Amphiphilic block copolymers have many unique physical and chemical properties

especially the strong self-assembling ability

because of the amphiphilic properties and microphase separation of their molecules. In this investigation

the amphiphilic block copolymers of acrylamide(AM) and styrene(St) were prepared in microemulsion medium．Two series of copolymers PAM-b-PSt were synthesized

one of them had variable composition

but an approximately constant molecular weight

and the other one had different molecular weight with an approximately constant composition．The composition of the copolymers was determined by ultraviolet spectrophotometry method

and the intrinsic viscosity of the copolymers from which the molecular weight of copolymers can be estimated relatively was determined by using an Ubbelohde viscometer．The association behavior of molecular chains of the amphiphilic block copolymer PAM-b-PSt in aqueous solution

its surface activity and solubilization ability were emphatically studied

and the effect of molecular composition and molecular weight on these properties was also investigated．The experimental result shows that the amphiphilic block copolymers PAM-b-PSt synthesized in microemulsion medium display some behavior of polymer surfacants．For example

because of the hydrophobic property of PSt blocks the molecular chains of PAM-b-PSt can form surface absorption on the surface layer of solutions resulting in an decreased surface tension of aqueous solutions

under hydrophobic interreaction the styrene blocks of PAM-b-PSt can form intermolecular and intramolecular micells in solution and the critical micell concentration of PAM-b-PSt is small．These micells can solubilize alkane substances

namely

the aqueous solution of PAM-b-PSt possesses solubilization ability for alkane substances．The higher the content of hydrophobic block sections is

the better the surface activity and solubilization ability of the copolymers are

and the smaller the molecular weight is

the better the surface activity and solubilization ability of the copolymers are．Obviously

because of the hydrophobic properties of PSt blocks the amphiphilic block copolymers synthesized in microemulsion medium have potential application prospects in enhanced oil recovery.