Core-Shell Double Gyroid Structure Formed by Linear ABC Terpolymer Thin Films

The synthesis and self-assembly in thin-film configuration of linear ABC triblock terpolymer chains consisting of polystyrene (PS), poly(2-vinylpyridine) (P2VP), and polyisoprene (PI) are described. For that purpose, a hydroxyl-terminated PS-b-P2VP (45 kg mol(-1)) building block and a carboxyl-terminated PI (9 kg mol-1) are first separately prepared by anionic polymerization, and then are coupled via a Steglich esterification reaction. This quantitative and metal-free catalyst synthesis route reveals to be very interesting since functionalization and purification steps are straightforward, and well-defined terpolymers are produced. A solvent vapor annealing (SVA) process is used to promote the self-assembly of frustrated PS-b-P2VP-b-PI chains into a thin-film core-shell double gyroid (Q(230), space group: Ia (3) over bard) structure. As terraces are formed within PS-b-P2VP-b-PI thin films during the SVA process under a CHCl3 vapor, different plane orientations of the Q(230) structure ((211), (110), (111), and (100)) are observed at the polymer-air interface depending on the film thickness.