Blocking-cyclization technique for precise synthesis of cyclic polymers with regulated topology

Abstract

Ring-closure and ring-expansion techniques are the two routes for extensive synthesis of cyclic polymers. Here, we report an alternative blocking-cyclization technique referred to as the third route to prepare cyclic polymers with regulated ring size and ring number by ring-opening metathesis polymerization of di- and monofunctional monomers in a one-pot process, where the polymer intermediates bearing two single-stranded blocks are efficiently cyclized by the cyclizing unit of propagated ladderphane to generate corresponding mono-, bis-, and tricyclic polymers, and the well-defined ladderphane structure plays a crucial role in forming the cyclic topology. Monocyclic polymer is further modified via Alder-ene reaction and the cyclic molecular topology is clearly demonstrated. The diversity features of cyclic polymers are comprehensively revealed. This strategy has broken through the limitations of previous two cyclizing routes, and indeed opens a facile and popular way to various cyclic polymers by commercial Grubbs catalyst and conventional metathesis polymerization.

Excitonic Effects in Polymeric Photocatalysts

“…Therefore, achieving the synthesis and characterization of well‐defined polymers can pave the way for gaining insights into relationships between structural factors and excitonic behaviors. Recent progress in the corresponding fields would be helpful: synthetic methods such as seeded growth, [59] grafting‐from strategy, [83] and blocking‐cyclization technique [84] exhibit remarkable advantage in precisely constructing well‐defined polymers. ; techniques like synchrotron radiation‐based spectroscopies [67] and electrostatic force microscopy [85] present feasibilities in characterizing the fine structures and electronic properties of polymers.…”

Rhodanine-based Knoevenagel reaction and ring-opening polymerization for efficiently constructing multicyclic polymers

“…n the past decades, cyclic polymers have attracted a large academic attention because cyclic polymers do not contain terminal groups 1 , and as a result exhibit lots of unique properties including a more significant difference in the refractive index, glass-transition temperature, viscoelasticity, mechanochemistry, stability in the presence of salt and protein, and surface properties in comparison with their linear analogues [2][3][4][5][6][7][8] . Multicyclic polymers, which contain more than three cycles in one polymer molecule, have attracted considerable interest.…”

“…Although there are some needs on the concentration and time-required synthetic procedures, ring-closure method takes the advantage of conveniently utilizing the developed controlled/living polymerization strategies and efficient coupling reactions to produce cyclic polymers with designed molecular structures. Thus, the existing reports towards synthesizing complex multicyclic polymers are limited to only ring-closure strategy [22][23][24][25][26][27] and a few cyclopolymerization strategy 6,28 . For example, Tezuka, etc.…”

ROMP of supramolecular norbornene monomers containing β-cyclodextrin–ferrocene (/adamantane) inclusion complexes

“…Thus, using this technique, various well-defined homopolymers and copolymers, whose polydispersity indexes (PDIs) are normally less than 1.2, can be prepared for all kinds of functional applications, such as their use in drug delivery [7], bioimaging [8], and catalysis [9], along with their preparation as nanoparticles [10] and hydrogels [11]. Through the use of norbornene-based monomers, polynorbornenes with various types of configurations can be synthesized, such as brush polymers [12], dendronized polymers [13], branched polymers [14], star polymers [15], ladderphanes [16], and multicyclic polymers [17][18][19]. The extensive application of ROMP is attributed to the high group tolerance of Grubbs' catalyst [1,20].…”