The intention of this study is to investigate the evolution and transition of lyotropic lamellar phase and the formation of multi-lamellar vesicles (MLVs) under shear flow, since the shear technology can be used to produce well defined multi-lamellar vesicles which are useful for encapsulating drugs in medical or research fields. The system was designed to stabilize and track one single multi-lamellar vesicle, which is being sheared under Couette shear flow between two co-rotational disks, by using polarizing microscope and a LabView program. For the whole system, most parts of the hardware instrument and all the software programs were originally designed and homemade, which makes this a unique undertaking. Eighty percent of the time was spent on designing, assembling, testing and improving the hardware instrument and software programs to make sure the system can achieve our aim as accurately as possible. The lyotropic lamellar phase sample is made of pentanol, dodecane, SDS and water. Nine different concentrations from 16% to 32% of SDS+Water were explored under five different shear rates from 3.3 to 13.2 . Sodium dodecyl sulfate (SDS) is a kind of surfactant which has an amphiphilic molecular structure, and a certain liquid crystal structure (such as a lamellar phase) will be formed when it is dissolved in a water/oil mixture solvent. It is a great achievement that one single multi-lamellar vesicle is able to be followed for over 20 minutes under shear, and it is found that the multi-lamellar vesicle does not exhibit any obvious changes with time once it was already formed. Three different structural regions were found for the dilute lamellar phase while evolving to the multi-lamellar vesicle orientation state under shear. However, only two regions were found for the lamellar phase with higher concentrations under low shear rate since the lamellar phase will not reach to the multi-lamellar vesicle state. Besides, on the basis of the results of these experiments, it can be concluded that either higher shear rate or higher concentration of SDS+Water will hasten the formation of multi-lamellar vesicles. For the transition time of reaching a uniform multi-lamellar vesicle orientation state, it can be reduced by increasing shear rate. In addition, the results show that the transition time is decreasing more slowly for high concentrated lamellar phases than dilute lamellar phases with increasing the shear rate.

none

No description available.

The increasingly stringent environmental regulations worldwide demand the use of efficient methods for air purification. Moreover, the alarming effect of greenhouse gases on the world climate requires the removal and sequestration of large quantities of anthropogenic carbon dioxide (CO2). This work is contributed towards the development of efficient, amine-containing, lamellar structured silica adsorbents for CO2 removal. Seven different materials were prepared by impregnation of various amounts of PEI, over as synthesized, or partially extracted or calcined lamellar silica. Materials were characterized by powder XRD and SEM. CO2 adsorption capacity was measured by thermogravimetry. The effects of PEI loading, temperature, CO2 partial pressure and surface alkyl chains were investigated. PEI seems to be dispersed better in a consistent surface alkyl chain network, leading to enhanced CO2 uptake. VB-13, the material with 50 wt% of PEI, recorded the highest CO2 uptake at 75 °C, in the presence of both 15% CO2/N2 and 100% CO2 with values of 3.02 and 3.50 mmol/g respectively. The optimum temperature for CO2 uptake was found to be 75 °C for samples with high PEI loading. Moreover, higher uptake was recorded in the presence of 100% CO2 versus 15% CO2/N2 for all temperatures. Another objective of this study was to investigate the effect of humidity on the CO2 adsorption process. In that case use of the column-breakthrough technique coupled with mass spectrometry to discriminate between CO2 and water was considered. Complete understanding of the technique and the different effects of moisture on CO2 adsorption over amine-containing materials, namely promotion of CO2 uptake and stabilization of the adsorbent, were achieved, based on a thorough scrutiny of the literature. Nonetheless, because of the Covid-19 pandemic and several technical issues, some experiments could not be undertaken.

No description available.

Since decades, nucleation, or the ability of certain organic or inorganic substances to trigger the crystal growth, has been empirically used in the plastics industry. Talc, for instance, is a well-known nucleating agent of poly(ethylene terephthalate) (PET) and other polymers, that allows one to enhance the crystallisation rate of the polymer material and to control its spherulites size. The exact mechanism involved in this nucleation had however remained unknown at the onset of this thesis. Through electron diffraction, performed on thin PET films nucleated by macroscopic talc particles as model samples, this work demonstrates an epitaxial relationship between polymer and substrate and thus confirms the seemingly ubiquitous role of epitaxy in the nucleation of polymers. However, in order to compare the talc-nucleated morphology of PET with the virgin one, new methods of sample preparation for transmission electron microscopy (TEM) have also been developed. Coupled with theoretically justified image analysis techniques, they allow the direct observation of PET crystalline lamellae, both in the bulk and in thin films. Analyses of the semicrystalline structure in the reciprocal and direct spaces were performed from small-angle X-ray scattering (SAXS) data and from observations by TEM on melt-crystallised samples. These independent results were shown to be in good agreement and bring strong evidence in favour of a semicrystalline space-filling model, where the average crystalline thickness is slightly smaller than the average width of the amorphous regions. Discrepancies between characteristic distances derived by several methods from the same experimental results were attributed to the broad distribution of thicknesses, in contrast with the ideal linear stack model commonly used to analyse the data.

Orientador: Claudio Airoldi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-04T03:16:55Z (GMT). No. of bitstreams: 1 Machado_MargareteOliveira_M.pdf: 2375635 bytes, checksum: f083ccbf844356a5d576d3d1a2311e97 (MD5) Previous issue date: 2004 / Mestrado / Quimica Inorganica / Mestre em Química

The crystallization behavior of bisphenol-A polycarbonate (BAPC) was studied, focusing on the initial stage of crystallization and the secondary stage of crystallization. Bisphenol-A polycarbonate was the polymer chosen for this study because of its slow crystallization rate. With slow crystallization kinetics, the polymer morphology does not change when quenched below its glass transition temperature, enabling the study of different stages of crystallization through the frozen morphology. The study of the initial stages of crystallization pertained to crystallization times prior to the growth of detectable crystallinity. This study employed BAPC because of the long induction period, a direct result of the slow crystallization kinetics. During the induction period of polycarbonate crystallized at 190°C there was no evidence of polymer chain ordering that was seen in literature for other polymers. The length of the induction period determined by differential scanning calorimetry and wide-angle X-ray diffraction varied by over 6 hours because differential scanning calorimetry can detect a smaller amount of crystallinity than wide-angle X-ray diffraction. Signs of pre-ordering in the literature could be a result of experimental sensitivity. The study of the secondary crystallization dealt with the isothermal lamellar thickening of BAPC crystals during annealing, after crystallization for an extended period of time. Small-angle X-ray scattering and differential scanning calorimetry experiments were performed on bisphenol-A polycarbonate samples crystallized near 190°C for 8 days and annealed at either 223°C or 228°C for various times. The Gibbs-Thomson relationship, which can be defined using the experiments mentioned, yielded two thermodynamic constants, the equilibrium melting temperature and the surface free energy. Including data from literature in the determination of the constants, the equilibrium melting temperature and surface free energy of BAPC is 303°C and 36.6mJ/m2, respectively. Comparing the lamellar thickness measurements by small-angle X-ray diffraction with direct measurements by microscopy was difficult because the morphology of the polymer was not easily seen in the bulk using atomic force microscopy or scanning electron microscopy. Etching the sample was the most promising technique for future investigations of revealing the bulk morphology for direct lamellar thickness measurements. Crystallizing thin films of polycarbonate on calcite substrates allowed the measurement of lamellar thickness using scanning electron microscopy because the lamellae grow epitaxially to the substrate. The measurement of the long spacing in thin film samples was comparable to that of bulk samples. / Master of Science

The distinctive architecture of the stratum corneum with its unique nature of an interstitial lipoidal environment plays the major role in regulating the barrier function of the skin. The major problem with the transdermal delivery of 5-fluorouracil or idoxuridine is the permeation of sufficient amounts to the deeper layers of the skin and into the systemic circulation. In an attempt to enhance the transdermal permeability of 5-fluorouracil and idoxuridine, the aim of this study was to evaluate two lamellar gel phase systems (Physiogel dermaquadrille® and Physiogel NT®) and Emzaloids® as transdermal delivery vehicles for the two actives. Lamellar gel phase systems (LGPS) and Emzaloids® are both novel drug delivery systems. The epidermis of female abdominal skin was used in vertically mounted Franz diffusion cell experiments. An average amount of 250 mg of the 1% m/m LGPS was applied to cover the entire diffusion area of 1,075 cm2 of the skin, which contained 2,5 mg of the active. Samples of the actives in Emzaloids® were prepared and applied in the same way. The control solutions of the actives in water were prepared so that 1 ml of the applied solution contained the same amount of drug that was applied to the experimental cells. The entire receptor phase of the cells was removed at 2,4,6, 8, 10, 12 and 24 hours and was replaced with fresh 37°C receptor phase. The amount of active in the receptor phase was determined by HPLC analysis. Graphs of the cumulative amount of the active that permeated the skin over the 24 hour period were drawn and the slope of the graphs represented the flux in µg/ml/h. The average flux values of six experimental cells and six control cells were compared. Entrapment of the actives in the Emzaloid® vesicles was confirmed with the use of confocal laser scanning microscopy. Results for the LGPS indicate an enhancement ratio in the order of 4,2 for 5-fluorouracil and 1,7 for idoxuridine when compared to the control cells. There were no viscosity changes in the LGPS samples containing 1% m/m of the active when compared with the blank LGPS samples, suggesting that no change in the internal structure of the LGPS occurred after the addition of the actives to it. There were also no significant changes in the pH of the samples. Entrapment of the actives in the Emzaloid® vesicles occurred readily. The Emzaloid® vehicle showed a lower rate of release for idoxuridine than the LGPS did during the VanKel dissolution experiments. This suggests that higher flux values would be obtained with the LGPS for idoxuridine than with the Emzaloid® formulation, since more drug was available for permeation through the skin. This was, however, not the case. The Emzaloid® formulation showed much higher flux values, showing that even with a smaller amount of active available to permeate the skin higher flux values were obtained. Enhancement ratios of 20,33 and 3,50 were achieved with the Emzaloid® formulation for 5-fluorouracil and idoxuridine respectively. The internal LGPS structure which mimics the skins lipid components remained unchanged after the addition of the actives. Greater success might be achieved with the LGPS for different model drugs, since the drugs' physicochemical properties play an important part in its permeation through the skin. The Emzaloid® formulation, which is closely related to liposomes and transfersomes, showed great potential for commercially marketable formulations for the drugs tested but further research on the formulation has to be done. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.

The distinctive architecture of the stratum corneum with its unique nature of an interstitial lipoidal environment plays the major role in regulating the barrier function of the skin. The major problem with the transdermal delivery of 5-fluorouracil or idoxuridine is the permeation of sufficient amounts to the deeper layers of the skin and into the systemic circulation. In an attempt to enhance the transdermal permeability of 5-fluorouracil and idoxuridine, the aim of this study was to evaluate two lamellar gel phase systems (Physiogel dermaquadrille® and Physiogel NT®) and Emzaloids® as transdermal delivery vehicles for the two actives. Lamellar gel phase systems (LGPS) and Emzaloids® are both novel drug delivery systems. The epidermis of female abdominal skin was used in vertically mounted Franz diffusion cell experiments. An average amount of 250 mg of the 1% m/m LGPS was applied to cover the entire diffusion area of 1,075 cm2 of the skin, which contained 2,5 mg of the active. Samples of the actives in Emzaloids® were prepared and applied in the same way. The control solutions of the actives in water were prepared so that 1 ml of the applied solution contained the same amount of drug that was applied to the experimental cells. The entire receptor phase of the cells was removed at 2,4,6, 8, 10, 12 and 24 hours and was replaced with fresh 37°C receptor phase. The amount of active in the receptor phase was determined by HPLC analysis. Graphs of the cumulative amount of the active that permeated the skin over the 24 hour period were drawn and the slope of the graphs represented the flux in µg/ml/h. The average flux values of six experimental cells and six control cells were compared. Entrapment of the actives in the Emzaloid® vesicles was confirmed with the use of confocal laser scanning microscopy. Results for the LGPS indicate an enhancement ratio in the order of 4,2 for 5-fluorouracil and 1,7 for idoxuridine when compared to the control cells. There were no viscosity changes in the LGPS samples containing 1% m/m of the active when compared with the blank LGPS samples, suggesting that no change in the internal structure of the LGPS occurred after the addition of the actives to it. There were also no significant changes in the pH of the samples. Entrapment of the actives in the Emzaloid® vesicles occurred readily. The Emzaloid® vehicle showed a lower rate of release for idoxuridine than the LGPS did during the VanKel dissolution experiments. This suggests that higher flux values would be obtained with the LGPS for idoxuridine than with the Emzaloid® formulation, since more drug was available for permeation through the skin. This was, however, not the case. The Emzaloid® formulation showed much higher flux values, showing that even with a smaller amount of active available to permeate the skin higher flux values were obtained. Enhancement ratios of 20,33 and 3,50 were achieved with the Emzaloid® formulation for 5-fluorouracil and idoxuridine respectively. The internal LGPS structure which mimics the skins lipid components remained unchanged after the addition of the actives. Greater success might be achieved with the LGPS for different model drugs, since the drugs' physicochemical properties play an important part in its permeation through the skin. The Emzaloid® formulation, which is closely related to liposomes and transfersomes, showed great potential for commercially marketable formulations for the drugs tested but further research on the formulation has to be done. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.