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Lipase Catalyzed HEMA Initiated Ring-Opening Polymerization: In Situ Formation of Mixed Polyester Methacrylates by Transesterification
KTH, School of Biotechnology (BIO), Biochemistry.
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: 0000-0002-8348-2273
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2008 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 9, no 2, 704-710 p.Article in journal (Refereed) Published
Abstract [en]

2-Hydroxyethyl methacrylate (HEMA) was used as initiator for the enzymatic ring-opening polymerization (ROP) of ω-pentadecalactone (PDL) and ∈-caprolactone (CL). The lipase B from Candida antarctica was found to catalyze the cleavage of the ester bond in the HEMA end group of the formed polyesters, resulting in two major transesterification processes, methacrylate transfer and polyester transfer. This resulted in a number of different polyester methacrylate structures, such as polymers without, with one, and with two methacrylate end groups. Furthermore, the 1,2-ethanediol moiety (from HEMA) was found in the polyester products as an integral part of HEMA, as an end group (with one hydroxyl group) and incorporated within the polyester (polyester chains acylated on both hydroxyl groups). After 72 h, as a result of the methacrylate transfer, 79% (48%) of the initial amount of the methacrylate moiety (from HEMA) was situated (acylated) on the end hydroxyl group of the PPDL (PCL) polyester. In order to prepare materials for polymer networks, fully dimethacrylated polymers were synthesized in a one-pot procedure by combining HEMA-initiated ROP with end-capping using vinyl methacrylate. The novel PPDL dimethacrylate (>95% incorporated methacrylate end groups) is currently in use for polymer network formation. Our results show that initiators with cleavable ester groups are of limited use to obtain well-defined monomethacrylated macromonomers due to the enzyme-based transesterification processes. On the other hand, when combined with end-capping, well-defined dimethacrylated polymers (PPDL, PCL) were prepared.

Place, publisher, year, edition, pages
2008. Vol. 9, no 2, 704-710 p.
Keyword [en]
Catalysis, Lipases, Monomers, Polyesters, Transesterification
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-8005DOI: 10.1021/bm7010449ISI: 000253102100040Scopus ID: 2-s2.0-39749139410OAI: oai:DiVA.org:kth-8005DiVA: diva2:13208
Note
QC 20100921. Uppdaterad från In press till Published (20100921).Available from: 2008-02-20 Created: 2008-02-20 Last updated: 2012-03-21Bibliographically approved
In thesis
1. Enzymatic Synthesis of Functional Polyesters
Open this publication in new window or tab >>Enzymatic Synthesis of Functional Polyesters
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Enzymes are successfully employed in the synthesis of different types of polymers. Candida antarctica lipase B is a highly efficient catalyst for the synthesis of polyesters by ring opening polymerization. ω-Pentadecalactone is an interesting lactone due to the unique proprieties of its polymer (poly-pentadecalactone). These polymers have not been applied in any industrial application due to the difficulties to reach them by chemical polymerization. Enzymatically, poly-pentadecalactone macromonomers can be obtained to high conversion.

In this investigation we synthesized difunctionalized poly-pentadecalactone with different functional groups. Taking advantage of the selectivity of Candida antarctica lipase B, we introduced different functional end groups. α,ω-Difunctionalized poly-pentadecalactone macromonomers with two thiol ends, two (meth)acrylate ends or with one thiol and one acrylate end were obtained with a high degree of functional ends. We have improved the difunctionalization procedure to a single-step route for the synthesis of α,ω-functionalized poly-pentadecalactones. This procedure has a great potential for industrial applications due to the simplicity of the process and the clean products afforded. Macromonomers with functionalized ends can be used to obtain new polymer architectures with novel proprieties.

We also show how the use of enzymes could have some limitations when using an initiator with a cleavable ester bond. 2-Hydroxyethyl methacrylate (HEMA) was used as initiator for the ring opening polymerization (eROP) of ε-caprolactone and ω-pentadecalactone aiming for methacrylate functional polyester. However, the lipase catalyzed not only the ring opening polymerization but also the cleavage of the HEMA moiety resulting in a mixture of polymer products with various end groups. A kinetics study of the eROP and the transesterification processes when using HEMA showed that the transesterification processes occurs at moderate frequency at low monomer concentration, it becomes dominant at longer reaction times. We showed that fully difunctionalized polymers can be obtained when using HEMA as initiator for the eROP of lactones by adding a proper end capper.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. viii, 25 p.
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-4641 (URN)978-91-7178-881-8 (ISBN)
Presentation
2008-03-07, FB54, AlbaNova, Roslagstullsbacken 21, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20101124Available from: 2008-02-20 Created: 2008-02-20 Last updated: 2010-11-24Bibliographically approved
2. Lipase Specificity and Selectivity: Engineering, Kinetics and Applied Catalysis
Open this publication in new window or tab >>Lipase Specificity and Selectivity: Engineering, Kinetics and Applied Catalysis
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The specificity and selectivity of the enzyme Candida antarctica lipase B (CALB) were studiedfor several substrates and applications.With help of molecular modeling, the active site of CALB was redesigned for the ring openingpolymerization of D,D‐lactide. Two mutants, with about 90‐fold increase in activity ascompared to the wild‐type enzyme, were created. Changing a glutamine into alanineaccounted for this increase in both mutants by creating a larger space in the acyl donorpocket. The new space made it possible to accommodate the bulky substrate and improvethe transition state‐active site complementarity during polymer chain propagation.The enantioselectivity of CALB towards secondary alcohols was engineered by rationalredesign of the stereoselectivity pocket in the enzyme active site. A larger space created by asingle point mutation resulted in an 8’300’000 times change in enantioselectivity towards 1‐phenylethanol and the enantiopreference was inverted into S‐preference. The activitytowards the S‐enantiomer increased 64’000 times in the mutant as related to the wild‐type.The solvent and temperature effects on the enantioselectivity were studied for severalsubstrates and revealed the importance of entropy in the change in enantioselectivity.Substrate selectivity is of great importance for the outcome of enzyme catalyzed polymersynthesis. Ring opening polymerization (ROP) of γ‐acyloxy‐ε‐caprolactones will result in apolyester chain with pendant functional groups. CALB was found to have activity not onlytowards the lactone but also towards the γ‐ester leading to rearrangement of the monomersyielding γ‐acetyloxyethyl‐γ‐butyrolactone. This selectivity between the lactone and the γ‐ester was dependent on the type of group in the γ position and determined the ratio ofpolymerization and rearrangement of the monomers. Molecular dynamics simulations wereused to gain molecular understanding of the selectivity between the lactone and γ‐ester.In order to obtain (meth)acrylate functional polyesters we investigated the use of 2‐hydroxyethyl (meth)acrylate (HEA and HEMA) as initiators for ring opening polymerization.We found that, in addition to the ring opening polymerization activity, CALB catalyzed thetransacylation of the acid moiety of the initiators. The selectivity of CALB towards thedifferent acyl donors in the reaction resulted in a mixture of polymers with different endgroups. A kinetic investigation of the reaction showed the product distribution with timewhen using HEA or HEMA with ε‐caprolactone or ω‐pentadecalactone.The high selectivity of CALB towards lactones over (meth)acrylate esters such as ethyleneglycol di(meth)acrylate was used to design a single‐step route for the synthesis ofdi(meth)acrylated polymers. By mixing ω‐pentadecalactone with the ethylene glycoldi(meth)acrylate and the enzyme in solvent free conditions, we obtained >95 % ofdi(meth)acrylated polypentadecalactone.Taking advantage of the high chemoselectivity of CALB, it was possible to synthesizepolyesters with thiol and/or acrylate functional ends. When using a thioalcohol as initiatorCALB showed high selectivity towards the alcohol group over the thiol group as acyl acceptorfor the ROP reaction. The enzymatic ability of catalyzing simultaneous reactions (ROP andtransacylation) it was possible to develop a single‐step route for the synthesis ofdifunctionalized polyesters with two thiol ends or one thiol and one acrylate end by mixingthe initiator, lactone and a terminator.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. viii, 48 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2010:17
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:kth:diva-25039 (URN)978-91-7415-729-1 (ISBN)
Public defence
2010-10-22, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20101006Available from: 2010-10-06 Created: 2010-10-06 Last updated: 2010-10-06Bibliographically approved

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Malmström, Eva M.Martinelle, Mats

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