Iskanje po katalogu digitalne knjižnice

Opis: Namen diplomskega dela je bil sintetizirati polisaharidne aerogele na osnovi škroba z dodatkom hitozana ter preučiti vpliv dodatka hitozana na njihove termične in strukturne lastnosti. Polisaharidni aerogeli so izjemno lahki in porozni materiali, ki so se zaradi svoje biokompatibilnosti in biorazgradljivosti v zadnjem desetletju izkazali kot obetavni kandidati za razvoj novih metod v biomedicinskih aplikacijah. V eksperimentalnem delu smo s sol-gel sintezo pripravili škrobno-hitozanske aerogele pri različnih koncentracijah obeh polimerov, ki smo jih nato posušili s superkritičnim ogljikovim dioksidom. Sušenje smo izvedli pri 40 °C in 120 bar na polindustrijski napravi za superkritično sušenje UHDE. Lastnosti škrobno-hitozanskih aerogelov smo karakterizirali z metodami plinske adsorpcije, vrstične elektronske mikroskopije (SEM), Fourierjeve transformacijske infrardeče spektroskopije (FTIR), termogravimetrične analize (TGA) in diferencialne vrstične kalorimetrije (DSC). Nazadnje smo z izvedbo testov nabrekanja in stabilnosti preučili njihovo obnašanje v vodnem mediju. Rezultati so pokazali, da se je hitozan uspešno vgradil v strukturo škrobnih aerogelov ter izboljšal njihove strukturne in termične lastnosti.
Ključne besede: Aerogeli, polisaharidi, škrob, hitozan, superkritični fluidi, sol-gel sinteza
Objavljeno v DKUM: 24.09.2024; Ogledov: 0; Prenosov: 29
Celotno besedilo (5,38 MB)

Opis: Developing double porous biodegradable and biocompatible scafolds that can incorporate and release drugs in a controlled manner holds immense potential in regenerative medicine. This study presents a synthesis method for preparing a macro-mesoporous scafold, where poly(lactic acid) adds to the macroporous region and mechanical properties, and ethyl cellulose adds to the surface area (182 m2 /g). High surface area enables the incorporation of model drug indomethacin with an entrapment efciency of 17.0% and its later controlled release profle. The resulting scafold has desirable mechanical properties in the range of a natural trabecular bone with a compressive modulus of 22.4 MPa. The material is stable in the simulated body fuids for 120 days before the slow degradation starts. In vitro studies demonstrate the material’s ability to support bone cell adhesion, proliferation, and diferentiation, promoting osteogenic activity. Overall, the unique combination of poly(lactic acid) and ethyl cellulose produces advanced materials with tailored macro and mesopore properties, remarkable mechanical properties, optimal degradation rate, and drug delivery potential, making it a promising candidate for bone scafolds in regenerative medicine and tissue engineering
Ključne besede: bio composite, polymer-matrix composites (PMCs), polymers, porosity/voids, secondary ion mass spectrometry
Objavljeno v DKUM: 23.08.2024; Ogledov: 130; Prenosov: 9
Celotno besedilo (2,87 MB)

Opis: Access to conjugated porous polymers via synthetically sustainable and straightforward routes is highly desirable, as many polymer systems exhibit high performance but require arduous synthetic protocols that rarely pave the way to commercial reality. In this article, we describe an easily fabricated series of novel highly porous poly(Schiff bases) that feature an aliphatic conjugated backbone obtained with low synthetic complexity from simple reagents such as glyoxal and hydrazine monohydrate in water. The effective synthesis enables the preparation of three different functional scaffolds, i.e., aerogels, polyHIPEs (polymerized HIPEs), and even carbon foams from aliphatic poly(azine) (PAZ) networks. The reported synthetic approach is compared to the literature using ″green chemistry metrics″, such as the E-factor and synthetic complexity (SC) index, and shows dramatic improvements. An E-factor of up to 0.27 for aerogels or 80 for polyHIPEs and an SC index of 2.7 are much lower than those for poly(arylene)-based conjugated analogues, indicating good scalability, sustainability, and low cost. PAZ materials feature impressive red/near IR-shifted optical absorption band edges, with an electrochemical band gap of 1.45 eV. Aliphatic PAZ scaffolds are characterized by high flexibility compared to aromatic analogues and do not fail at compressive loads of up to 70%. Finally, carbonization at 500 °C leads to highly porous carbonaceous scaffolds with a high N content of up to 29 wt % (21 mmol of nitrogen per gram carbon material).
Objavljeno v DKUM: 13.03.2024; Ogledov: 696; Prenosov: 20
Celotno besedilo (11,24 MB)
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Opis: This review provides a concise overview of up-to-date developments in the processing of neat poly(lactic acid) (PLA), improvement in its properties, and preparation of advanced materials using a green medium (CO2 under elevated pressure). Pressurized CO2 in the dense and supercritical state is a superior alternative medium to organic solvents, as it is easily available, fully recyclable, has easily tunable properties, and can be completely removed from the final material without post-processing steps. This review summarizes the state of the art on PLA drying, impregnation, foaming, and particle generation by the employment of dense and supercritical CO2 for the development of new materials. An analysis of the effect of processing methods on the final material properties was focused on neat PLA and PLA with an addition of natural bioactive components. It was demonstrated that CO2-assisted processes enable the control of PLA properties, reduce operating times, and require less energy compared to conventional ones. The described environmentally friendly processing techniques and the versatility of PLA were employed for the preparation of foams, aerogels, scaffolds, microparticles, and nanoparticles, as well as bioactive materials. These PLA-based materials can find application in tissue engineering, drug delivery, active food packaging, compostable packaging, wastewater treatment, or thermal insulation, among others.
Ključne besede: aerogels, drying, foaming, impregnation, particle generation, PLA
Objavljeno v DKUM: 06.02.2024; Ogledov: 395; Prenosov: 31
Celotno besedilo (5,02 MB)
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Opis: Diplomsko delo prikazuje študijo Schiffove bazne kondenzacije med substituiranim tereftaldehidom in 1,4-fenildiaminom za pripravo poliHIPE materialov na osnovi poliazometinov. Π-konjugirane poliHIPE pene smo pripravili s polimerizacijo emulzij z visokim deležem notranje faze (HIP emulzije). Sintetizirane polimere smo očistili s Soxhlet ekstrakcijo z metanolom. Uspešnost organo-katalizirane sinteze poliazometinov smo preverili s spektroskopskimi tehnikami kot so FTIR analiza, UV-Vis DRS analiza in 13C CP/MAS NMR spektroskopijo v trdnem. Morfološke lastnosti smo preverili z vrstično elektronsko mikroskopijo (SEM). S He-piknometrijo smo določili gostoto in določili poroznost polimera. Informacije o porazdelitvi por in specifični površini smo dobili z dušikovo fizisorpcijo.
Ključne besede: Schiff-bazna kondenzacija, π-konjugirani polimeri, vpliv substituente, poliHIPE, karakterizacija polimerov
Objavljeno v DKUM: 18.09.2023; Ogledov: 403; Prenosov: 31
Celotno besedilo (4,66 MB)