Molecular architecture effect on the self-assembly behavior of comb-coil block copolymers displaying lamellae-within-lamellae morphology

Supramolecular comb-coil block copolymers formed by the stoichiometric complexation of two amphiphilic surfactants, dodecylbenzenesulfonic acid (DBSA) and 3-pentadecylphenol (PDP), with the poly(4-vinylpyridine) (P4VP) blocks in a linear PS-b-P4VP and a nonlinear A_nB_n-type heteroarm star PS-P4VP copolymer have been investigated. All linear and heteroarm star systems under study exhibited lamellae-within-lamellae morphology even at high PS volume fraction, at which the previously studied systems showed lamellae- withincylinder or lamellae-within-sphere morphology. The interlamellar distances of the larger-scale copolymer microdomains were found to be much larger in all heteroarm complexes than those in their linear counterparts. This was attributed to the chain crowding effect coupled with the different types of arrangement of comb blocks forming the smaller-scale lamellar mesophase. Moreover, the order-disorder transition temperatures of both the larger- and smaller-scale structures in the heteroarm star systems were higher than those associated with the linear diblocks due to the lower entropy of transition.