Supramolecular copolymerization driven by integrative self-sorting of hydrogen-bonded rosettes

Abstract

Molecular recognition to preorganize noncovalently polymerizable supramolecular complexes is a characteristic process of natural supramolecular polymers, and such recognition processes allow for dynamic self-alteration, yielding complex polymer systems with extraordinarily high efficiency in their targeted function. We herein show an example of such molecular recognition-controlled kinetic assembly/disassembly processes within artificial supramolecular polymer systems using six-membered hydrogen-bonded supramolecular complexes (rosettes). Electron-rich and poor monomers are prepared that kinetically coassemble through a temperature-controlled protocol into amorphous coaggregates comprising a diverse mixture of rosettes. Over days, the electrostatic interaction between two monomers induces an integrative self-sorting of rosettes. While the electron-rich monomer inherently forms toroidal homopolymers, the additional electrostatic interaction that can also guide rosette association allows helicoidal growth of supramolecular copolymers that are comprised of an alternating array of two monomers. Upon heating, the helicoidal copolymers undergo a catastrophic transition into amorphous coaggregates via entropy-driven randomization of the monomers in the rosette.

Consequences of hidden kinetic pathways on supramolecular polymerization

“…Therefore, the transition from Agg II in solution to higher ordered superstructures is of hierarchical nature, as also observed for other psystems with interesting properties. 17,20,23 The morphology of the different aggregates could be visualized by atomic force microscopy (AFM, Fig. 3 and S4 †) using highly ordered pyrolytic graphite (HOPG) as substrate.…”

“…Therefore, the transition from Agg II in solution to higher ordered superstructures is of hierarchical nature, as also observed for other π-systems with interesting properties. 17 , 20 , 23 …”

“…For the vast majority of supramolecular polymers, competing kinetic pathways can be readily detected spectroscopically, but ultimately evolve to the thermodynamically stable species over an experimentally observable time scale. 3,[9][10][11][12][13][14][15][16][17] In some cases, this transformation can be accelerated by mixing the kinetic product with seeds of the thermodynamic assembly, thereby inducing controlled growth in a living manner. 3,10,12,13,18 Only in rare cases, no spontaneous relaxation into the thermodynamic minimum occurs due to the close energy of kinetic and thermodynamic species 19 or the lack of active polymerization termini.…”

“…During cooling, kinetically controlled assemblies are the rst to form and, subsequently, transform to the thermodynamic product either upon further cooling [21][22][23][24][25] or over time at a constant temperature. 3,[9][10][11][12][13][14][15]17 Thus, the onset of the kinetic polymerization always precedes the thermodynamic process. This is logical considering that kinetic assemblies are typically formed through an isodesmic mechanism, which does not require to overcome a critical temperature/concentration.…”

A Highly Ordered Quantum Dot Supramolecular Assembly Exhibiting Photoinduced Emission Enhancement

“…In biological systems,m ultiple biomolecules and their nanostructures with individual functions self-organize into am ulticomponent sophisticated assembly,s uch as ac ell, leading to the generation of desirable and essential functions depending on the external environment under dynamic conditions. [1][2][3] Inspired by these systems,s cientists have attempted the construction of supramolecular assemblies consisting of several different materials through social (integrative) self-sorting [4][5][6][7][8][9][10] to realize the high-performance and unexpected physical properties that are not obtained from single materials.A sfunctional nanomaterials,c olloidal semiconductor nanocrystals,r eferred to as quantum dots (QDs), have attracted much attention because of their outstanding photoluminescence (PL) properties,s uch as ah igh photodurability,s harp PL spectra and tunable energy band gap depending on the QD size. [11][12][13] Owing to the high dispersibility of QDs,m ost studies using QDs have been focused on the photophysical properties under single conditions,such as dispersed QDs in solution [14,15] and single QD levels.…”