Unraveling the Complexity of Supramolecular Copolymerization Dictated by Triazine–Benzene Interactions

Abstract

Supramolecular copolymers formed by the noncovalent synthesis of multiple components expand the complexity of functional molecular systems. However, varying the composition and microstructure of copolymers through tuning the interactions between building blocks remains a challenge. Here, we report a remarkable discovery of the temperature-dependent supramolecular copolymerization of the two chiral monomers 4,4′,4″-(1,3,5triazine-2,4,6-triyl)tribenzamide (S-T) and 4,4′,4″-(benzene-1,3,5-triyl)tribenzamide (S-B). We first demonstrate in the homopolymerization of the two individual monomers that a subtle change from the central triazine to benzene in the chemical structure of the monomers significantly affects the properties of the resulting homopolymers in solution. Homopolymers formed by S-T exhibit enhanced stability in comparison to S-B. More importantly, through a combination of spectroscopic analysis and theoretical simulation, we reveal the complex process of copolymerization: S-T aggregates into homopolymers at elevated temperature, and upon slow cooling S-B gradually intercalates into the copolymers, to finally give copolymers with almost 80% alternating bonds at 10 °C. The formation of the predominantly alternating copolymers is plausibly contributed by preferred heterointeractions between triazine and benzene cores in S-T and S-B, respectively, at lower temperatures. Overall, this work unravels the complexity of a supramolecular copolymerization process where an intermediate heterointeraction (higher than one homointeraction and lower than the other homointeraction) presents and proposes a general method to elucidate the microstructures of copolymers responsive to temperature changes.

Harmonizing Topological Features of Self-Assembled Fibers by Rosette-Mediated Random Supramolecular Copolymerization and Self-Sorting of Monomers by Photo-Cross-Linking

“…Below 70 °C, the fractions of the 1−1 homointeraction and the 1−2/2−1 heterointeractions increased, which nicely reflected the incorporation of a considerable amount of 1 (Figure 4H, center). 47 Importantly, the fractions of all interactions became almost equal at 20 °C, which corroborated the copolymerization of 1 and 2, i.e., SP spiral , had a random sequence of the two monomers (Figure 4H, right).…”

“…Importantly, an inflection point suggesting the onset of spontaneous nucleation of 1 was not recognized around T e ′[ 1 ], which would have been clearly visible if their narcissistic self-sorting had occurred, as indicated by the simple summation (black circles) of the individual polymerization curves of 1 (red circles) and 2 (yellow circles). This observation suggested that 2 initially nucleated upon cooling the mixture and 1 was gradually incorporated in the elongation process of 2 . ,− Indeed, the variation in the monomer composition ( 1 : 2 = 2:1 and 1:2) while keeping c t at 400 μM resulted in similar nonsigmoidal curves with T e ′, which was almost identical to T e ′[ 2 ] at the same concentrations (Figure S12). The subsequent heating of the cooled 1:1 mixture at a rate of 1 °C min –1 provided a depolymerization curve that matched well with the polymerization curve.…”

“…The three temperature-dependent curves shown in Figure G reveal that the 2 – 2 homointeraction was predominant above 70 °C, which was consistent with the polymerization of 2 while incorporating a small amount of 1 (Figure H, left). Below 70 °C, the fractions of the 1 – 1 homointeraction and the 1 – 2 / 2 – 1 heterointeractions increased, which nicely reflected the incorporation of a considerable amount of 1 (Figure H, center) . Importantly, the fractions of all interactions became almost equal at 20 °C, which corroborated the copolymerization of 1 and 2 , i.e., SP spiral , had a random sequence of the two monomers (Figure H, right).…”

Helical Induction, Chiroptical Properties, and Quantitative Prediction of the Dissymmetry Factor on the Circularly Polarized Phosphorescence of Iminopyrrolyl Platinum(II) Complexes

“…For convenient access to enantiopure Pt­(II) complexes, we utilized chiral induction from a commercially available chiral source. This strategy has been commonly utilized in supramolecular, polymer, − and coordination chemistry, including platinum complexes. , Recently, planar chirality and helicity inductions of Pt­(II) complexes for CPP emitters have been using axial and point chirality . In this study, we demonstrated the helical induction of d-π-conjugated iminopyrrolyl − Pt­(II) complex 1 by the point chirality of 1,2-diaminocyclohexane (Figure ).…”

Self-sorting assembly of artificial building blocks

“…However, assembly behaviours in reality can be extremely complicated, and multiple metastable or kinetically-trapped states can be involved during the process. [133][134][135] Therefore, by elongating the transformation time between a meta-stable and thermodynamically stable state, in other words, making the self-sorting assemblies kinetically trapped is also a very effective approach to achieve selfsorting assembly. A fascinating kinetically-trapped self-sorting system, which consisted of the enantiomers of the perylene bisimides derivative (PBI1) and controlled by differentiating the cooling speed, was reported by Wu ¨rthner et al 136 When cooling down from 90 1C to 20 1C, PBI1 assembled into homochiral fibres at a cooling rate of 10 K min À1 , but formed a heterochiral sheet at 0.6 K min À1 .…”