Polymeric surfactant

A block copolymer prepared by anionic polymerization comprising polymeric blocks (A)x and (B)y, wherein block (A)x is directly chemically linked at one end thereof to one end of block (B)y, the block (A)x of said copolymer consisting of recurring units A of at least one homo- or copolymerized non-polar alpha, beta-ethylenically unsaturated monomer and the block (B)y of said copolymer consists of recurring units B each containing a hydroxy-substituted ionic group, said recurring unit B being derived from an epoxy-substituted alpha-beta-ethylenically unsaturated monomer, and x and y are integers and are sufficiently large that block (A)x and block (B)y constitute a hydrophobic group and a hydrophilic group, respectively, and the block copolymer as a whole exhibits surface-active properties in aqueous media, is miscible with hydrophilic colloids and aqueous media containing such colloids, and is resistant to diffusion from water-wet hydrophilic colloid layers containing the same, said ionic group of recurring units B corresponding to one of the following structural formulae (I), (II), (III), (IV), (V), (VI), (VII), and (VIII):

• ##STR7## wherein:
• X.sup.+ is a cation.