Supramolecular Copolymers: Structure and Composition Revealed by Theoretical Modeling

Abstract

Supramolecular copolymers, non-covalent analogues of synthetic copolymers, constitute a new and promising class of polymers. In contrast to their covalent counterparts, the details of their mechanism of formation, as well as the factors determining their composition and length, are still poorly understood. Here, the supramolecular copolymerization between two slightly structurally different benzene-1,3,5-tricarboxamide (BTA) monomers functionalized with either oligodimethylsiloxane (oDMSi) or alkyl side chains is unraveled by combining experimental and theoretical approaches. By applying the “sergeant-and-soldiers” approach using circular dichroism (CD) experiments, we are able to obtain detailed insights into the structure and composition of these supramolecular copolymers. Moreover, we observe an unexpected chiral induction upon mixing two independently CD-silent solutions of the achiral (soldier) and chiral (sergeant) monomers. We find that the subtle differences in the chemical structure of the two monomers impact their homopolymerization mechanism: whereas alkyl-BTAs cooperatively self-assemble, oDMSi-BTAs self-assemble in an isodesmic manner. The effect of these mechanistic differences in the supramolecular copolymerization process is investigated as a function of the composition of the two monomers and explicitly rationalized by mathematical modeling. The results show that, at low fractions of oDMSi-BTA sergeants (<10 mol%), the polymerization process is cooperative and the supramolecular helicity is biased toward the helical preference of the sergeant. However, at higher fractions of oDMSi-BTA sergeant (>25 mol%), the isodesmic assembly of the increasing amounts of sergeant becomes more dominant, and different species start to coexist in the copolymerization process. The analysis of the experimental data with a newly developed theoretical model allows us to quantify the thermodynamic parameters, the distribution of different species, and the compositions and stack lengths of the formed supramolecular copolymers existing at various feed ratios of the two monomers.

Mechanistic Insights into Statistical Co‐Assembly of Metal Complexes

“…In a recent example, Palmans, Meijer, and co‐workers relied on the effects of steric hindrance and side‐chain incompatibility to efficiently create random supramolecular copolymers using ca. 10 % of the bulky co‐monomer . Herein, we introduce a straightforward strategy to control the outcome of statistical co‐assembly processes at any ratio by merely changing the nature of the metal ion while keeping an identical molecular design of the monomer units.…”

Synthesis, resolution, and chiroptical properties of hemicryptophane cage controlling the chirality of propeller arrangement of a C3 triamide unit

“…13 Besides their use as enantioselective receptors for carbohy-the chirality of the arrangement of the linkers, but also that of the south unit, in particular that of a benzene-1,3,5tricarboxamide (BTA) moiety ubiquitous in supramolecular chemistry. [19][20][21][22][23][24][25][26][27] Herein, we report the synthesis of the new hemicryptophane cage 1. The resolution of the racemic mixture was performed by chiral high-performance liquid chromatography (HPLC), and the assignment of the absolute configuration of the two enantiomers was achieved from electronic circular dichroism (ECD) spectra.…”

Supramolecular Copolymerization as a Strategy to Control the Stability of Self‐Assembled Nanofibers

“…[1][2][3][4][5][6] Introducing such ac oncept in the area of supramolecular polymers will expand their potential in applications and demonstrate the advantage of am odular, non-covalent synthetic approach. [12][13][14][15] Am ajor challenge to be addressed in these supramolecular copolymers is the ability to control their stability and/or dynamic behavior in the equilibrium exchange dynamics between monomers and polymers. [12][13][14][15] Am ajor challenge to be addressed in these supramolecular copolymers is the ability to control their stability and/or dynamic behavior in the equilibrium exchange dynamics between monomers and polymers.…”