Synthesis of Main-Chain-Type Polyrotaxanes by New Click Polymerization Using Homoditopic Nitrile N-Oxides via Rotaxanation−Polymerization Protocol

Abstract

rotaxanes (9 and 12) and poly [3]rotaxanes (10 and 13) were synthesized by a new click polymerization using unstable and stable homoditopic nitrile N-oxides according to rotaxanation and polymerization protocol. Rotaxane monomers were prepared from ethynyl-functionalized crown ether and sec-ammonium salt via the typical urethane end-capping protocol. The homoditopic nitrile N-oxide 8 0 was generated in situ through the reaction of the corresponding hydroxamoyl chloride 8 with molecular sieves 4 A ˚. The click polymerization of diethynyl-functionalized [2]rotaxane 5 and [3]rotaxane monomer 7 with 8 0 efficiently proceeded in the absence of a catalyst to afford well-defined polyrotaxanes 9 and 10 containing a polyisoxazole backbone in high yields. The polymerization of a newly developed kinetically stabilized homoditopic nitrile N-oxide 11 with rotaxane monomers yielded well-defined polyrotaxanes 12 and 13 in high yields under similar conditions. The structures of poly[2]rotaxanes (9 and 12) and poly[3]rotaxanes (10 and 13) were confirmed by 1 H NMR, SEC, and IR analyses. The properties of polyrotaxanes such as solubility and thermal stability were evaluated. These polyrotaxanes showed relatively high thermal stability and good film-forming property based on their good solubility toward ordinary organic solvents.

Fluorescent poly(boron enaminoketonate)s: synthesis via the direct modification of polyisoxazoles obtained from the click polymerization of a homoditopic nitrile N-oxide and diynes

“…Building upon our previous study, [24][25][26][27][28][29][30][31][32][33][34][35][36] we selected bis(2-alcoxy-naphthalene nitrile N-oxide) as a skeleton, speculating that it should serve well as a framework for a sufficiently-stabilized homoditopic nitrile N-oxide. Synthesis of the homoditopic nitrile N-oxide 1 was accomplished in 58% overall yield via a three-step reaction (Scheme 1, m.p.…”

Polymer architectures assisted by dynamic covalent bonds: synthesis and properties of boronate-functionalized polyrotaxane and graft polyrotaxane

“…Axle component 1, 38 boronic acid 3, 39 bis(hydroxymethyl)dibenzo-24-crown-8-ether 9, 40 poly(crown ether) polyester-10 19 and stable homoditopic nitrile Noxide 12 23 were prepared according to the literature. Other materials are available commercially and were used without further purification.…”

“…However, construction of the interlocked framework generally requires specific conditions to avoid decomposition of the intermediary pseudorotaxane or half rotaxane. Among crown-ether-based main-chain-type polyrotaxanes, [19][20][21][22][23] those containing poly(crown ether) as the trunk polymer are particularly fascinating because of their unique structure. Notably, they are capable of conversion to 'graft polyrotaxanes' with interlocked graft chains, which are of interest because of their structure, dynamic behavior and physical properties.…”

Crown Ether‐Based Polymeric Rotaxanes

“…In an attempt to find easier and alternative methods for the synthesis of polyrotaxanes, Takata and coworkers have taken advantage of [2 þ 3] nitrile N-oxide/ acetylene cycloadditions to produce poly [2]rotaxanes and poly [3]rotaxanes (the latter being discussed in the next section) [26]. While assessing possible cycloaddition reactions, the nitrile N-oxide/acetylene reaction was chosen over the more popular Huisgen type click chemistry due to the explosive nature of azides and the difficulty of removal of the copper catalyst required in the latter method.…”