Synthesis and polymerization of new self-polymerizable quinoxaline monomers

Abstract

Extended self-polymerizable poly(phenylquinoxaline) monomer mixtures {i.e.,2-[4-(4-hydroxyphenoxy)phenyl]-3-phenyl-6-chloroquinoxaline and 3-[4-(4-hydroxyphenoxy)phenyl]-2-phenyl-6-chloroquinoxaline, 2-[4-(4-hydroxyphenoxy)phenyl]-3-phenyl-6-fluoroquinoxaline and 3-[4-(4-hydroxyphenoxy)phenyl]-2-phenyl-6-fluoroquinoxaline, and 2-(4-fluorophenyl)-3-phenyl-6-(4-hydroxyphenoxy)quinoxaline and 3-(4-fluorophenyl)2-phenyl-6-(4-hydroxyphenoxy)quinoxaline} more flexible and nucleophilic than a previously reported monomer mixture [i.e., 3-(4-hydroxyphenyl)-2-phenyl-6-fluoroquinoxaline and 2-(4-hydroxyphenyl)-3-phenyl-6-fluoroquinoxaline] were synthesized. The monomer mixtures were then polymerized into high-molecular-weight polymers. A sample was obtained, through a chlorine displacement reaction, that was a semicrystalline polymer with an intrinsic viscosity of 1.11 dL/g in m-cresol at 30 +/- 0.1 degreesC and two melting temperatures at 339 and 377 C in the first differential scanning calorimetry scan. There was a melting temperature at 328 degreesC without a detectable glass-transition temperature (T-g) when the sample was subjected to a second differential scanning calorimetry scan. The samples from fluorine displacement reactions were completely amorphous polymers. They had intrinsic viscosities of 0.53-0.90 dL/g in m-cresol at 30 +/- 0.1 degreesC and T-g's of 220-224 degreesC. The polymer samples from fluorine displacement reactions were evaluated with gel permeation chromatography and matrix-assisted laser desorption/ionization time-of-flight analyses, which monitored the existence of certain amounts of cyclic oligomers. The thin films of the polymers had room-temperature tensile strengths of 97-113 MPa, room-temperature Young's moduli of 2.30-2.35 GPa, and room-temperature elongations at break of 40-150%. The melt viscosity decreased from 10(7) to less than 10(4) Pa s at 310 degreesC as the frequency was increased from 10(-2) to 10(2) rad/s.