Molecular Reorganization of Rod−Coil Diblock Copolymers at the Air−Water Interface

Abstract

Amphiphilic rod-coil diblock copolymers consisting of flexible poly(ethylene oxide) (PEO) and rodlike poly{(+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS) with predominant hydrophobic contents formed ordered monolayers at the air-water interface. The structures of monolayers transferred to a mica substrate at different surface pressures by the Langmuir-Blodgett method were investigated by atom force microscopy (AFM). For PEO(104)-b-PMBPS(17) copolymer (the subscripts denote the number-averaged polymerization degree of each block), a complete spectrum of molecular reorganization at variable surface pressures was observed. Spherical surface aggregates of LB monolayers were spontaneously formed during the solvent evaporation after the deposition of polymer solution. Continuous compression led to the pancake-to-brush conformation transition of the copolymer that PEO chains desorbed from the air-water interface and went into the water subphase. The effective content of the rod block changed continuously from 61% at zero pressure to 93% at the start of the monolayer collapse, igniting the molecular reorganization. As a result, coalescence of individual spherical aggregates into long cylindrical aggregates with an increase of the surface pressure was observed. For a series of block copolymers PEO(104)-b-PMBPS(m)() (m = 17, 30, 45, 53), as the rod contents increased from 61% to 83%, the morphological transition from spherical aggregates to long cylindrical aggregates in orientational order developed at zero pressure, which showed a similar dependence on the effective contents of the rod block to PEO(104)-b-PMBPS(17) at different pressures. In comparison to coil-coil block copolymers PEO-b-PS, the rod-coil block copolymers PEO-b-PMBPS exhibited distinct structure reorganization behavior, in which the orientation of rod block might play an important role.

Jacketed polymers: Controlled synthesis of mesogen‐jacketed polymers and block copolymers

“…If one of the monomers can not be tolerant with ATRP, functionalization of end groups has to be carried out. The most frequently used procedure was by reaction of 2-bromo-2-methylprorionyl bromide with existing hydroxy end groups, such as the synthesis of PDMS-b-PMPCS, 57 PEO-b-PMPCS, 58 PCL-b-PMPCS, 59 PEO-b-PMBPS, 60 PMPCS-b-PDMS-b-PMPCS, 61 and so on. For example, the diblock copolymer of PCL-b-PMPCS was synthesized by ring-opening polymerization of e-caprolactone and subsequent ATRP of MPCS (see Scheme 14).…”

Electron tomographic analysis of synaptic ultrastructure

“…The supramolecular organization of rod‐coil copolymers attracts a great deal of attention for their ability to form nanoscale aggregates with novel architectures, functions, and physical properties 1–29. The self‐assembly of rod‐coil block copolymers are driven not only by the solvent selectivity but also influenced by the tendency of the rigid segments to aggregate, which differs distinctly from those of conventional coil–coil block copolymers.…”

Two-dimensional Self-assembly of a Designed Amphiphilic Peptide at Air/Water Interface

“…Such a disk-like structure, where hydrophobic and hydrophilic segment located on the core and periphery, respectively, is often obtained by phase separation of an amphiphilic diblock copolymer without particular compressing process. 17,18 The phase separated structure in disk-like shape is one of the most stable structure in two-dimensional self-assembly based on the amphiphilicity. It is worthy of note that the constructed structure was successfully obtained in nano-meter scale, since the hydrophobic domain was composed of -sheet peptide of 16 residues.…”