Self-Assembly of Stereoblock Copolymers Driven by the Chain Folding of Discrete Poly(<scp>d</scp>-lactic acid-<i>b</i>-<scp>l</scp>-lactic acid) via Intramolecular Stereocomplexation
Yongbeom Kwon, Hyunji Ma, Kyoung Taek Kim
Abstract
The encoding of information by defining the sequence of monomers is a highly anticipated strategy for controlling the three-dimensional structures of polymers via information-driven chain folding and self-assembly. In this paper, we report the controlled chain folding of stereoblock poly(lactic acid)s (PLAs) composed of two oligo(lactic acid) domains, [DLAn] and [LLAn], constructed by using precisely defined numbers of d- and l-lactic acids, respectively. Under the crystallization-driven self-assembly (CDSA) condition, block copolymers (BCPs) of stereoblock PLA and poly(ethylene glycol) formed planar nanostructures having unilamellar crystalline cores of stereoblock PLA. [DLAn]-[LLAn] stereoblocks were folded predominantly by intramolecular stereocomplexation (SCN) in dilute solutions in which the intermolecular interaction between BCPs was suppressed. The thickness of the planar nanostructures was precisely defined by the number of repeating units constituted of [DLAn] and [LLAn] domains. The convergent synthesis of PLA permitted the addition of a single monomer unit between the [DLAn] and [LLAn] domains, resulting in the introduction of a desired functional group at the apex of the folded chain. Our results demonstrate that information encoded in the form of a monomer sequence may shape the polymer chain and guide its self-assembly toward specific nanostructures having the desired dimensions and functions.