k9254.pdf

3.2.3. Synthesis of PNIPA-COOH.
PNIPA-N3 (20.0 mg, 0.0655 mmol) and 4-ethanoic benzoic acid (173 mg, 1.31 mmol) were
dissolved in dry DMF (0.3 mL) and to this were added L-ascorbic acid (23.1 mg, 0.131 mmol) in
DMF (0.131 mL) and CuSO4.5H2O (16.4 mg, 0.0655 mmol) in DMF (0.262 mL), and the
reaction mixture was stirred at ambient temperature. After 12 h, L-ascorbic acid (23.1 mg, 0.131
mmol) in DMF (0.131 mL) and CuSO4.5H2O (16.4 mg, 0.0655 mmol) in DMF (0.262 mL) were
added again to the reaction mixture, and the reaction mixture was again stirred at room
temperature for 9 h. The obtained polymer was then precipitated into a large amount of methanol
and collected by centrifugation. The resulting polymer was dissolved in a small amount of DMF
containing LiCl and the solution was poured into a large amount of hexane. This purification
cycle was repeated three times. The obtained product was dried overnight in a vacuum dryer.
(73% yield). Complete conversion of PNIPA-N3 to PNIPA-COOH was confirmed by the FT-IR
spectrum (Figure 3-4)which showed the disappearance of the azide signal of PNIPA-N3.
According to the 1 H-NMR data (Figure 3-3) of 4-ethanoic benzoic acid, proton peak for aromatic
portion is appeared at 7.6 ppm. After converting PNIPA-COOH, we have found that integration
ration of that position has increased which proves the presence of aromatic group at that position.
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