Study On The Synthesis And Rheology Properties Of Hydrophobically Associating Polyacrylamide Of A New Family

The homogeneous copolymerizations of AM and Sodium 2-acrylamido-tetradecane sulfonate (NaAMC₁₄S), which is a kind of anionic surface-active monomer with acrylamide-type, were carried out in aqueous solution. The concentrations of NaAMC₁₄S were controlled above critical micellar concentration (CMC), respectively, and the copolymer NaAMC₁₄S/AM with microblocky were obtained. The structures of the copolymers were characterized using by FTIR spectrum, and their molecular weights were correspondingly expressed with the intrinsic viscosities obtained through determining viscosity with Ubbelohde viscometer. The hydrophobically associating properties of the copolymers and rheological characters of their aqueous solutions were studied mainly by using fluorescence probe method and apparent viscosity measurement. The experiment results show that copolymer NaAMC₁₄S/AM is hydrophobically associating polyacrylamide of a new family, which have longer the hydrophobic blocks, so the copolymers have strong hydrophobically associating property, and the apparent viscosities of their aqueous solutions increase rapidly as their concentrations are over 0.2%(wt%). The shear thinning behaviour of their aqueous solutions is obviously reversible, and they exhibit strong shearing resistance. There is a special finding about positive salinity sensitivity of the aqueous solution viscosity of copolymers in this investigation. For those copolymers with microblocky structure, the apparent viscosity of their brine solution is much higher than that of their pure water solution. The apparent viscosity of the salt solution is enhanced actually by three orders of magnitude as the concentration of the copolymer is 0.3%(wt%) and the concentration of CaCl2 is 2%(wt%), and a unique positive salt sensitivity, i.e. salinity thickening, is displayed. By varying the feed ratio of NaAMC₁₄S and AM, the added amount of electrolyte NaCl and the amount of initiator, respectively, the copolymers NaAMC₁₄S/ AM with the microstructures varied in series were prepared. The dependences of hydrophobic associating property of the copolymers on the microstructures were studied by fluorescence probe method and apparent viscosity measurement method, and the effects of the content and length of the hydrophobic blocks and the molecular weight of the copolymers were explored thoroughly. The experiment results show that the hydrophobic associating property of copolymer NaAMC₁₄S/ AM is strengthened with the increase of the content and length of the hydrophobic blocks, and is enhanced with the increase of the molecular weight of the copolymers.Based on the above research, Cationic gemini surfactant hexylene-1,6-bis(dodecdimethylammonium bromide) (C₁₂C₆C₁₂Br₂) was synthesized. Apparent viscosity measurement and fluorescence probe methods were used to study the interaction between copolymer NaAMC₁₄S/ AM and Gemini surfactant C₁₂C₆C₁₂Br₂.The experiment results show that there is strong interaction between them, and the strong interaction exhibits in several aspects as follows: addition of C₁₂C₆C₁₂Br₂ enables the copolymer NaAMC₁₄S/ AM to produce intermolecular association below the critical association concentration without the presence of C₁₂C₆C₁₂Br₂; the mixed micells of NaAMC₁₄S/ AM and C₁₂C₆C₁₂Br₂ form below the critical micellar concentration of C₁₂C₆C₁₂Br₂; for the aqueous solution of 0.3wt% copolymer NaAMC₁₄S/ AM, the apparent viscosity increases dramatically with the increase of C₁₂C₆C₁₂Br₂ concentration, and the maximum value of the viscosity is enhanced three orders of magnitude higher than the initial value without C₁₂C₆C₁₂Br₂. It is found that the interaction between copolymer NaAMC₁₄S/ AM and C₁₂C₆C₁₂Br₂ is dependent on the microstructure of copolymer NaAMC₁₄S/ AM, and the greater the content of hydrophobic microblocks, the stronger the interaction and the greater the enhanced magnitude of viscosity.