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Design of polyester and porous scaffolds
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-5850-8873
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The use of synthetic materials for tissue and organ reconstruction, i. e. tissue engineering, has become a promising alternative to current surgical therapies and may overcome the shortcomings of the methods in use today. The challenge is in the design and reproducible fabrication of biocompatible and bioresorbable polymers, with suitable surface chemistry, desirable mechanical properties, and the wanted degradation profile. These material properties can be achieved in various manners, including the synthesis of homo- and copolymers along with linear and star-shaped architectures. In many applications the materials’ three-dimensional structure is almost as important as its composition and porous scaffolds with high porosity and interconnected pores that facilitate the in-growth of cells and transportation of nutrients and metabolic waste is desired.

In this work linear and star-shaped polymers have been synthesized by ring-opening polymerization using a stannous-based catalyst and a spirocyclic tin initiator. A series of linear copolymers with various combinations of 1,5-dioxepane-2-one (DXO), Llactide (LLA) and ε-caprolactone (CL) have been polymerized using stannous octoate as catalyst. It is shown that the composition of the polymers can be chosen in such a manner that the materials’ mechanical and thermal properties can be predetermined. A solvent-casting and particulate leaching scaffold preparation technique has been developed and used to create three-dimensional structures with interconnected pores. The achieved physical properties of these materials’ should facilitate their use in both soft and hard tissue regeneration.

Well defined star-shaped polyesters have been synthesized using a spirocyclic tin initiator where L-lactide was chosen as a model system for the investigation of the polymerization kinetics. Neither the temperature nor the solvent affects the molecular weight or the molecular weight distribution of the star-shaped polymers, which all show a molecular weight distribution below 1.19 and a molecular weight determined by the initial monomer-to-initiator concentration.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 47 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:36
Keyword [en]
ring-opening polymerization, porous scaffold, L-lactide, 5-dioxepane-2-one, ε-caprolactone, spirocyclic initiator, star-shaped polyester
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-493ISBN: 91-7178-182-X (print)OAI: oai:DiVA.org:kth-493DiVA: diva2:14207
Presentation
2005-11-25, Salongen, KTHB, Osquara backe 31, Stockholm, 11:00
Opponent
Supervisors
Note
QC 20101217Available from: 2005-11-17 Created: 2005-11-17 Last updated: 2010-12-17Bibliographically approved
List of papers
1. Elastomeric hydrolyzable porous scaffolds: Copolymers of aliphatic polyesters and a polyether-ester
Open this publication in new window or tab >>Elastomeric hydrolyzable porous scaffolds: Copolymers of aliphatic polyesters and a polyether-ester
2005 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 6, no 5, 2718-2725 p.Article in journal (Refereed) Published
Abstract [en]

Porous scaffolds of 1,5-dioxepan-2-one (DXO), L-lactide (LLA), and epsilon-caprolactone (CL) were prepared by a solvent casting, salt particulate leaching technique in which the composites were detached from their mold using a novel methanol swelling procedure. By incorporating DXO segments into polymers containing LLA or CL, an increase in hydrophilicity is achieved, and incorporating soft amorphous domains in the crystalline sections enables tailoring of the mechanical properties. The porosities of the scaffolds ranged from 89.2% to 94.6%, and the pores were shown to be interconnected. The materials were synthesized by bulk copolymerization of 1,5-dioxepan-2-one (DXO), L-lactide (LLA), and epsilon-caprolactone (CL) using stannous 2-ethylhexanoate as catalyst. The copolymers formed varied in structure; poly(DXO-co-CL) is random in its arrangement, whereas poly(DXO-co-LLA) and poly(LLA-co-CL) are more blocky in their structures.

Keyword
biodegradable polymeric scaffolds, epsilon-caprolactone, l-lactide, mechanical-properties, phase-separation, 1, 5-dioxepan-2-one, degradation, poly(epsilon-caprolactone), poly(l-lactide), polylactones
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-14414 (URN)10.1021/bm050190b (DOI)000231899200042 ()2-s2.0-25844458172 (Scopus ID)
Note
QC 20100805Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-12-17Bibliographically approved
2. Versatile and controlled synthesis of resorbable star-shaped polymers using a spirocyclic tin initiator: Reaction optimization and kinetics
Open this publication in new window or tab >>Versatile and controlled synthesis of resorbable star-shaped polymers using a spirocyclic tin initiator: Reaction optimization and kinetics
2006 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 44, no 1, 596-605 p.Article in journal (Refereed) Published
Abstract [en]

A spirocyclic tin initiator was synthesized from pentaerythritol ethoxylate and dibutyltin oxide and used to polymerize L-lactide with dichloromethane, chloroform, toluene, and chlorobenzene as solvents. The reactions were performed at different temperatures and it is concluded that neither the temperature nor the solvent affects the molecular weight or the molecular weight distribution of the star-shaped polymers. The reaction rate was significantly increased by raising the reaction temperature or choosing a solvent with a low dielectric constant. All polymers showed a molecular-weight distribution below 1.19 and a molecular-weight determined by the initial monomer to initiator concentration ([M](0)/[1]). No induction period was seen for the polymerizations. They were all first order in initiator and the degree of aggregation in toluene at 110 degrees C was found to be 4/5. The glass transition temperature and the melting temperature of the star-shaped polymers increase with increasing arm length.

Keyword
narrow molecular-weight distribution, poly(L-lactide), polymerization kinetics, spirocyclic tin initiator, star-shaped architecture
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-8048 (URN)10.1002/pola.21192 (DOI)000234091800058 ()2-s2.0-30344470475 (Scopus ID)
Note
QC 20100901Available from: 2008-03-03 Created: 2008-03-03 Last updated: 2010-09-01Bibliographically approved

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