Chain‐growth condensation polymerization approach to synthesis of well‐defined polybenzoxazole: Importance of higher reactivity of 3‐amino‐4‐hydroxybenzoic acid ester compared to 4‐amino‐3‐hydroxybenzoic acid ester. Issue 12 (3rd April 2014)

• Record Type: Journal Article
• Authors: Ohta, Yoshihiro; Niiyama, Tetsurou; Yokoyama, Akihiro; Yokozawa, Tsutomu
• Is Part Of: Journal of polymer science. Volume 52:Issue 12(2014:Jun.)
• Page Start: 1730
• Page End: 1736
• Publication Date: 2014-04-03
• Subjects: 547
• DOI: 10.1002/pola.27174
• Languages: English
• ISSNs: 0887-624X

Abstract

<abstract abstract-type="main"> <title>ABSTRACT</title> <p>Application of chain‐growth condensation polymerization (CGCP) to obtain well‐defined polybenzoxazole (PBO) was examined. CGCP of both phenyl 3‐{(2‐methoxyethoxy)methoxy (MEM‐oxy)}‐4‐(octylamino)benzoate (<bold>1b</bold>) (<italic>para</italic>‐substituted monomer) and phenyl 4‐MEM‐oxy‐3‐(octylamino)benzoate (<bold>3b</bold>) (<italic>meta</italic>‐substituted monomer) was examined in the presence of metal disilazide base and phenyl 4‐nitro‐ or methylbenzoate <bold>2</bold> as an initiator. Polymerization of the latter monomer, but not the former, afforded polymer with controlled molecular weight based on the feed ratio of monomer to initiator and with a narrow molecular weight distribution. Accordingly, monomer <bold>3c</bold>, in which the octyl group on the amino nitrogen of <bold>3b</bold> was replaced with a 4‐(octyloxy)benzyl (OOB) group, was polymerized in the presence of lithium 1, 1, 1, 3, 3, 3‐hexamethyldisilazide (LiHMDS), phenyl 4‐methylbenzoate (<bold>2b</bold>), and LiCl in THF at 0 °C to yield poly<bold>3c</bold> with well‐defined molecular weight (<italic>M</italic><sub>n</sub> = 4520–9080) and low polydispersity (<italic>M</italic><sub>w</sub>/<italic>M</italic><sub>n</sub> ≤ 1.11). Treatment of poly<bold>3c</bold> with trifluoroacetic acid simultaneously removed the MEM and OOB groups, affording poly(<italic>o</italic>‐hydroxyamide) (poly<bold>4</bold>) without scission of the amide linkages. Cyclodehydration of poly<bold>4</bold> proceeded at 350 °C to yield PBO (poly<bold>5</bold>), which was insoluble in organic solvents and acids. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. <bold>2014</bold>, <italic>52</italic>, 1730–1736</p> </abstract>