One‐shot block copolymerization

This paper describes a new method of the preparation of block copolymer, in which a mixture of two monomers is subjected to polymerization (simultaneous feeding) by the aid of an initiator. The new method is performed with the polymerization of a family of 2‐oxazolines, which proceeds via electrophilic propagating species, cation or covalent bond having electrophilic reactivity. The key to the block copolymer formation with one‐shot feeding of monomers is the difference of reactivity of polymerization (nucleophilicity) between the two monomers. First the monomer of higher reactivity is polymerized to completion, and then the monomer of decreased reactivity is polymerized starting from the propagating species of the first polymerization. For the high selectivity of the production of block copolymer, each of two propagations should be of “living mechanism”. Two combinations of monomers, i.e., 2‐methyl‐2‐oxazoline/2‐(heptafluoro‐ n ‐propyl)‐2‐oxazoline and 2‐phenyl‐2‐oxazoline/2‐(pentafluoroethyl)‐2‐oxazoline, together with an initiator of methyl tosylate were found to follow the pattern of the new process. Block copolymer of the former monomers' combination was water‐soluble, and its aqueous solution showed an excellent value of surface tension.