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.
Two amphiphilic brush‐rod block copolymers, PEGMA37‐b‐MBPS87 and PEGMA37‐b‐MBPS141, were synthesized via ATRP of poly(ethylene glycol)monomethyl ether methacrylate (PEGMA) and (+)‐2,5‐bis[4′‐((S)‐2‐methylbutoxy)phenyl]styrene (MBPS). The self‐assembly of the copolymers in THF/H2O was induced by different methods. Spheres were dominant morphologies of PEGMA37‐b‐MBPS87 regardless of the initial concentration and the rate of water addition. Increase of the length of hydrophobic block, as in PEGMA37‐b‐MBPS141, led to the coexistence of primary spheres, large compound spherical and rod‐like micelles at a slow water addition rate. Injecting water into the THF solution of PEGMA37‐b‐MBPS141 quickly or pouring the THF solution into large amount of water resulted only in the formation of spheres.magnified image
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