Novel Bowl-Shaped Morphology of Crew-Cut Aggregates from Amphiphilic Block Copolymers of Styrene and 5-(N,N-Diethylamino)isoprene

Abstract

A new morphology of crew-cut aggregates prepared from highly asymmetric triblock copolymers of 5-(N,N-diethylamino)isoprene and styrene in dilute solution is reported. After quaternization of the polar block, using dimethyl sulfate, the copolymers consist of a long block of polystyrene (PS) with short poly[5-(N,N,N-diethylmethylammonium)isoprene] (PAI) blocks at both chain ends. The aggregates were prepared by first dissolving the copolymers in a common solvent for both blocks and then adding water to induce the segregation of the PS chains. 1,4-Dioxane, THF, or a DMF/THF mixture was used as the common solvent in the preparation of these structures. The bowl-shaped aggregates are essentially highly polydisperse spheres, containing an asymmetrically placed single void space, which has broken through the surface. The continuous phase is composed of an assembly of reverse micelles (PAI core and PS corona) with hydrophilic PAI chains surrounding the structure at the polymer/aqueous solution interface. It is believed that the formation of the bowl-shaped morphology is under kinetic control and does not represent an equilibrium state. A possible mechanism for the formation of this aggregate is proposed, based on two other previously reported crew-cut morphologies from diblock copolymers. This study illustrates the importance of the preparative conditions on the self-assembly of nonequilibrium aggregates from amphiphilic block copolymers.

Water-Soluble Stimuli Responsive Star-Shaped Segmented Macromolecules

“…In neutral aqueous solutions, this star self-assembled forming spherical aggregates coexisting with bowl shaped morphologies, due to a possible viscosity control mechanism. The bowl-like morphology has been reported by Eisenberg et al for linear copolymers [41]. This was the first time that such morphology was observed in the aggregation of star block copolymers.…”

Preparation of block copolymer vesicles in solution

“…More information about these nonclassical vesicle structures can be found in a review by Burke et al, 54 and a brief summary (including vesicle sizes) and additional references are given in Table 2. Recently, Riegel et al 55 observed a bowl-shaped morphology from triblock copolymers [5- 11 -PS 228 -b-PAI 11 )] in THF/water or dioxane/water mixtures. They showed that these structures, which had some similarity to vesicles although they were not unilamellar structures, were only kinetically stable and not under equilibrium control.…”

4‐hydroxythiophenol grafted PS‐b‐PAA block copolymers: Preparation and formation of porous and bowl‐shaped assemblies

“…[25][26][27] The porous spheres of PS-b-PAA and PS-b-PEO BCPs were encountered only under some preparative conditions. 25 A bowl-like structure was prepared from 5-(N,N,Ndiethylmethylammonium)isoprene and styrene triBCPs (PAIb-PS-b-PAI) in dilute solution.…”

“…26 It has been found that the internal viscosity and the rate of water addition are the main factors for the formation of bowl-shaped structure or porous spheres. 26 Jiang et al reported bowl and dimpled shape supramolecular assemblies from mono-component polyimide. 28 Recently bowl-and porous sphere-shaped supramolecular assemblies were prepared by self-assembly of a supramolecular copolymer which was formed through end group ionic interaction between hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine) with amino end groups (PMPC-NH 2 ) and hydrophobic polystyrene with carboxyl end groups (PSt-COOH).…”