Thermally reversible covalently bonded linear polymers prepared from a dihalide monomer and a salt of dicyclopentadiene dicarboxylic acid
✍ Scribed by Xiaonong Chen; Eli Ruckenstein
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 200 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0887-624X
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✦ Synopsis
Alkali and earth-alkali salts of dicyclopentadiene dicarboxylic acid (DCP-DCA) were prepared and employed as monomers in the polyesterification with an ␣,-dihalide monomer, such as 1,4-dichlorobutane (DCB), 1,4-dibromobutane (DBB), ␣,␣Ј-dichloro-p-xylene (DCX), and ␣,␣Ј-dibromo-p-xylene (DBX). Novel linear polymers that possessed repeating moieties of dicyclopentadiene (ODCPDO) in the backbone were thus prepared. The IR and NMR spectra indicated that poly(tetramethylene dicyclopentadiene dicarboxylate) (PTMDD) with a number-average molecular weight (M n ) of about 1ϫ 10 4 and poly(p-xylene dicyclopentadiene dicarboxylate) (PXDD) with a M n of 4 -6 ϫ 10 3 were obtained with an yield of about 80% via the polyesterification of the alkali salts with DBB and DCX, respectively. The reaction was carried out in the presence of a phase transfer catalyst, such as BzMe 3 NBr or poly(ethylene glycol), in DMF at 100 °C for 4 h. Oligomers with a lower M n (1-2 ϫ 10 3 ) were obtained when the earth-alkali salts were employed as salt monomers. Compared to the irreversible linear polymers, poly(p-xylene terephthalate) (PXTP) and poly(p-xylene maleate) (PXM), prepared through the reaction between DCX and the potassium salts of terephthalic and maleic acid, respectively, the specific viscosities ( sp ) of the new linear polymers increased abnormally with the decrease of the temperature from 200 °C to 100 °C. This occurred due to the thermally reversible dedimerization/redimerization of ODCPDO moieties of the backbone of the polymers via the catalyst-free Diels-Alder/retro Diels-Alder cycloadditive reactions. The ratio of the sp at 100 °C and 200 °C of the reversible polymers was found to be much higher than that of PXTP and PXM, even when the heating/cooling cycle was carried out several times under a N 2 atmosphere. The obtained results indicated that thermally reversible covalently bonded linear polymer can be obtained by introducing the ODCPDO structure into the backbone of the polymer through the polymerization of a monomer containing the ODCPDO moiety. The reversible natures of the polymers and oligomers might be useful in preparing easily processable and recyclable polymers and thermosensor materials.