Modification and characterization of poly[styrene-co-maleic anhydride] with fluorescent probes

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Title: Modification and characterization of poly[styrene-co-maleic anhydride] with fluorescent probes
Author: DiFelice, Ronald
Abstract: In this study, various poly[styrene-co-(maleic anhydride)] copolymers (50/50, 75/25, 86/14, and 92/8) were modified with the 4-nitroaniline and 4-phenylazoaniline dyes. A synthesis, collection, and purification procedure was developed, and the resulting modified polymers were characterized primarily using elemental analysis, Fourier Transform Infrared analysis (FT-IR), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). Elemental analysis allowed percent incorporation results to be determined for each copolymer-dye synthesis. Percent incorporation was approximately 70% for the 50/50 copolymers, and 55% for the 75/25 copolymers, with no significant difference between the 4-nitroaniline and the 4-phenylazoaniline modified copolymers. For the 86/14 and 92/8 modified copolymers, however, there was a very noticeable difference in the percent incorporation corresponding to the different dyes: the 86/14 4- phenylazoaniline modified copolymer yielded an 8.3% incorporation, while the 86/14 4-nitroaniline modified copolymer showed a 4.9% incorporation. Similarly, the 92/8 4-phenylazoaniline modified copolymer had a percent incorporation of 11%, while the 92/8 4-nitroaniline modified copolymer showed a percent incorporation of 7.4%. FT-IR results confirmed these numbers qualitatively. TGA was utilized to compare the thermal stability of the copolymers before and after modification. These results demonstrate that the 50/50 and 75/25 modified copolymers degrade differently than the original unmodified species. Each of these modified copolymers exhibits two distinct decomposition steps, while the original copolymers exhibit single decomposition temperatures (Td) of approximately 350 C. Also, the thermal stability of each modified copolymer (total of eight) was noticeably lowered in each sample. The lowering of Td ranged from approximately a 100 C change for the 50/50 copolymers, to only a 15 C change for the 86/14 copolymers. DSC was employed to compare changes in the glass transition temperature (Tg) between the modified and unmodified copolymers. Drastic changes in Tg were observed for the 50/50 and 75/25 modified copolymers, while negligible changes in Tg were seen for the 86/14 and 92/8 samples. The pure 50/50 copolymer exhibited a Tg at 165 C, the 50/50 4-phenylazoaniline modified copolymer's Tg was at 100 C, while the 50/50 4-nitroaniline modified copolymer demonstrated dual Tg's at 120 C and 170 C. The pure 75/25 showed a Tg at 135 C , the 75/25 4-phenylazoaniline modified copolymer exhibited its Tg at 100 C, while the 75/25 4-nitroaniline modified copolymer demonstrated dual Tg's at 1 15 C and 170 C. The Tg's for all of the 86/14 copolymers hovered around 138 C. Likewise, all of the 92/8 copolymers showed their Tg's at approximately 122 C. Dual Tg's indicate that two distinct regions are present in the copolymer. These copolymers were developed to be used in phase separation studies using fluorescence spectroscopy. Fluorescence studies were performed on the 50/50 and 92/8 modified copolymers to determine each modified copolymer's quenching ability. This was done using a 10"2 M polystyrene solution as the standard emission signal. Initial fluorescence results indicate that both the 50/50 and 92/8 modified copolymers behave as excellent quenching species, with the 4-phenylazoaniline modified copolymers quenching to a greater degree than the 4-nitroaniline modified species. In conclusion, the 86/14 and 92/8 modified copolymers are the most promising for future phase separation studies, offering good fluorescence sensitivity with a minimal change of polymer properties after modification.
Record URI: http://hdl.handle.net/1850/12129
Date: 1995-09

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