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Bio-Safe Synthesis of Linear and Branched PLLA
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.
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: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 48, no 5, 1214-1219 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic activities of Bi(III) acetate (Bi(OAc)(3)) and of creatinine towards the ring-opening polymerization of L-lactide have been compared with those of a stannous (II) ethylhexanoate ((SnOct)(2))-based system and with those of a system catalyzed by enzymes. All four were suitable catalysts for the synthesis of high and moderate molecular weight poly(L-lactide)s and the differences in reactivity and efficiency have been studied. Linear and branched poly(L-lactide)s were synthesized using these bio-safe initiators together with ethylene glycol, pentaerythritol, and myoinositol as coinitiators. The polymerizations were performed in bulk at 120 and 140 degrees C and different reactivities and molecular weights were achieved by adding different amounts of coinitiators. A molecular weight of 105,900 g/mol was achieved with 99% conversion in 5 h at 120 degrees C with a Bi(OAc)(3)-based system. This system was comparable to Sn(Oct)(2) at 140 degrees C. The reactivity of creatinine is lower than that of Bi(OAc)(3) but higher compared with enzymes lipase PS (Pseudomonas fluorescens). A ratio of Sn(Oct)(2) M-o/I-o 10,000:1 was needed to achieve a polymer with a reasonable low amount of tin residue in the precipitated polymer, and a system catalyzed by creatinine at 140 degrees C has a higher conversion rate than such a system.

Place, publisher, year, edition, pages
2010. Vol. 48, no 5, 1214-1219 p.
Keyword [en]
Bi(III) acetate, creatinine, initiator, polyester, ring-opening, polymerization, tin 2-ethylhexanoate, ring-opening polymerization, l-lactide, epsilon-caprolactone, porous, scaffolds, in-vitro, initiators, copolymers, bismuth, poly(epsilon-caprolactone), polylactones
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-19255DOI: 10.1002/pola.23884ISI: 000274942000024Scopus ID: 2-s2.0-76249099182OAI: oai:DiVA.org:kth-19255DiVA: diva2:337302
Funder
Swedish Research Council, 2008-5538
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically 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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