Self-assembly of an ultra-high-molecular-weight comb block copolymer at the air–water interface

Abstract

The self-assembly of a newly synthesized, amphiphilic comb block copolymer (CBCP) at the air–water interface was systematically explored using the Langmuir–Blodgett (LB) technique. The CBCP had an ultra-high molecular weight (M_w = 510 × 10³ g mol⁻¹) with polystyrene arms grafted along one block of long hydrophilic backbone. At the air–water interface, the CBCP molecules spontaneously assembled into ribbon-like structures and cellular patterns at zero surface pressure when a volatile solvent (i.e., chloroform) and a less volatile solvent (i.e., toluene) were used, respectively. This spontaneous self-assembly behavior of the CBCP was induced by the dewetting process. The mechanism for the morphological change as a function of surface pressure was scrutinized and further confirmed by compression–expansion cycle and solvent vapor annealing studies. To the best of our knowledge, this is the first study of self-assembly of ultra-high-molecular-weight, amphiphilic CBCPs at the air–water interface. As such, it provides insight into the design of controllable pattern formation using amphiphilic copolymers.