Normally, P(SPMA-co-MAA) can not be directly synthesized by ATRP for the reason that carboxylic group in the molecular structure of MAA is likely to poison the catalyst.
On account of it,carboxylic unit is first strategically protected by the introduction of tert-butyl functional group, and the targeted P(SPMA-co-MAA) can be obtained by the hydrolysis of the resulting precursor P(SPMA- co-tBMA) as presented in Scheme 3.
The FT-IR spectra of the precursor P(SPMA-co-tBMA) and amphiphilic copolymer P(SPMA-co-MAA) are shown in Fig.1.
We can clearly observe the structure change from the intermediate product to targeted copolymer during the hydrolysis process by comparing the curve of the copolymer before and after hydrolysis.
The decreases of the frame vibration of tert-butyl at around 848 cm$1 and the CeH bond of methyl at about 2978 cm$1, the chemical shift of carboxyl from 1724 to 1707 cm$1, and the appearance of new characteristic peak of hydroxyl at 3460 cm$1 indicate that tBMA unit have transformed into MAA unit during the hydrolysis.
Meanwhile, the CeCeN bending vibration at 1033 cm$1, the OeCeN stretching band at 958 cm$1 and the NO2 asymmetrical stretching peak at 1339 cm$1 confirm the existence of SPMA unit.