NMR Studies On Surfactants And Water-soluble Functional Polymer

Nuclear magnetic resonance (NMR) is an effective method to investigate the microstructure of surfactant micelles and the arrangement of the surfactant molecules in the micellar core. In this dissertation, we studied the aggregation behavior of soluble functional polymer and two kinds of surfactants in aqueous solution by NMR technique.1) gemini surfactant 16-4-16The cationic gemini surfactant of alkanediyl-α,ω-bis(alkyldimethylammonium) bromide is designated as m-s-m, where m and s are the number of carbon atoms in the alkyl chain and the alkanediyl spacer, respectively. The protons of 16-4-16 in the spacer group and a part of hydrophobic protons next to the polar head groups are involved in the surface layer of the micellar core. The hydrophobic protons away from the polar head group are situated internal in the micellar core. The motion of the molecules in the micelles is relatively more restricted than that of their monomeric homologue CTAB. A special arrangement of the molecules in the spherical 16-4-16 micelles is postulated.2) NaDC and NaDC/CTAB mixed solutionThe proton (H3) behaves differently from the other protons in the individual deoxycholate (NaDC) solution. It seems that H3 exits in two states. Its transverse relaxation times obey bi-exponential decay. We consider that bile salts form head-to-tail molecular pairs via hydrogen bonding between 3-OH and carboxyl oxygen atom in dilute aqueous solution. Furthermore, a 1:1 mixed micelles form in NADC/CTAB binary aqueous solution. The results of NOESY and ROESY indicate that the polar heads of CTAB are located in the near vicinity of the carboxyl groups of NaDC molecules in the mixed micelles which is due to the strong ionic interaction between these two components.3) acrylamide/methacrylic acid template copolymerAt quite low pH values, intra-molecular hydrogen bonds between the PAM and PAA blocks lead to compact molecular arrangement and the motion of the phenoxy side chains of the POA blocks is somewhat restricted. With the increase in pH value of the solution, the carboxylic acid gradually dissociates, the electro-static-repulsion of the carboxylic ions and the inter-copolymer hydrogen bonding interactions result in the growth in aggregate size. After the carboxylic acid of the PAA block is completely dissociated in alkaline solution, the electro-static repulsion of the carboxylic ion makes the molecular chain of the copolymer exhibit more outstretched, and the phenoxy side chains have more space to move.