Free radical polymerization is the most common polymerization technique that is used for the manufacturing of polymers, due to the ease of the polymerization initiation, wide latitude of the material design for a large variety of monomers, and the excellent process robustness for commercial production. In the 1990’s, research activities for the precise control of radical polymerization process resulted in the discovery of ‘Living Radical Polymerization’. The discoveries opened the door for the next generation of radical polymerizations. Extensive research has been conducted to understand the mechanisms and kinetics for numerous practical applications, particularly for polymerization in bulk and solution systems. However, despite the interest of industry, the mechanistic understanding in aqueous dispersed systems such as emulsion and miniemulsion polymerization is far behind the aforementioned two systems. There are still major challenges from the production viewpoint. One reason for the poor understanding is the complexity of the heterogeneous system, which includes multiple　reaction phases that are accompanied by the segregation and transfer of the reaction species among different phases. The purpose of this research was to investigate living radical polymerization or “Stable Free Radical Polymerization” (SFRP) in aqueous dispersed systems to obtain better mechanistic understanding of how the heterogeneous nature of the system interacts with the novel living radical chemistry. The theoretical and experimental feasibility of the SFRP emulsion process were studied in this research, in particular, focusing on the compartmentalization effect. Particle size influence on the polymerization kinetics and the polymer livingness was experimentally confirmed, and compared to bulk polymerization. In addition, a comprehensive mathematical model including all major chemical and physical events was developed to further our mechanistic understanding. Based on the results from the experimental and modeling studies, it was shown that rate reduction in the smaller particles is the primary cause of difficulty in implementing a conventional emulsion process (i.e. ab initio emulsion polymerization). Finally, for overcoming this difficulty, a new approach using a combination of TEMPO with highly hydrophobic 4-stearoyl TEMPO was proposed for a coagulum free ab initio emulsion process. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-02-18 09:49:52.336

Controlled radical polymerization (CRP) has emerged as a powerful method of creating polymers with tailored molecular architectures under mild reaction conditions. However, production of these polymers efficiently at an industrial scale will likely require them to be synthesized in the dispersed phase. Three types of CRP are explored, Atom Transfer Radical Polymerization (ATRP), Nitroxide Mediated Polymerization (NMP) and Catalytic Chain Transfer (CCT) to elucidate the intricacies of creating these novel polymer colloids. Compartmentalization in an ATRP dispersed phase system is explored theoretically to understand the effects of particle size and catalyst concentration on the polymerization. The results suggest that there is an optimal range of particle sizes where the rate of polymerization is greater than that in an equivalent bulk system while maintaining both a lower PDI (polydispersity index) and higher livingness. All three factors are desirable in ATRP but generally cannot be achieved simultaneously in bulk. Compartmentalization manifests itself differently in CCT dispersed phase systems, where the segregation of the CCT agents into different polymer particles leads to multimodal molecular weight distributions. Control over the particle size is notoriously difficult for nitroxide mediated polymerization, as it is challenging to decouple an increase in the particle size with an increase in target molecular weight using a two stage emulsion polymerization approach. This often leads to colloidally unstable latexes for low molecular weight, high solids conditions which are the result of superswelling. We offer several strategies to minimize this problem and create colloidally stable, high solids, n-butyl acrylate latexes by NMP with moderate to high molecular weight targets (>70 kg/mol). Using this synergy between target molecular weight and particle size, high solids (>40 wt.%), high molecular weight (<200 kg/mol) microemulsions (~20 nm) of methyl methacrylate-co-styrene were prepared. Finally, the monomer type and nucleation mechanisms also play a role in determining the particle size distribution in NMP emulsion systems. Using n-butyl methacrylate in emulsion with surfactant concentrations above the critical micelle concentration yields latexes with bimodal particle size distributions. However a surfactant-free approach allows monomodal latexes to be created. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-12-03 13:30:15.346

Amidine-based switchable surfactants can be used as stabilizers during emulsion polymerization and the resulting latexes can then be destabilized by the removal of CO2. High Tg polymers have been successfully redispersed, as shown by recovery of primary particle size (measured by light scattering methods), but an input of energy was required. Sonication was the first method used, but lower-energy methods such as rotor-stators and a blender have also been successful in redispersing aggregated latexes. Colloidal stability was found to be reversible for at least three aggregation/redispersion cycles, and redispersibility was retained after the removal of water and addition of fresh water. Stimuli-responsive polymer colloids with reversible colloidal stability may have many uses. The shipping of latexes, for example, would be easier and less energy intensive if the latex particles could be aggregated and the bulk of the water removed. The latexes would then have to be redispersed prior to use. Switchable surfactants have also been used for the semi-continuous copolymerization of butyl acrylate and methyl methacrylate to form a high solids content (42 wt%), low-Tg latex. The latex can be destabilized with air and heat but cannot undergo redispersion because the low Tg polymer particles fuse upon aggregation. The copolymer, when dried at room temperature, formed a continuous film. Latexes with high solids content and low Tg’s are representative of latex paint formulations. Because the switchable surfactants have been shown to be successful in preparing these latexes, it is possible that they may be useful in the latex paint industry, for example as fast setting paints. / Thesis (Master, Chemistry) -- Queen's University, 2011-09-26 13:18:33.905

No description available.

The study evaluated the effect of canola (Brassica juncea) derived antioxidants on the oxidation in whey protein stabilized canola oil-in-water emulsion at elevated temperature. 10 % canola oil in water emulsion using 1% whey protein as emulsifier was first prepared by passing through homogeniser. Canola antioxidants extracts such as sinapic acid extract (SAE), sinapine (SP), Canolol (CAN) and whole extract, (WE) at two concentrations (100 and 350 µM), were added and incubated at 30° C. Sinapic acid (SA) and Butylated hydroxyl toluene (BHT) standards were also used as references. Primary oxidation marker like peroxides and secondary oxidation volatile products like hexanal, pentanal and 2,4-heptadienal were monitored to assess the anti-oxidative effect. BHT was found to be the most effective AO. WE and SP were also equally good as BHT. Peroxide values were significantly different (P<0.05) in case of BHT-100* (*concentration in µM), BHT-350, SP-350 and WE-350 compared to control. Same pattern was also followed in volatiles measurement. WE and SP were also shown to be potent AO as shown by DPPH, chelating and reducing assays. The physical stability of the emulsion was determined by particle size measurement. The particle size (diameter) of oil droplets remains constant throughout experimental period (0.162-0.188 µm). Viscosity was also determined by rheometer and found to be stable over 15 days (7.0 - 8.5 mPa.s). This also demonstrated that WE and SP have the potential to replace other synthetic antioxidants in a concentration dependant manner.

No description available.

Insect repellent N,N-diethyl-m-toluamide (DEET) and sunscreen oxybenzone are commonly incorporated into commercially available consumer care products that are utilized to prevent vector-borne diseases and skin aging and damage. Semisolid emulsion-based formulation has been extensively selected for active repellent and sunscreen ingredients due to their excellent solubilizing properties for both lipophilic and hydrophilic components and satisfactory customer acceptance. Under the ideal use situation, an appropriate and elegant emulsion-based formulation can minimize transdermal absorption of DEET and oxybenzone and maximize their skin protection effect. The percutaneous penetration profiles of DEET and oxybenzone from several emulsion-based formulations were evaluated and compared by using the in vitro diffusion experiments in this thesis. Various parameters in the emulsion formulations, such as emulsion type, emulsifier, emollient, penetration enhancer, thickening agent, and thixotropic properties of the emulsions, could exert significant influence on percutaneous permeation of the active ingredients from the preparations. An emulsion-based preparation using the emulsifier, Emulium 22, possessed the relatively lower skin permeation of DEET and oxybenzone than other emulsion-based preparations; it was selected for the in vivo animal study. This emulsion-based formulation containing DEET and/or oxybenzone was topically applied to rats once daily for a 60-day period to investigate systemic concentration and tissue deposition of DEET, oxybenzone, and their respective metabolites. This formulation produced lower systemic absorption of DEET and oxybenzone than the commercially available products reported in a previous animal study. The concurrent application of DEET and oxybenzone in this study did not show synergistic enhancement between the two compounds in plasma. The percutaneous penetration profiles of DEET and oxybenzone from different semisolid emulsions in the in vitro diffusion experiment provided the important information in selecting the appropriate formulation of DEET and oxybenzone for topical application. The in vivo animal study identified pharmacokinetics and biodistribution characteristics of DEET and oxybenzone from the promising lab-developed emulsion. Studies are ongoing to further improve formulation characteristics so that this emulsion-based preparation could be used to minimize overall transdermal permeation of DEET and oxybenzone from topical skin application.

The study evaluated the effect of canola (Brassica juncea) derived antioxidants on the oxidation in whey protein stabilized canola oil-in-water emulsion at elevated temperature. 10 % canola oil in water emulsion using 1% whey protein as emulsifier was first prepared by passing through homogeniser. Canola antioxidants extracts such as sinapic acid extract (SAE), sinapine (SP), Canolol (CAN) and whole extract, (WE) at two concentrations (100 and 350 µM), were added and incubated at 30° C. Sinapic acid (SA) and Butylated hydroxyl toluene (BHT) standards were also used as references. Primary oxidation marker like peroxides and secondary oxidation volatile products like hexanal, pentanal and 2,4-heptadienal were monitored to assess the anti-oxidative effect. BHT was found to be the most effective AO. WE and SP were also equally good as BHT. Peroxide values were significantly different (P<0.05) in case of BHT-100* (*concentration in µM), BHT-350, SP-350 and WE-350 compared to control. Same pattern was also followed in volatiles measurement. WE and SP were also shown to be potent AO as shown by DPPH, chelating and reducing assays. The physical stability of the emulsion was determined by particle size measurement. The particle size (diameter) of oil droplets remains constant throughout experimental period (0.162-0.188 µm). Viscosity was also determined by rheometer and found to be stable over 15 days (7.0 - 8.5 mPa.s). This also demonstrated that WE and SP have the potential to replace other synthetic antioxidants in a concentration dependant manner.

Jena, Universiẗat, Diss., 2006. / Beitr. teilw. dt., teilw. engl. - Enth. u.a. 4 Sonderabdr. aus verschiedenen Zeitschr.

Zugl.: Hamburg, Techn. Univ., Diss., 2006