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Polymers 2018, 10(7), 764; https://doi.org/10.3390/polym10070764

Bimetallic Aluminum 5,6-Dihydro-7,7-dimethyl quinolin-8-olates as Pro-Initiators for the ROP of ε-CL; Probing the Nuclearity of the Active Initiator

1
Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China
2
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
3
Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, UK
*
Authors to whom correspondence should be addressed.
Received: 24 June 2018 / Revised: 10 July 2018 / Accepted: 10 July 2018 / Published: 12 July 2018
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Abstract

Six examples of aluminum 5,6-dihydro-7,7-dimethylquinolin-8-olates, [{2-R1-7,7-Me2-8-R2C9H6N-8-O}AlR32]2 (R1 = R2 = H, R3 = Me C1; R1 = R2 = H, R3 = Et C2; R1 = R2 = H, R3 = i-Bu C3; R1 = Cl, R2 = H, R3 = Me C4; R1 = H, R2 = R3 = Me C5; R1 = Cl, R2 = R3 = Me C6), have been prepared by treating the corresponding pro-ligand (L1L4) with either AlMe3, AlEt3 or Al(i-Bu)3. All complexes have been characterized by 1H and 13C NMR spectroscopy and in the case of C1 and C4 by single crystal X-ray diffraction; dimeric species are a feature of their molecular structures. In the presence of PhCH2OH (BnOH), C1C6 displayed good control and efficiency for the ROP of ε-CL with almost 100% conversion achievable in 10 min at 90 °C; the chloro-substituted C4 and C6 notably exhibited the lowest activity of the series. However, in the absence of BnOH, C1 showed only low activity with 15% conversion achieved in 30 min forming a linear polymer capped with either a methyl or a L1 group. By contrast, when one or more equivalents of BnOH was employed in combination with C1, the resulting catalyst was not only more active but gave linear polymers capped with BnO end-groups. By using 1H and 27Al NMR spectroscopy to monitor solutions of C1, C1/BnOH and C1/BnOH/10 ε-CL over a range of temperatures, some support for a monomeric species being the active initiator at the operational temperature is presented. View Full-Text
Keywords: aluminum complexes; ring opening polymerization; ε-caprolactone; bidentate; reaction mechanism aluminum complexes; ring opening polymerization; ε-caprolactone; bidentate; reaction mechanism
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Zhang, Q.; Zhang, W.; Solan, G.A.; Liang, T.; Sun, W.-H. Bimetallic Aluminum 5,6-Dihydro-7,7-dimethyl quinolin-8-olates as Pro-Initiators for the ROP of ε-CL; Probing the Nuclearity of the Active Initiator. Polymers 2018, 10, 764.

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