Macromolecular engineering of polylactones and polylactides. 4. Mechanism and kinetics of lactide homopolymerization by aluminum isopropoxide

Dubois, Philippe; Jacobs, Christian; Jérôme, Robert; Teyssié, Philippe

doi:10.1021/ma00009a022

Cited by 487 publications

(320 citation statements)

References 6 publications

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“…The PLLA by-product formed in solution during the surface-initiated ring-opening polymerization reaction was analyzed via size exclusion chromatography and found to have a molecular weight of approximately 9434 g/mol with a polydispersity of 1.13. This poly dispersity value is indicative of a well-controlled polymerization reaction [71,72]. The determined average molecular weight also fits well with estimates from our previous work, which used TGA to estimate the average molecular weight of the surface-bound polymer produced on the pSi film at approximately 10,000 g/mol [38].…”

Section: Resultssupporting

confidence: 86%

Controlled Drug Delivery From Composites of Nanostructured Porous Silicon and Poly( L -Lactide)

et al. 2012

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Aims: Porous silicon (pSi) and poly(L-lactide) (PLLA) both display good biocompatibility and tunable degradation behavior, suggesting that composites of both materials are suitable candidates as biomaterials for localized drug delivery into the human body. The combination of a pliable and soft polymeric material with a hard inorganic porous material of high drug loading capacity may engender improved control over degradation and drug release profiles and be beneficial for the preparation of advanced drug delivery devices and biodegradable implants or scaffolds. Materials & methods: In this work, three different pSi and PLLA composite formats were prepared. The first format involved grafting PLLA from pSi films via surface-initiated ring-opening polymerization (pSi–PLLA [grafted]). The second format involved spin coating a PLLA solution onto oxidized pSi films (pSi–PLLA [spin-coated]) and the third format consisted of a melt-cast PLLA monolith containing dispersed pSi microparticles (pSi–PLLA [monoliths]). The surface characterization of these composites was performed via infrared spectroscopy, scanning electron microscopy, atomic force microscopy and water contact angle measurements. The composite materials were loaded with a model cytotoxic drug, camptothecin (CPT). Drug release from the composites was monitored via fluorimetry and the release profiles of CPT showed distinct characteristics for each of the composites studied. Results: In some cases, controlled CPT release was observed for more than 5 days. The PLLA spin coat on pSi and the PLLA monolith containing pSi microparticles both released a CPT payload in accordance with the Higuchi and Ritger–Peppas release models. Composite materials were also brought into contact with human lens epithelial cells to determine the extent of cytotoxicity. Conclusion: We observed that all the CPT containing materials were highly efficient at releasing bioactive CPT, based on the cytotoxicity data. Original submitted 16 December 2010; Revised submitted 29 September 2011; Published online 6 March 2012

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Section: Resultssupporting

confidence: 86%

Controlled Drug Delivery From Composites of Nanostructured Porous Silicon and Poly( L -Lactide)

et al. 2012

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“…Zhang et al 68,69 reported similar observations with aluminum complexes of functionalized phenolate ligands, which he interpreted to arise from higher reaction temperatures resulting in transesterification. [70][71][72] However, it could also be that when 4 and 5 are used, initiation proceeds via acid-initiation (HCl generated in situ from adventitious water) and this reaction is more uncontrolled than in reactions catalyzed by an Al-alkyl/alcohol system. Another possibility is that the reaction may be proceeding via a reaction pathway involving insertion of the monomer into the Al-Cl bond.…”

Section: Ring-opening Polymerization Of ε-Caprolactonementioning

confidence: 99%

Aluminum Methyl and Chloro Complexes Bearing Monoanionic Aminephenolate Ligands: Synthesis, Characterization, and Use in Polymerizations

et al. 2012

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Abstract:A series of aluminum methyl and chloride complexes bearing 2(N-piperazinyl-N′-methyl)-2-methylene-4-R′-6-R-phenolate or 2(N-morpholinyl)-2-methylene-4-R′-6-R-phenolate ([ONE R1,R2 ]-) {[ R 1 = t Bu, R 2 = Me, E = NMe (L1); R 1 = R 2 = t Bu, E = NMe (L2); R 1 = R 2 = t Bu, 1 E = O (L3)} ligands were synthesized and characterized through elemental analysis, 1 H, 13 The catalytic activity of complexes 1-3 toward ring-opening polymerization (ROP) of ε-caprolactone was assessed. These complexes are more active than analogous Zn complexes for this reaction but less active than the Zn analogs for ROP of rac-lactide. Characteristics of the polymer as well as polymerization kinetics and mechanism were studied. Polymer end-group analyses were achieved using 1 H NMR spectroscopy and MALDI-TOF MS. Eyring analyses were performed and the activation energies for the reactions were determined, which were significantly lower for 1 and 2 compared with 3. This could be for several reasons: (1) the methylamine (NMe) group of 1 and 2, which is a stronger base than the ether (O) group of 3, might activate the incoming monomer via non-covalent interactions, and/or (2) the ether group is able to temporarily coordinate to the metal center and blocks the vacant coordination site towards incoming monomer, whilst the amine cannot do this. Preliminary studies using 4 and 5 towards copolymerization of cyclohexene oxide with carbon dioxide have been performed. 4 was inactive and 5 afforded polyethercarbonate (66.7% epoxide conversion, polymer contains 54.0% carbonate linkages).

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“…From the integration of the peaks, c. 1% of cyclics contaminate the lower-polydispersity sample (M w /M n = 1.15) compared to c. 2% for the second sample (M w /M n = 1.30). It is known that the growth of polylactide chains initiated by Al(O i Pr) 3 is limited by competing transesterification reactions [15]. These side reactions also occur, even at low temperature, in case of the homopolymerization of DHO2.…”

Section: Resultsmentioning

confidence: 99%

Novel unsaturated ε-caprolactone polymerizable by ringopening and ring-opening metathesis mechanisms

et al. 2002

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Ring-opening polymerization (ROP) and ring-opening metathesis polymerization (ROMP) of an unsaturated ε-caprolactone, 6,7-dihydro-2(3H)-oxepinone (DHO2), are alternative routes to produce unsaturated aliphatic polyesters with the same molecular structure. Polymerization of DHO2 initiated by Al isopropoxide in toluene at room temperature or at 0°C proceeds by a coordination-insertion mechanism, although intramolecular transesterification takes place beyond complete monomer conversion. The molecular weight distribution is narrow as long as monomer conversion does not exceed 90%. Ring-opening metathesis polymerization of DHO2 initiated by Schrock's Mo-based catalyst, 1, at 60°C allows higher molecular weight unsaturated polyester to be prepared, even though an intramolecular side reaction also operates. The structure of poly(DHO2) synthesized by ROP and ROMP is the same, as confirmed by 1 H, 13 C NMR, and FT-IR spectra. Copolymers of DHO2 with norbornene, cis-cyclooctene, and 1,5-cyclooctadiene have been successfully prepared.

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Macromolecular engineering of polylactones and polylactides. 4. Mechanism and kinetics of lactide homopolymerization by aluminum isopropoxide

Cited by 487 publications

References 6 publications

Controlled Drug Delivery From Composites of Nanostructured Porous Silicon and Poly( L -Lactide)

Controlled Drug Delivery From Composites of Nanostructured Porous Silicon and Poly( L -Lactide)

Aluminum Methyl and Chloro Complexes Bearing Monoanionic Aminephenolate Ligands: Synthesis, Characterization, and Use in Polymerizations

Novel unsaturated ε-caprolactone polymerizable by ringopening and ring-opening metathesis mechanisms

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