 1:2:1). It was demonstrated that the more polar THF/NMP mixture was a better reaction medium for the synthesis of PUUSs. The following conditions were optimal: a temperature of 40 °C, a catalyst concentration of 0.05 mol % (calculated to PDMS), a monomer concentration in the reaction mixture of 25 wt. % and a reaction time for the second step of 3 h, at the co-solvent ratio of THF/NMP = 1:9. A series of PUUS copolymers with different hard segment content was synthesized under optimal reaction conditions, in THF/NMP mixture with a large proportion of polar NMP solvent, which provided good solubility of the growing chains, thus ensuring copolymers of relatively high molecular weight. The molar ratio of PDMS, MDI and ED was varied from 1:2:1 to 1:6:5, which resulted in the predetermined content of the hard segments from 36 to 64 wt. %. The structure and composition of the PUUSs were confirmed by 1H NMR and FTIR spectroscopy. The mean sequence length of the soft and hard segments, as well as the sequence distribution of the hard segments in the PUUS series, were obtained by 13C NMR and two-dimensional correlation spectroscopy. The copolymers with lower hard segment content were random, while the others with the hard segment content higher than ~ 55 wt. % were multi-block copolymers. Detailed structural analysis showed that the mean sequence length of the hard urea segments increased from 2.2 to 4.9 with increasing hard segments content from 38 to 65 wt. %. Thermal, mechanical, small-angle X-ray scattering (SAXS) and hydrogen bonding analyses by FTIR indicated the formation of the microphase-separated copolymers with high tensile strength. Globular superstructures observed in the copolymer films by scanning electron microscopy (SEM) and atomic force microscopy (AFM) were probably arisen from the microstructural organization of the MDI–ED segments, depending on their content and length. The high initial elastic modulus and high values of tensile strength of the PUUSs are the consequences of the presence of a very strong urea bidentate hydrogen bonding. The PUUS copolymers showed high water resistance, their surface became more hydrophobic and the values of the surface roughness slightly increased with increasing the weight fraction of the PDMS segment, which suggested a great promise for the possible use of PUUS copolymers in potential biomedical applications..

Synthesis and structure-property relationships of biodegradable polyurethanes

This chapter deals with a commercially very important part of the polyurethane (PU) polymer family, biodegradable polyurethanes (BioPUs). PUs are multiblock copolymers composed of a high molecular weight macrodiol, called a soft segment, and a hard segment composed of a diisocyanate and a low molecular weight diol. As a result of the thermodynamic incompatibility of the hard and soft segments in PU copolymers the phenomenon of microphase separation occurs. Nowadays, it is generally accepted that the overall properties, as well as the biocompatibility, of segmented PU and poly(urethane urea) (PUU) copolymers are correlated to the degree of microphase separation. The thermoplastic and elastic behaviour of these copolymers can be explained by their multiphase structure. The elastomeric properties of these copolymers are generally attributed to the phase separation of the hard and soft segments; the hard domains serve as crosslinks and reinforcing fillers in the matrix of the soft segment. It is generally assumed that the soft phase is responsible for the reversible elasticity of the polymeric material, whereas the hard phase is responsible for the mechanical strength properties

Supplementary material for the article: Samelak, I.; Balaban, M.; Vidović, N.; Koljančić, N.; Antić, M.; Šolević-Knudsen, T.; Jovančićević, B. Application of Alkane Biological Markers in the Assessment of the Origin of Oil Pollutants in the Soil and Recent River Sediments (River Vrbas, Bosnia and Herzegovina). Journal of the Serbian Chemical Society 2018, 83 (10), 1167–1175. https://doi.org/10.2298/JSC180501061S

Supplementary material for: [https://doi.org/10.2298/JSC180501061S]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2237

Application of alkane biological markers in the assessment of the origin of oil pollutants in the soil and recent river sediments (River Vrbas, Bosnia and Herzegovina)

In this paper, an attempt was made to contribute to the use of biological markers, n-alkanes, and polycyclic alkanes of the sterane and terpane type, in the assessment of the source of oil pollutants in the environment using the example of the correlation between recent river and coastal sediments,. Four samples of recent river sediments of the Vrbas River and four samples of adjacent bank sediments (soils), in the part of the River that belongs to the city of Banja Luka (Bosnia and Herzegovina) were analyzed. In the alkane fractions of isolated extracts, a bimodal distribution of the n-alkanes was observed. Lower homologues dominated in the recent river sediments with maximum at C15, but higher n-alkanes dominated in the soil samples, with a maximum at n-C29 or at n-C31. The higher concentration of steranes and terpanes with oil type distributions in the recent/fresh river sediments (compared to the bank sediments) represents evidence that lower n-alkanes originate from oil sources. The higher content of total hydrocarbons in the recent river sediments than in the bank sediments further confirms this conclusion. At the same time, these fundamental considerations provide evidence that oil pollution primarily occurred in the water flow and then the oil pollutants propagated towards the riverbank

Influence of a storage conditions on migration of bisphenol A from epoxy-phenolic coating to canned meat products

The migration of bisphenol A (BPA) from epoxy-phenolic can coating into canned meat products, produced for the needs of the Serbian Armed Forces, was investigated in this work. The tinplate cans were made according to the special military demands, filled with the beef goulash or the meatballs in tomato sauce, and preserved by sterilization. The structure of internal can coating was analyzed by FTIR spectroscopy. The migration of BPA into content of the cans was investigated after storage under regular conditions in typical military facilities. The samples of beef goulash (BG) produced in 2010-2016, and the meatballs in tomato sauce (MB) produced in 2014-2017 were tested for the presence of BPA. Thereafter, the impact of storage temperature and degree of can damage on BPA migration was examined. Both meat products were thermostated on 20 and 40 degrees C, and BPA level was measured after 3, 6, 9 and 12 months of storage. The level of BPA was determined in the content of undamaged cans, and cans with lower and higher degree of damage. The BPA was extracted from food with acetonitrile and the extracts were purified by QuEChERS procedure. The level of BPA was determined by LC-MS

Study of oil type pollutant adsorption on Vrbas River sediments (Bosnia and Herecgovina)

PAHs are a group of ubiquitous persistent organic pollutants that cause sever global environmental concerns for ecosystems and human health due to their potential toxicity and carcinogenicity. PAHs are a group of organic pollutants strongly related to anthropogenic activities such as settlement, transport, and industrial development. Due to their lipophilicity and persistence, PAHs are readily adsorbed in the particulate matter once they enter the urban river system and are finally deposited in the sediment. [1] The aim of this work was to evaluate the distribution of PAHs in the sediments of Vrbas River, to assess their occurrence and to establish the origin (pyrogenic/petrogenic) of pollution sources.This study focussed on investigation on the state of pollution and identification of potential sources of contamination of river sediments by polycyclic aromatic hydrocarbons along entire course of the Vrbas River (Bosnia and Herzegovina). Nineteen sampling points were selected covering the entire course of the Vrbas River (Bosnia and Herzegovina). The samples were extracted in a Soxhlet apparatus and fractionated using column chromatography. In the fraction of aromatic hydrocarbons, PAHs were analysed by gas chromatography - mass spectrometry (GC-MS) in a selected ion monitoring (SIM) mode. The ions monitored were: m/z = 128 (naphthalene), m/z = 152 (acenaphthylene), m/z = 154 acenaphthene), m/z = 166 (fluorene), m/z = 178 (phenanthrene andanthracene), m/z = 202 (fluoranthene and pyrene), m/z = 228 (benzo[a]anthracene and chrysene), m/z = 252 (benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[j]fluoranthene, benzo[e]pyrene and benzo[a]pyrene), m/z = 276 (indeno[1,2,3-c,d]pyrene and benzo[g,h,i]perylene), and m/z = 278 (dibenzo[a,h]anthracene) [2]. Thereafter numerous PAH diagnostic ratios were calculated and analysed. High molecular weight polycyclic aromatic hydrocarbons (4, 5 or 6 rings) are more prevalent in the observed samples. The analysis of different PAH diagnostic ratios indicate the pyrogenic PAHs origin. In most samples, according to calculated parameters, these are combustion products of coal, grass, and wood, while in some samples these parameters implicate the fuel combustion origin of PAHs. No regularity was observed in the distribution of PAHs in the samples, indicating the existence of multiple sources of these compounds in the investigated area. Thus, the conclusion is that this area was exposed to both point and diffuse sources of PAH contaminants.[https://www.mrs-serbia.org.rs/index.php/yucomat-books-of-abstracts/yucomat-wrtcs-202

Supplementary material for the article: Samelak, I.; Balaban, M.; Vidović, N.; Koljančić, N.; Antić, M.; Šolević-Knudsen, T.; Jovančićević, B. Application of Alkane Biological Markers in the Assessment of the Origin of Oil Pollutants in the Soil and Recent River Sediments (River Vrbas, Bosnia and Herzegovina). Journal of the Serbian Chemical Society 2018, 83 (10), 1167–1175. https://doi.org/10.2298/JSC180501061S

Supplementary material for: [https://doi.org/10.2298/JSC180501061S]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2237

Determination of bisphenol A traces in water samples from the Vrbas River and its tributaries, Bosnia and Herzegovina

The bisphenol A (BPA) concentration was determined in 12 surface water samples of the Vrbas River and its five tributaries. The samples were taken in the area that belongs to the city of Banja Luka (Bosnia and Herzegovina). BPA was isolated using micro liquid-liquid extraction followed by derivatization and gas chromatography-mass spectrometry analysis (GC-MS). Silylation was used as a derivatization method to increase volatility and allow the GC-MS determination of BPA. The limits of detection (LOD) and quantification (LOQ), obtained by validating the procedure, were determined at 4 and 10 ng L-1, respectively. The concentrations of BPA were ranged between 33 and 354 ng L-1, and all were above the LOQ value. The lowest amount of BPA was found in the sample collected in the river Vrbas, near Švrakava estuary upstream from the city of Banja Luka. The highest concentration of BPA was recorded at the confluence of the Crkvena and Vrbas rivers, which is located in the city center. This study shows that population and human activity could affect the level of BPA in the environment

CANNED MEAT PRODUCTS FOR MEMBERS OF THE SERBIAN ARMED FORCES: Na, K, Ca, AND Mg CONTENT AND HEALTH RISKS/BENEFITS

Macroelements such as Na, K, Ca, and Mg play a significant physiological role, and their inadequate intake has been linked to severe diseases, such as high blood pressure. Data on risk assessment for human health in Serbia, from the intake of these macroelements through the consumption of canned food, are minimal. Therefore, the content of Na, K, Ca, and Mg in five types of canned meat that members of the Serbian Armed Forces regularly use was examined. Macroelements were determined by inductively coupled plasma mass spectrometry in cans of beef goulash, pork ragout, spam, liver pate, and meatballs in tomato sauce, which were stored from one month to six years. The sodium content was significantly higher than the potassium content in all types of food, so the Na/K ratio below 1, desirable for good health, was not found in any of the analyzed products. Also, a significant number of samples had an unfavorable Ca/Mg ratio above 1. However, due to the low consumption of canned food by members of the Serbian Armed Forces, its contribution to the average daily intake of macroelements is almost negligible. The concentration of macroelements decreased with the shelf life, while a significant source of Ka and Mg, among analyzed ingredients, was ground red pepper. © 2022 University of Belgrade - Faculty of Agriculture. All Rights Reserved

Poly(Ethylene Terephthalate): Synthesis and physicochemical properties

This chapter summarizes the synthesis and physicochemical properties of thermoplastic polyester, poly(ethylene terephthalate) (PET). PET, along with poly(butylene terephthalate) (PBT) is an aliphaticaromatic and semicrystalline thermoplastic polyester of prime commercial and industrial importance. Namely, PET is a very important industrial polymer due to its excellent properties such as processability, chemical resistance, high tensile impact strength, high thermal stability and clarity. PET is synthesized from ethylene glycol and terephthalic acid or dimethyl terephthalate by a two-stage polycondensation process. High molecular weight of PET can be achieved by solid-state polymerization. This chapter presents different types of nanoparticles, such as organoclays, carbon nanotubes and carbon black, which are used for the improvement of the physical, mechanical, thermal and barrier properties of PET nanocomposites. It also highlights the recent developments in PET/layered silicate nanocomposites. The blending of PET with other polymers, as an excellent method of preparing materials with enhanced property/cost performance, is described. Processing, recycling and degradation of PET are also presented. This chapter discusses the surface modification of PET by physical treatment, chemical treatment and grafting polymerization in order to modify its surface properties, for enhanced surface wettability, adhesion activities and biocompatibility improvement. Moreover, this chapter also surveys the most relevant aspects related to the preparation and characterization of thermoplastic copolyester elastomers, especially PET and PBT copolyesters. The application potential of PET is discussed and selected examples of commercially available PET are given. Future trends in PET-based material synthesis and design are also discussed