Hyperbranched polyphenylquinoxalines from self-polymerizable AB(2) and A(2)B monomers

Abstract

A self-polymerizable AB 2 monomer, 2,3-bis(4-hydroxyphenyl)-6-fluoroquinoxaline, and an A 2B monomer, 2,3-bis(4-fluorophenyl)-6-(4-hydrcixyphenoxy)quinoxaline) were prepared and polymerized to afford phenol-terminated and aryl fluoride terminated, hyperbranched polyphenylquinoxalines (HPPQs), respectively. MALDI-TOF analysis showed that intramolecular cyclization was a dominant process for the low molecular weight portion during the polymerizations. After isolation and complete dryness, the phenol-terminated HPPQ 1 was only soluble in strong organic acids, while the aryl fluoride terminated HPPQ 2 was soluble in most common organic solvents. HPPQ 1 was treated with allyl bromide to afford an allyl ether terminated HPPQ 3, which was also soluble in most organic solvents. Intrinsic viscosity measurements and SEC analysis indicated that HPPQ 2 had a much higher M w and a much broader molecular weight distribution (PDI ∼ 60) than HPPQ 1 and HPPQ 3 (PDI ∼ 4). The results also suggested that HPPQ 1 formed aggregates in solution and that HPPQ 2 had a much more extended and open conformation. All the HPPQs, which were highly fluorescent, had UV absorption maxima near 375 nm in THF. However, the wavelength of their emission maxima, which ranged from 424 to 466 nm, depended on their end groups.