A novel cationic and acrylamide-type surface-active monomer

dimethyltetradecyl (2-acrylamidopropyl) ammoniumbromide (DTAB)

was successfully synthesized

and cationic DTAB-co-acrylamide (AM) copolymer p(DTAB-co-AM)with hydrophobically associative property was prepared by free radical homogeneous copolymerization of DTAB and AM in aqueous solution

which had both ionic and hydrophobic groups.The effects of the hydrophobe content in the polymer chains

inorganic salts (NaCl)

sodium dodecyl sulfate（SDS）and cetyltrimethylammonium bromide（CTAB）on the hydrophobic association behavior were studied by viscosimetry and fluorescence probe method.It was found the copolymer with 0.3%(mole) hydrophobic units exhibited pronounced positive salinity sensitivity because of strong hydrophobic association.The critical association concentration (CAC) decreased from 0.15 g·dL-1 in pure water to 0.11 g·dL-1 in 1%(mass) NaCl solution.When the content of hydrophobic units was below 0.3%(mole)

the copolymer solution showed positive salinity sensitivity in aqueous solutions only at concentrations of NaCl above 5%(mass) because hydrophobic association was largely enhanced by the strong polarity of solution.SDS could significantly increase the viscosity of copolymer solution by two orders of magnitude (from 12 mPa·s to 1634 mPa·s) compared with thatof their corresponding aqueous solutions，which was attributed to both hydrophobic association and electrostatic interactions.However

the viscosity of copolymer solution with the addition of CTAB was only slightly enhanced due to weak hydrophobic association.