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Stereoselective homo- and co-polymerization of lactides and ε-caprolactone catalysed by highly active racemic zinc(II) pyridyl complexes

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Abstract

A series of Zn(II) chlorido complexes (1′–5′) supported by N,N′-bidentate N-(pyridin-2-ylethyl)amine ligands have been synthesized. Zn(II) alkyl and alkoxy complexes 1′-Me–5′-Me and 1′-OBn–5′-OBn were synthesized in situ by first reacting complexes 1′–5′ with methyl lithium and subsequently with benzyl alcohol. Both species 1′-Me–5′-Me and 1′-OBn–5′-OBn showed excellent catalytic activity in ring-opening polymerization (ROP) of cyclic esters with the alkoxyl species performing better. The ROP reactions exhibited pseudo-first-order kinetics with respect to monomer concentration. Polymer molecular weights increased as ligand steric hindrance decreased and they lie between 3096 and 8837 g mol−1 and relatively high molecular weight distributions with dispersity (Ð) values ca. 2 were observed. The poly(rac-lactide) polymers were predominantly heterotactic, while poly(ʟ-lactides) formed were largely isotactic. All polymerization reactions proceeded through coordination insertion mechanism followed by hydrolysis of the metal. Notably, the stereogenic centres of the ligand skeleton influenced control of polymer stereochemistry. Random copolymerization of ε-caprolactone (ε-CL) and lactides (LA) resulted in block gradient copolymers. The sequential addition of lactides after ε-CL gave diblock PCL-b-PLA, and reversing monomer addition did not form any copolymer.

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References

  1. Hong S, Min K-D, Nam B-U, Park OO (2016) High molecular weight bio furan-based co-polyesters for food packaging applications: synthesis, characterization and solid-state polymerization. Green Chem 18(19):5142–5150

    Article  CAS  Google Scholar 

  2. Surnar B, Sharma K, Jayakannan M (2015) Core-shell polymer nanoparticles for prevention of GSH drug detoxification and cisplatin delivery to breast cancer cells. Nanoscale 7(42):17964–17979

    Article  CAS  PubMed  Google Scholar 

  3. Samuel R, Girard E, Chagnon G, Dejean S, Favier D, Coudane J, Nottelet B (2015) Radiopaque poly(ε-caprolactone) as additive for X-ray imaging of temporary implantable medical devices. RSC Adv 5(102):84125–84133

    Article  CAS  Google Scholar 

  4. Akpan ED, Ojwach SO, Omondi B, Nyamori VO (2016) Structural and kinetic studies of the ring-opening polymerization of cyclic esters using N, N′ diarylformamidines Zn(II) complexes. Polyhedron 110:63–72

    Article  CAS  Google Scholar 

  5. Keram M, Ma H (2017) Ring-opening polymerization of lactide, ε-caprolactone and their copolymerization catalyzed by β-diketiminate zinc complexes. Appl Organomet Chem 31(12):e3893–e3908

    Article  CAS  Google Scholar 

  6. Munzeiwa WA, Omondi B, Nyamori VO (2017) Synthesis and polymerization kinetics of ε-caprolactone and ʟ-lactide to low molecular weight polyesters catalyzed by Zn(II) and Cu(II) N-hydroxy-N, N′-diarylformamidine complexes. Polyhedron 138:295–305

    Article  CAS  Google Scholar 

  7. Zhang J, Xiong J, Sun Y, Tang N, Wu J (2014) Highly iso-selective and active catalysts of sodium and potassium monophenoxides capped by a crown ether for the ring-opening polymerization of rac-lactide. Macromolecules 47(22):7789–7796

    Article  CAS  Google Scholar 

  8. Chen H-Y, Mialon L, Abboud KA, Miller SA (2012) Comparative study of lactide polymerization with lithium, sodium, magnesium, and calcium complexes of BHT. Organometallics 31(15):5252–5261

    Article  CAS  Google Scholar 

  9. Bouyhayi M, Sarazin Y, Casagrande OL, Carpentier J-F (2012) Aluminum, calcium and zinc complexes supported by potentially tridentate iminophenolate ligands: synthesis and use in the ring-opening polymerization of lactide. Appl Organomet Chem 26(12):681–688

    Article  CAS  Google Scholar 

  10. Bhunora S, Mugo J, Bhaw-Luximon A, Mapolie S, Van Wyk J, Darkwa J, Nordlander E (2011) The use of Cu and Zn salicylaldimine complexes as catalyst precursors in ring opening polymerization of lactides: ligand effects on polymer characteristics. Appl Organomet Chem 25(2):133–145

    Article  CAS  Google Scholar 

  11. Kirubakaran B, Beesam R, Nareddula DR (2017) Zinc(II) complexes of triaza and amidinate ligands: Efficient initiators for the ring-opening polymerization of ε-caprolactone and rac-lactide. Appl Organomet Chem 31(12):e3833

    Article  CAS  Google Scholar 

  12. Munzeiwa WA, Nyamori VO, Omondi B (2018) Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring-opening polymerization of cyclic esters. Appl. Organomet. Chem. 32(4):e4247

    Article  CAS  Google Scholar 

  13. Stolt M, Södergård A (1999) Use of monocarboxylic iron derivatives in the ring-opening polymerization of L-lactide. Macromolecules 32(20):6412–6417

    Article  CAS  Google Scholar 

  14. Biernesser AB, Li B, Byers JA (2013) Redox-controlled polymerization of pactide catalyzed by bis(imino)pyridine iron bis(alkoxide) complexes. J Am Chem Soc 135(44):16553–16560

    Article  CAS  PubMed  Google Scholar 

  15. Lamberti M, Botta A, Mazzeo M (2014) Ring-opening polymerization of cyclic esters by pincer complexes derived from alkaline earth metals. Appl Organomet Chem 28(3):140–145

    Article  CAS  Google Scholar 

  16. Basiak D, Dobrzycki Ł, Socha P, Rzepiński P, Plichta A, Bujnowski K, Synoradzki L, Orłowska N, Ziemkowska W (2017) Aminophenolates of aluminium, gallium and zinc: synthesis, characterization and polymerization activity. Appl Organomet Chem 31(11):e3748

    Article  CAS  Google Scholar 

  17. Tai W-J, Li C-Y, Lin P-H, Li J-Y, Chen M-J, Ko B-T (2012) Synthesis and characterization of aluminum complexes based on amino-benzotriazole phenoxide ligand: luminescent properties and catalysis for ring-opening polymerization. Appl Organomet Chem 26(10):518–527

    Article  CAS  Google Scholar 

  18. Qian F, Liu K, Ma H (2010) Amidinate aluminium complexes: synthesis, characterization and ring-opening polymerization of rac-lactide. Dalton Trans 39(34):8071–8083

    Article  CAS  PubMed  Google Scholar 

  19. Pensec S, Leroy M, Akkouche H, Spassky N (2000) Stereocomplex formation in enantiomeric diblock and triblock copolymers of poly (ɛ-caprolactone) and polylactide. Polym Bull 45(4):373–380

    Article  CAS  Google Scholar 

  20. Spassky N, Wisniewski M, Pluta C, Le Borgne A (1996) Highly stereoelective polymerization of rac-(D, L)-lactide with a chiral schiff’s base/aluminium alkoxide initiator. Macromol Chem Phys 197(9):2627–2637

    Article  CAS  Google Scholar 

  21. Ovitt TM, Coates GW (2002) Stereochemistry of lactide polymerization with chiral catalysts: new opportunities for stereocontrol using polymer exchange mechanisms. J Am Chem Soc 124(7):1316–1326

    Article  CAS  PubMed  Google Scholar 

  22. Cho J, Nayab S, Jeong JH (2016) Stereoselective polymerisation of rac-lactide catalysed by Cu(II) complexes bearing chloro derivatives of N, N′-bis(benzyl)dimethyl-(R, R)-1,2-diaminocyclohexane. Polyhedron 113:81–87

    Article  CAS  Google Scholar 

  23. Radano CP, Baker GL, Smith MR (2000) stereoselective polymerization of a racemic monomer with a racemic catalyst: direct preparation of the polylactic acid stereocomplex from racemic lactide. J Am Chem Soc 122(7):1552–1553

    Article  CAS  Google Scholar 

  24. Chisholm MH, Delbridge EE (2001) Ring-opening of lactides and related cyclic monomers by triaryltin(IV) alkoxides and amides. Chem Commun 2001:1308–1309

    Article  CAS  Google Scholar 

  25. Dove AP, Gibson VC, Marshall EL, Rzepa HS, White AJP, Williams DJ (2006) Synthetic, structural, mechanistic, and computational studies on single-Site β-diketiminate tin(II) initiators for the polymerization of rac-lactide. J Am Chem Soc 128(30):9834–9843

    Article  CAS  PubMed  Google Scholar 

  26. Nomura N, Ishii R, Akakura M, Aoi K (2002) Stereoselective ring-opening polymerization of racemic lactide using aluminum-achiral ligand complexes: Exploration of a chain-end control mechanism. J Am Chem Soc 124(21):5938–5939

    Article  CAS  PubMed  Google Scholar 

  27. Drumright RE, Gruber PR, Henton DE (2000) Polylactic acid technology. Adv Mater 12(23):1841–1846

    Article  CAS  Google Scholar 

  28. Webster RL (2014) Random copolymerisations catalysed by simple titanium α-amino acid complexes. RSC Adv 4(10):5254–5260

    Article  CAS  Google Scholar 

  29. Sun Z, Duan R, Yang J, Zhang H, Li S, Pang X, Chen W, Chen X (2016) Bimetallic Schiff base complexes for stereoselective polymerisation of racemic-lactide and copolymerisation of racemic-lactide with ε-caprolactone. RSC Adv 6(21):17531–17538

    Article  CAS  Google Scholar 

  30. Lin L, Xu Y, Wang S, Xiao M, Meng Y (2016) Ring-opening polymerization of l-lactide and ε-caprolactone catalyzed by versatile tri-zinc complex: Synthesis of biodegradable polyester with gradient sequence structure. Eur Polym J 74:109–119

    Article  CAS  Google Scholar 

  31. Bruker (ed.), (2009) APEXII, APEXII Bruker AXS Inc, Madison, Wisconsin, USA

  32. Bruker (2009) SAINT, SAINT Bruker AXS Inc, Madison, Wisconsin, USA

  33. Bruker (2009) SADABS. Bruker SADABS Bruker AXS Inc, Madison, Wisconsin, USA

  34. Sheldrick G (2008) Shelx. Acta Crystallogr Sect A Found Crystallogr 64:112–122

    Article  CAS  Google Scholar 

  35. Dolomanov OV, Bourhis LJ, Gildea RJ, Howard JAK, Puschmann H (2009) Olex: a complete structure solution, refinement and analysis program. Appl Crystallogr 42:339–341

    Article  CAS  Google Scholar 

  36. Dong Y-W, Fan R-Q, Chen W, Zhang H-J, Song Y, Du X, Wang P, Wei L-G, Yang Y-L (2016) Luminescence properties of a Zn(II) supramolecular framework: easily tunable optical properties by variation of the alkyl substitution of (E)-N-(pyridine-2-ylethylidyne)arylamine ligands. RSC Adv 6(111):110422–110432

    Article  CAS  Google Scholar 

  37. Basu Baul TS, Kundu S, Linden A, Raviprakash N, Manna SK, Guedes da Silva MFC (2014) Synthesis and characterization of some water soluble Zn(II) complexes with (E)-N-(pyridin-2-ylmethylene)arylamines that regulate tumour cell death by interacting with DNA. Dalton Trans 43(3):1191–1202

    Article  CAS  PubMed  Google Scholar 

  38. Alonso-Moreno C, Garcés A, Sánchez-Barba LF, Fajardo M, Fernández-Baeza J, Otero A, Lara-Sánchez A, Antiñolo A, Broomfield L, López-Solera MI, Rodríguez AM (2008) Discrete heteroscorpionate lithium and zinc alkyl complexes: synthesis, structural studies, and ROP of cyclic esters. Organometallics 27(6):1310–1321

    Article  CAS  Google Scholar 

  39. Li J, Deng Y, Jie S, Li B-G (2015) Zinc complexes supported by (benzimidazolyl)pyridine alcohol ligands as highly efficient initiators for ring-opening polymerization of ε-caprolactone. J Organomet Chem 797:76–82

    Article  CAS  Google Scholar 

  40. Ahn SH, Chun MK, Kim E, Jeong JH, Nayab S, Lee H (2017) Copper(II) complexes containing N, N′-bidentate N-substituted N-(pyridin-2-ylmethyl)amine: synthesis, structure and application towards polymerisation of rac-lactide. Polyhedron 127:51–58

    Article  CAS  Google Scholar 

  41. Zheng X-X, Zhang C, Wang Z-X (2015) Synthesis and characterization of zinc complexes supported by NHC-based CNN- and CNP-tridentate ligands and their catalysis in the ring-opening polymerization of rac-lactide and ε-caprolactone. J Organomet Chem 783:105–115

    Article  CAS  Google Scholar 

  42. Nayab S, Lee H, Jeong JH (2011) Synthesis and X-ray crystal structure of dichloro[S-1-phenyl-N-(S-pyrrolidin-2-ylmethyl)ethanamine]zinc(II) and its catalytic application to rac-lactide polymerization. Polyhedron 30(2):405–409

    Article  CAS  Google Scholar 

  43. Nayab S, Lee H, Jeong JH (2012) Synthesis and structural characterization of a dichloro zinc complex of N, N′-bis-(2,6-dichloro-benzyl)-(R, R)-1,2-diaminocyclohexane: application to ring opening polymerization of rac-lactide. Polyhedron 31(1):682–687

    Article  CAS  Google Scholar 

  44. Balke ST, Cheng HN (1991) Modern methods of polymer characterization. In: HGM Barth (ed.), Wiley-Interscience, New York, Characterization of complex polymers by size exclusion chromatography and high-performance liquid chromatography pp. 10–30

  45. Steudel R, Steudel Y (2006) Geometries, thermodynamic properties and reactions of methylzinc alkoxide clusters studied by density functional theory calculations. J Phys Chem A 110(28):8912–8924

    Article  CAS  PubMed  Google Scholar 

  46. Hormnirun P, Marshall EL, Gibson VC, Pugh RI, White AJP (2006) Study of ligand substituent effects on the rate and stereoselectivity of lactide polymerization using aluminum salen-type initiators. Proc Natl Acad Sci 103(42):15343–15348

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  47. Rezayee NM, Gerling KA, Rheingold AL, Fritsch JM (2013) Synthesis and structures of tridentate ketoiminate zinc complexes bearing trifluoromethyl substituents that act as L-lactide ring opening polymerization initiators. Dalton Trans 42(15):5573–5586

    Article  CAS  PubMed  Google Scholar 

  48. Yang J, Sun Z, Duan R, Li L, Pang X, Chen X (2016) Copolymer of lactide and ε-caprolactone catalyzed by bimetallic Schiff base aluminum complexes. Sci China Chem 59(11):1384–1389

    Article  CAS  Google Scholar 

  49. Kan C, Ma H (2016) Copolymerization of l-lactide and ε-caprolactone catalyzed by mono-and dinuclear salen aluminum complexes bearing bulky 6,6’-dimethylbipheyl-bridge: random and tapered copolymer. RSC Adv 6(53):47402–47409

    Article  CAS  Google Scholar 

  50. Ghosh S, Spannenberg A, Mejía E (2017) Cubane-type polynuclear zinc complexes containing tridentate Schiff base ligands: synthesis, characterization, and ring-opening polymerization ptudies of rac-Lactide and ε-caprolactone. Helv Chim Acta 100(11):e1700176

    Article  CAS  Google Scholar 

  51. Della Monica F, Luciano E, Buonerba A, Grassi A, Milione S, Capacchione C (2014) Poly(lactide-co-ε-caprolactone) copolymers prepared using bis-thioetherphenolate group 4 metal complexes: synthesis, characterization and morphology. RSC Adv 4(93):51262–51267

    Article  CAS  Google Scholar 

  52. Gilmour DJ, Webster RL, Perry MR, Schafer LL (2015) Titanium pyridonates for the homo- and copolymerization of rac-lactide and ε-caprolactone. Dalton Trans 44(27):12411–12419

    Article  CAS  PubMed  Google Scholar 

  53. Keram M, Ma H (2017) Ring-opening polymerization of lactide, ε-caprolactone and their copolymerization catalyzed by β-diketiminate zinc complexes. Appl Organomet Chem 31:e3893–e3908

    Article  CAS  Google Scholar 

  54. Honrado M, Otero A, Fernández-Baeza J, Sánchez-Barba LF, Garcés A, Lara-Sánchez A, Martínez-Ferrer J, Sobrino S, Rodríguez AM (2015) New racemic and single enantiopure hybrid scorpionate/cyclopentadienyl magnesium and zinc initiators for the stereoselective ROP of lactides. Organometallics 34(13):3196–3208

    Article  CAS  Google Scholar 

  55. Wang H, Yang Y, Ma H (2014) Stereoselectivity switch between zinc and magnesium initiators in the polymerization of rac-lactide: Different coordination chemistry, different stereocontrol mechanisms. Macromolecules 47(22):7750–7764

    Article  CAS  Google Scholar 

  56. Kasperczyk JE (1999) HETCOR NMR study of poly(rac-lactide) and poly(meso-lactide). Polymer 40:5455–5458

    Article  CAS  Google Scholar 

  57. Honrado M, Otero A, Fernández-Baeza J, Sánchez-Barba LF, Garcés A, Lara-Sánchez A, Rodríguez AM (2016) Copolymerization of cyclic esters controlled by chiral NNO-scorpionate zinc initiators. Organometallics 35(2):189–197

    Article  CAS  Google Scholar 

  58. Nomura N, Akita A, Ishii R, Mizuno M (2010) Random copolymerization of ε-caprolactone with lactide using a nomosalen−Al complex. J Am Chem Soc 132(6):1750–1751

    Article  CAS  PubMed  Google Scholar 

  59. Li G, Lamberti M, Pappalardo D, Pellecchia C (2012) Random copolymerization of ε-caprolactone and lactides promoted by pyrrolylpyridylamido aluminum complexes. Macromolecules 45(21):8614–8620

    Article  CAS  Google Scholar 

  60. Kasperczyk J, Bero M (1991) Coordination polymerization of lactides, 2: Microstructure determination of poly[(L, L-lactide)-co-(ε-caprolactone)] with 13C nuclear magnetic resonance spectroscopy. Makromol Chem 192(8):1777–1787

    Article  CAS  Google Scholar 

  61. Kasperczyk J, Bero M (1993) Coordination polymerization of lactides, 4: The role of transesterification in the copolymerization of L, L-lactide and ε-caprolactone. Makromol Chem 194(3):913–925

    Article  CAS  Google Scholar 

  62. Qian H, Wohl AR, Crow JT, Macosko CW, Hoye TR (2011) A strategy for control of “random” copolymerization of lactide and glycolide: application to synthesis of PEG-b-PLGA block polymers having narrow dispersity. Macromolecules 44(18):7132–7140

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  63. Huang Y, Wang W, Lin C-C, Blake MP, Clark L, Schwarz AD, Mountford P (2013) Potassium, zinc, and magnesium complexes of a bulky OOO-tridentate bis(phenolate) ligand: synthesis, structures, and studies of cyclic ester polymerisation. Dalton Trans 42(25):9313–9324

    Article  CAS  PubMed  Google Scholar 

  64. Ajellal N, Carpentier J-F, Guillaume C, Guillaume SM, Helou M, Poirier V, Sarazin Y, Trifonov A (2010) Metal-catalyzed immortal ring-opening polymerization of lactones, lactides and cyclic carbonates. Dalton Trans 39(36):8363–8376

    Article  CAS  PubMed  Google Scholar 

  65. Li D, Peng Y, Geng C, Liu K, Kong D (2013) Well-controlled ring-opening polymerization of cyclic esters initiated by dialkylaluminum β-diketiminates. Dalton Trans 42(31):11295–11303

    Article  CAS  PubMed  Google Scholar 

  66. Yu T-L, Wu C-C, Chen C-C, Huang B-H, Wu J, Lin C-C (2005) Catalysts for the ring-opening polymerization of ε-caprolactone and l-lactide and the mechanistic study. Polymer 46(16):5909–5917

    Article  CAS  Google Scholar 

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Acknowledgements

The authors acknowledge University of KwaZulu-Natal (UKZN), National Research Foundation (NRF), South Africa, and German Academic Exchange Service (DAAD) for financial support.

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Funding was provided by Deutscher Akademischer Austausch Dienst Kairo, A/13/94655/91560116, Wisdom Archford Munzeiwa.

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  1. School of Chemistry and Physics, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban, 4000, South Africa

    Wisdom A. Munzeiwa & Vincent O. Nyamori

  2. Chemistry Department, Bindura University of Science Education, Private Bag 1020, Bindura, Zimbabwe

    Wisdom A. Munzeiwa

  3. School of Chemistry and Physics, University of KwaZulu-Natal, Private Bag X01, Pietermaritzburg Campus Scottsville, Pietermaritzburg, 3201, South Africa

    Bernard Omondi

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Munzeiwa, W.A., Nyamori, V.O. & Omondi, B. Stereoselective homo- and co-polymerization of lactides and ε-caprolactone catalysed by highly active racemic zinc(II) pyridyl complexes. Transit Met Chem 47, 93–111 (2022). https://doi.org/10.1007/s11243-022-00493-9

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