Raman spectroscopic study of the structure of water in aqueous solutions of amphoteric polymers

Abstract

Methacrylic acid (MA) and [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) were polymerized to give amphoteric copolymers with various compositions. The structure and H-bonding of water in an aqueous solution of the copolymer were analyzed using the contours of the O-H stretching in the polarized Raman spectra. For comparison, the H-bonded network structure of aqueous solutions of homopolymers (polyMA and polyMAPTAC) was also examined. From the relative intensity of the collective band (C value) corresponding to a long range coupling of the O-H stretching in the aqueous polymer solutions, the number of H-bonds disrupted due to the presence of one monomer residue of the polymers (Ncorr) was determined. The Ncorr value for polyMA was largely positive, and with an increase in the content of the MAPTAC residue, the Ncorr value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio, the Ncorr value increased again. This is in significant contrast with the larger positive Ncorr values for the homopolymers (both polyMA and polyMAPTAC), and other ordinary polyelectrolytes such as sodium polyethylenesulfonate, poly-L-lysine hydrobromide and sodium polyacrylate. Furthermore, the Ncorr value for the copolymer (MA ratio MAPTAC = 56:44) became much smaller by the neutralization of MA residues in the copolymer with sodium hydroxide, and comparable to those for neutral polymers such as poly(ethylene glycol) and poly(N-vinylpyrrolidone) and zwitterionic polymers such as poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and poly[3-sulfo-N,N-dimethyl-N-(3'-methacryloylaminopropyl)propanaminium inner salt]. The present results clearly indicate that the amphoteric polymers with comparative contents of cationic and anionic groups do not significantly disturb the H-bonded network structure of water, probably due to the counteraction of the electrostatic hydration effect by the proximity between the anionic and cationic side groups.

Structure of water in the vicinity of amphoteric polymers as revealed by Raman spectroscopy

“…The large N corr values for polyDMAPMA and polyMA were not contradictory to the general knowledge and our previous reports [18][19][20][21][22][23][24][25][26]. However the disturbing effects of the amphoteric copolymers on the water structure were much smaller than that of the ordinary polyelectrolytes.…”

“…The N corr values of ordinary polyelectrolytes with one kind of ionic side group (sodium polyacrylate (NaPAA) [18,22], sodium poly(ethylene sulfonate) (NaPES), poly-L-lysine HBr salt (PLL·HBr) [22] and poly[(3-(methacryloyl)amino)propyltrimethylammonium chloride] (polyMAPTAC)) [26] are much larger than those of water-soluble nonionic polymers (PEG and PVPy) [18,22], indicating that ionic groups and the counterions of polyelectrolytes strongly disturb the structure of water in their hydration shells (electrostatic hydration).…”

“…In these fifteen years, we have been interested in analyses of the structure of water in aqueous polymer solutions from a Raman scattering attributable to the O-H stretching vibration band of water (2800-3800 cm −1 ) [17][18][19][20][21][22][23][24][25][26][27][28][29]. It was found that, when the molecular weight of the polymers was small enough to avoid a formation of "pseudo-network structure" (i.e., entanglement of the polymer chains), the number of H-bonds disrupted due to the presence of one monomer residue (N corr value) of a polyelectrolyte with an ionic group in the side chain (sodium polyacrylate, poly-L-lysine hydrobromide, etc.)…”

Temperature-responsive polymer brush constructed on a colloidal gold monolayer

“…For example, zwitterionic materials such as phosphobetaine, sulfobetaine and carboxybetaine polymers have been found to be highly biocompatible [36][37][38][39]. This property has been ascribed to mildness of the zwitterionic polymers to the hydrogen-bonded network structure of surrounding water [39][40][41][42][43]. Furthermore, (meth)acrylate polymers with pendent ω-methoxy oligo(ethylene glycol) side chains (for example, poly(ω-methoxy tri(ethylene glycol) methacrylate)) have been found to be biocompatible, too [44], while these polymers are temperature-responsive [45,46].…”

Dispersion and Reinforcement of Nanotubes in High Temperature Polymers for Ultrahigh Strength and Thermally Conductive Nanocomposites

“…The Au NPs were prepared and the sizes maintained by the thiols, according to the procedures of Brust et al [77,78,81,82]. The procedure is as following (Scheme 13): Pyreneburtic acid dissolved in toluene were reacted with sodium ethoxyliate an hour in ultra-sonication 40 ℃, after that, a mixture was obtained and (2-chloroethyl) trimethylammonium chloride was added in the mixture then stirred overnight at 60℃ [83].…”