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The environmental influence in enzymatic polymerization of aliphatic polyesters in bulk and aqueous mini-emulsion
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.ORCID iD: 0000-0002-1922-128X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
2010 (English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 51, no 23, 5318-5322 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic effect of enzymes in different environments has been compared. Biodegradable polyesters and corresponding nanoparticles have been synthesized by an "eco-friendly" technique; enzyme-catalyzed ring-opening polymerization of lactones in bulk and in an aqueous mini-emulsion. Lipases from Burkholderia cepacia (lipase PS), B. cepacia immobilized on ceramic, Pseudomonas fluorescens and Candida Antarctica have been used as catalysts in the polymerization of L-Lactide (LLA), pentadecanolide (PDL) and hexadecanolide (HDL). The reaction conditions during the bulk polymerization of LLA were varied by adding different amounts of ethylene glycol at 100 degrees C or 125 degrees C. A number average molecular weight (M-n) of 78,100 was obtained when lipase PS was used at 125 degrees C. Lipase PS had a high catalytic activity in an aqueous environment with 100% conversion in 4 h, and the nanoparticles obtained from mini-emulsion polymerization were between 113 and 534 nm in size. The amount of hydrophobe affected the size of the PDL nanoparticles produced, less than the amount of surfactant in both systems.

Place, publisher, year, edition, pages
2010. Vol. 51, no 23, 5318-5322 p.
Keyword [en]
Enzyme, Ring-opening polymerization, Mini-emulsion
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-27052DOI: 10.1016/j.polymer.2010.09.016ISI: 000284029200006Scopus ID: 2-s2.0-77958161284OAI: oai:DiVA.org:kth-27052DiVA: diva2:377031
Note
QC 20101213Available from: 2010-12-13 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Macromolecular synthesis of functional degradable aliphatic polyesters and porous scaffold design
Open this publication in new window or tab >>Macromolecular synthesis of functional degradable aliphatic polyesters and porous scaffold design
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is an increasing demand for new materials in biomedical applications with material properties that are highly specific for each application area. The search for new materials requires the creation of materials with suitable mechanical properties, functionalities, three-dimensional structures and a controlled degradation profile. The focus of the work described in this thesis has been on the synthesis of functional degradable aliphatic polyesters, on the design of porous scaffolds and on their synthesis with bio-safe catalyst/initiator systems.  

An unsaturated aliphatic polyester has been synthesized by condensation polymerization to produce poly(but-2-ene-1,4-diyl malonate) (PBM), which was applicable as a cross-linked network and as a macro-co-initiator for the ring-opening polymerization (ROP) of cyclic ester monomers. The method of preparation of PBM was simple and straightforward and there was no need to purify the monomers or add a catalyst. PBM was successfully cross-linked with UV-radiation to form a transparent, colorless, flexible and strong film. When PBM was used as a macro-co-initiator, a triblock copolymer was formed with PBM middle blocks and poly(L-lactide) (PLLA) or poly(ε-caprolactone) side blocks. The ductility of the triblock copolymer of PLLA was greatly enhanced and the strength was maintained compared to the polymer obtained when PLLA was polymerized with ethylene glycol as co-initiator. The triblock copolymers were easily cross-linked to give materials with greater strength and higher modulus as a result. When these polymers were subjected to hydrolysis, a rapid initial hydrolysis of the amorphous PBM middle block changed the microstructure from triblock to diblock, with a significant reduction in ductility and number average molecular weight. Highly porous scaffolds were created from these functional materials and the mechanical properties were evaluated by a cyclic compression test under mimicked physiological conditions.

Copolymers of L-lactide (LLA) and ε-caprolactone (CL), trimethylene carbonate (TMC) or 1,5-dioxepane-2-one (DXO) have been synthesized with a low stannous-2-ethyl hexanoate  (Sn(Oct)2) ratio and used to fabricate porous tubular scaffolds. The tubes were designed to have a range of mechanical properties suitable for nerve regeneration, with different porosities and different numbers of layers in the tube wall. The adaptability of an immersion-coating and porogen-leaching technique was demonstrated by creating tubes with different dimensions.

Although a low amount of residual tin (monomer-to-initiator ratio of 10000:1) is accepted in biomedical applications, an efficient bio-safe catalyst/initiator system would be favored. The catalytic activities of bio-safe Bi (III) acetate and creatinine towards the ROP of LLA have been compared with those of Sn(Oct)2-based systems and with those of a system catalyzed by enzymes. All these systems were shown to be suitable catalysts for the synthesis of high and moderate molecular weight PLLAs.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 75 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:45
Keyword
functional polyesters, condensation polymerization, L-lactide, ε-caprolactone, triblock copolymer, mechanical properties, porous scaffolds, tissue engineering, ring-opening polymerization, Bi(III) acetate, creatinine, stannous 2-ethylhexanoate, enzyme, degradation products
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-38583 (URN)978-91-7501-060-1 (ISBN)
Public defence
2011-09-22, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20110901Available from: 2011-08-30 Created: 2011-08-29 Last updated: 2011-09-01Bibliographically approved

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Finne Wistrand, Anna

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