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

Abstract

Summary: A series of helix‐coil diblock copolymers based on poly(ethylene oxide) and optically active helical poly{(+)‐2,5‐bis[4′‐((S)‐2‐methylbutoxy)phenyl]styrene} (PMBPS) were synthesized via atom transfer radical polymerization (ATRP). The synthetic methodology permitted straightforward preparation of the diblock copolymers with relatively low polydispersities and a broad range of compositions and molecular weights. Depending on the composing block length and the initial concentration, the copolymers self‐assembled into different supramolecular structures in aqueous solution, including spherical micelles, vesicles, multilamellar vesicles, large compound vesicles, and tubules.Schematic representation of the synthesis of PEO‐b‐PMBPS block copolymers and their aggregation in aqueous solution.magnified imageSchematic representation of the synthesis of PEO‐b‐PMBPS block copolymers and their aggregation in aqueous solution.

Synthesis and Self‐Assembly of Brush‐Rod Diblock Copolymers in the Mixed Solvent of THF/H2O

“…The specific optical rotation [a] , in THF) of MBPS was þ60.58; yet the two copolymers showed negative values of [a] 25 365 as MBPS homopolymer (Table 1). [20,21] The opposite sign of the copolymers to MBPS and the increase in magnitude suggested that the optical activity of the copolymer did not simply arise from the asymmetric centers within the side groups and that a higher structure, most likely a secondary helical conformation for a vinyl polymer such as PMBPS, was formed.…”

“…The similar tendency has also been found in the system of helix-coil block copolymers. [20] In the present study, the initial copolymer concentrations varied from H. Cao, W. Lin, A. Liu, J. Zhang, X. Wan, Q. Zhou 0.005 to 1.0 wt.-%. However, no discernible changes in the morphology, size, and polydispersity of the aggregates with concentration were found.…”

“…The assignments of resonance peaks is shown in the Figure. [18, [24][25][26] The M n of macroinitiator was determined according to the area ratio of methoxy to aromatic group, [22] while the DP n of PMBPS block was determined based on the area ratio of alkoxy protons of both blocks to aromatic protons of PMBPS blocks. [20] The characterization results of GPC and 1 H NMR are summarized in Table 1. It is evident that DP n s determined by 1 H NMR were larger than those deduced from GPC.…”

“…The bulky and highly crowded terphenyl groups of PMBPS serve to enforce an extended helical chain conformation and the chiral end substituents appended to the terphenyl moieties induce an excess screw sense. [20,21] It is expected that a combination of brush-like and rod-like polymers would give a block copolymer different from others in self-assembly behavior and supramolecular structures.…”

Organic–inorganic rod–coil block copolymers comprising substituted polyacetylene and poly(dimethylsiloxane) segments

“…17 The helical conformation of the polypeptide and polyisocyanate is due to the intramolecular hydrogen bonding, chiral center in the repeat units, and/or short range restriction of rotation. [22][23][24][25][26][27][28] The rigidity of these polymers arises from the close wrapping of the side-on mesogens around the flexible backbone, forcing the latter to extend to form a supramolecular rod. An important class of mesogen-bearing block copolymers is those containing mesogen-jacketed liquid crystalline polymers (MJLCPs), [19][20][21] which were synthesized mostly through controlled/"living" radical polymerizations of designed monomers with laterally attached mesogenic side groups.…”