29 research outputs found
Modification of poly(methyl methacrylate) denture base materilas with diesters of itaconic acid
Cilj ovog rada je ispitivanje moguÄnosti modifikacije komercijalnih
dvokomponentnih sistema za dobijanje materijala za bazu proteza dodavanjem estara
itakonske kiseline u teÄnu komponentu sistema, radi dobijanja materijala veÄeg stepena
biokompatibilnosti.
U prvom delu ovog rada izvrŔena je karakterizacija tri sistema za dobijanje baza
proteze (Biocryl, Poli Hot i Futura Basic Hot) i ispitan je uticaj veliÄine zrna i raspodele
veliÄina zrna Ävrste komponente sistema koja se sastoji od PMMA praha. Komercijalni
sistem za bazu proteza se sastoji od Ävrste i teÄne komponente. TeÄna komponenta
sadrži monomer metil metakrilat i umreživaÄ nejÄeÅ”Äe etilenglikol-dimetakrilat
(EGDM) dok se Ävrsta komponenta sastoji od praha PMMA i inicijatora, najÄeÅ”Äe dibenzoil
peroksida (DBO). Proteze sa dobijaju meÅ”anjem Ävrste i teÄne komponente u
odnosu 2:1 i polimerizacijom pri odabranom temperaturnom režimu. Ispitan je uticaj
veliÄine zrna i raspodele veliÄina zrna Ävrste komponente sistema na apsorpciju vode i
mehaniÄke karakteristike gotovog proizvoda radi odreÄivanja najpovoljnijeg
komercijalnog sistema. Kao optimalni komercijalni sistem pokazao se Byocril koji
poseduje najužu raspodelu veliÄina zrna Ävrste komponente i srednju preÄnik zrna od 55
Ī¼m.
U drugom delu ovog rada izvrŔena je modifikacija komercijalnog sistema za
bazu proteza dimetil itakonatom, dibutil itakonatom i ditetrahidrofurfuril itakonatom
(2,5 - 10 masenih % itakonata). Ispitan je uticaj tipa i koliÄine itakonata na: apsorpciju
teÄnosti (voda i smeÅ”a etanol/voda), koliÄinu zaostalog monomera, termiÄke,
dinamiÄko-mehaniÄke i mehaniÄke karakteristike (tvrdoÄa, žilavost, napon pri kidanju)
sintetisanih materijala. TakoÄe je ispitan i uticaj ubrzanog starenja na mehaniÄka
svojstva sintetisanih materijala. UtvrÄeno je da dodatak itakonata u sastav komercijalnih
sistema za dobijanje baze proteza znaÄajno smanjuje koliÄinu zaostalog metil
metakrilata Å”to materijal Äini niže toksiÄnim i biokompatibilnijim. Kao najoptimalniji
uzorak pokazao se materijal modifikovan sa 2,5 masena % dimetil itakonata. Äinjenica
II
da za dobijanje itakonske kiseline nije potrebno koristiti petrohemijske izvore sirovina
predstavlja veliku prednost u odnosu na akrilnu i metakrilnu kiselinu i njihove derivate.The aim of this work is to examine the possibility of modification of commercial
denture base materials with itaconic acid esters, in order to obtain a higher degree of
material biokompatibility.
In the first part of this work characterization of three commercial materials was
carried out. The effect of bead size and bead size distribution of prepolymer powder
onto water absorption and mechanical characteristics of the end product in order to
determine the optimal commercial material for the further course of study. The Byocril
that has the narrowest bead size distribution and mean bead diameter of 55 Ī¼m is found
to be the optimal commercial material.
In the second part of this work modification of commercial PMMA denture base
material with dimethyl itaconate, di-n-butyl itaconate and ditetrahydrofurfuryl itaconate
(2.5 to 10 wt%) was carried out. The effect of the itaconate content on the absorption of
fluids (water and a mixture of ethanol/water), the residual monomer content, thermal,
dynamic-mechanical and mechanical properties (hardness, toughness, stress at break)
was investigated. The effect of the accelerated aging on the mechanical properties of
synthesized materials was also investigated. It was found that the addition of itaconate
in the denture base materials formulation significantly reduces the amount of residual
methyl methacrylate, which makes the material less toxic. The optimal sample was
found to be the material modified with 2.5 wt% of dimethyl itaconate.
In the third part of this work, the influence of isothermal microwave
polymerization on the applicative properties of denture base materials was investigated.
It was found that the samples synthesized under isothermal microwave field have better
application properties compared to the samples synthesized by conventional
polymerization
Dual responsive hybrid hydrogels for controlled release of local anesthetic
Inteligentni hidrogelovi, kao Å”to su pH osetljivi hidrogelovi na bazi poli(metakrilne kiseline) (PMAA), imaju veliku primenu u ciljanoj dostavi lekova. MeÄutim, slaba mehaniÄka svojstva Äesto ograniÄavaju primenu PMAA. Kako bi se prevaziÅ”lo navedeno ograniÄenje, nanoceluloza (NC) je prvo ekstrakovana iz drvnog otpadnog materijala, a zatim dodata u PMAA, zato Å”to je NC biokompatibilna, netoksiÄna i ima odliÄna mehaniÄka svojstva. Zatim je dodata karboskimetil celuloza (CMC) (celulozni derivat koji se Äesto koristi za kontrolisano otpuÅ”tanje lekova). CMC može da stabilizuje nanoÄestice magnetita (MN) koje su takoÄe dodate. MN mogu znaÄajno da poboljÅ”aju mehaniÄka svojstva hidrogelova i takoÄe poseduju magnetna svojstva zbog Äega imaju primenu za ciljano otpuÅ”tanje lekova. Ovako dobijeni materijal bi mogao da zaÅ”titi lek, dostavi ga do mesta delovanja, kontroliÅ”e brzinu njegovog otpuÅ”tanja i na taj naÄin omoguÄi efikasno dejstvo leka sa smanjenim neželjenim efektima. Lokalni anestetik ā lidokain hidrohlorid (LH) se Äesto u tretmanima injektira Å”to može imati ozbiljne neželjene efekte. Inkapsulacijom LH u hidrogelove na bazi PMAA, NC, CMC i MN (PMNC/MN-L) reÅ”en je navedeni problem. Karakterizacija PMNC/MN-L hidrogelova je izvedena primenom FTIR i SEM spektroskopija i kompresionim testovima, a zatim je analizirano bubrenje hidrogelova i otpuÅ”tanje LH. U ovom radu predstavljen je jedinstveni naÄin āzeleneā sinteze hibridnih hidrogelova osetljivih na spoljne stimulanse unapreÄenih svojstava i njihove primene za kontrolisano otpuÅ”tanje lokalnog anestetika sa smanjenim neželjnim efektima
Supplementary data for article : Panic, V. V.; Seslija, S. I.; Popovic, I. G.; Spasojevic, V. D.; Popovic, A. R.; Nikolic, V. B.; Spasojevic, P. M. Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid. Biomacromolecules 2017, 18 (12), 3881ā3891. https://doi.org/10.1021/acs.biomac.7b00840
Supporting information for: [https://doi.org/10.1021/acs.biomac.7b00840]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2568]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3058
Supplementary data for article : Panic, V. V.; Seslija, S. I.; Popovic, I. G.; Spasojevic, V. D.; Popovic, A. R.; Nikolic, V. B.; Spasojevic, P. M. Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid. Biomacromolecules 2017, 18 (12), 3881ā3891. https://doi.org/10.1021/acs.biomac.7b00840
Supporting information for: [https://doi.org/10.1021/acs.biomac.7b00840]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2568]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3058
Biohidrogelovi poli(metakrilne kiseline): bubrenje i kontrolisano otpuŔtanje kofeina
Modern society are faced with lot of challenges in the treatment of many diseases, especiallywith serious ones such as cancer. Safer and more efficient treatment of the cancer patients are maingoals which researchers are aiming. One of the good approaches can be drug delivery systems.Still, a lot of anticancer drugs are poorly water-soluble and their encapsulation and controlled releasecan be quite challenging. Present study is focused to improve drug delivery system based onhydrophilic poly(methacrylic acid) and amphiphilic casein with encapsulated poorly water-solublecaffeine, which has been developed through our previous research. The hydrogels with 1.6mol% ofcrosslinker and 100% of neutralization degree of methacrylic acid are synthetized (PMAC-100N-4M). The swelling process of the PMAC-100N-4M hydrogels and caffeine release are analyzed intwo environments which simulate human stomach and intestines. It is also investigated how thechange in the encapsulated caffeine weight and the addition of liposomes with encapsulated caffeine,affect swelling degree of the PMAC-100N-4M hydrogels and release of caffeine. The resultsshow that controlled release of caffeine is improved, therefore overall therapy can be enhanced.Savremeno druÅ”tvo je suoÄeno sa mnogim izazovima u tretamanu raznih bolesti, naroÄito ozbiljnih oboljenja kao Å”to je rak. Glavni ciljevi nauÄnika su da se postigne bezbednija i efikasnija terapija pacijenata koji se leÄe od raka. Jedan od dobrih naÄina da se to postigne su sistemi za dostavu lekova. Ipak, mnogi antikancerogeni lekovi su slabovodorastvorni, pa bi veliki izazov mogao da bude inakpsulacija i njihovo kontorlisano otpuÅ”tanje iz sistema za dostavu lekova. Cilj ovog rada je da se unapredi sistem za dostavu lekova na bazi hidrofilne poli(metakrilne kiseline) i amfifilnog kazeina sa inkapsuliarnim slabo vodorastvornim kofeinom, koji je razvijen tokom naÅ”eg prethodnog istraživanja. U ovom radu sintetisani su hidrogelovi sa 1,6mol% umreživaÄa i 100% neutralisanom metakrilnom kiselinom (PMAC-100N-4M). Procesi bubrenja PMAC-100N-4M hidrogelova i kontrolisanog otpuÅ”tanja kofeina su ispitivani u dve sredine koje simuliraju želudac i tanko crevo Äoveka. TakoÄe je ispitano kako promena koliÄine inkapsuliranog kofeina i dodatak lipozomne suspenzije sa inkapsuliranim kofeinom utiÄe na procese bubrenja PMAC-100N-4M hidorgelova i otpuÅ”tanje kofeina. Rezultati pokazuju da je proces kontrolisanog otpuÅ”tanje kofeina unapreÄen, a samim tim je moguÄe unaprediti i celokupnu terapiju
Synthesis, Structure and Properties of Nickel-Iron-Tungsten Alloy Electrodeposits PART I: Effect of Synthesis Parameters on Chemical Composition, Microstructure and Morphology
Kinetic and operational electrolysis parameters determine the polarization characteristics, electrodeposition current efficiency, morphology, chemical composition and microstructure of nickel/iron/tungsten alloy deposits. The alloys electrodeposited at a current density of 50 mA cm(-2) to 1000 mA cm(-2) contain an amorphous phase and nanocrystals of an FCC solid solution of iron and tungsten in nickel. During annealing at temperatures above 500 degrees C, amorphous phase crystallization, crystalline grain growth of the FCC phase and a reduction in both internal microstrain and minimum density of chaotically distributed dislocations take place in the alloy. Milling the spongy deposit of the alloy causes amorphous phase crystallization, FCC-phase crystalline grain growth, and size reduction and rounding of powder particles
Microstructure of new composite electrocatalyst and its anodic behavior for chlorine and oxygen evolution
The first layer of active coating made from a rutile-structured solid solution of ruthenium and titanium dioxides having an average crystal grain size of 30 nm was thermally deposited on an adequately prepared titanium metal substrate. Then, at a temperature of 500 degrees C, the second layer was formed on the first layer from a mixture of amorphous particles of metallic platinum and rutile-structured iridium dioxide nanocrystals having an average crystal grain size of 26 nm. Rutile phase nanocrystals are characterized by a high density of chaotically distributed dislocations and high internal microstrain values. The coatings exhibit a compact granular morphology without cracks on the surface. Their catalytic activity is similar to that of conventional DSAs for the anodic oxidation of chloride ions from both concentrated and dilute sodium chloride solutions. The anodic current efficiency both during chlorate formation and active chlorine production was several percentage points higher in electrolyzers containing these anodes than in those containing DSAs. The catalytic activity of anodes having these coatings is about 50 mV lower than that of DSAs and about 350 mV higher than that of lead/antimony alloy electrodes, for oxygen evolution from acid sulfate solutions (0.5 mol dm(-3) H2SO4) characteristic of processes for the production of some metals. An accelerated corrosion test showed that the stability of the double-layer anodes is about twelve-fold higher than that of conventional DSAs
Structure and magnetic properties of electrodeposited Ni87.3Fe11.3W1.4 alloy
A dark gray nanostructured coating of an alloy composed of 87.3 wt.% Ni, 11.3 wt.% Fe and 1.4 wt.% W (Ni87.3Fe11.3W1.4) was electrodeposited from an ammonia citrate bath on a titanium cathode at a current density of 500 mA cm(-2). A cathodic polarization curve was recorded and dependence of the current efficiency of alloy deposition on current density was determined. Partial polarization curves for alloy deposition and hydrogen evolution were also measured. Alloy deposition at current densities of up to 300 mA cm(-2) is an activation-controlled process which turns into a diffusion-controlled process at higher current densities. At potentials more positive than -960 mV, hydrogen is evolved from NH4+ and (HCit)(3-) ions (where (HCit)(3-) denotes triply deprotonated citric acid, C6H5O73-). At potentials more negative than -960 mV, hydrogen evolution from water is the dominating reaction. SEM images show that the surface of the deposit obtained at 500 mA cm(-2) has a globular structure containing a large number of craters, mostly located between the globules. XRD analysis revealed that the alloy contains an amorphous matrix with embedded nanocrystals of the FCC-structured solid solution of Fe and Win Ni with a mean particle size of 8.8 nm. The deposit has a high internal microstrain value and a high density of chaotically distributed dislocations. Heating and milling the alloy cause structural changes involving changes in the magnetic properties of the alloy. Structural relaxation takes place in the temperature interval of 80 degrees C to 420 degrees C. In this temperature range, magnetization of both as-deposited and milled alloy samples increases with increasing temperature, reaching maximum at a certain temperature, but decreases thereafter with further heating. During structural relaxation, short-term structural arrangement facilitates the expansion and orientation of magnetic domains, leading to increased magnetization of the alloy. The abrupt decline in magnetization at higher temperatures is the result of a heatinduced change in magnetic domain orientation. Annealing the alloy at temperatures above 420 degrees C causes amorphous phase crystallization and growth of crystal grains of the FCC-structured solid solution of Fe and W in Ni, as well as a simultaneous decrease in internal microstrain and mean density of chaotically distributed dislocations. The same structural changes, somewhat lower in intensity, are also caused by alloy milling. The new state of the microstructure achieved through annealing and milling is best illustrated by the mean crystal size. The increase in mean crystal size results in a shift of the Curie temperature towards lower temperatures, whereas magnetization increases at first, reaching maximum at a certain mean crystal size, but decreases, thereafter, with a further increase in mean crystal size
The effect of annealing temperatures on magnetic and electric properties of electrodeposited Ni85,3Fe10,6W1,4Cu2,2 alloy
Ni-85,Ni-8 Fe-10,Fe-6 W-1,W-4 Cu-2,Cu-2 alloy powder consisting of an amorphous matrix and nanocrystals of an FCC solid solution of Fe, W and Cu in nickel was produced by electrodeposition. Heating the pressed powder sample over the temperature range of 20 to 600 degrees C permitted structural changes to take place in the alloy, causing changes in its electrical resistivity and magnetic permeability. The alloy exhibits structural stability up to 150 degrees C. In the temperature interval 150-360 degrees C, the alloy undergoes intensive structural relaxation resulting in an increase in electrical conductivity and magnetic permeability. Less intensive structural relaxation occurs at temperatures between 360 degrees C and 460 degrees C. In this interval, under heat treatment, magnetic domain arrangement decreases and, hence, the interaction between magnons and conduction electrons is reduced, leading to a decrease in the temperature coefficient of electrical resistivity (TCER). Amorphous matrix crystallization and FCC crystal growth take place in the temperature interval 460-520 degrees C, causing a decline in electrical resistivity and magnetic permeability
Effect of Electrodeposition Current Density on the Microstructure and Magnetic Properties of Nickel-cobalt-molybdenum Alloy Powders
Nanostructured nickel-cobalt-molybdenum alloy powders were electrodeposited from an ammonium sulfate bath. The powders mostly consist of an amorphous phase and a very small amount of nanocrystals with an mean size of less than 3 nm. An increase in deposition current density increases the amorphous phase percentage, the density of chaotically distributed dislocations and internal microstrains in the powders, while decreasing the mean nanocrystal size. The temperature range over which the structural relaxation of the powders deposited at higher current densities occurs is shifted towards lower temperatures. A change in relative magnetic permeability during structural relaxation is higher in powders deposited at higher current densities. Powder crystallization takes place at temperatures above 700 degrees C. The formation of the stable crystal structure causes a decrease in relative magnetic permeability