William Feld (Committee Member), Eric Fossum (Advisor), Daniel Ketcha (Committee Member)
Master of Science (MS)
Two routes to semi-crystalline, potentially functionalizable poly(ether ether ketone), PEEK, analogues were explored using varying percentages of 4,4’-difluorobenzophenone and either 3,5-difluorobenzophenone or 2,4-difluorobenzophenone as the electrophilic component in nucleophilic aromatic substitution polycondensation reactions with hydroquinone. PEEK analogues utilizing 3,5-difluorobenzophenone were carried out in a “one-pot” fashion and their properties were compared to the same materials prepared previously by a multi-step synthetic procedure. The use of 2,4-difluorobenzophenone led to completely new PEEK analogues. The polymers were characterized via NMR spectroscopy, Size Exclusion Chromatography, Thermogravimetic Analysis, and Differential Scanning Calorimetry. Molecular weight determinations showed the synthesized polymers to be of a variety of molecular weights, with weight averaged molecular weight (Mw) values between 7,500 and 83,000 Da and dispersity (Ð) values between 2.5 and 2.9. The polycondensation reactions were also accompanied by the formation of cyclic species that could be, and were, removed via precipitation/trituration with isopropanol or mostly avoided by a judicious choice of reaction conditions. Solubility tests showed that the 3,5-homopolymers, which were semi-crystalline, and 2,4-homopolymers, which were completely amorphous, were soluble in many common organic solvents, while the solubility of the copolymers decreased as the percentage of 4,4’-difluorobenzophenone increased. Thermal analysis of the 3,5-difluorobenzophenone polymers possessed 5 % weight loss temperature values (Td 5%) that were similar to those of the previously synthesized polymers1, with values between 330 and 500°C. For both polymer systems, the glass transition temperatures (Tg) were between 86 and 129°C, which is consistently lower than those of the materials previously synthesized via the multistep protocols. The 3,5 homopolymer and 75%/25% (PEEK/PAMPPO) copolymers displayed crystallization temperatures (Tc) between 156 and 210°C with melting temperatures (Tm)¬ between 252 and 254°C. The 2,4-difluorobenzophenone polymers had Tg values ranging from 113 to 152°C with Tc and Tm values, for polymers containing 35% or less 2,4-difluorobenzophenone, ranging from 220 to 230°C, and 280 to 320°C, respectively.
Department or Program
Department of Chemistry
Year Degree Awarded
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