Stereochemical Sequence Dictates Unimolecular Diblock Copolymer Assembly

Abstract

Deciphering the significance of length, sequence, and stereochemistry in block copolymer self-assembly remains an ongoing challenge. A dearth of methods to access uniform block co-oligomers/polymers with precise stereochemical sequences has precluded such studies. Here, we develop iterative exponential growth (IEG) methods for the synthesis of a small library of unimolecular stereoisomeric diblock 32-mers. X-ray scattering reveals that stereochemistry modulates the phase behavior of these polymers, which we rationalize based on simulations carried out on a theoretical model system. This work demonstrates that stereochemical sequence can play a crucial role in unimolecular polymer self-assembly.

Discrete and Stereospecific Oligomers Prepared by Sequential and Alternating Single Unit Monomer Insertion

“…7,[75][76][77] To mimic the natural precision of biopolymers, both sequence-and stereo-controls are vital, which requires monodisperse or uniform synthetic polymers. In recent elegant reports by Johnson's group, 41,[78][79] exponential chain growth of chiral monomers (R and S configurations) can be incorporated into discrete polymers with different block sequences using "click" chemistry. Hawker and Qiao's work employed column chromatography to separate discrete and monodisperse isotactic and syndiotactic poly(methyl methacrylate) (PMMA) with defined monomer units, which were used to investigate the triple helix formation of such polymers.…”

Precise modulation of molecular weight distribution for structural engineering

“…Discrete polymers (Đ ¼ 1) having a denite composition, sequence, and topology exhibit unique phase behaviors compared to their dispersed analogues, 31,32 revealing high sensitivity of microstructures to the chain length heterogeneity. [33][34][35][36][37][38][39] In this study, we will demonstrate a method for precisely tailoring the molecular weight distribution. By rationally blending discrete oligo-L-lactic acid (oLLA) according to certain distribution functions (such as the Schulz-Zimm distribution, Gaussian distribution, skew-normal distribution, etc.…”

Direct comparison of solution and solid phase synthesis of sequence-defined macromolecules

“…6,24 A common route towards sequence-defined oligomers, offering full control over each monomer unit, is the iterative synthesis approach. 7,[25][26][27][28][29][30][31][32] This step-by-step growth of the macromolecule is necessary to ensure a perfectly defined sequence as well as monodispersity. Whilst many different approaches exist, the use of multi-component reactions seems to be a logical choice within this area and such reactions have indeed been shown to be highly effective tools for the synthesis of sequence-defined macromolecules.…”