Ketene-based aliphatic polyketones obtained by cationic copolymerization of dimethylketene (DMK) with diethylketene (DEK
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ORIGINAL PAPER
Ketene‑based aliphatic polyketones obtained by cationic copolymerization of dimethylketene (DMK) with diethylketene (DEK) or diphenylketene (DPK): synthesis, characterization and reactivity ratio estimation Bo Jiang1 · Nicolas Desilles1 · Fabrice Burel1 Received: 28 April 2020 / Accepted: 10 August 2020 © The Polymer Society, Taipei 2020
Abstract Cationic copolymerizations of different ketoketenes are conducted to explore the structure and properties of the afforded copolymers. Diethylketene (DEK) and diphenylketene (DPK) are both copolymerized with dimethylketene (DMK), via a cationic mechanism using the mixture AlCl3 / (CH3)3CCl as initiator. The experiments confirmed that two series of polyketones, containing a main DMK chain comprising few DEK or DPK units, are successfully obtained. The reactivity ratios are calculated. The structures and thermal performances of the obtained copolymers are discussed. An interesting DMK / DEK copolymer with a broad processing window was obtained (Tm = 164 °C, Td5% = 259 °C). Keywords Ketene · Polyketone · Reactivity ratio · Cationic polymerization · Copolymerization
Introduction Ketenes (R1R2C = C = O) are known to be highly reactive difunctional species, and hence have already shown potential utility and fascinating value in different fields of organic synthesis, as nucleophile, electrophile and cycloaddition reactions [1–4]. Most of these reactions were based on the unique adjacent double-double bond structure, which addresses a partial negative charge on both the end carbon and oxygen atoms as well as a partial positive charge on the central carbon atom [5]. These two contiguous double bonds contributed to form critical intermediates in considerable organic procedures [6–8], whereas it also makes ketenes intrinsically unstable when isolated and exposed to air or moderate temperature [9]. Regarding their functional groups R1 and R 2, ketenes are generally classified by aldoketenes (R1 = H, R2 ≠ H, very unstable) and ketoketenes (R1, R2 ≠ H, less unstable) [10].
* Nicolas Desilles nicolas.desilles@insa‑rouen.fr 1
Normandie Université, INSA Rouen Normandie, CNRS, UMR 6270, 685 avenue de l’Université, 76800 Saint‑Etienne‑du‑Rouvray, France
First synthesized and characterized in 1905 by Hermann Staudinger, diphenylketene (DPK) was obtained from the reaction of 2-chlorodiphenylacetyl chloride with zinc, commonly known as the Staudinger method [11]. Dimethylketene (DMK) was later prepared with the same method [12]. Several other synthetic ways have already proved their efficiency. For example, as far as we are concerned in this work: (1) the dehydrohalogenation reaction was successfully used to generate and isolate DPK [13], (2) the pyrolysis of ketones, acids, malonic acids, acid anhydrides, esters, ketene dimers and other substances afforded neat ketenes in satisfying yields [14–16]. As a result, DMK synthesis was optimized by the thermal decomposition of isobutyric anhydride [17], and diethylketene (DEK) was isolated from the pyrolysis of a m
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