Fluorine- and Hydroxyl-Terminated Hyperbranched Poly(phenylquinoxalines) (PPQs) from Copolymerization of Self-Polymerizable AB and AB2, BA, and BA2 Monomers

Abstract

The AB and AB2 quinoxaline monomers 2-(4-hydroxyphenyl)-3-phenyl-6-fluoroquinoxaline and 3-(4-hydroxyphenyl)-2-phenyl-6-fluoroquinoxaline (HPFQ) and 2,3-bis(4-hydroxyphenyl)-6-fluoroquinoxaline (BHFQ) were copolymerized to afford different degree of linear defects in hydroxyl-terminated hyperbranched poly(phenylquinoxalines) (HT-HPPQs). The other set of BA and BA2 monomers 2-(4-fluorophenyl)-3-phenyl-6-(4-hydroxyphenoxy)quinoxaline and 2-(4-fluorophenyl)-3-phenyl-6-(4-hydroxyphenoxy)quinoxaline (FPHPQ) and 2,3-bis(4-fluorophenyl)-6-(4-hydroxyphenoxy)quinoxaline (BFHPQ) were also copolymerized to prepared fluorine-terminated hyperbranched poly(phenylquinoxalines) (FT-HPPQs). On the basis of a MALDI−TOF study of the HT-HPPQ sample (AB2 20 mol %), random copolymerization indeed occurred. In the case of HT-HPPQ, the properties of polymer such as solubility, solution viscosity, Tg, and polymer degradation temperature were greatly influenced by the number of hydroxyl group on the surface. However, the properties of FT-HPPQ were much less influenced by the number of fluorine on the surface. The copolymers of AB and AB2 were soluble in most of aprotic solvents and phenolic solvents displaying intrinsic viscosities ranged from 0.27 to 1.11 dL/g in m-cresol at 30.0 ± 0.1 °C and glass transition temperatures (Tgs) ranged from 239 to 274 °C. Copolymers of BA and BA2 were also soluble in most of aprotic solvents and phenolic solvents displaying intrinsic viscosities ranged from 1.01 to 1.15 dL/g in m-cresol at 30.0 ± 0.1 °C. HT-HPPQs and FT-HPPQs underwent 5% weight losses when subjected to thermal gravimetric analysis ranged from 511 to 568 °C and from 556 to 588 °C in nitrogen atmosphere, respectively. The enhanced thermal stabilities of FT-HPPQs could be attributed to the fluorine terminal groups on the macromolecule surfaces. The melt viscosities of the HT-HPPQ sample (AB2 20 mol %) was greater than 107 Pa·s in the lower frequency range determined as a function of frequency sweep on a RMS-800 rheometer at 320 °C. The melt viscosity linearly decreased as the frequency increased. Thus, HT-HPPQ containing a 20 mol % AB2 monomer unit displayed a lower melt viscosity compared to its linear analogue at whole frequency range. However, the relative melt viscosity decrease of hyperbranched PPQ compared to its linear analogue was less than expected due to the formation of possible inter- and intramolecular hydrogen bonding.