Impact of Side-Chain Length on the Self-Assembly of Linear-Bottlebrush Diblock Copolymers
Lucy Liberman, McKenzie L. Coughlin, Steven Weigand, Jerrick Edmund, Frank S. Bates, Timothy P. Lodge
Abstract
Diblock polymers are known to self-assemble into a variety of structures, and the effects of block molecular weights and volume fractions, along with the interactions between chemically different blocks, have been extensively studied. However, the consequences of molecular architectural differences between the blocks on phase behavior, particularly self-assembly into network morphologies, are less well explored. In this work, 223 linear-bottlebrush diblock polymers were synthesized using grafting-through living ring-opening metathesis polymerization. The linear block was poly(norbornene exo,exo-dimethyl ester), while five different bottlebrush blocks were used in order of increasing side-chain length: poly(norbornene exo,exo-di-isoamyl ester), poly(norbornene exo,exo-di-3,7-dimethyloctyl ester), poly(norbornene exo,exo-di-hexahydrofarnesyl ester), poly(norbornene exo,exo-di-dihydrophytyl ester), and poly(norbornene exo,exo-di-perhydrosolanesyl ester). Diblock polymer compositions ranged from approximately 30 to 70% by volume of the linear block, with total backbone degrees of polymerization ranging from 30 to 140, and side chains containing 5–45 carbon atoms. Phase behavior was studied in the vicinity of the double gyroid network window using a combination of small-, mid-, and wide-angle X-ray scattering.