Thesis (Ph. D.)--Institute of Paper Chemistry, 1963. / Bibliography: leaves 110-118.

Aqueous solution surface tension as a function of vapor-phase solute pressure isotheims were measured at atmospheric pressure for single and binary component benzene, methyl-substituted benzene (i.e., methylbenzene, 1,2-dimethylbenzene, 1,3- dimethylbenzene, 1,4-dimethylbenzene, 1,3,5-trimethylbenzene), and trichloroethene adsorption. Solute-induced surface tension variations were quantified using a dynamic adsorption protocol in conjunction with Axisymmetric Drop Shape Analysis-Profile (ADSA-P) applied to pendant drop tensiometry. For single component adsorption, isotherms were measured at temperatures of 285.2K, 291.2 K, 297.2 K, 298.2 K, 303.2 K, and 315.2 K, for vapor-phase solute pressures ranging from zero to near/at saturated vapor pressure. For binary solute experiments, three intermediate constant vapor-phase mole ratio isotherms were developed for each solute pair (i.e., benzene and each of the five methyl-substituted benzenes) at temperatures of 285.2 K, 291.2 K, 298.2 K. Results for single component adsorption studies indicate that for a given vapor-phase solute pressure, interface-phase solute activity increases with molecular size (mass) among the benzene homologues. Similarly, compounds are more strongly adsorbed at the vapor/water interface as the system temperature decreases. Ideal standard free energy, enthalpy, and entropy changes of adsorption, calculated from limiting isotherm data, suggest specific solute-water interactions and a perturbation of the interface-phase water structure on adsorption. Further analysis of binary solute isotherms indicates that interface-mixing is well described by a two-dimensional application of Raoult's law, implying ideal interface-phase solute-solute interactions. Consideration of the twodimensional second virial coefficients suggests that interface-phase solute molecules engage in attractive interactions, with greater interactions for larger molecular sizes.

Neonatal respiratory distress syndrome (RDS) is a disease that affects premature infants born prior to 32 weeks gestation. The main cause is a deficiency in pulmonary surfactant due to immature type II pneumocyte cells found in the alveoli. These cells are not capable of producing the required surfactant which normally functions to reduce the surface tension at the air-liquid interface of the lungs, as well as reduce the work of breathing and prevent alveolar collapse. A current treatment method for RDS is exogenous surfactant replacement therapy involving application of an exogenous surfactant preparation directly into the lungs of premature infants. Current surfactant preparations are animal-derived and very costly. Synthetic preparations, on the other hand, are an attractive alternative. The goal of this research is to synthesize a diether phosphonolipid analogue of dipalmitoyl phosphatidylcholine (DPPC), designated DEPN-8. When incorporated into a synthetic exogenous surfactant mixture, DEPN-8 exhibits greater adsorption and surface activity compared to its natural counterpart, DPPC. The synthesis of several components related to the re-tailored synthesis of DEPN-8 will be presented and discussed below. / National Institute of Health, NSERC

No description available.

The objective of this thesis was to further develop a methodology for surface tension measurement called Axisymmetric Drop Shape Analysisn(ADSA) and to adapt it to studies of lung surfactants, i.e. the material that coats and facilitates the functioning of the lungs of all mammals. The key property of a functioning lung surfactant is its surface tension, which can reach extremely low values. Such values are difficult to measure; but a certain configuration of ADSA, using a constrained sessile drop (ADSA--CSD), is capable of performing such measurements. Clinically, lung surfactant films can be altered from both sides, i.e. from the airspace as well as from the bulk liquid phase that carries the film. Therefore, being able to access the interface from both sides is important. Here, ADSA--CSD was redesigned to be used as a micro film balance allowing access to the interface from both gas- and liquid-side. This allows deposition from the gas side as well as complete exchange of the bulk liquid phase. The new design was used to study lung surfactant inhibition and inhibition reversal. A dynamic compression-relaxation model (CRM) was developed to describe the mechanical properties of lung surfactant films by investigating the response of surface tension to changes in surface area. The model evaluates the quality of lung surfactant preparations -- beyond the minimum surface tension value -- and calculates the film properties, i.e. elasticity, adsorption and relaxation, independent of the compression protocol. The accuracy of the surface tension measurement can depend on drop size. A detailed analysis of drop shapes and accuracy of measured surface tension values was performed using a shape parameter concept. Based on this analysis, the design of ADSA--CSD was optimized to facilitate more accurate measurements. The validity analysis was further extended to the more conventional pendant drop setup (ADSA--PD). An overall upgrade of both hardware and software of ADSA--CSD, together with extensive numerical work, is described and applied to facilitate a more efficient operation. Finally, it is noted that the ADSA--CSD setup developed here can be used for a wide range of colloid and surface chemical applications.

In the present study a parallel three dimensional Volume of Fluid (VOF) method is developed to simulate Marangoni force in immiscible fluids with variable surface tension. Conservation equations are solved based on cell-averaged one-field volume tracking scheme. Evaluating the convective term in the energy equation along the boundary between the fluids highly depends on the position and orientation of the interface; hence, using average cell values simply ignores the interface shape and leads to computational uncertainty. As a remedy to this issue, the original idea behind the volume tracking method is used not only to advect mass and momentum but also energy across cells. To verify the proposed algorithm, results are compared against theoretically predicted thermocapillary migration velocity of a droplet at the limit of zero Marangoni number. However, at relatively high Marangoni numbers, thermal boundary layers are very thin and challenging to resolve. To demonstrate the capabilities of the heat transfer module, simulations of a Fluorinert droplet moving in silicon oil under applied temperature gradient in microgravity are compared against the available experimental results and the migration velocity of the droplet are reported.

The objective of this thesis was to further develop a methodology for surface tension measurement called Axisymmetric Drop Shape Analysisn(ADSA) and to adapt it to studies of lung surfactants, i.e. the material that coats and facilitates the functioning of the lungs of all mammals. The key property of a functioning lung surfactant is its surface tension, which can reach extremely low values. Such values are difficult to measure; but a certain configuration of ADSA, using a constrained sessile drop (ADSA--CSD), is capable of performing such measurements. Clinically, lung surfactant films can be altered from both sides, i.e. from the airspace as well as from the bulk liquid phase that carries the film. Therefore, being able to access the interface from both sides is important. Here, ADSA--CSD was redesigned to be used as a micro film balance allowing access to the interface from both gas- and liquid-side. This allows deposition from the gas side as well as complete exchange of the bulk liquid phase. The new design was used to study lung surfactant inhibition and inhibition reversal. A dynamic compression-relaxation model (CRM) was developed to describe the mechanical properties of lung surfactant films by investigating the response of surface tension to changes in surface area. The model evaluates the quality of lung surfactant preparations -- beyond the minimum surface tension value -- and calculates the film properties, i.e. elasticity, adsorption and relaxation, independent of the compression protocol. The accuracy of the surface tension measurement can depend on drop size. A detailed analysis of drop shapes and accuracy of measured surface tension values was performed using a shape parameter concept. Based on this analysis, the design of ADSA--CSD was optimized to facilitate more accurate measurements. The validity analysis was further extended to the more conventional pendant drop setup (ADSA--PD). An overall upgrade of both hardware and software of ADSA--CSD, together with extensive numerical work, is described and applied to facilitate a more efficient operation. Finally, it is noted that the ADSA--CSD setup developed here can be used for a wide range of colloid and surface chemical applications.

In the present study a parallel three dimensional Volume of Fluid (VOF) method is developed to simulate Marangoni force in immiscible fluids with variable surface tension. Conservation equations are solved based on cell-averaged one-field volume tracking scheme. Evaluating the convective term in the energy equation along the boundary between the fluids highly depends on the position and orientation of the interface; hence, using average cell values simply ignores the interface shape and leads to computational uncertainty. As a remedy to this issue, the original idea behind the volume tracking method is used not only to advect mass and momentum but also energy across cells. To verify the proposed algorithm, results are compared against theoretically predicted thermocapillary migration velocity of a droplet at the limit of zero Marangoni number. However, at relatively high Marangoni numbers, thermal boundary layers are very thin and challenging to resolve. To demonstrate the capabilities of the heat transfer module, simulations of a Fluorinert droplet moving in silicon oil under applied temperature gradient in microgravity are compared against the available experimental results and the migration velocity of the droplet are reported.

Adsorption-mediated self-assembly of nanoparticles at fluid interfaces, driven by reduction in interfacial energy, leads to stabilization of emulsions and foams and can be used for the bottom-up fabrication of functional nanostructured materials. Improved understanding of the parameters that control the self-assembly, the structure of nanoparticles at the interface, the barrier properties of the assembly and the rate of particle attachment and exchange is needed if such nanoparticle assemblies are to be employed for the design and fabrication of novel materials and devices. Here, I report on the use of dynamic surface tension (DST) measurements to probe the kinetics of irreversible adsorption and self-assembly of hydrophobic ethyl-cellulose (EC) nanoparticles at the air-water interface. Using thermodynamic arguments, I make a direct connection between the DST and the time-dependent surface coverage. I show that adsorption models appropriate for surfactants (e.g., Ward and Tordai model) break down for irreversible adsorption of nanoparticles, when the adsorption energy far exceeds the mean energy of thermal fluctuations (kBT) and surface blocking effects give rise to a steric barrier to adsorption. I show instead that irreversible adsorption kinetics are unequivocally characterized in terms of the adsorption rate constant and the maximum (jamming) coverage, both of which are determined on the basis of DST data using the generalized random sequential adsorption theory (RSA) for the first time. Novel accurate estimates of the adsorption energy of 42 nm and 89 nm EC nanoparticles are also provided. Coverage of the interface to the jamming limit of 91%, corresponding to a triangular lattice in 2D, is experimentally demonstrated. Colloidal solutions of EC nanoparticles are stabilized at neutral pH by electrostatic repulsive forces. Strong adsorption of these particles at an interface of like charge suggests the parallel action of attractive hydrophobic forces.

In this thesis, the results from molecular dynamics (MD) simulations of nanoaerosol clusters are discussed. The connecting link of these studies is the Köhler theory, which is the theory of condensational growth and activation of cloud droplets to form clouds. By investigating parameters such as the surface tension, state of mixture and morphology of nanoaerosol particles, conclusions can be drawn to improve the Köhler theory to include the effects of organic compounds previously unaccounted for. For the terrestrial environment, the simulations show that the natural surfactant cis-pinonic acid, an oxidation product evaporated from boreal trees, spontaneously accumulates at the surface of nanoaerosol clusters and thereby reduces the surface tension. The surface tension depression is related to the concentration of the surfactant and the size of the clusters. Surface tension is an important parameter of the Köhler theory. A decrease of the surface tension can lower the critical water vapour supersaturation needed for cloud droplet activation, giving rise to more, but smaller cloud droplets (Twomey effect) which in turn could change the optical properties of the cloud. It was also shown that the three organic surfactants, being model compounds for so called Humic-like substances (HULIS) have the ability to form aggregates inside the nanoaerosol clusters. These HULIS aggregates can also promote the solubilization of hydrophobic organic carbon in the form of fluoranthene, enabling soot taking part in cloud drop formation. Dissolved intermediately surface-active free amino acids were shown to be of some relevance for cloud formation over remote marine areas. The MD simulations showed differences between the interacting forces for spherical and planar interfaces of amino acids solutions. This thesis has emphasized the surface-active properties of organic compounds, including model HULIS and amino acids and their effect on surface tension and molecular orientation including aggregate formation in nanoaerosol clusters and their activation to form droplets. This thesis shows that the Köhler equation does not fully satisfactory describe the condensational growth of nano-sized droplets containing organic surfactants. Different approaches are suggested as revisions of the Köhler theory. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Manuscript.</p>