Cationic ring-opening copolymerization of a cyclic acetal and γ-butyrolactone: monomer sequence transformation and polymerization–depolymerization control by vacuuming or temperature changes

Polymerization–depolymerization equilibrium is a promising strategy for the construction of polymerization systems through which sustainable polymers can undergo reversible polymer–monomer transformations. In this study, we perform monomer sequence transformation and copolymer depolymerization, which are based on transacetalization reactions and polymerization–depolymerization equilibrium, in the cationic ring-opening copolymerization of 2-methyl-1,3-dioxepane and γ-butyrolactone with a protonic acid. The removal of monomer molecules from the copolymerization solution by vacuuming with a vacuum pump caused monomer sequence to transform into pseudo-alternating copolymer chains and subsequently depolymerize into oligomers. Increasing the temperature during copolymerization also resulted in depolymerization, while copolymers were regenerated by the subsequent decrease in temperature.Takebayashi K., Kanazawa A., Aoshima S.. Cationic ring-opening copolymerization of a cyclic acetal and γ-butyrolactone: monomer sequence transformation and polymerization–depolymerization control by vacuuming or temperature changes. Polymer Journal , (2023); https://doi.org/10.1038/s41428-023-00847-9

カチオン重合による機能性ポリマーの合成 : リビング重合及び移動反応の規制

京都大学0048新制・課程博士工学博士甲第3645号工博第948号新制||工||681(附属図書館)UT51-62-C82京都大学大学院工学研究科高分子化学専攻(主査)教授 東村 敏延, 教授 今西 幸男, 教授 三枝 武夫学位規則第5条第1項該当Kyoto UniversityDFA

Two-step degradable ABAC-type periodic poly(cyclic acetal)s synthesized by sequence-programmed monomer formation and subsequent polyaddition based on cyclotrimerization of one vinyl monomer and two aldehydes

ABAC-type periodic poly(cyclic acetal)s were synthesized via a two-step method consisting of the synthesis of a sequence-programmed cyclic trimers from one vinyl monomer and two bifunctional aldehydes (isophthalaldehyde or terephthalaldehyde) and the successive cyclotrimerization of the cyclic trimer with another vinyl monomer. The use of 1,1-diphenylethylene (DPE) was important for synthesizing the cyclic trimer in high yield because the successive cyclotrimerization and other side reactions were suppressed due to the steric hindrance of DPE. The ABA-type sequence-programmed cyclic trimer consisting of one DPE molecule (unit B) and two dialdehydes (unit A) possesses two unreacted aldehyde moieties; hence, the cyclic trimer successfully underwent successive cyclotrimerization with vinyl ethers (VEs) (unit C), such as 2-chloroethyl VE (CEVE) and ethyl 2-methyl-1-propenyl ether (EMPE). As a result, ABAC-type periodic poly(cyclic acetal)s with alternately arranged two phenyl rings and VE-derived side chains were produced. The two types of cyclic acetal structures in the main chain exhibited different acid degradability. Indeed, the CEVE-derived cyclic acetal structures were selectively degraded under acidic conditions at 60 °C for 15 min, which was followed by the subsequent degradation of the DPE-derived cyclic acetal structures in 24 h. In addition, the ABAC-type periodic polymers exhibited good thermal properties, which were attributed to the cyclic acetal structures

Exclusive One-Way Cycle Sequence Control in Cationic Terpolymerization of General-Purpose Monomers via Concurrent Vinyl-Addition, Ring-Opening, and Carbonyl-Addition Mechanisms

Cationic terpolymerization of vinyl ether (VE), oxirane, and ketone successfully proceeded via unprecedented concurrent vinyl-addition, ring-opening, and carbonyl-addition mechanisms. In particular, the use of cyclohexene oxide as an oxirane resulted in terpolymerization via an exclusive one-way cycle, i.e., the reactions occurred only in the VE → oxirane, oxirane → ketone, and ketone → VE directions. Terpolymers that have repeating units of (VE_∼2–oxirane_∼2–ketone)_<i>n</i> were obtained under appropriate conditions. In addition, no two-monomer combination achieved efficient copolymerization, which suggests that three specific types of crossover reactions are required for successful terpolymerization. The presence of a ketone, a compound that has rarely been employed as a monomer, is indispensable for a one-way cycle: terpolymerization also proceeded with an aliphatic aldehyde but resulted in two-way crossover reactions at the aldehyde-derived propagating ends

Temperature-induced switchable magnetite nanoparticle superstructures

In this study we describe the green synthesis of temperature-switchable polymer-magnetite nanoparticles (PMNPs) in water at room temperature via an improved co-precipitation pathway. The temperature responsiveness was achieved through the surface modification with a vinyl-based dual-stimuli-responsive block copolymer. Furthermore, these PMNPs enable the investigation of temperature-induced magnetic superstructures and their medical application.publishe