Efficient Polymer Cyclization by Electrostatic Self-Assembly and Covalent Fixation with Telechelic Poly(tetrahydrofuran) Having Cyclic Ammonium Salt Groups

• Published in: Macromolecules Vol. 34; no. 19; pp. 6592 - 6600
• Main Authors: Oike, Hideaki, Mouri, Takayuki, Tezuka, Yasuyuki
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 11.09.2001
• Subjects: Applied sciences; Chemical modifications; Chemical reactions and properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Intramolecular reaction; Self assembly; Telechelic polymer; Experimental study; Tetrahydrofuran polymer; Pyrrolidine derivatives; Quaternary ammonium compound; Anion exchange; Monodispersed polymer; Cyclization; Cyclic polymer; Preparation; Carboxylate; Counter ion
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma0102417

Uniform-size poly(tetrahydrofuran)s (poly(THF)s) having N-phenyl or N-methylpyrrolidinium salt end groups (1 p and 1 m , respectively) carrying a dicarboxylate counteranion have been prepared as ionic polymer precursors for an intramolecular cyclization reaction. Thus, 4,4‘-biphenyldicarboxylate (2a) was first introduced quantitatively as a counteranion by repeated precipitation of the polymer precursor 1 p into an aqueous solution containing dicarboxylate sodium salt. The efficient cyclization was confirmed with the ion-exchange product I p a having the molecular weight ranging from 4 to 12 kg/mol in diluted THF. The polymer cyclization proceeded effectively also with I m a having N-methylpyrrolidinium salt end groups. There was a pronounced effect upon changing the reaction solvent from THF to chloroform, acetone, toluene, and ethanol. A series of dicarboxylate salts, that is, terephthalate (2b), o-phthalate (2c), succinate (2d), adipate (2e), and trans-2-butene-1,4-dicarboxylate (2f), was then employed for the ion-exchange reaction. The ion-exchange reaction was quantitative with 2b and 2c, while the carboxylate content reached at most around 80% with 2d, 2e, and 2f even after five precipitations. Nevertheless, the corresponding cyclic poly(THF)s II were obtained in high yields by the subsequent heat treatment of the precursors I p d−f and I p a−c. A partially ion-exchanged polymer precursor carrying mixed counteranions I p (f/triflate = 42/58) (42% trans-2-butene-1,4-dicarboxylate and 58% triflate) was then subjected to the reaction under dilution. Besides the unreacted I p (triflate), the cyclic polymer product II p f was effectively produced through the exclusive formation of electrostatic self-assemblies by a single polymer precursor unit, in which cations and anions balance the charges.