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Control of the morphology of biodegradable polymer blends
Ostafińska, Aleksandra ; Šlouf, Miroslav (advisor) ; Kosek, Juraj (referee) ; Vohlídal, Jiří (referee)
This dissertation, entitled »Control of the morphology of biodegradable polymer blends«, has been running parallel with the grant project »Multiphase biodegradable polymer systems« and it represents a new research direction in the Department of morphology and rheology of polymer materials at the Institute of Macromolecular Chemistry. The main idea was to employ our long-lasting work and experience in the field of morphology control of synthetic polymer blends in the very analogous field of the biodegradable polymer blends. We have chosen three most common, widely used and relatively cheap bio-based polymers - starch, poly(lactic acid) and poly(ε-caprolactone) - in order to investigate how the properties of their blends might be improved if we control the blend morphology in targeted, reproducible and well-defined way from the very beginning. It has been well established that morphology (phase structure, supramolecular structure) is one of the key factors influencing final properties of polymer blends, including mechanical performance, rate of (bio)degradation, gas permeability etc. In this work, numerous preliminary experiments showed that there are two systems in which the morphology control could significantly help in the improving of their end-use properties: PLA/PCL/TiX (where PLA = poly(lactic acid),...
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Synthesis and properties of supramolecular polymers
Vitvarová, Tereza ; Vohlídal, Jiří (advisor) ; Jindřich, Jindřich (referee) ; Royal, Guy (referee)
New π-conjugated building blocks (unimers) for metallo-supramolecular polymers (MSPs), whose comprise: (i) substituted phosphole ring surrounded by two thiophene rings as the central block, (ii) 2,2':6',2''-terpyridine-4'-yl (tpy) end-groups as ion-selectors, and (iii) different linkers inserted between the central block and tpy end-groups, are described. Chemical and physical properties of those unimers were studied with attention on correlation between properties and structure of unimers. For example the unimer without linkers shows the UV/vis absorption maximum red shifted about 60 to 100 nm compared to bis(tpy)terthiophenes, which proves that replacing of the thiophene with phosphole unit significantly enhances the delocalization of electrons within the unimer molecule and significant area of absorption spectra can be covered. Introduction of linkers (ethynediyl, ethynediyl-thiophene-2,5-diyl, ethynediyl-1,4-phenylene) has a minor effect on the bandgap energy. All prepared unimers underwent self-assembling process with various metal ions (Co2+ , Cu2+ , Fe2+ , Ni2+ and Zn2+ ) resulting into metallo-supramolecular polymers. Three stages of the assembly of unimers into related MSPs were observed and characterized by absorption, fluorescence spectroscopy and size exclusion chromatography: 1)...
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Synthesis and characterization of new polymers of substituted acetylenes
Sivkova, Radoslava Parusheva ; Vohlídal, Jiří (advisor) ; Strachota, Adam (referee) ; Sedlařík, Vladimír (referee)
New procedures for preparation of polyacetylenes with highly luminescent naphthalimide groups that might be potentially utilized in optoelectronics and sensors are developed within the framework of present doctoral thesis. The procedures provide luminescent a) linear polyacetylenes that can be processed from solutions, and b) mesoporous network polyacetylenes with high pore volume. Two paths to soluble polyacetylenes are used: (i) copolymerization of ethynyl- functionalized naphthalimide (monomer PN) and a monoethynyl aromate catalyzed with [Rh(nbd)acac], and (ii) modification of poly(disubstituted acetylene)s carrying -chloroalkyl pendants involving the exchange of chlorine atoms for azido groups and subsequent "click"- reaction of Huisgen type of azido groups with ethynyl groups of PN. The PN does not homopolymerize but copolymerizes with ethynylaromates. The highest possible molar fraction of the PN units in copolymers is of 0.5, which suggests the absence of PN dyads or longer sequences in copolymers and the alternating arrangement of PN units in the copolymers of the composition of 0.5. Surprisingly, ethynylarenes that give insoluble homopolymers gave soluble copolymers with PN. The modification procedure requires knowledge on the effect of the monomer structure symmetry and substituent...
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Ruthenium alkylidenes immobilized on mesoporous molecular sieves as catalysts for olefin metathesis
Shinde, Tushar Raghunath ; Balcar, Hynek (advisor) ; Vohlídal, Jiří (referee) ; Kvíčala, Jaroslav (referee)
The main emphasis of the dissertation focuses on the preparation of new heterogeneous metathesis catalysts, their characterization, and testing their activity and selectivity in different metathesis reactions. This work has been completed at the Department of Synthesis and Catalysis, J. Heyrovský Institute of Physical Chemistry, AS CR. Hoveyda-Grubbs type catalyst ZC (Zhan catalyst 1-B) was immobilized on mesoporous molecular sieves of different architecture and pore diameter, d, (hexagonal: MCM-41, d = 4.0 nm; SBA-15, d = 6.8 nm; SBA-15 large pore (LP), d = 11.1 nm and cubic: MCM-48, d = 6.0 nm) and conventional silica (Merck) for comparison. The immobilization was done by simple mixing of ZC solution with appropriate support at room temperature. Ru loading in all immobilized catalyst was 0.93 wt%. The catalysts and supports were characterized by X-ray diffraction and nitrogen adsorption measurement. XPS and UV-Vis spectroscopic studies of ZC immobilized on SBA-15 (ZC/SBA-15) indicated the attachment of ZC on mesoporous sieve surface by non-covalent interactions. The immobilized catalysts exhibited high activity and 100% selectivity in ring-closing metathesis of diethyl diallylmalonate and 1,7-octadiene, in metathesis of methyl oleate and methyl 10-undecenoate, and in the ring-opening metathesis...
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Synthesis and characterization of conjugated polymers containing fluorene and thiophene units
Bondarev, Dmitrij ; Vohlídal, Jiří (advisor) ; Štěpánek, Petr (referee) ; Kmínek, Ivan (referee)
This Thesis is devoted to synthesis and characterization of conjugated polymers of three types: (i) copolymers of fluorene-based units with comonomers derived from benzene, anthracene and diphenyloxadiazole; (ii) copolymers combining new thiophene monomers carrying oxadiazole and triazole moieties with various comonomers. Copolymers are designed with the respect to the tuning the optical properties and an improvement in charge transport properties; (iii) polythiophene based polyelectrolytes of two types and the basic characterization of selected physical and optical properties is reported as well as a study of interactions with noble metal nanoparticles. An incorporation of oxadiazole side groups into the fluorene copolymers was followed by the substantial increase in the stability of emission (photoluminescence). Another increase in the emission stability was achieved by the substitution of alkyl side groups on fluorene for the aryl counterparts. Such a change resulted in almost complete suppression of the undesired green emission. Further method was the incorporation of anthracene monomeric units into the main chains which resulted in the best stabilization of emission. An experiment was also made in order to shed some light on the explanation of the mechanism of emission stabilization caused by...
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Catalytic synthesis of polyanilines
Bláha, Michal ; Vohlídal, Jiří (advisor) ; Omastová, Mária (referee) ; Trchová, Miroslava (referee)
This Ph.D. thesis is dealing with catalytic polymerization of aniline (ANI) and partially also of substituted anilines with FeCl3/H2O2 catalyst system, in which according to obtained results both active species, Fe3+ and HO , participate in the overall polymerization mechanism, creating a synergic system. The Fe3+ /H2O2 catalyst system, also called Fenton's system can considerably lower contamination of forming neat polyanilines (PANIs) by side-products characteristic of stoichiometric polymerization. However, catalytically prepared PANIs exhibit reduced conductivity related most probably to side reactions involving radicals generated as integral components of the FeCl3/H2O2 system. Catalytic polymerization of ANI with FeCl3/H2O2 system was found to be the reaction of approx. 2nd order with respect to ANI and gives PANIs of a good quality only when [H2O2] in the reaction mixture was kept low, i.e., at under- stoichiometric ratios [H2O2]/[ANI]. At over-stoichiometric ratio [H2O2]/[ANI], PANIs of lowered conductivity, worse spectroscopic characteristics and increased size of PANI nanostructures were obtained; nevertheless, these PANIs were not over-oxidized to pernigraniline state. The reaction-time profiles of the open-circuit potential of reaction mixtures exhibited an inflection related to the...
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Preparation and properties of thin layers of conjugated polyelectrolytes
Slunečková, Veronika ; Vohlídal, Jiří (advisor) ; Svoboda, Jan (referee)
The study shows strong influence of the conformation of the main chains of polythiophenes in solutions on their spectroscopic properties. The conformational changes affect strength of interactions between neighboring chains and lead to the formation of aggregates of stacked polythiophene chains. Stacked chains show red shift of the optical absorption and lead to visible vibronic structure of absorption bands. Multilayered systems prepared by periodic adsorption of the cationic and anionic polythiophene polyelectrolytes on various substrates show proportionality of the overall layer thickness to the number of coatings, which allows a control of the layer thickness. Adsorption of the conjugated polyelectrolytes on the anatase form of titanium dioxide show better penetration of the anionic polythiophene to porous anatase. The adsorption of polymer into the mesoporous structure is not complete: maximum adsorption of PTTA (poly(thiophene-3-ylacetic acid)) adsorbed on anatase do not correspond to the inner surface of mesoporous anatase. Alternating adsorption from the solutions of polythiophene with anionic and cationic side groups on mesoporous anatase allows preparation of the Graetzel-like photovoltaic cell provided that the adsorption process starts with the anionic polythiophene and the layers are deposited...
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