Micelle Formation of a Rod−Coil Diblock Copolymer in a Solvent Selective for the Rod Block

Abstract

Aggregation of an amphiphilic rod-coil diblock copolymer, poly(n-hexyl isocyanate)-b-poly-(ethylene glycol) (PHIC-b-PEG), in toluene, a selective solvent for the rodlike PHIC block, was studied using light scattering and polarized optical microscopy. Static and dynamic light scattering data indicate the formation of cylindrical micelles with a hydrodynamic radius of 279 nm in very dilute solutions (weight fraction of polymer, w, from 0.0002 to 0.008) at 25°C. The cylindrical micelles were determined to be disklike (planar), 0.9 µm in diameter and 20 nm in thickness, based on a comparison between the experimental data and the theory of scattering and self-diffusion of ellipsoids. Planar aggregates are expected if nematic interactions of the coronal rod block are dominant. The aggregate size decreases with increasing temperature. The micelles were observed visually in solution with the help of a polarized optical microscope due to the optical anisotropy of the PHIC block. Disklike objects with diameters in the micron range were observed to undergo translational and rotational motion in and out of the focal plane of the microscope.

Micellar Structures of Hydrophilic/Lipophilic and Hydrophilic/Fluorophilic Poly(2‐oxazoline) Diblock Copolymers in Water

“…Non-spherical micelles have been predicted [55] and experimentally observed with diblock copolymers containing very hydrophobic [56] or fluorinated blocks. [12,14,57] Conformational changes from spherical to disk-like shape of carbosilane dendrimers after introducing perfluoroalkyl end groups have been reported as well.…”

Synthesis and Characterization of Helix‐Coil Diblock Copolymers with Controlled Supramolecular Architectures in Aqueous Solution

“…[6][7][8][9][10] The incorporation of helical chains as the rigid-rod component in rod-coil copolymers represents a unique approach to creating novel supramolecular architectures. [11][12][13][14][15][16] In the studies of polystyrene-block-poly(isocyanodipeptide) in aqueous solution, the chirality of the macromolecules results in the formation of superstructures that have a helical sense bias opposite to that of the constituent block copolymers. [11] It was believed that the helical conformation Summary: A series of helix-coil diblock copolymers based on poly(ethylene oxide) and optically active helical poly-{(þ)-2,5-bis[4 0 -((S)-2-methylbutoxy)phenyl]styrene} (PMBPS) were synthesized via atom transfer radical polymerization (ATRP).…”

“…Nonetheless, mainly due to the difficulties in synthesis, only a few rod-coil block copolymers based on helical rods are known to date, including polyisocyanides, [11] polypeptides, [12][13][14] and polyisocyanates. [15,16] In the past decade, living free radical polymerizations have proven to be a potent technique to prepare macromolecules with well-defined structures, [17] such as rod-coil block copolymers. [18] We previously described the synthesis of an optically active polymer, poly{(þ)-2,5-bis[4 0 -((S)-2-methylbutoxy)phenyl]styrene} (PMBPS), exhibiting a helical secondary structure via free radical polymerization of a chiral vinyl monomer (þ)-2,5-bis[4 0 -((S)-2-methylbutoxy)phenyl]styrene (MBPS).…”

Tuning the hydrophilic–hydrophobic balance of block-graft copolymers by click strategy: synthesis and characterization of amphiphilic PCL-b-(PαN3CL-g-PBA) copolymers

“…As the length of hydrophobic segment increased, micelle morphology converted from a spherical to a spindle shape, presumably because of the strong repulsion of the hydrophobic blocks from the environment. 30 The effect of micelle concentration on the micelle size was also investigated ( Table 5). As the concentration decreased from 300 to 2.93 mg l À1 , the sizes increased from 177 to 193 nm, and from 94 to 113 nm for PCL29-b-(PaN 3 CL6-g-PBA5), and PCL29-b-(PaN 3 CL28-g-PBA21), respectively.…”