Preparation of photocatalysts by atomic layer deposition

The use of semiconductor-based photocatalysts (e.g. metal oxides) in sewage water treatment is expected to be of great interest despite its shortcomings [1]. High surface area organic semiconductor-based structures are promising alternatives for the photodegradation of various organic pollutants. In addition, these polymer structures could be great backbones to produce polymer/metal oxide composite photocatalysts by Atomic Layer Deposition (ALD)

Ring opening metathesis polymerisation (ROMP) as a tool for polyhipes with extraordinary mechanical properties

PolyHIPE materials have been prepared by Ring Opening Metathesis Polymerisation (ROMP) of dicyclopentadiene. Two characteristic features for successful stabilization of high internal phase emulsions (HIPEs) were tuned in order to achieve improvements regarding mechanical properties of polyHIPEs.Mechanical properties of the new materials were related to variations of the surfactant concentration and the volume ratio of the internal phase in HIPEs. Values for Youngʼs moduli were about a hundred times higher than in standard polyHIPE materials with the same level of porosity, which represents a major improvement for highly porous cellular polymeric materials. Moreover, fully interconnected macroporous morphology was found forpolyHIPEs, where respective HIPEs were stabilized with only 0.25 v% of surfactant.Za pripravo poliHIPE materialov smo uporabili polimerizacijo pri kateri smo polimerizirali ciklične monomerje (diciklopentadien) z metodo odpiranjem obroča (ROMP). PoliHIPE materiali polimerizirani s ROMP mehanizmom so se iz- kazali z izjemnimi mehanskimi lastnostmi, saj so meritve mehanske jakosti pokazale sto krat višje vrednosti v primerjavi s poliHIPE materiali polimeriziranimi z navadno radikalsko polimerizacijo. ROMP v kombinaciji s HIPE templatiranjem se je izkazal kot izredno dobra kombinacija za proizvodnjo visoko poroznih polimernih materialov z izjemnimi mehanskimi lastnostmi

HIBRIDNI PoliHIPE MATERIALI

A new class of polyHIPE materials has been prepared using high internal phase emulsions (HIPEs) with monomers in both phases. Resulting materials, namely hybrid polyHIPE materials, are obtained consisting of hydrophobic matrix (consisted of styrene cross-linked with DVB or dicyclopentadiene) filled with hydrophilic polymer gel (polyacrylic acid or polyNIPAM) and exhibit morphology changes according to pH and temperature of the surrounding medium. Our focus with regards to the production of hybrid polyHIPE materials was the responsiveness of such materials used for flow control. This property is beneficial for controlling the flow of the solution through the monolithic polymers. Furthermore, polyHIPE materials have also been prepared by using ring opening metathesis polymerisation of monomers, such as dicyclopentadiene and norbornene. Obtained materials have Young’s moduli in the range of hundred times higher than standard polyHIPE materials with the same level of porosity which represents a very important improvement in the development of highly porous cellular polymeric materials.Predmet mojega doktorskega dela je priprava novih poliHIPE materialov iz emulzij z visokimi deležem notranje faze, pričemer bodo monomerji prisotni v obeh fazah emulzije. Pridobljeni poliHIPE materiali, hibridni poliHIPE materiali, bodo sestavljeni iz hidrofobnega skeleta (poli stirena zamreženega z DVB oz. diciklopentadien) pri čemer bo celična struktura materiala napolnjena s hidrofilnim polimernim gelom (poli akrilna kislina ali poli NIPAM zamrežena z MBA). Tako pripravljene hibridne poliHIPE materiale z dvofazno morfologijo bomo testirali v pretočnih sistemih kot polimerne ventile. Dvofazno morfologijo hibridnih poliHIPE materialov bomo izkoristili za kontroliranje pretoka raztopine skozi monolitni polimeri. Notranja polimerna domena (t.i. polimerni gel) bo ob spremembi pH ali temperature črpane raztopine nabreknila ali se skrčila in s tem omogočila ali onemogočila pretok skozi material. Za pripravo poliHIPE materialov smo uporabili dve polimerizacijski tehniki, termično inicirano radikalsko polimerizacijo in polimerizacija pri kateri polimeriziramo ciklične monomerje (diciklopentadien ali norbornen) z odpiranjem obroča (ROMP). PoliHIPE materiali polimerizirani s ROMP mehanizmom so se izkazali z izjemnimi mehanskimi lastnostmi, saj so meritve mehanske jakosti pokazale sto krat višje vrednosti v primerjavi s poliHIPE materiali polimeriziranimi z navadno radikalsko polimerizacijo

Use of emulsion-templated, highly porous polyelectrolytes for in vitro germination of chickpea embryos

The application of highly porous and 3D interconnected microcellular polyelectrolyte polyHIPE (PE-PH) monoliths based on (3-acrylamidopropyl)-trimethylammonium chloride as soilless cultivation substrates for in vitro embryo culture is discussed. The embryo axes isolated from chickpea seeds are inoculated onto the surface of the monoliths and allowed to germinate. Germination study show that the newly disclosed PE-PH substrate performs much better than the conventionally used agar as the germination percentage, shoot and root length, fresh and dry weight as well as the number of leaves are enhanced. The PE-PHs exhibit a higher absorption capacity of the plant growth medium, that is, 36 g·g–1 compared to agar, that is, 20 g·g–1, and also survive autoclaving conditions without failing. The key advantage over standard agar substrates is that they can be reused several times and also without prior sterilization. These results suggest that PE-PHs with exceptional absorption/retention properties and robustness have great potential as soilless substrates for in vitro plant cultivation

The influence of Ce3+Ce^{3+} ions on the corrosion rate of stainless steel in acidic solutions of different pH-values

The corrosion resistance of AISI 420 stainless steel in 0.1 mol $L^{−1}$ $H_2SO_4$ + 0.1 mol $L^{−1}$ $Na_2SO_4$ solutions at different pH-values and the inhibiting effect of $Ce^{3+}$ ions was studied using electrochemical polarization methods. The results reveal decreasing of the corrosion rate with an increasing the pH of the solution, which demonstrates the progressive protective character of the inhibitor used. At pH lower than 3.33, the corrosion inhibition was most probably a result of the competitive adsorption of $Ce^{3+}$ with $H^+$ ions on the cathodic sites of the electrode surface, and it was found to be dependent on the relative concentration of $H^+$/$Ce^{3+}$. The peroxide generated from the oxygen reduction reaction at pH 3.33 was found to be capable oxidize trivalent cerium (Ce) to the tetravalent state. As obtained hydroxide precipitates act as diffusion barrier hindering the corrosion processes, whereafter a spontaneous passivity occurs on the steel surface at this pH

Nanocomposite foams from iron oxide stabilized dicyclopentadiene high internal phase emulsions

Nanocomposite polyHIPE foams with open-cellular morphology were obtained using nanoparticles ($γFe_2O_3/Fe_3O_4$), surfactant (Pluronic L121) or nanoparticle/surfactant stabilized dicyclopentadiene high internal phase emulsions (DCPD HIPEs). Upon curing, cavity sizes were found to vary drastically between 950 ± 360 µm down to 7 ±3 µm de- pending on the HIPE formulations. As-obtained nanocomposite polyHIPE foams were functionalized using elemental bromine in THF. Upon bromination the nanoparticles are moved from the cavities surfaces into the bulk phase of the polymer scaffold, which affects the inductive-heating capability of the magnetic nanocomposite foams decreasing it by the factor of 2.V tem strokovnem članku opisujem pripravo makroporoznih nanokompozitnih pen iz diciklopentadienskih HIP emulzij stabiliziranimi z $γFe_2O_3/Fe_3O_4$ nanodelci, t.i. Pickering emulzij in HIP emulzij stabiliziranimi s kombinacijo surfaktanta in nanodelcev. Tako pripravljene nanokompozitne pene smo primerjali s penami pripravljenimi iz HIP emulzij stabiliziranimi le s surfaktanti in ugotovili da se premer por spreminja in sicer od 7 ± 3 m do 950 ± 360 µm. V nadaljevanju smo nanokompozitne makroporzne pene funkcionalizirali z elementarnim bromom, ter raziskali vpliv bromiranja na samo lokacijo nanodelcev in sposobnost $γFe_2O_3/Fe_3O_4$ nanodelcev da ob prisotnosti zunanjega alternirajočega magnetnega polja proizvajajo toploto. V ta namen smo bromirano nanokompozitno peno izpostavili zunanjemu izmeničnemu magnetnem polju, ter ugotovili da se sposobnost segrevanje zmanjša za faktor 2

Sustainable in-water synthesis of aliphatic porous polyazines

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)