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

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journal contribution
posted on 2019-09-13, 11:02 authored by Qiurui Zhang, Wenjuan Zhang, Gregory A. Solan, Tongling Liang, Wen-Hua Sun
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 (L1–L4) 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), C1–C6 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.

Funding

This research was funded by National Natural Science Foundation of China (Nos 51473170, 51273202 and U1362204). G.A.S. thanks the Chinese Academy of Sciences for a President’s International Fellowship for Visiting Scientists.

History

Citation

Polymers 2018, 10(7), 764;

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Chemistry

Version

  • VoR (Version of Record)

Published in

Polymers 2018

Publisher

MDPI

issn

2073-4360

Acceptance date

2018-07-10

Copyright date

2018

Available date

2019-09-13

Publisher version

https://www.mdpi.com/2073-4360/10/7/764

Notes

The following are available online at http://www.mdpi.com/2073-4360/10/7/764/s1, Figures S1–S4: The 1H NMR and MALDI-TOF spectrum of PCL obtained by C1 with different amount BnOH, Figures S5–S9: The MALDI-TOF spectrum of PCL obtained by C2–C6/BnOH.

Language

en