Aromatic aldehyde functionalized polycaprolactone and polystyrene macromonomers: Synthesis, characterization and aldehyde-aminooxy click reaction

New bis-aldehyde functionalized initiators, viz, 4,4′-(4,4′-(5-hydroxypentane-2,2-diyl)bis(4,1-phenylene))bis(oxy)dibenzaldehyde (1) and 4,4′-bis(4-(4-(formylphenoxy) phenyl) pentyl 2-bromopropanoate (2) were synthesized starting from commercially available 4,4′-bis(4-hydroxyphenyl) pentanoic acid. These initiators were utilized, respectively, for ring opening polymerization of ε-caprolactone and atom transfer radical polymerization of styrene. Well-defined polycaprolactone macromonomers (MnGPC: 2600-19400, PDI: 1.37-1.47) and polystyrene macromonomers (MnGPC: 2800-28200, PDI: 1.11-1.16) with bis-aldehyde functionality were synthesized. The kinetic study of styrene polymerization showed controlled polymerization behaviour. The presence of aldehyde functionality in macromonomers was confirmed by 1H NMR spectroscopy. The reactivity of aldehyde functionality was demonstrated by carrying out aldehyde-aminooxy click reaction of polycaprolactone macromonomer with O-(2-azidoethyl) hydroxylamine which proceeded in a quantitative manner without backbone degradation.