Synthesis of Biomedical Polymers and Scaffold Design
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
This work has focused on the development of new improved synthesis methods of biodegradable aliphatic polymers and on the preparation of porous scaffolds for tissue engineering applications. The aim of the first part of the work was the synthesis of poly(p-dioxanone) (PPDX) homopolymers with high molecular weights using the cyclic tin alkoxide initiator 1-di-n-butyl-1-stanna-2,5-dioxacyclopentane. PPDX is a polymer with both mechanical properties and a degradation rate suitable for many biomedical applications. The polymerizations were carried out in bulk and the results were compared with polymerizations using tin (II) 2-ethylhexanoate (stannous octoate, Sn(Oct)2), a co-initiator which has previously been found effective in the polymerization of p-dioxanone (PDX). The hypothesis of this work was that the cyclic tin alkoxide initiator would bring several benefits to the synthesis of PPDX. It has been shown to catalyze low amounts of transesterfication reactions and materials with very low amounts of tin residues have been synthesized using an efficient purification technique. Our work demonstrated that the cyclic tin alkoxide initiator is indeed a promising alternative in the synthesis of PPDX with high inherent viscosities. Under the appropriate reaction conditions, PPDX polymers with inherent viscosities over, or around, 1 dL/g were synthesized. One of the most interesting materials made had an inherent viscosity of 1.16 dL/g, a strain-at-break of 515 %, a stress-at-break of 43 MPa, and was synthesized using the cyclic tin alkoxide initiator.
As a second part of this work, copolymers of L-lactide (LLA) and trimethylene carbonate (TMC) were synthesized using either Sn(Oct)2 with ethylene glycol or the cyclic tin alkoxide initiator 1-di-n-butyl-1-stanna-2,5-dioxacyclopentane. The copolymers, which had molecular weights ranging from close to 60 000 g/mol to over 300 000 g/mol, were composed of 12 to 55 molar percentages of TMC and 88 to 45 molar percentages of LLA. The copolymers were evaluated as porous scaffold materials intended for tissue engineering, using a combined phase separation and particulate leaching technique, in which sugar templates were used as the leachable porogens. The aim of this part of the work was to develop a simple and effective method for preparing scaffolds with high porosities and well interconnected pores and to overcome problems with formation of a solid surface side and limitations in scaffold thickness. The preparation method was successfully used on several copolymers. Differences in molecular weights, molar compositions and degrees of crystallinity were all factors which influenced the properties of the prepared scaffolds. Copolymers with TMC contents of up to 55 % were successfully used in the preparation of scaffolds. The results indicated however that materials with lower TMC contents and higher degrees of crystallinity in many cases were better suited for the combined phase separation and particulate leaching technique used.
Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , 42 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2008:74
ring-opening polymerization, tin alkoxide initiator, stannous octoate, poly(p-dioxanone), copolymer, L-lactide, trimethylene carbonate, degradable porous scaffold
IdentifiersURN: urn:nbn:se:kth:diva-9674ISBN: 978-91-7415-185-5OAI: oai:DiVA.org:kth-9674DiVA: diva2:126939
2008-12-11, K1, Teknikringen 56, 100 44, Stockholm, KTH, 09:15 (English)
Albertsson, Ann-Christine, Professor
QC 201011252008-11-282008-11-262010-11-25Bibliographically approved
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