Domiński Adrian, Konieczny Tomasz, Zięba Magdalena, Klim Magdalena, Kurcok Piotr
Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34, M. Curie-Sklodowskiej St., 41-819 Zabrze, Poland.
Faculty of Mathematics and Natural Science, Jan Dlugosz University in Czestochowa, 13/15, Armii Krajowej Ave., 42-200 Czestochowa, Poland.
Polymers (Basel). 2019 Jul 22;11(7):1221. doi: 10.3390/polym11071221.
It was shown that selected sodium phenoxide derivatives with different basicity and nucleophilicity, such as sodium -nitrophenoxide, -chlorophenoxide, 1-napthoxide, phenoxide and -methoxyphenoxide, are effective initiators in anionic ring-opening polymerization (AROP) of -butyrolactone in mild conditions. It was found that phenoxides as initiators in anionic ring-opening polymerization of -butyrolactone behave as strong nucleophiles, or weak nucleophiles, as well as Brønsted bases. The resulting polyesters possessing hydroxy, phenoxy and crotonate initial groups are formed respectively by the attack of phenoxide anion at (i) C2 followed by an elimination reaction with hydroxide formation, (ii) C4 and (iii) abstraction of acidic proton at C3. The obtained poly(3-hydroxybutyrate) possesses carboxylate growing species. The ratio of the observed initial groups strongly depends on the basicity and nucleophilicity of the sodium phenoxide derivative used as initiator. The proposed mechanism of this polymerization describes the reactions leading to formation of observed end groups. Moreover, the possibility of formation of a crotonate group during the propagation step of this polymerization is also discussed.
结果表明，所选的具有不同碱性和亲核性的苯氧化钠衍生物，如对硝基苯氧化钠、对氯苯氧化钠、1-萘氧化钠、苯氧化钠和对甲氧基苯氧化钠，在温和条件下是γ-丁内酯阴离子开环聚合（AROP）的有效引发剂。研究发现，在γ-丁内酯阴离子开环聚合中作为引发剂的苯氧化物既表现为强亲核试剂，也表现为弱亲核试剂，同时还表现为布朗斯特碱。所得的具有羟基、苯氧基和巴豆酸酯端基的聚酯分别是由苯氧阴离子在（i）C2处进攻，随后与形成的氢氧化物发生消除反应、（ii）在C4处进攻以及（iii）在C3处夺取酸性质子而形成的。所得到的聚（3-羟基丁酸酯）具有羧酸盐增长链端。观察到的端基比例强烈取决于用作引发剂的苯氧化钠衍生物的碱性和亲核性。该聚合反应的提出的机理描述了导致形成观察到的端基的反应。此外，还讨论了在该聚合反应的增长步骤中形成巴豆酸酯基团的可能性。
