Efficient Synthesis and Cyclic Molecular Topology of Ultralarge-Sized Bicyclic and Tetracyclic Polymers

Abstract

Cyclic polymers have been extensively studied because of their unique topology and physical properties, while the methods for efficient synthesis of well-defined bicyclic and multicyclic polymers are limited. Herein, an effective strategy was developed to synthesize ultralarge-sized bicyclic polymers by a ring-opening metathesis polymerization (ROMP)-based blocking-cyclization technique in a simplified feeding procedure, using the short ladderphane bearing four living ends as the initial motif. The molecular topology of the bicyclic polymer was clarified by pieces of evidence and validated by theoretical simulation. Importantly, the visualized eight-shaped molecular topology was observed. Meanwhile, the bicyclic polymer exhibited stronger thermal, fluorescence emission, and mechanical properties and better dielectric and energy storage performance than its four-arm counterpart, which elucidated the difference in molecular topology between bicyclic and four-arm polymers. Moreover, a tetracyclic polymer with a large ring size could be readily obtained. Therefore, this designed strategy opens new horizons for building bicyclic and multicyclic polymers using the conventional ROMP and commercial Grubbs catalyst.

Cyclic–hanging-multicyclic polymer synthesized by ladderphane-mediated blocking-cyclization technique for the direct visualization of cyclic macromolecular topology

“…The blocking-cyclization technique 29–31 was performed well via successive ROMPs of the difunctional monomer BNP , a mixture of monofunctional monomer TNP and macromonomer NB ( c - PPMT ), and finally bifunctional BNP to afford a cyclic–hanging-multicyclic polymer c -{ PBNP n -[ b - P ( TNP m – k - co - NB ( c - PPMT ) k )] 2 - b - PBNP n } (Scheme 1). It is noteworthy that the last formed short ladderphane PBNP was used as a cyclization unit to ensure the formation of a cyclic structure via multiple reactions, which can avoid a residue of the linear polymer precursor.…”

“…Lately, we established a new strategy with a ringopening metathesis polymerization (ROMP)-based blockingcyclization technique for the readily synthesis of monocyclic, bicyclic, and tricyclic polymers, 29 and especially the preparation of multicyclic polymers was achieved by the blockingcyclization technique through precisely designing the starting norbornene monomers with different functionalities. 30,31 In contrast to the traditional methods for synthesizing cyclic polymers, this method possesses some prominent features, including the direct use of the commercial catalyst, permitting a relatively high monomer concentration, the availability of a cyclic structure with high purity and without the treatments of separation and purification of the linear polymer precursor, owing to using the short ladderphane as the multiple cyclizing unit. 29,32 However, how to develop an efficient route for the synthesis of multicyclic polymers with a complex cyclic topology and plenty of cyclic macromolecular units remains a great challenge, and the direct visualization of cyclic molecular topology was still rarely realized.…”

“…29,32 However, how to develop an efficient route for the synthesis of multicyclic polymers with a complex cyclic topology and plenty of cyclic macromolecular units remains a great challenge, and the direct visualization of cyclic molecular topology was still rarely realized. On the basis of the previous investigation, we proposed a feasible and convenient route for the construction of cyclic-hanging-multicyclic polymers by a ROMP-based blocking-cyclization technique [29][30][31] of a bulky cyclic side chain-contained norbornene macromonomer, which was obtained by a rhodanine-mediated ROP of episulfide, 28 and then transformed into the main chain of cyclic polynorbornene bearing multicyclic polythioether side chains. As a result, a unique cyclic-hanging-multicyclic polymer topology was developed by an efficient grafting-through strategy, and the introduction of cyclic polythioether side chains in the macrocyclic architecture would be beneficial to reveal the physical features in the bulk and solution states, which not only effectively weakens the intramolecular entanglement of the polymer chain, but also increases the rigidity of the main chain, and thereby creates conditions for the direct visualization of the cyclic macromolecular morphology.…”

Fabrication of Double-Stranded Vinyl Polymers Mediated by Coordination Nanochannels

“…Moreover, the [η] values decreased with increasing crosslinking ratio, which was attributed to the compactization of vinyl polymer duplexes via crosslinking. 11,40,41 Remarkably, the slopes of the plots (α = log[η]/log M w ) were not influenced by the crosslinker amount or even by double-strand formation. α provides information about the morphology of the polymer chains in solution.…”

“…Double-stranded polymers such as DNA, RNA, and polysaccharides are ubiquitous in nature. − As the basis for life on earth, they are ultimately responsible for the biological functions of every living thing. Inspired by these elegant polymeric compounds, chemists have envisaged several strategies to produce double-stranded polymers artificially, , including supramolecular approaches using multiple noncovalent chain–chain interactions, connections between reactive side chains arranged along primary polymers, , and simultaneous chain propagation with two strands. , However, these strategies, which often require laborious and elaborate molecular designs to promote the formation of double strands, lack monomer generality or polymer stability. These drawbacks prompted us to establish a new methodology for fabricating double-stranded polymers using common monomers.…”