bisazo polymers is close to 100%, which can also be confirmed by
the ratios of the integration areas for the protons on the bisazo
chromophores. This high efficiency of the post-functionalization is
consistent with those reported before for post-polymerization azocoupling
reactions used to prepare monoazo polymers [38,48,49].
For BP-BAZ-NT and BP35-BAZ-NT, the DFs are relatively low, which
are 45% and 55%, respectively. For these two polymers, the diazonium
salt of 4-(40-nitrophenylazo)aniline was used for the azocoupling
reaction (Scheme 2). Above results indicate that the
3,5-dimethyl substituents on the aminoazobenzene derivatives are
critical for the azo-coupling reaction to yield the bisazo polymers
with the high DF. This substituent effect could be attributed to the
role of the 3,5-dimethyl substituents to stabilize the diazonium
cations, which increase the possibility of the diazonium reactants
to approach the reaction sites. From the 1H NMR and other
analytical results given in the Experimental Section and Supporting
Information (Figs. S1eS5), it is concluded that the target bisazo
polymers have been successfully synthesized through the postpolymerization
azo-coupling scheme.