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Synthesis of functional degradable polymers by radical ring-opening polymerization
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.ORCID iD: 0000-0001-6044-586X
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The increased demand for understanding cell-material interactions and subsequently create personalized implants for tissue engineering has resulted in an increased interest in developing new monomers with functional groups. The focus of the work presented in this thesis has been on the synthesis of functional monomers and the polymerization of these into functional amorphous aliphatic polyesters.

The cyclic ketene acetal 2-methylene-1,3,6-trioxocane (MTC) was synthesized in a two-step reaction and subsequently polymerized at different temperatures using either 2,2’-azoisobutyronitrile (AIBN) or dicumyl peroxide as initiator. It was shown that the polymerization mechanism was not temperature-dependent and the polymerization proceeded with 100% ring-opening at all evaluated temperatures.

The polyester-ether was then successfully copolymerized with another cyclic ketene acetal 2-methylene-1,3-dioxepane (MDO) and a functional, hydrophilic and  amorphous copolymer was obtained. The feed ratios were varied between 90 to 25 mol% of MTC and it was shown that the proportion of MTC in the copolymers was in general higher than the proportion of MTC in the feed, confirming that the reactivity ratio was higher for MTC. A number average molecular weight of 6500 g/mol was obtained after 2 days at 70 °C in bulk. The high polydispersity index as well as the glass transition temperatures indicated a significant amount of branching.

MDO was also copolymerized with vinyl acetate (VAc). A series of copolymers with various combinations of MDO and VAc were synthesized by using AIBN as radical initiator. It was shown that the proportion of MDO in the copolymers was strictly controlled by the feed ratios and that the composition of the copolymers, the thermal properties and the molecular weights could be predetermined. The reactivity ratios for MDO and VAc were determined to be rMDO = 0.93 and rVAc = 1.71. The copolymerization resulted in a high degree of conversions and a high number average molecular weights, where both the molecular weight and the glass transition temperature increased with increased proportion of VAc in the feed. It was also confirmed that the copolymer were susceptible to both alkali and enzymatic hydrolysis and it was apparent that it is possible to synthesize various degradable materials based on VAc and MDO with predetermined polymer compositions and high number average molecular weights.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 44 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:6
Keyword [en]
tissue engineering, ring-opening polymerization, 2, 2´-azoisobutyronitrile, cyclic ketene acetals, 2-methylene- 1, 3, 6-trioxocane, 2-methylene- 1, 3-dioxepane, vinyl acetate, coopolymerization
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-90826ISBN: 978-91-7501-253-7 (print)OAI: oai:DiVA.org:kth-90826DiVA: diva2:506746
Presentation
2012-03-09, K2, KTH, Teknikringen 28, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20120229Available from: 2012-02-29 Created: 2012-02-29 Last updated: 2012-03-28Bibliographically approved
List of papers
1. Synthesis of Amorphous Aliphatic Polyester-Ether Homo- and Copolymers by Radical Polymerization of Ketene Acetals
Open this publication in new window or tab >>Synthesis of Amorphous Aliphatic Polyester-Ether Homo- and Copolymers by Radical Polymerization of Ketene Acetals
2010 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 48, no 22, 4965-4973 p.Article in journal (Refereed) Published
Abstract [en]

Radical ring-opening polymerization has been efficiently used to copolymerize 2-methylene-1,3,6-trioxocane (MTC) and 2-methylene-1,3-dioxepane (MDO). The cyclic ketene acetal MTC was first synthesized and homopolymerized at different temperatures using either 2,2-azobisisobutyronitrile or dicumyl peroxide as initiator. The polymerization mechanism was not temperature-dependent, and the polymerization proceeded with 100% ring-opening at all the temperatures evaluated. The structures of MTC and PMTC were verified by H-1-nuclear magnetic resonance (NMR) and C-13-NMR spectroscopies. A number-average molecular weight of 6500 was obtained after 2 days at 70 degrees C in bulk, which was somewhat higher than the theoretical molecular weight. A significant amount of branching was detected from the high polydispersity index as well as the glass-transition temperatures. The polyester-ether was then successfully obtained by copolymerization of MTC with MDO. Different feed ratios and temperatures were used to map the reaction, and the copolymers were characterized by NMR, size exclusion chromatography, and differential scanning calorimetry. The amount of MTC within the polymer was independent of the feed ratio and always higher than the amount of MDO.

Keyword
aliphatic polyesters, copolymerization, cyclic ketene acetal, free-radical ring-opening polymerization, 2-methylene-1, 3, 6-trioxocane, 2-methylene-1, 3-dioxepane
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-27069 (URN)10.1002/pola.24292 (DOI)000284109000008 ()2-s2.0-78649544332 (Scopus ID)
Note
QC 20101210Available from: 2010-12-10 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
2. Random introduction of degradable linkages into functional vinyl polymers by radical ring-opening polymerization, tailored for soft tissue engineering
Open this publication in new window or tab >>Random introduction of degradable linkages into functional vinyl polymers by radical ring-opening polymerization, tailored for soft tissue engineering
2012 (English)In: Polymer Chemistry, ISSN 1759-9954, Vol. 3, no 5, 1260-1266 p.Article in journal (Refereed) Published
Abstract [en]

Vinyl polymers, e.g. polyvinyl acetate and polyvinyl alcohol, have properties which suit tissue engineering in many perspectives. A copolymer of 2-methylene-1,3-dioxepane (MDO) with vinyl acetate (VAc) should combine the desirable properties of vinyl polymers with the degradability of aliphatic polyesters. Our results and detailed kinetics information show that it is possible to vary the amount of MDO widely in the copolymer. Between 1 and 70% MDO was incorporated into the polymer when copolymerized with VAc at 60 degrees C using 2,2-azobisisobutyronitrile (AIBN) as an initiator. The amount of MDO in the copolymer was strictly controlled by the feed ratio, the copolymerization resulted in a high conversion, and the copolymers had high number average molar masses. The polymerization kinetics indicated that the ester units were added in a randomized manner to the vinyl backbone. This was a crucial point since the distribution of degradable bonds provides the opportunity to design the degradation profile of the polymer. The reactivity ratios for MDO and VAc were determined to be r(MDO) 0.93 and r(VAc) 1.71. The glass transition temperature and the number average molar masses increased with increasing amount of VAc in the feed. We confirmed that the copolymer degraded rapidly in alkali hydrolysis and less in enzymatic hydrolysis and it was apparent that it is possible to synthesize various degradable materials based on VAc and MDO with predetermined polymer compositions and high number average molar masses.

National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-90825 (URN)10.1039/C2PY20034A (DOI)000302315800021 ()2-s2.0-84859742475 (Scopus ID)
Note
QC 20120509Available from: 2012-02-29 Created: 2012-02-29 Last updated: 2014-05-14Bibliographically approved

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