Self-Assembly of Carbohydrate-block-Poly(3-hexylthiophene) Diblock Copolymers into Sub-10 nm Scale Lamellar Structures

Abstract

We here report the synthesis of a new class of carbohydrate-based block copolymers, poly(3-hexylthiophene)-block-peracetylated maltoheptaose (P3HT-b-AcMal 7 ) and poly(3-hexylthiophene)-block-maltoheptaose (P3HT-b-Mal 7 ), and their bulk and self-assembled thin films morphological characterizations by atomic force microscopy, transmission electron microscopy, and small-angle X-ray scattering. The block copolymers were synthesized via copper(I)-catalyzed 1,3-dipolar azide−alkyne cycloaddition of azido-functionalized AcMal 7 and end-functionalized P3HT with alkyne group prepared by modified Grignard metathesis polymerization, followed by deacetylation of the AcMal 7 block. The half-pitch of sub-10 nm scale lamellar structures, one of the smallest domain sizes of microphase separated block copolymers reported to date, was self-organized in the bulk and thin films of P3HT-b-AcMal 7 by thermal annealing above the melting temperature of the P3HT segment. Meanwhile, thermodynamic microphase separation of P3HT-b-Mal 7 was restricted due to strong inter-and intrachain hydrogen bonding among the hydroxyl groups of the Mal 7 block, which was confirmed by an in situ stepwise heating and cooling Fourier transform infrared spectroscopy study.

Competing Molecular Packing of Blocks in a Lamella-Forming Carbohydrate-block-poly(3-hexylthiophene) Copolymer

“…22 In the previous study, an in situ end-functionalization was used to prepare regioregular alkyne-P3HT. 22 However, this method yields P3HTs with a small amount of high molecular weight impurities possibly due to alkyne-alkyne homocoupling between reactive ethynyl-capped P3HTs during the end-capping process. To circumvent these undesirable by-products which may affect the morphology of the self-assembled block copolymer film, an alternative synthetic route based on a post-polymerization modification method was applied.…”

Ring-Opening of Cyclodextrins: An Efficient Route to Pure Maltohexa-, Hepta-, and Octaoses

“…We can also mention R. Borsali et al who proposed a class of copolymers based on maltoheptaosides [41,54]. They also describe a lamellar structure smaller than 10 nm [55].…”

Directed Self‐Assembly of Liquid‐Crystalline Molecular Building Blocks for Sub‐5 nm Nanopatterning

“…The second domain is formed by the remaining noninteracting block (e.g., C). Shape anisotropy, for example through the incorporation of rod‐like carbohydrate blocks, is another powerful means to access ultra‐dense BCP nanopatterns …”