Contribution of intramolecular C=O...H-N hydrogen bonding to the solvent-induced reentrant phase separation of poly(N-isopropylacrylamide).
Changes in the local environment around amide groups of poly(N-isopropylacrylamide) (PNiPA) during a solvent-induced reentrant phase separation have been investigated by infrared spectroscopy combined with quantum chemical calculations. The addition of methanol or tetrahydrofuran as a cosolvent to an aqueous solution of PNiPA causes spectral changes in the amide I regions. By preparing a dimer model compound for PNiPA, we can establish the assignment of the amide I bands for the polymer in solutions. Hydrogen-deuterium exchange experiments of the amide protons of PNiPA and its dimer models have revealed that the amide groups of PNiPA form an intramolecular C=O...H-N hydrogen bond even in a good solvent. The result has suggested that the change in the amide I envelope of PNiPA observed during the solvent-induced phase transition reflects the modification of the intramolecular C=O...H-N hydrogen bond of PNiPA as well as the variation in solvation state of the amide groups. On the basis of the assignment, we have discussed contributions of the intramolecular C=O...H-N hydrogen bond to the phase behavior of PNiPA.
Katsumoto
Yukiteru
Y
Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan. katsumot@hiroshima-u.ac.jp
Tanaka
Takeyuki
T
Ihara
Katsunori
K
Koyama
Misao
M
Ozaki
Yukihiro
Y
D000178:Acrylamides / Q000737:chemistry*; D000180:Acrylic Resins; D000438:Alcohols / Q000737:chemistry; D006860:Hydrogen Bonding; D000432:Methanol / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D000178:Acrylamides; D000180:Acrylic Resins; D000438:Alcohols; D011108:Polymers; D012996:Solutions; D012997:Solvents; D014867:Water; C052970:poly-N-isopropylacrylamide; D000432:Methanol