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Novel methods to synthesize aliphatic polyesters of vivid architectures
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
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 [en]
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: urn:nbn:se:kth:diva-511ISBN: 91-7178-191-9 (print)OAI: oai:DiVA.org:kth-511DiVA: diva2:14266
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
List of papers
1. Potential tissue implants from the networks based on 1,5-dioxepan-2-one and epsilon-caprolactone
Open this publication in new window or tab >>Potential tissue implants from the networks based on 1,5-dioxepan-2-one and epsilon-caprolactone
2005 (English)In: Polymer journal, ISSN 0032-3896, Vol. 46, no 18, 6746-6755 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis and characterization of degradable polymeric networks for biomedical applications was performed. Cross-linked films of poly(epsilon-caprolactone) (PCL) and poly(1,5-dioxepan-2-one) (PDXO) having various mole fractions of monomers and different cross-link densities were successfully prepared using 2,2'-bis-(epsilon-caprolactone-4-yl) propane (BCP) as cross-linking agent. Reaction parameters were carefully examined to optimise, the film-formin.,, 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. High CL content or degree of cross-linking led to increase in Young's modulus and decrease in elongation at break. An increase in crystalline domains in films having a higher CL content was observed by optical microscopy. A greater thermal stability was observed in films having a high CL content. The hydrophilicity of the materials could be tailored by changing the CL content. The surface of the films became rougher with higher CL content.

Keyword
Characterization, Crosslinking, Degradation, Implants (surgical), Monomers, Plastic films, Synthesis (chemical), Tissue, 1, 5-dioxepan-2-one, Biomedical applications, Cross-linking agents, Organic polymers
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-8817 (URN)10.1016/j.polymer.2005.06.038 (DOI)000231397200003 ()2-s2.0-23744514731 (Scopus ID)
Note
QC 20100629Available from: 2005-11-24 Created: 2005-11-24 Last updated: 2010-12-21Bibliographically approved
2. High molecular weight poly(1,5-dioxepan-2-one) via enzyme-catalyzed ring-opening polymerization
Open this publication in new window or tab >>High molecular weight poly(1,5-dioxepan-2-one) via enzyme-catalyzed ring-opening polymerization
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.

Keyword
1, 5-dioxepan-2-one, enzymes, lipase CA, molecular weight, ring-opening, polymerization, epsilon-caprolactone
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7005 (URN)10.1002/pola.20888 (DOI)000231524100019 ()2-s2.0-25144483563 (Scopus ID)
Note
QC 20100818Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2010-12-21Bibliographically approved
3. Enzyme-Catalyzed Ring-Opening Polymerization of Seven-Membered Ring Lactones Leading to Terminal-Functionalized and Triblock Polyesters
Open this publication in new window or tab >>Enzyme-Catalyzed Ring-Opening Polymerization of Seven-Membered Ring Lactones Leading to Terminal-Functionalized and Triblock Polyesters
2006 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 39, no 1, 46-54 p.Article in journal (Refereed) Published
Abstract [en]

Terminal-functionalized polyesters and triblock polyesters were synthesized by lipase-CA-catalyzed ring-opening polymerization of seven-membered ring lactones, i.e., 1,5-dioxepan-2-one (DXO) and epsilon-caprolactone (CL), in the bulk in the presence of an appropriate alcohol that acts as an initiator. To introduce a double bond at the chain end, 4-pentene-2-ol was used to initiate the polymerization of the lactones. The unsaturation introduced at the chain end in this way is a useful approach for synthesizing comb polymers. Two different dihydroxyl compounds, viz. poly(caprolactone diol) and poly(ethylene glycol), were used as macro-initiators. Triblock copolymers were synthesized in this way, where the macro-initiator formed the middle block. Polymers having different degrees of polymerization were synthesized by varying the molar feed ratio of monomer to initiator. DXO and CL showed significant differences in reactivity toward lipase-CA-catalyzed polymerization initiated by different alcohols as initiators. The polymers were characterized by FTIR, NMR, SEC, optical microscopy, and DSC techniques.

Keyword
Alcohols, Copolymers, Monomers, Nuclear magnetic resonance, Optical microscopy, Polyesters, Dihydroxyl compounds, DSC techniques, Ring lactones, SEC, Polymerization
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7006 (URN)10.1021/ma0518508 (DOI)000234500100012 ()2-s2.0-30944444008 (Scopus ID)
Note
QC 20100818Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2010-12-21Bibliographically approved
4. Enzyme catalyzed synthesis of polyesters
Open this publication in new window or tab >>Enzyme catalyzed synthesis of polyesters
2005 (English)In: Progress in polymer science, ISSN 0079-6700, E-ISSN 1873-1619, Vol. 30, no 10, 949-981 p.Article in journal (Refereed) Published
Abstract [en]

In vitro enzyme catalyzed synthesis of polyesters is a new technique of polymer synthesis and is an eco-friendly process having several benefits over conventional chemical polymerization. In this article lipase-catalyzed ring-opening polymerization of lactones, lactides and macrolides, cyclic carbonates, cyclic phosphates, cyclic depsipeptides and copolymerization of oxiranes with dicarboxylic acid anhydrides leading to the formation of polyesters, polycarbonates, polyphosphates and poly(ester-amides) has been reviewed in detail. The effect of reaction parameters, i.e. solvent, temperature, enzyme and monomer concentration, on the rate and molecular weight of the polymers is discussed. Synthesis of polyesters by step-growth polycondensation reactions using simple diacids and diols, hydroxy acids or transesterification reaction of simple or activated diesters with diols has also been surveyed. The general mechanisms of ring-opening and step-growth polymerization have also been considered. Lipase hydrolyzes the ester bonds of polyesters in an aqueous medium and recombines the cleaved moiety in non-aqueous medium. The possibility of utilizing such reactions for the repetitive recycling of biodegradable polyesters has been highlighted.

Keyword
Hydrolase, Lactides, Lactone, Lipase, Macrolides, Ring-opening polymerization, Biodegradation, Catalysis, Enzymes, Monomers, Polymerization, Synthesis (chemical), Diacids, Eco-friendly process, Non-aqueous medium, Polyphosphates, Polyesters
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7012 (URN)10.1016/j.progpolymsci.2005.06.010 (DOI)000232522000001 ()2-s2.0-25144492819 (Scopus ID)
Note
QC 20100818Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2010-12-21Bibliographically approved

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