Transient dormant monomer states for supramolecular polymers with low dispersity

Temporally controlled cooperative and living supramolecular polymerization by the buffered release of monomers has been recently introduced as an important concept towards obtaining monodisperse and multicomponent self-assembled materials. In synthetic, dynamic supramolecular polymers, this requires efficient design strategies for the dormant, inactive states of the monomers to kinetically retard the otherwise spontaneous nucleation process. However, a generalized design principle for the dormant monomer states to expand the scope of precision supramolecular polymers has not been established yet, due to the enormous differences in the mechanism, energetic parameters of self-assembly and monomer exchange dynamics of the diverse class of supramolecular polymers. Here we report the concept of transient dormant states of monomers generated by redox reactions as a predictive general design to achieve monodisperse supramolecular polymers of electronically active, chromophoric or donor-acceptor, monomers. The concept has been demonstrated with charge-transfer supramolecular polymers with an alternating donor-acceptor sequence.

collection in the range of 570 nm to 650 nm for Nile red dye. The microscope objective of 63X (NA 1.4) and 100X (NA 0.5) were employed. The images were captured by drop casting the freshly prepared sample on a glass bottom petridish and closed with cap to avoid drying.

Structured Illumination Microscopy (SIM) measurements: Structured Illumination Microscopy (SIM)
images were captured using an inverted Zeiss ELYRA PS1 microscope. The prepared sample solution was dispersed on a coverslip attached with a 35 mm dish and kept under the microscope.
Fluorescence microscopic images were captured by structured illumination method using laser excitation at λexc = 561 nm (200 mW) and emission collection in the range of 570 nm to 650 nm for Nile red dye.
Here, the total hydrophobic length of PNF foldamer includes the C12 alkyl chain along with NDI and pyrene components. Thus a total length of = 24.27 Å was measured for hydrophobic segment from the energy minimized structure which corresponds to the hydrophobic chain length equivalent to =

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Supplementary Note 1: the source of weak pyrene emission for PNF is because of the residual pyrene which is weakly bound with NDI and not involved in CT co-assembly, proved by lifetime measurement.  Supplementary Note 3: Generation of NDI reduced species from PNF with concomitant unfolding of the foldamer and various steps of reduction and oxidation kinetics is explained as follows.
Step A, corresponds to the instantaneous formation of PNF-NDI 2 ̶ and PNF-NDI  ̶ from PNF on addition of excess eq. of SDT, where the rate of reduction is much faster than the rate of oxidation.
PNF-NDI  ̶ due to its aggregation induced stabilization tends to be in PNF-NDI  ̶ assembled state (depicted by the DLS size data at t = 0 min) protecting it from spontaneous oxidation.
Step B follows after step A, having a steady state of PNF-NDI  ̶ species, here PNF-NDI 2 ̶ gets oxidized to PNF-NDI  ̶ which in turn is reduced back to PNF-NDI 2 ̶ due to the presence of excess of SDT present in the solution (simultaneously any PNF formed is reduced back to PNF-NDI 2 ̶ and PNF- Here the rate of oxidation equals to the rate of reduction and a steady concentration of PNF-NDI  ̶ (or its assembly, depicted by the DLS size data at t = 2 min.  15 min.) is obtained.
Since PNF-NDI  ̶ is stabilized in its assembled state, it has lower tendency to get oxidized to PNF, however, still this possibility cannot be ignored. The steady state is confirmed by minimal increase in size, ascribed to the formation of more PNF-NDI  ̶ species.
Step C corresponds to the generation of PNF-NDI  ̶ from PNF-NDI 2 ̶ by controlled oxidation process where the rate of oxidation takes over the rate of reduction due to continuous consumption of oxygen, leading to an increase in the PNF-NDI  ̶ population as depicted by increased absorption and also the formation of neutral PNF molecules which takes part in the formation of tape structures giving rise to slight increase in DLS size (depicted by the DLS size data at t = 45 min.). Finally at step D, the concentration of SDT becomes extremely low and the rate of reduction tends to zero and rate of oxidation dominates to convert all PNF-NDI  ̶ into active PNF molecules in a controlled rate that can undergo supramolecular polymerization into tape structures with increasing DLS size (depicted by the DLS size data at t = 50 min.).
Here, we expect the rate of dissolution of atmospheric oxygen into the solution, 1) remains constant throughout the cycle (system under equilibrium) and 2) is slower than the consumption of dissolved oxygen, as a result the rate of oxidation is mainly determined by amount of dissolved oxygen at t = 0 min. which is taken care while sample preparation. On addition of SDT, dissolved oxygen in the solution gets consumed. A lower amount of dissolved oxygen, keeps rate of oxidation low such that step B and step C will be longer. As a consequence, the kinetics of PNF formation are controlled by initial SDT concentration.