a pharmaceutically - active polymeric compound of the general formula , y − m − link b wherein x is a coupled biological coupling agent of the general formula bio − link a − bio wherein bio is a biologically active agent fragment or precursor thereof linked to link a through a hydrolysable covalent bond ; and link a is a coupled central flexible linear first segment of & lt ; 2000 theoretical molecular weight linked to each of said bio fragments ; y is link b - oligo ; wherein link b is a coupled second segment linking one oligo to another oligo and an oligo to x or precursor thereof ; and oligo is a short length of polymer segment having a molecular weight of less than 5 , 000 and comprising less than 100 monomeric repeating units ; m is 1 - 40 ; and n is selected from 2 - 50 . the compounds are useful as biomaterials , particularly , providing antibacterial a . i . in vivo . also provided are biological coupling agents useful as intermediates in the preparation of the pharmaceutically - active polymeric compounds .