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Effect of the Molecular Weight Distribution of the Hydrophobic Block on the Formation of Inverse Cubic Mesophases of Block Copolymers with a Discrete Branched Hydrophilic Block

Abstract

The molecular weight distribution (MWD) of polymer blocks constituting block copolymers (BCPs) directly influences their self-assembly in the bulk and the resulting periodic nanostructures. However, the effect of the MWD of core-forming hydrophobic blocks on the structures of BCPs self-assembled in solution has rarely been studied in relation to the formation of highly ordered mesophases. Herein, we report the effects of core-forming hydrophobic block MWD on the formation of bicontinuous cubic mesophases of BCPs in solution. Specifically, a series of BCPs with tunable-MWD hydrophobic blocks is prepared by coupling a discrete (Ð = 1.0) branched poly(ethylene glycol) (bPEG) hydrophilic block with a hydrophobic polystyrene (PS) block with the desired MWD. The MWDs of PS blocks were adjusted by controlling the addition rate of the initiator for the atom-transfer radical polymerization of styrene, with the resulting Ð values ranging from 1.08 to 1.72. The solution self-assembly of the thus produced branched-linear BCPs (bPEG-PS) indicated that an increase of PS block Ð value from 1.09 to 1.72 resulted in a gradual deterioration of the internal order of bPEG-PS polymer cubosomes from a cubic crystalline phase to a disordered cubic and sponge phase. It was concluded that the MWD of the core-forming hydrophobic block is the major parameter determining the internal structure disorder of polymer cubosomes. In addition, when the Ð value of the core-forming hydrophobic PS block of bPEG-PS was increased at constant Mn, the dominant symmetry of self-assembled cubosomes changed from Pn3 @#x0305;m to Im3 @#x0305;m.

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Publication details

The article was received on 12 Aug 2019, accepted on 09 Oct 2019 and first published on 09 Oct 2019


Article type: Paper
DOI: 10.1039/C9PY01211G
Polym. Chem., 2019, Accepted Manuscript

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    Effect of the Molecular Weight Distribution of the Hydrophobic Block on the Formation of Inverse Cubic Mesophases of Block Copolymers with a Discrete Branched Hydrophilic Block

    S. Ha and K. T. Kim, Polym. Chem., 2019, Accepted Manuscript , DOI: 10.1039/C9PY01211G

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