Norbornenyl-pendant aromatic (co)poly(ether ether ketone)s

Abstract

4, 4'-(Bicyclo (2.2.1) hept-5-en-2 yl methylene) bis (2-methoxyphenol) (BPA-NB) was utilized as a step-growth monomer for the synthesis of (co)poly(ether ether ketone)s (PEEK-NBs) via nucleophilic aromatic substitution polycondensation. A homo and five PEEK-NBs were synthesized by polycondensation of 4, 4'-difluorobenzophenone with BPA-NB and various compositions of BPA-NB and bisphenol-A, respectively. ¹H NMR spectroscopy confirmed the chemical structure and composition of PEEK-NBs. Inherent viscosity and number-average molecular weight values of PEEK-NBs were in the range 0.64 to 0.78 dL g⁻¹ and 62,670 to 84,470 g mol⁻¹, respectively, indicating the formation of polymers of reasonably high molecular weight. It was easy to dissolve PEEK-NBs in common organic solvents such as chloroform, dichloromethane, and tetrahydrofuran. Tough, transparent, and flexible films of PEEK-NBs could be cast from chloroform solution. X-Ray diffraction studies indicated amorphous nature of PEEK-NBs. Glass transition temperature (T_g) values, determined by DSC analysis, of PEEK-NBs were in the range 163 to190 °C and T_g values increased with the increase in mol % of BPA-NB. The post-polymerization modification of a representative PEEK-NB was demonstrated using two azido compounds, namely, 4-(azidomethyl)-7-methoxy-2H-chromen-2-one and 9-(azidomethyl)anthracene, via metal-free azide-alkene 1,3-dipolar cycloaddition reaction to obtain copoly(ether ether ketone)s appended with coumarinyl and anthracenyl moieties, respectively.

Graphical Abstract

Keywords:

• (Co)poly(ether ether ketone)s
• norbornenyl groups
• post-polymerization modification
• azide-alkene click reaction

Acknowledgements

Authors are grateful to Dr. P. R. Rajamohanan for help with interpretation of NMR data.

Disclosure statement

No potential conflict of interest was reported by the author(s).