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High molecular weight poly(1,5-dioxepan-2-one) via enzyme-catalyzed ring-opening polymerization
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2005 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 43, no 18, 4206-4216 p.Article in journal (Refereed) Published
Abstract [en]

To avoid organometallic catalysts in the synthesis of poly(1,5-dioxepan-2-one), the enzymatic ring-opening polymerization of 1,5-dioxepan-2-one (DXO) was performed with lipase CA (derived from Candida antarctica) as a biocatalyst. A linear relationship between the number-average molecular weight and monomer conversion was observed, and this suggested that the product molecular weight could be controlled by the stoichiometry of the reactants. The monomer consumption followed a first-order rate law with respect to the monomer, and no chain termination occurred. Water acted as a chain initiator, but it could cause polymer hydrolysis when it exceeded an optimum level. An initial activation via the heating of the enzyme was sufficient to start the polymerization, as the monomer conversion occurred when samples were left at room temperature after an initial heating at 60 degrees C. A high lipase content led to a high monomer conversion as well as a high molecular weight. An increase in the monomer conversion and molecular weight was observed when the polymerization temperature was increased from 40 to 80 degrees C. A further increase in the polymerization temperature led to a decrease in the monomer conversion and molecular weight because of the denaturation of the enzyme at elevated temperatures. The polymerization behavior of DXO under lipase CA catalysis was compared with that of epsilon-caprolactone (CL). The rate of monomer conversion of DXO was much faster than that of CL, and this may have been due to differences in their specificity toward lipase CA.

Place, publisher, year, edition, pages
2005. Vol. 43, no 18, 4206-4216 p.
Keyword [en]
1, 5-dioxepan-2-one, enzymes, lipase CA, molecular weight, ring-opening, polymerization, epsilon-caprolactone
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-7005DOI: 10.1002/pola.20888ISI: 000231524100019Scopus ID: 2-s2.0-25144483563OAI: oai:DiVA.org:kth-7005DiVA: diva2:11879
Note
QC 20100818Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2010-12-21Bibliographically approved
In thesis
1. Aliphatic Polyesters for Soft Tissue Engineering: Development from Conventional Organometallic to Novel Enzymatic Catalysis
Open this publication in new window or tab >>Aliphatic Polyesters for Soft Tissue Engineering: Development from Conventional Organometallic to Novel Enzymatic Catalysis
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The development of macromolecules with defined structure and properties, aimed specifically for biomedical applications, has resulted in diverse biodegradable polymers with advanced architectures. Among them, aliphatic polyesters synthesized by ring-opening polymerization (ROP) of lactones and lactides have a leading position due to their good mechanical properties, hydrolyzability and biocompatibility. To achieve tailored properties and controlled architecture, the technique for ROP of lactones and lactides has been continuously refined in the past years. Enzyme-catalyzed ROP is one of the most promising tools, which avoids the use of toxic organometallic catalysts and brings a “green-chemistry” appeal with it. In the work described in this thesis, enzyme-catalyzed ROP of 1,5-dioxepan-2-one (DXO), ε-caprolactone (CL) and lactides (L-, D- and D,L-lactide) was performed in bulk using Lipases from different sources. The effects of enzyme concentration, polymerization temperature and reaction water content on the monomer conversion and the polymer molecular weight during DXO polymerization were studied, and the role of water as initiator was confirmed. Terminal functionalized, block, comb and star polymers were synthesized using different alcohols as initiator in the enzyme-catalyzed ROP of DXO, CL or lactides under strictly anhydrous conditions. The effect of simultaneous and sequential copolymerization of DXO and CL on the micro-block structure of the copolymers was studied and the reactivity ratios of DXO and CL were determined under Lipase catalysis. High molecular weight copolymers of DXO and CL thus obtained were fabricated into porous scaffolds for tissue implant applications. Enzymatic degradation and alkaline hydrolysis of lactides was performed to study the effect of molecular branches and the stereochemistry of the monomer on the degradation profile. In another approach, cross-linked films of DXO and CL were prepared using 2,2´-bis-(ε-caprolactone-4-yl) propane (BCP) as the cross-linking agent and Sn(Oct)2 as the catalyst. The networks obtained thereof were elastomeric materials, easy to cast and remove from the mould.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 125 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:2
Keyword
aliphatic polyester, 1, 5-dioxepan-2-one, ε-caprolactone, L-lactide, D-lactide, D, L-lactide, enzyme, lipase CA, lipase PS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-4341 (URN)978-91-7178-595-4 (ISBN)
Public defence
2007-05-04, F3, KTH, Lindstedtsvägen 26, Stoclholm, 10:15
Opponent
Supervisors
Note
QC 20100818Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2011-02-21Bibliographically approved
2. Novel methods to synthesize aliphatic polyesters of vivid architectures
Open this publication in new window or tab >>Novel methods to synthesize aliphatic polyesters of vivid architectures
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Cross-linked films of ε-caprolactone (CL) and 1,5-dioxepan-2-one (DXO) having various mole fractions of monomers and different cross-link densities were prepared using 2,2’-bis-(-caprolactone-4-yl) propane (BCP) as cross-linking agent and Sn(Oct)2 as catalyst. Reaction parameters were examined to optimize the film-forming conditions. Networks obtained were elastomeric materials, easy to cast and remove from the mould. Effect of CL content and cross-link density on the final properties of the polymer network was evaluated. Thermal, mechanical and surface properties of the films were controlled by monomer feed composition and cross-link density. The films have potential to be used for tissue engineering applications as shown by preliminary cell growth studies. To avoid organometallic catalysts in the synthesis of poly(1,5-dioxepan-2-one) (PDXO), the enzyme-catalyzed ring-opening polymerization (ROP) of DXO was performed with lipase-CA (derived from Candida antarctica) as a biocatalyst. A linear relationship between number-average molecular weight (Mn) and monomer conversion was observed, which suggested that the product molecular weight can be controlled by the stoichiometry of the reactants. The monomer consumption followed a first-order rate law with respect to monomer and no chain termination occurred. Effect of reaction water content, enzyme concentration and polymerization temperature on monomer conversion and polymer properties was studied. An initial activation by heating the enzyme was sufficient to start the polymerization as monomer conversion occurred at room temperature afterwards. Terminal-functionalized polyesters and tri-block polyesters were synthesized by lipase-CA catalyzed ROP of DXO and CL in the presence of an appropriate alcohol as initiator. Alcohol bearing unsaturation introduced a double bond at the chain end of the polyester, which is a useful pathway to synthesize comb polymers. Dihydroxyl compounds were used as macro-initiators to form tri-block polyesters. The enzyme-catalyzed polymerization of lactones has been shown to be a useful method to synthesize metal-free polyesters.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 84 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:38
Keyword
Polyesters, 1, 5-dioxepan-2-one, Caprolactone, Sn(Oct)2, Enzyme, Lipase-CA, Ring-Opening Polymerization, Architecture, Tissue Engineering
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-511 (URN)91-7178-191-9 (ISBN)
Presentation
2005-12-02, E2, Huvudbyggnaden, Lindstedtsvägen 3, Entreplan KTH, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101221Available from: 2005-11-24 Created: 2005-11-24 Last updated: 2010-12-21Bibliographically approved

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