The structure and hydrogen bonding of water in an aqueous solution of amphoteric copolymers (poly(MA-r-DMAPMA), 3 x 10(3) < M-w < 10(4)) composed of various ratios of methacrylic acid (MA) and N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) were analyzed using the band shapes of the O-H stretching in the polarized Raman spectra. The number of hydrogen bonds disrupted due to the presence of one monomer residue (N-corr value) evaluated for poly(methacrylic acid) was largely positive, and with an increase in the content of the DMAPMA residue, the N-corr value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio (P(M47D53); M, methacrylic acid; D, N-[3-(dimethylamino)propyl]methacrylamide), increased again. This is in a significant contrast with the largely positive N-corr values for the homopolymers of MA and DMAPMA, and other ordinary polyelectrolytes. The small N-corr value for P(M47D53) was comparable to those for water-soluble nonionic polymers such as poly(ethylene glycol) and zwitterionic polymers such as polycarboxybetaine. These results suggested that the balance of electric charges in polymeric materials is important to be inert to the structure of vicinal water. (c) 2007 Elsevier Inc. All rights reserved.