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Thermoreversible Diels-Alder reactions of fullerenes: Applications in polymers and materials
Abstract
Diels-Alder cycloaddition reactions have played an essential role on chemical modification of fullerenes. The torsionally strained alkene system makes fullerenes excellent dienophiles, accommodating dienes which react in a reversible fashion. This research investigated the use of fullerene Diels-Alder methodology as a means to reversibly incorporate fullerenes into polymers, materials and also as building blocks of polymeric materials. Furan-functionalized Merrifield's polymer resin was synthesized. HPLC analysis demonstrated that C$\sb{60}$ attached to the furan-functionalized polymer resin via Diels-Alder cycloadditions through pendant diene moieties. The release of C$\sb{60}$ from the bound polymer resin required a high temperature of $180\sp\circ$C. A thermal stress-resistant silicate-based material was also investigated in reacting with fullerenes. Cyclopentadiene-functionalized silica gel and methylcyclopentadiene-functionalized silica gel reacted with fullerene C$\sb{60}$,C$\sb{70}$ and fullerene soot solutions readily at room temperature, providing fullerene-silicate adducts. These adducts could undergo decomposition to original fullerenes and diene-functionalized silica gel upon heating at relatively lower temperature. A method for non-chromatographic purification of fullerenes was demonstrated capable of isolating fullerenes from non-fulleroid impurities and selectively separating individual fullerene species by means of reversible Diels-Alder reactions of fullerenes with diene-functionalized silica gel. Further studies of fullerene (C$\sb{60},$ C$\sb{70})$ reactivity towards different diene functions and in retro-Diels-Alder cycloreversions were performed by HPLC assays and spectrochemical analysis through variable temperature UV-VIS spectroscopy. Fullerene-Diels-Alder methodology was also investigated as a means to create polymeric materials. Intermolecular Diels-Alder condensation of C$\sb{60}$ and bis-anthracene ether provided fullerene-diene polymer and oligomer. This material was characterized by gel permeation chromatography, infrared spectroscopy and solubility tests. Variable temperature UV-VIS spectroscopy demonstrated that the polymerization occurred at room temperature and was completely reversible to the original bis-diene monomer and C$\sb{60},$ upon heating above $70\sp\circ$C for a short period of time. The thermal decomposition studies assisted by HPLC assays examined the thermal stability of the monomers, showing no visually detectable degradation of monomers.
Subject Area
Organic chemistry|Polymers
Recommended Citation
Nie, Bing, "Thermoreversible Diels-Alder reactions of fullerenes: Applications in polymers and materials" (1997). Doctoral Dissertations Available from Proquest. AAI9737568.
https://scholarworks.umass.edu/dissertations/AAI9737568