Ring-Opening Polymerization Reactions of ε-Caprolactone and Lactides Initiated by (Benzimidazolylmethyl)amino Magnesium(ii) Alkoxides
Ekemini D. Akpan A , Bernard Omondi A and Stephen O. Ojwach B C
+ Author Affiliations
- Author Affiliations
A School of Chemistry and Physics, Westville Campus, University of KwaZulu–Natal, Private Bag X54001, Durban 4000, South Africa.
B School of Chemistry and Physics, Pietermaritzburg Campus, University of KwaZulu–Natal, Private Bag X01, Scottsville 3209, South Africa.
C Corresponding author. Email: ojwach@ukzn.ac.za
Australian Journal of Chemistry 71(5) 341-347 https://doi.org/10.1071/CH17506
Submitted: 15 September 2017 Accepted: 26 February 2018 Published: 16 March 2018
Abstract
Reactions of (benzimidazolylmethyl)amine ligands N-((1H-benzo[s]imidazol-2-yl)methyl)-2,6-dimethylaniline (L1), N-((1H-benzo[d]imidazol-2-yl)methyl)-2,6-diisopropylaniline (L2), and N-((1H-benzo[d]imidazol-2-yl)methyl)-2,4,6-trimethylaniline (L3) with Mg(nBu)2 in the presence of either benzyl alcohol (BnOH) or tert-butyl alcohol (t-BuOH) afforded the respective MgII alkoxides [Mg(L1)(OBn)]2 (1), [(Mg(L2)(OBn)]2 (2), [Mg(L3)(OBn)]2 (3), [Mg(L2)(t-BuO)]2 (4). Complexes 1–4 formed efficient catalysts for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL), d,l-lactide (d,l-LA) and l-lactide (l-LA) at 110°C. The catalytic activities of these complexes in the ROP reactions were influenced by the steric effect of the ligands. Kinetic studies showed pseudo-first-order dependency on monomer. Polycaprolactone and polylactides of moderate weight-average molecular weights of 15285 and 5200 g mol−1 and fairly narrow polydispersity indexes from 1.24 to 1.58 were produced.
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