Since the discovery of organic conducting polymers more than 20 years ago, these materials are finding an increasing use in various branches of technology, such as metallization of dielectrics, primary and secondary batteries, antistatic coatings, electromagnetic shielding, electrochromic systems. One of the most striking properties of conducting polymers is their ability to catalyze some electrode reactions. A thin layer of a conducting polymer, deposited onto the surface of substrate electrode, is able to enhance the kinetics of electrode processes of some solution species. These electrocatalytic processes, proceeding at conducting polymer electrodes, present a fast growing area of investigation, which may yield many unexpected applications in various fields of applied electrochemistry.

Polymers, typically known, as plastics, long time were only insulators. In 1977 D.J. Heeger, A.G. Diarmid ir H. Shirakawa discovered a new type of this organic material – conductive polymers. Conductive polymers have a unique property of high electrical conductivity, where the electronic structure of polymer chains plays essential role. In this work we theoretically investigate conductive organic materials. Conductance of this materials is the result of charge carriers tunnelling. Tunnelling is a temperature-dependent process due to the interaction of electrons with phonons (phonon – kvaziparticle describing the periodical motion of cristal atoms). The basic quantum-mechanical theory what helps us to interpret the experimental results – phonon-assisted tunnelling theory. Experimental results were taken from other authors papers. In this theory is assumed that tunnelling rate depends on both – temperature and field. All the calculations were taken in Mathematica 5.0. Programs made in this algebrical system helped us to fit experimentical and theoretical data. It let us to describe tunnelling rate variating parameters. The main attention was taken to investigate how some of this parameters change tunnelling rate (W) and estimate parameters of polyacetylene and carbon nanotubes (CNT). This materials were taken because of it`s unique properties. Polyacetylene can become very good conductor by it`s doping. Carbon is one of the most abundant ellements in the Earth crust. It... [to full text]

The Aim of the Doctoral Dissertation is to investigate the influence of geo-metrical parameters of microstructure, pores distribution mode, microdefects on soft porous polymer materials deformation behaviour and determine the laws of dependences of above-mentioned factors on the material stress and strain.

Konjuguotieji polimerai kaip funkcinės medžiagos gali būti panaudoti įvairiuose prietaisuose: organiniuose šviestukuose, organiniuose lauko tranzistoriuose, organiniuose saulės elementuose. Šio darbo tikslas - nustatyti fotogeneruotų krūvininkų pernašos dėsningumus π – konjuguotuose polimeruose panaudojant naują žadinimo-zondavimo metodą pagrįstą išoriniu elektriniu lauku indukuota antrosios optinės harmonikos generacija. Pagrindinis dėmesys buvo skiriamas pernašos dinamikai. Molekulinių darinių fizikos laboratorijoje buvo įrengta matavimų schema ir įvertintas metodo tinkamumas krūvio pernašos tyrimams. Buvo atlikti krūvio pernašos matavimai trijuose skirtinguose konjuguotuosiuose polimeruose. Nustatyta, kad fotogeneruotų krūvininkų judris tuoj po sužadinimo yra daug didesnis lyginant su stacionaria judrio verte, o krūvio pernašos dinamiką lemia konjuguoto polimero struktūrinė hierarchija, krūvininkų judėjimas yra daugialypis, susidedantis iš greito judėjimo viena polimero grandine ar konjuguotais polimero grandinės segmentais ir lėto šokavimo tarp atskirų polimero grandinių Pirmą kartą detaliai išnagrinėta šviesa sugeneruotų krūvininkų pernašos dinamika konjuguotuose polimeruose. Darbo rezultatai suteikia žinių apie fundamentalius krūvininkų pernašos mechanizmus konjuguotuose polimeruose, kurios gali būti panaudotos kuriant organinius elektronikos prietaisus. / Conjugated polymers are promising candidates for applications in all kinds of organic optoelectronic devices: OLEDs, organic field-effect transistors (OFETs) and organic photovoltaic cells. The main goal of this work was to investigate transport features of photogenerated electrical charge in pi-conjugated polymers by means of novel technique based on time-resolved electric field-induced second harmonic generation (TREFISH). TREFISH measurement setup was implemented in the laboratory of Molecular compounds physics, and applicability of the method has been verified. Measurements were performed on three different model polymers: methyl substituted ladder-type poly(para-phenylene) (MeLPPP), poly(fluorene-co-benzothiadiazole) (F8BT) and poly(spirobifluorene-co-benzothiadiazole) (PSF-BT), having different morphological and chemical structure. It has been found that motion of photogenerated charge carriers in π-conjugated polymer films experiences rapid dynamics after excitation. Different time domains of charge transport were distinguished. Initial fast transport of photogenerated charge carriers corresponds to the carrier motion along the single polymer chain or conjugated segment of the polymer chain. Slowest carrier motion phase is well described by the stochastic drift, which is attributed to interchain jumps and determines the macroscopic equilibrium mobility. Thus, the equilibrium mobility value is not applicable to the transport on nanometer scale up to tens of nanometers... [to full text]

Mechanical properties of polymers are reviewed and the phenomenon of the abrasive wear is analyzed in the literary part. The researches of other authors on the abrasive wear and their results are surveyed. Laboratory equipment for carrying out the abrasive wear researches is introduced. Optimal mount of laboratory simulation for modeling polymeric material wear in the abrasive environment is chosen. The testing materials‘ properties are characterized. The results of researches on polymeric materials, used in enginery, on the wear in the abrasive environment are presented. The carried out research showed that wear results of the same materials under different testing conditions (“polymer-abrasive”, “polymer-steel disc” ASTM G176-03) the dependence of wear on hardness end on the coefficient of friction differs. That is influenced by the choice of polymeric materials. The scope of the work is 62 pages: 57 pictures, 1 table, 7 appendixes are included, 25 sources of literature were referred to in this work.

The aim of this thesis “Interactions of biodegradable drug carriers with hydrophilic medium” is the study of polymer-hydrophilic medium interactions from the point of view of swelling, erosion and glass transition. In the theoretical part attention was paid to basic information about polyester amides and polyesters with molecule linear, branched, and chain extended. In this part, some basic relations were used, concerning various aspects of biodegradation of polymers, thermal analysis of amorphous phase of polymers and pharmaceutical particulate systems. The main part of the thesis is focused on experiment. Fifteen recently synthesized oligomeric and polymeric carriers were studied in the aspect of their swelling and erosion course. Some of these oligoesters with molecular linear constitution were evaluated during in vitro degradation process via glass transition tested by DSC method measurements. No correlation signs between swelling kinetics and glass transition temperature values course were found. These two molecular relaxation parameters are the manifestations of different mechanism. Swelling extent is influenced by osmotic phenomena, whilst glass transitions by molecule polarization effects. This work is one of the first steps examining these drug carriers. The results of this work will be used in choosing perspective drug carriers and in further researches. / Šio darbo „Biodegraduojančių vaistų nešėjų sąveika su hidrofiline terpe“ tikslas ištirti polimero bei hidrofilinės terpės sąveiką atsižvelgiant į brinkimą, eroziją bei stiklėjimo temperatūros pokyčius, galimą ryšį tarp polimero brinkimo ir stiklėjimo temperatūros, apžvelgti nano ir mikro dalelių paruošimo bei įvertinimo teoriją. Literatūros apžvalgoje dėmesys skiriamas informacijai apie poliesteramidus ir linijinius, šakotus ar praplėstos grandinės poliesterius. Šioje dalyje aptariami įvairūs polimerų biodegradacijos, amorfinės fazės polimerų terminės analizės aspektai, taip pat nano bei mikrodalelės kaip vaisto forma. Pagrindiniai darbo uždaviniai yra ištirti penkiolika neseniai susintetintų oligomerinių bei polimerinių vaistų nešėjų atsižvelgiant į jų brinkimą bei eroziją, įvertinti kai kurių linijinių oligoesterių degradacija in vitro atsižvelgiant į stiklėjimo temperatūrą matuojant diferencinės skenuojančios kalorimetrijos metodu. Atkreiptas dėmesys į galimą ryšį tarp stiklėjimo temperatūros ir brinkimo kinetikos, kurio nepastebėta; manoma, kad dėl to, jog molekulės grandinės atsipalaidavimas pasireiškia dėl skirtingų mechanizmų. Brinkimo laipsnis priklauso nuo osmotinių reiškinių, o stiklėjimo temperatūrai įtaką daro molekulės poliarizacija. Šis darbas yra pradinis etapas tiriant šiuos polimerus. Šio darbo rezultatai padės atrenkant perspektyvias medžiagas tolimesniems tyrimams, prognozuojant galimas jų panaudojimo galimybes.

The goal of the dissertation was to investigate the peculiarity of morphological changes of the modified polychloroprene adhesive in the aim to predict the mechanical and adhesive behaviour and to produce composition with useful and essential properties.

Conjugated polymers are promising candidates for applications in all kinds of organic optoelectronic devices: OLEDs, organic field-effect transistors (OFETs) and organic photovoltaic cells. The main goal of this work was to investigate transport features of photogenerated electrical charge in pi-conjugated polymers by means of novel technique based on time-resolved electric field-induced second harmonic generation (TREFISH). TREFISH measurement setup was implemented in the laboratory of Molecular compounds physics, and applicability of the method has been verified. Measurements were performed on three different model polymers: methyl substituted ladder-type poly(para-phenylene) (MeLPPP), poly(fluorene-co-benzothiadiazole) (F8BT) and poly(spirobifluorene-co-benzothiadiazole) (PSF-BT), having different morphological and chemical structure. It has been found that motion of photogenerated charge carriers in π-conjugated polymer films experiences rapid dynamics after excitation. Different time domains of charge transport were distinguished. Initial fast transport of photogenerated charge carriers corresponds to the carrier motion along the single polymer chain or conjugated segment of the polymer chain. Slowest carrier motion phase is well described by the stochastic drift, which is attributed to interchain jumps and determines the macroscopic equilibrium mobility. Thus, the equilibrium mobility value is not applicable to the transport on nanometer scale up to tens of nanometers... [to full text] / Konjuguotieji polimerai kaip funkcinės medžiagos gali būti panaudoti įvairiuose prietaisuose: organiniuose šviestukuose, organiniuose lauko tranzistoriuose, organiniuose saulės elementuose. Šio darbo tikslas - nustatyti fotogeneruotų krūvininkų pernašos dėsningumus π – konjuguotuose polimeruose panaudojant naują žadinimo-zondavimo metodą pagrįstą išoriniu elektriniu lauku indukuota antrosios optinės harmonikos generacija. Pagrindinis dėmesys buvo skiriamas pernašos dinamikai. Molekulinių darinių fizikos laboratorijoje buvo įrengta matavimų schema ir įvertintas metodo tinkamumas krūvio pernašos tyrimams. Buvo atlikti krūvio pernašos matavimai trijuose skirtinguose konjuguotuosiuose polimeruose. Nustatyta, kad fotogeneruotų krūvininkų judris tuoj po sužadinimo yra daug didesnis lyginant su stacionaria judrio verte, o krūvio pernašos dinamiką lemia konjuguoto polimero struktūrinė hierarchija, krūvininkų judėjimas yra daugialypis, susidedantis iš greito judėjimo viena polimero grandine ar konjuguotais polimero grandinės segmentais ir lėto šokavimo tarp atskirų polimero grandinių Pirmą kartą detaliai išnagrinėta šviesa sugeneruotų krūvininkų pernašos dinamika konjuguotuose polimeruose. Darbo rezultatai suteikia žinių apie fundamentalius krūvininkų pernašos mechanizmus konjuguotuose polimeruose, kurios gali būti panaudotos kuriant organinius elektronikos prietaisus.

Evaluation of solid-phase microextraction as an alternative official method for analysis of polymers migration. The objective this study was to compaire the official methods with solid-phase microextraction (SPME)for the analysis of compounds migrating from cross-linked polyethylene into water. A medium polarity polydimethylsiloxane/divinylbenzene (PDMS/DVB)was proved most efficient for the SPME extraction. However, when applied to water samples in contact with polyethylene, SPME proved to be immensely more sensitive and have a greater extraction range than liquid-liquid extraction (LLE). It was proved the migration of Phenol, 2,4-bis(1,1-dimethylethyl). Concentration of this compound 0,6-0,15mg/l.It was proved the migration of Cyclohexadiene-1,4-dione, 2,6-bis(1,1-dimethylethyl).