Jump to main content
Jump to site search

Issue 30, 2013
Previous Article Next Article

Structural and kinetic studies of the polymerization reactions of ε-caprolactone catalyzed by (pyrazol-1-ylmethyl)pyridine Cu(II) and Zn(II) complexes

Author affiliations

Abstract

The structural and kinetic studies of polymerization reactions of ε-caprolactone (ε-CL) using (pyrazolylmethyl)pyridine Cu(II) and Zn(II) complexes as initiators is described. Reactions of 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2-(3,5-diphenylpyrazol-1-ylmethyl)pyridine (L2) with Zn(Ac)2·2H2O or Cu(Ac)2·2H2O produced the corresponding complexes [Zn(Ac)2(L1)] (1), [Cu(Ac)2(L1)] (2), [Zn(Ac)2(L2)] (3) and [Cu2(Ac)4(L2)2] (4) respectively. Solid state structures of 1 and 4 confirmed that complexes 1 and 4 are monomeric and dimeric respectively and that L1 is bidentate in 1 while L2 is monodentate in 4. X-band EPR spectra of 2 and 4 revealed that complex 2 is monomeric both in solid and solution state, while the paddle-wheel structure of 4 is retained in solution. Complexes 1–4 formed active initiators in the ring opening polymerization of ε-CL. Zn(II) complexes 1 and 3 exhibited higher rate constants of 0.044 h−1 and 0.096 h−1 respectively compared to rate constants of 0.017 h−1 and 0.031 h−1 observed for the corresponding Cu(II) complexes 2 and 4 respectively at 110 °C. All the polymerization reactions follow pseudo first-order kinetic with respect to ε-CL monomer. Initiator 1 showed first-order dependency on the polymerization reactions and utilizes only one active site as the initiating group. The molecular weights of the polymers produced range from 1982 g mol−1 to 14 568 g mol−1 and exhibited relatively broad molecular weight distributions associated with transesterification reactions.

Graphical abstract: Structural and kinetic studies of the polymerization reactions of ε-caprolactone catalyzed by (pyrazol-1-ylmethyl)pyridine Cu(ii) and Zn(ii) complexes

Back to tab navigation

Supplementary files

Publication details

The article was received on 22 May 2013, accepted on 04 Jun 2013 and first published on 17 Jun 2013


Article type: Paper
DOI: 10.1039/C3DT51338F
Citation: Dalton Trans., 2013,42, 10735-10745
  •   Request permissions

    Structural and kinetic studies of the polymerization reactions of ε-caprolactone catalyzed by (pyrazol-1-ylmethyl)pyridine Cu(II) and Zn(II) complexes

    S. O. Ojwach, T. T. Okemwa, N. W. Attandoh and B. Omondi, Dalton Trans., 2013, 42, 10735
    DOI: 10.1039/C3DT51338F

Search articles by author

Spotlight

Advertisements