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Issue 24, 2009
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Macromolecular dumbbells: synthesis and photophysical properties of hyperbranched poly(etherketone)-b-polybenzobisthiazole-b-hyperbranched poly(etherketone) ABA triblock copolymers

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Abstract

A series of hyperbranched poly(etherketone)-b-poly(benzobisthiazole)-b-hyperbranched poly(etherketone) triblock copolymers were synthesized. Two different types of hyperbranched poly(etherketone)s (PEKs) were utilized as dendritic A-block units and carboxylic acid-terminated polybenzobisthiazoles (PBZTs) with two different molecular weights as a conjugated, optically responsive, rigid-rod B-block units to afford dumbbell-shaped ABA triblock copolymers. Although all dumbbell-shaped samples are soluble in strong acids such as trifluoroacetic acid (TFA), methanesulfonic acid (MSA), trifluoromethanesulfonic acid (TFMSA) and sulfuric acid, only phenoxy-terminated dumbbell shaped triblock copolymers (3a and 3b) were soluble in common polar aprotic solvents such as NMP, DMF, DMAc and DMSO. Their solubility in common organic solvents was apparently a consequence arising from the obstruction of the close packing of PBZT components by the bulky dendritic PEK ends. A very surprising and interesting observation was made when the 3a and 3b solutions in NMP were placed under room light for 24 h: all major absorption peaks became featureless and blue-shifted. This photochromism was investigated by static and dynamic UV-absorption and fluorescence spectroscopy under various conditions. Although the response time was quite long, it could be controlled as a function of excitation wavelength, light intensity, and solvent viscosity and/or polarity. We propose that the origin of observed spectral changes is caused by the change in conjugation lengths of PBZT in the dumbbell-shaped ABA triblock copolymers.

Graphical abstract: Macromolecular dumbbells: synthesis and photophysical properties of hyperbranched poly(etherketone)-b-polybenzobisthiazole-b-hyperbranched poly(etherketone) ABA triblock copolymers

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Article information


Submitted
23 Jan 2009
Accepted
30 Mar 2009
First published
08 May 2009

J. Mater. Chem., 2009,19, 4172-4182
Article type
Paper

Macromolecular dumbbells: synthesis and photophysical properties of hyperbranched poly(etherketone)-b-polybenzobisthiazole-b-hyperbranched poly(etherketone) ABA triblock copolymers

J. Baek, C. B. Lyons and L. Tan, J. Mater. Chem., 2009, 19, 4172
DOI: 10.1039/B901483G

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