Traditional fluorosilicones contain a siloxane backbone and pendant fluorinated group leading to low temperature ductility and excellent thermal stability. However, acidic or basic catalysts can reduce the thermal stability from a potential 350 °C to 150 °C. The predominant decomposition mechanism is through chain scission and it is hypothesized that preventing this will result in polymers with higher thermal stability. Three approaches were taken to prevent chain scission. First, a series of hybrid fluorosilicones based on (trifluorovinyl)benzene were synthesized through condensation polymerization with initial decomposition temperatures of approximately 240 °C. These were compared to similar aromatic polyethers and removal of the ether oxygen lowered the initial decomposition temperature by approximately 190 °C demonstrating the importance of this oxygen to the stability of polyethers. Second, reverse fluorosilicone (fluorinated backbone and pendant siloxane) terpolymers of chlorotrifluoroethylene (CTFE), vinyl acetate (VAc) and methacryloxypropyl-terminated polydimethylsiloxane (PDMSMA) were synthesized in supercritical CO2 (scCO2) or by emulsion polymerization. Chain scission was prevented as initial decomposition occurred between 231 and 278 °C. In both the emulsion and scCO2 cases, VAc was essential in facilitating cross-propagation between CTFE and PDMSMA and the branching was similar suggesting polymerization media does not affect polymer structure. Emulsion-based polymers had higher molar masses and thermal stability whereas comparable scCO2 polymers had higher yields and incorporated more PDMSMA. Third, a series of homo-, co-, and terpolymers of CTFE, VAc and methacryloxypropyl-terminated silsesquioxane (POSSMA) were synthesized representing the first synthesis of POSSMA containing polymers in scCO2 and demonstrating reverse fluorosilicones can be synthesized without VAc. Chain scission was prevented as initial decomposition occurred from 244 to 296 °C with thermal stability increasing with CTFE content to a limit. Decomposition of the polymers was examined and mechanism elucidated. In air, the copolymers give 40 to 47 wt% char since the silsesquioxane oxidizes to SiO2 while in N2, no residue is seen. In contrast, the terpolymers give a carbonaceous residue of approximately 20 wt% in N2. The flammability and surface properties of the polymers were examined with the terpolymers having flammability similar to p(CTFE) and surface properties comparable to p(POSSMA) giving a low-flammability, hydrophobic polymer.

Traditional fluorosilicones contain a siloxane backbone and pendant fluorinated group leading to low temperature ductility and excellent thermal stability. However, acidic or basic catalysts can reduce the thermal stability from a potential 350 °C to 150 °C. The predominant decomposition mechanism is through chain scission and it is hypothesized that preventing this will result in polymers with higher thermal stability. Three approaches were taken to prevent chain scission. First, a series of hybrid fluorosilicones based on (trifluorovinyl)benzene were synthesized through condensation polymerization with initial decomposition temperatures of approximately 240 °C. These were compared to similar aromatic polyethers and removal of the ether oxygen lowered the initial decomposition temperature by approximately 190 °C demonstrating the importance of this oxygen to the stability of polyethers. Second, reverse fluorosilicone (fluorinated backbone and pendant siloxane) terpolymers of chlorotrifluoroethylene (CTFE), vinyl acetate (VAc) and methacryloxypropyl-terminated polydimethylsiloxane (PDMSMA) were synthesized in supercritical CO2 (scCO2) or by emulsion polymerization. Chain scission was prevented as initial decomposition occurred between 231 and 278 °C. In both the emulsion and scCO2 cases, VAc was essential in facilitating cross-propagation between CTFE and PDMSMA and the branching was similar suggesting polymerization media does not affect polymer structure. Emulsion-based polymers had higher molar masses and thermal stability whereas comparable scCO2 polymers had higher yields and incorporated more PDMSMA. Third, a series of homo-, co-, and terpolymers of CTFE, VAc and methacryloxypropyl-terminated silsesquioxane (POSSMA) were synthesized representing the first synthesis of POSSMA containing polymers in scCO2 and demonstrating reverse fluorosilicones can be synthesized without VAc. Chain scission was prevented as initial decomposition occurred from 244 to 296 °C with thermal stability increasing with CTFE content to a limit. Decomposition of the polymers was examined and mechanism elucidated. In air, the copolymers give 40 to 47 wt% char since the silsesquioxane oxidizes to SiO2 while in N2, no residue is seen. In contrast, the terpolymers give a carbonaceous residue of approximately 20 wt% in N2. The flammability and surface properties of the polymers were examined with the terpolymers having flammability similar to p(CTFE) and surface properties comparable to p(POSSMA) giving a low-flammability, hydrophobic polymer.

Fouling is a chronic problem in many heat transfer systems and results in the need for frequent heat exchanger (HEX) cleaning. In the dairy industry, the associated operating cost and environmental impact are substantial. Antifouling coatings are one mitigation option. In this work, the fouling behaviour of fluoropolymer, polypropylene and stainless steel heat transfer surfaces in processing raw milk and whey protein solution are studied. Methodologies to assess the economics of antifouling coatings are developed and applied. Two experimental apparatuses were designed and constructed to study fouling at surface temperatures around 90 °C. A microfluidic system with a 650 x 2000 µm flow channel enables fouling studies to be carried out by recirculating 2 l of raw milk. The apparatus operates in the laminar flow regime and the capability to probe the local composition of delicate fouling deposit $\textit{in-situ}$ with histological techniques employing confocal laser scanning microscopy. A larger bench-scale apparatus with a 10 x 42 mm flow channel was built to recirculate 17 l of solution in the turbulent flow regime which is more representative of conditions in an industrial plate HEX. Experimental results demonstrate that fluoropolymer coatings can reduce fouling masses from raw milk and whey protein solution by up to 50 %. Surface properties affect the structure and composition of the deposit. At the interface with apolar surfaces raw milk fouling layers are high in protein, whereas a strongly attached mineral-rich layer is present at the interface with steel. Whey protein deposits generated on apolar surfaces are more spongy and have a lower thermal conductivity and/or density than deposits on steel. The attraction of denatured protein towards apolar surfaces and the formation of a calcium phosphate layer on steel at later stages of fouling are explained with arguments based on the interfacial free energy of these materials in water. The financial attractiveness of coatings is considered for HEX subject to linearly and asymptotically increasing fouling resistance and using a spatially resolved fouling model. An explicit solution to the cleaning-scheduling problem is presented for the case of equal heat capacity flow rates in a counter-current HEX. Scenarios where the use of coatings may be attractive or where there is no financial benefit in cleaning a fouled exchanger are identified. Finally, experimental data are used to estimate the economic potential of fluoropolymer coated HEXs in the ultra-high-temperature treatment of milk. In the considered case, the value of a fluoropolymer coating inferred from the reduction in fouling is estimated to be around 2000 US$/m².

Mechanochromic polymers respond to external force by changing their color. This can be achieved by the incorporation of a molecular switch such as spiropyran (SP) into polymers. SPs can be isomerized by mechanical force from their colorless form into colored merocyanines. Main chain copolymerization of spiropyrans allows investigation of their mechanochromic behavior and potential use as force sensors. So far, several covalent polymer matrices have been used to investigate the mechanochromic response of SPs, among them poly(ε caprolactone) (PCL). Less investigated is how the mechanochromic response can be fine-tuned by substituent effects. First, PCL with differently substituted spiropyrans at the chain’s midpoint were used in order to investigate the effect of different substituents and their regiochemistry on the isomerization behavior of SPs under mechanical stress. A low activation barrier was observed for NO2 substitution of “ortho”-spiropyrans compared to no substitution (R = H). In order to investigate phenyl-substituted “para,para” spiropyrans, a newly developed kinked polyarylene was employed as covalent matrix material. This new polyarylene (PmmpP) has a meta,meta,para connection in its backbone and exhibits excellent mechanical properties. Its high strength allows the isomerization of this molecular switch with a large activation barrier. The phenyl-substituted “para,para” spiropyran showed transient mechanochromism and was switched 25 times in force-and-release cycles. The synthesis of PmmpP was carried out by a Suzuki polycondensation in three steps from commercial starting materials. To further capitalize on the simplicity and properties of PmmpP, a two step synthesis of a semifluorinated kinked polyarylene was demonstrated by direct arylation polycondensation with tetrafluorobenzene (F4). This partially fluorinated PmmpF4 was synthesized with a variety of side-chains. Resulting polymers exhibited a large range of glass transition temperatures, allowing for the production of tailor-made smart materials.

No description available.