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Mapping the Characteristics of the Radical Ring-Opening Polymerization of a Cyclic Ketene Acetal Towards the Creation of a Functionalized Polyester
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-1922-128X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2009 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 47, no 18, 4587-4601 p.Article in journal (Refereed) Published
Abstract [en]

Radical ring-opening polymerization of cyclic ketene acetals is a means to achieve novel types of aliphatic polyesters. 2-methylene-1,3-dioxe-5-pene is a seven-membered cyclic ketene acetal containing an unsaturation in the 5-position in the ring structure. The double bond functionality enables further reactions subsequent to polymerization. The monomer 2-methylene-1,3-dioxe-5-pene was synthesized and polymerized in bulk by free radical polymerization at different temperatures, to determine the structure of the products and propose a reaction mechanism. The reaction mechanism is dependent on the reaction temperature. At higher temperatures, ring-opening takes place to a great extent followed by a new cyclization process to form the stable five-membered cyclic ester 3-vinyl-1,4-butyrolactone as the main reaction product. Thereby, propagation is suppressed and only small amounts of other oligomeric products are formed. At lower temperatures, the cyclic ester formation is reduced and oligomeric products containing both ring-opened and ring-retained repeating units are produced at higher yield.

Place, publisher, year, edition, pages
2009. Vol. 47, no 18, 4587-4601 p.
Keyword [en]
cyclic ketene acetal, polyester, radical polymerization, reaction mechanism, ring-opening polymerization
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-14418DOI: 10.1002/pola.23511ISI: 000269632500011Scopus ID: 2-s2.0-69549083370OAI: oai:DiVA.org:kth-14418DiVA: diva2:332442
Note
QC 20100805Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Design of Functional Degradable Aliphatic Polyesters and Porous Tissue Engineering Scaffolds
Open this publication in new window or tab >>Design of Functional Degradable Aliphatic Polyesters and Porous Tissue Engineering Scaffolds
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The regeneration of damaged tissues or organs using porous scaffolds which act as temporary guides for the patient’s own cells, i.e. tissue engineering, is a means to overcome the shortcomings of current standard medical treatments. The large number of tissue engineering applications and the high demands on materials make it necessary to design materials and scaffolds with innovative characteristics tailored to suit specific applications. The purpose of the work presented in this thesis was to design aliphatic polyester (co)polymers and porous scaffolds in order to tailor material and scaffold properties and to control the property changes induced by radiation sterilization.

Porous scaffolds were created, with an emphasis on tailoring the scaffolds thermal and mechanical properties. Stannous octoate was used in ring-opening polymerizations of L,L-lactide (LLA), ε-caprolactone (CL) and 1,5-dioxepane-2-one (DXO) to attain three copolymer types with a wide assortment of monomer compositions. A solvent casting and salt leaching scaffold fabrication technique was developed, and highly porous scaffolds possessing a range of predetermined properties were obtained.

Highly porous tubular scaffolds of different designs for use in nerve regeneration were developed using copolymers of LLA, CL, DXO or trimethylene carbonate (TMC) and a versatile immersion coating and porogen leaching technique.

Reactions induced by electron beam and gamma irradiation were used to finalize the scaffold properties. By changing the nature of the radiation, the radiation dose, the type of monomers, the monomer composition and the chain microstructure, it was possible to alter the susceptibility and the degradation mechanisms of the polymers. Predicted end-properties were obtainable and the sterilization procedure was incorporated as a final step in the scaffold fabrication.

The free radical ring-opening polymerization of the cyclic ketene acetal 2-methylene-1,3-dioxe-5-pene was developed, a reaction mechanism was proposed and the reaction products were characterized as a first step towards the creation of an innovative multifunctional aliphatic polyester. The reaction mechanism was shown to be temperature-dependent and propagation was inhibited by the formation of an allylic radical in the ring-opening step. The primary reaction product at higher temperatures was the cyclic ester 3-vinyl-1,4-butyrolactone. At lower temperatures, the main product was oligomers of ring-opened and ring-retained repeating units.

Abstract [sv]

Regenerering av skadade vävnader eller organ genom användning av porösa bionedbrytbara implantat som temporära byggnadsställningar för patientens egna celler är ett sätt att lösa de tillkortakommanden som finns i dagens medicinska behandlingsmetoder. De många möjliga applikationerna för vävnadsersättning och de höga krav som ställs på materialen skapar ett behov av nya material med innovativa egenskaper. I denna avhandling används design av alifatiska polyetrar och porösa strukturer för att skräddarsy deras egenskaper och för att kontrollera de förändringar i egenskaper som sker när materialet strålningssteriliseras.

Porösa strukturer tillverkades med fokus på design av deras materialegenskaper. Genom sampolymerisation av L,L-laktid (LLA), ε-kaprolakton (CL) och 1,5-dioxepan-2-on (DXO) med utvalda sammansättningar och monomerkombinationer kunde dessa skräddarsys. Porösa strukturer med hög porositet och ett stort register av förutbestämbara mekaniska och termiska egenskaper framställdes via en utvecklad saltlakningsteknik.

Porösa tuber för nervregenerering, med olika design, utvecklades genom användning av sampolymerer av LLA, CL, DXO eller trimetylenkarbonat (TMC) och en mångsidig stöpnings- och saltlakningsteknik.

Genom att utnyttja de reaktioner som uppstod i de polymera materialen vid sterilisering, med elektron- eller gammastrålning, erhölls förutbestämbara slutgiltiga egenskaper för de porösa strukturerna. Detta uppnåddes genom att skapa material som påverkas på ett specifikt sätt vid bestrålning. Genom att förändra strålningstyp, strålningsdos, monomerer och sammansättningar ändrades känsligheten mot strålning och de reaktionsmekanismer som inducerats. Steriliseringsprocessen blir härmed inkorporerad som ett sista steg i framställningen av de porösa strukturerna.

En fri radikal ringöppningspolymerisation utvecklades för monomeren 2-metylen-1,3-dioxe-5-pen. Reaktionsprodukterna bestämdes och en reaktionsmekanism föreslogs, som ett första steg i framställningen av en innovativ multifunktionell polyester. Reaktionsmekanismen är temperaturberoende och propagering är hämmad på grund av stabiliteten av den allylradikal som bildas vid ringöppning. Vid högre reaktionstemperaturer bildades den cykliska estern 3-vinyl-1,4-butyrolakton som huvudprodukt. Vid lägre temperaturer var den huvudsakliga produkten oligomerer bestående av både ringöppnade och ringslutna repeterande enheter.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 58 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:20
Keyword
Ring-opening polymerization, Stannous octoate, 2, 2’-azoisobutyronitrile, 1, 5-dioxepane-2-one, ε-caprolactone, L-lactide, Trimethylene carbonate, 2-methylene-1, 3-dioxe-5-pene, Copolymer, Porous scaffold, Porous tubular scaffold, Electron beam, Gamma irradiation
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-10368 (URN)978-91-7415-309-5 (ISBN)
Public defence
2009-05-29, E1, KTH, Lindstedtsvägen 3, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100805Available from: 2009-05-14 Created: 2009-05-08 Last updated: 2010-08-05Bibliographically approved
2. Synthetic Pathways to Aliphatic Polyesters and Scaffold Design
Open this publication in new window or tab >>Synthetic Pathways to Aliphatic Polyesters and Scaffold Design
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

As the field of tissue engineering progresses, a continuous development of scaffold fabrication techniques and suitable degradable materials is required to obtain scaffolds with tunable characteristics. This thesis has focused on the development of pathways to synthesize degradable aliphatic polyesters and on the design of highly porous scaffolds from this class of materials.

Porous scaffolds aimed for tissue engineering applications were successfully created from poly(L-lactide-co-trimethylene carbonate) copolymers, with an emphasis on obtaining highly porous scaffolds, possessing well interconnected pores throughout the scaffold structure. To obtain the porous structures, sugar templates were used in a combined phase separation and porogen leaching scaffold fabrication technique. The technique developed for these materials was simple and versatile and scaffolds of up to 55 mol% TMC were effectively produced.

Poly(p-dioxanone) (PPDX) is a degradable polyether-ester with a comparatively short degradation time, making it useful for many biomedical applications. A synthetic route to PPDX polymers was developed using the cyclic tin (IV) alkoxide initiator 1-di-n-butyl-1-stanna-2,5-dioxacyclopentane. Our work demonstrated that the polymerization route with this initiator is indeed a promising alternative to the more commonly used stannous octoate. Under the appropriate reaction conditions, PPDX polymers with inherent viscosities over 1 dL/g and promising mechanical properties were synthesized.

The design of functional materials is an important step towards fulfilling the material demands within tissue engineering. The free radical ring-opening polymerization of the cyclic ketene acetal monomer 2-methylene-1,3-dioxe-5-pene was developed. As a first step towards the creation of a new multifunctional polyester, the reaction mechanism and the reaction products at different reaction temperatures were mapped. At higher reaction temperatures, the main reaction product was the cyclic ester 3-vinyl-1,4-butyrolactone. At lower reaction temperatures, low molecular weight oligomeric products of both ring-opened and ring-retained repeating units were formed.

Combining scaffold design with sugar templates and the synthesis of functional polyesters led to the creation of highly porous functional scaffolds. Both functional scaffolds and functional films were obtained from poly(ɛ-caprolactone) and poly(L-lactide), synthesized using multifunctional poly(but-2-ene-1,4-diyl malonate) and stannous octoate as initiating system. The mechanical characteristics of the cross-linkable scaffolds and films were evaluated by cyclic compression test under physiological conditions and by cyclic tensile tests.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:36
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-33875 (URN)978-91-7415-997-4 (ISBN)
Public defence
2011-06-10, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110527Available from: 2011-05-27 Created: 2011-05-20 Last updated: 2011-05-27Bibliographically approved

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