Přístupnostní navigace
E-přihláška
Vyhledávání Vyhledat Zavřít
Detail oboru
FCHZkratka: DPCO_MCHAk. rok: 2013/2014
Program: Makromolekulární chemie
Délka studia: 4 roky
Akreditace od: 13.10.2010Akreditace do: 1.11.2018
Profil
Cílem je získání nových, unikátních poznatků o vztazích mezi způsobem syntézy polymerních materiálů, jejich strukturou a fyzikálně chemickými vlastnostmi a nalezení způsobů, jak metodami přípravy řídit strukturu a funkce homogenních a heterogenních polymerních materiálů na jednotlivých rozměrových úrovních struktury a tím dosáhnout žádoucích vlastností. Dalším cílem je i rozvoj nových metod simulace a modelování vztahů mezi strukturou a vlastnostmi homogenních a heterogenních polymerních materiálů metodami molekulární dynamiky na molekulární úrovni a metodami fyziky kontinua na mikro- a makroskopické úrovni jakož mezních stavů heterogenních a neizotropních polymerních systémů.
Klíčové výsledky učení
Absolvent zvládá teoretické základy oboru, kterými jsou rozšířené základy kinetiky a mechanismů polymerací a polymeranalogových reakcí včetně vzniku fyzikálních a chemických sítí, termodynamiky polymerů a jejich směsí a roztoků, chemie povrchů tuhých polymerů, fyziky a mechaniky tuhých polymerů a základy adheze v heterogenních polymerních soustavách a kompozitech. Absolvent dokáže v oblasti přípravy, resp. modifikace polymerů tvůrčím způsobem aplikovat znalosti organických syntéz a strukturní analýzy a je připraven řešit vývoj speciálních polymerů, směsí a polymerních matric pro kompozitní materiály syntézní cestou. Absolvent dokáže samostatně formulovat vědecký problém, navrhnout hypotézu k jeho řešení a provést experimentální či teoretické pokusy k jejímu potvrzení. Nedílnou součástí základních znalostí absolventa DSP je schopnost kritického posouzení publikovaných vědeckých informací a schopnost vyjadřovat se písemně v anglickém jazyce. Nadstavbové znalosti absolventů nad teoretické základy oboru se liší podle typu projektu, který v rámci DSP řeší. Výraznou specifikou DSP MCH na FCH VUT v Brně je zaměření na heterogenní polymerní systémy, jako jsou polymerní směsi, kompozity a v poslední době i nano-strukturované heterogenní polymerní systémy.
Profesní profil absolventů s příklady
Absolvent DSP MCH dokáže v oblasti přípravy, resp. modifikace polymerů tvůrčím způsobem aplikovat znalosti pokročilých organických syntéz a strukturní analýzy a je připraven řešit vývoj speciálních polymerů, směsí a polymerních matric pro kompozitní materiály syntézní cestou. Absolvent dokáže samostatně formulovat vědecký problém, navrhnout hypotézu k jeho řešení a provést experimentální či teoretické pokusy k jejímu potvrzení. Nedílnou součástí základních znalostí absolventa je schopnost kritického posouzení publikovaných vědeckých informací a schopnost vyjadřovat se písemně v anglickém jazyce. Nadstavbové znalosti absolventů nad teoretické základy oboru se liší podle typu projektu, který v rámci doktorského studia řeší.
Vstupní požadavky
Řádné ukončení magisterského studijního programu stejného nebo příbuzného oboru. Dalšími předpoklady hodnocenými v rámci přijímacího řízení jsou: - dobré studijní výsledky v rámci předchozího magisterského studia - motivace ke studiu a zájem o vybrané téma - znalost anglického jazyka - odborné znalosti a schopnost uchazeče řešit problematiku disertační práce - kvalita dosavadních publikačních a odborných aktivit.
Garant
prof. RNDr. Josef Jančář, CSc.
Vypsaná témata doktorského studijního programu
Majority of research efforts in the field of polymers filled with individual nanoparticles is concentrated to the viscoelastic behavior, flammability and other physico-chemical properties. Fracture characteristics of this kind of polymer materials stay unrevealed. Hence, this work should represent a comprehensive investigation in the field of fracture behavior of polymer nanocomposites. The accent will be put on the investigation of the effect of surface treatment of nanoparticles as well as molecular parameters of polymer matrix. Student will go through laboratory preparation and processing procedures, machining of specimens and impact testing methods. The testing methods will involve use of instrumented impact pendulum equipped with high-speed camera. In addition, tensile testing and various imaging methods will be employed. In spite of the extensive experimental program, effort in the field of theoretical treatment will be accented.
Školitel: Jančář Josef, prof. RNDr., CSc.
Studying glycerine conversion into lactic acid and its lactides by the aid of non-conventional technologies
Školitel: Petrůj Jaroslav, doc. RNDr., CSc.
Generally, the scratch process is a function of the basic material properties such as the elastic modulus, the yield strength, tensile strength and fracture toughness as well as material surface characteristics such as the coefficient of friction. During scratching, materials such as polycarbonate (PC) and poly-methylmethacrylate (PMMA) preferably exhibit displacement of polymer material as “pile-ups” or ridges on the sides of the scratch. When an indenter in passed over the surface of a material the damage instituted in the material is a direct result of stresses (primarily compressive or tensile) that are generated in the affected part of the material. Material in the front part of the indenter experiences compressive stress whereas tensile stresses are generated at the rear end of the moving indenter. The elastic modulus of a polymer plays an important role in determining the scratch depth and the type of damage produced during scratching. The surface friction also affects the surface stresses that are generated in the material. High friction coefficients lead to high tensile stresses at the rear end of the indenter leading to failure of the material by cracking which is typical of brittle solids. Local strain represents one of the most important quantities involved in the scratching and visibility of scratches on polymer surfaces. Local deformation accompanying scratch formation involves considerable dissipation of deformation energy. Hence, appearance of scratches on polymer surface indicates that local strain exceeded the limit given by the yield point or material strength. Thus, one can anticipate strong correlation between mechanical behavior of bulky polymer specimens characterized by elastic modulus (E), yield strength, tensile strength and fracture characteristics (Kc and Gc).The mechanisms leading to the unique combinations of properties observed in nanofilled composites are not completely understood. The most significant difference between traditional fillers and nanofillers is the extremely large interfacial area in composites with filler particle sizes below 100 nm. Therefore, in addition to the volume replacement reinforcement of micron-scale fillers, nanofillers can provide a second mechanism of reinforcement. Namely, at the interface, the polymer chain mobility and kinetics, as well as local chemistry, can be different than in the bulk, creating an interfacial region (IR).
Natural composites such as nacre possess extraordinary toughness compared to their component materials. This is often attributed to the hierarchical structure, where features at many length scales are expected to play a role in the macroscopic deformation of the material. A hierarchical statistical model is desired to study these effects. Dental tissues have a multiscale gradient structure not reflected in existing dental materials. Unlike metals or ceramics, both having relatively simple structure, composites allow multiscale materials design based on the current state-of-the-art biomaterials science and tissue engineering. The teeth imaging has already reached appropriate level of sophistication and it is being further improved with new developments of medical imaging. An additional biomechanics optimization step based on on-line multiscale biomechanics modelling will be included between the image acquisition and restoration design steps. The implant manufacturing portion of the technology will be based on "accelerated growth-like manufacturing" (AGM) processes capable of producing the tissue-like hierarchical structure of the implanted restoration optimized to fit the individual patient. The new dental materials for use in the CAD/AGM technology will be nanostructured functional composites of varying local structure and composition and the AGM technologies will deposit them into hierarchical and gradient structures simulating dentin, enamel, complete teeth or its part individualized for any patient.
For cartilage and bone tissues, a suitable bioresorbable scaffold exhibiting optimal physical properties and biocompatibility provides initial mechanical stability and supports even cell distribution. Collagen/hydroxyapatite nanocomposites exhibit reasonable balance of physical and biological properties desired for designing scaffolds for bone tissue engineering. The mechanical performance of these bio-nanocomposites is controlled at various length-scales. In this paper, an attempt was made to model the discrete nano-scale interphase considering the dimensions of individual collagen molecules. Effect of content and shape of hydroxyapatite (HAP) nanoparticles weakly interacting with telopeptides of collagen I (Co) on the storage moduli (E') of model nanocomposites containing particles of varying shape with smilar specific surface area of approximately 190 m2/g will be investigated. Simple worm-like-chain reptation dynamics approach will be used to describe the molecular reinforcing mechanism at the nano-scale and the controlling role of the area of contact between the matrix and the reinforcement. A "hybrid network" approach to bridge the micro-scale continuum mechanics models with the nano-scale discrete chain dynamics models will be investigated to provide means for analyzing the meso-scale mechanical response of the Co/HAP nanocomposite considering nano-scale structural information. Potential applicability of the models derived for synthetic hierarchical composites in mechanics of hard tissues will also be discussed.
Práce bude zaměřena na vypracování nových metodických postupů roubování polypropylenu technologickým procesem reaktivní extruze s optimalizací pro získání maximální hodnoty poměru výtěžku reakcí konverze ku beta-štěpení.
Školitel: Kučera František, Mgr., Ph.D.
The objective of the research will be to investigate the properties and processability of nanoparticle filled controlled life time resins in the form of water-borne dispersions of core/shell particles that will be used, either alone or in combination with coarse grained powders, as the basic structural units for construction of a broad range of biomedical and agricultural applications. The technological goal will be to investigate the use of this technology for the preparation and utilization of a composite material in the form of an injectable paste or processable gel that will be useful as controlled lifetime scaffolds, tissue adhesives and bioactive gels. The shell will aid the formation of a stable aqueous suspension of the nanoparticles with a minimum of aggregation protecting the activity of the core during its delivery to the desired resulting in a wide range of potential applications of these "smart" materials for industrial semipermeable films, controlled fertilizer, seed or drug release films or as resorbable biomedical adhesives.
Adding of inorganic particles with size in the range of diameter from 5 to 30 nm into an amorphous polymer matrix causes considerable modification of the viscoelastic manifestations of a polymer. Above the glass transition temperature of matrix, polymer nanocomposite exhibits elastic modulus much higher than can be explained on the basis of simple micromechanical models. This effect occurs due to the interaction of polymer chains with extensive nano-filler surface. The interaction leads to significant change of segmental dynamics of polymer chains as well as statistical segmentation of polymer chains. Consequently, the addition of nanoparticles completely change relaxation spectrum of a polymer. The work will be focused on understanding fundamental molecular mechanisms responsible for the observed viscoelastic behavior. Student will break into the preparation and processing procedures of nanocomposite samples, various physical characterization methods, as well as fundamental concepts of polymer physics and basics of computer simulation methods.
Development of novel physico-chemical methods for preparing intelligent, controlled life-span polymeric materials from nanostructured building blocks combining synthesis of the polymeric component, preparation of nanoparticle amphiphiles and self-assembly of these substructures is targeted by this project. In addition,understanding processes of their formationand hierarchical morphology of their superstuructureson various dimensional and time scales,obtaining quantitative structure-property relationships in the various substructures and development of procedures for engineering properties of these materials in the process of their preparation is targeted.More specifically, the research goals include: (1) design of novel routes to prepare smart hierarchical polymer superstructures combining advanced syntheses (ATRP, ROMP, RAFT) of block copolymers and their attachment onto nanoparticle surface with self-assembly of these nanoparticle amphiphiles into nanostructured building blocks of prescribed supermolecular structure; (2) performing experiments providing data critical for relating the structural parameters to the physico-chemical properties of the synthetized materials at various length and time scales; (3) deriving the basic natural laws governing the molecular dynamics in the evolving multiparticle/multichain substructures and self-assembly of these substructures in the presence of polymer chains; (4) establishing quantitative bridging laws providing framework for transforming the discrete nano-scale structural features into continuum based description over multiple length and time scales and signaling effects at inter-scale interfaces; (5) applying the obtained knowledge in the design and manufacture of controlled life-span hierarchical superstructures for selected engineering and biomedical applications.
The existing constitutive models assume strain hardening the result of affine orientation of the underlying entanglement network with strain, considering entanglement a simple topological constraint to the chain movement. Despite their success in describing the stress-strain curve, there are many fundamental objections to this approach. The plastically deforming glass has almost isotropic local structure (9) and the cooperative flow of ensembles of chain segments during plastic deformation exhibits the correct temperature and strain rate dependence. Hence, scaling of the GH with the flow stress, flow was proposed. The segment scale model of strain hardening suggests, that above the yield point, the large deformation induces anisotropic chain conformations resulting in modified chain packing, suppressed density fluctuations, enhanced dynamic constraints and retarded segmental relaxations. Adding individual nanoparticles with their size, D, close to the chain radius of gyration, Rg, to the polymer glass modifies chain packing, density fluctuations and segmental relaxations, significantly and proportionally to the chain-particle interface area, hence, strong effect of nanoparticle content on the flow stress, flow, and GH should exist. The main goal of this research is experimental investigation of the effect of the process of adding rigid nanoparticles into various polymer glasses on the composition dependence of GH, y and yr and on the flow stress scaling of the GH.
Phase transitions in heterogeneous nanostructured polymers pose a serious scientific challenge. At the same time, practical importance of the crystallization kinetics is undisputable for packaging and barrier materials, engineering plastics and polymer fibers. Compared to metals, polymer crystallization is sluggish, kinetically controlled under conditions far from thermodynamic equilibrium involving molecular motions on various length and time scales. The presence of solid interfaces affects crystallization kinetics via only local modification of both nucleation and growth. However, its importance may become dominant with the reduction of specimen size or with addition of solid nanoparticles with large specific surface area into the polymer melt. This may distribute this effect throughout the entire volume of the heterogeneous melt and affect the crystal growth rate significantly. Moreover, the portion of inter particle distances, equal or smaller than the chain tube diameter, grows rapidly with reducing particle diameter even at very small nanoparticle volume fractions. This gives rise to retarded chain dynamics, interparticle chain confinement, bridging and forms additional constraints to chain dynamics with their length scale unrelated to chain characteristics. The goal of this project is to use the extended the LH model to the spherulite growth rate in heterogeneous melt investigating the effect of adding small amount of nanoparticles of varying shape and size on the crystal growth rate of polyolefins with varying backbone stiffness and particle-chain interactions isothermally crystallized from quiescent melt at small under-cooling or by varying the cooling rate in non-isothermal processes.