Bioabbaubare Polymernetzwerk-Systeme mit Formgedächtniseffekt und kristallisierbarem Schaltsegment

This work describes the synthesis and properties of new polymer systems of biodegradable shape memory thermosets. The combination of only four different monomer units and three network architectures allows the design of polymeric materials with a broad spectrum of properties. By variation of the molecular network parameters it is possible to adjust the shape memory transition temperature and the mechanical properties of the thermosets below and above the transition temperature. The networks are synthesized by crosslinking polymerization of oligo(Epsilon -hydroxycaproate-ran-glycolate)dimethacrylates. By variation of the glycalate content the shape memory transition temperature can be adjusted between 27°C and 49°C. By polymerization of the macromonomers in the presence of butyl acrylate, AB-crosslinked materials are obtained. The elastic modulus E of the AB-networks in tensile tests at 22°C decreases with increasing content of butyl acrylate and can be adjusted between 64 MPa and 6.4 MPa. If the macromonomers are crosslinked in the presence of phase-segregated poly(ester urethanes), mix-interpenetrated polymer networks (mix-IPN) are formed consisting of a covalently and a physically crosslinked partial network that interpenetrate each other. The used poly(ester urethanes) are synthesized by copolyaddition of oligo(Epsilon-hydroxycaproate)diol and oligo(Omega-hydroxypentadecanoate)diol with trimethylhexanediisocyanate. This way, mix-IPN are made with a oligo(Omega-hydroxypentadecanoate) content up to 22 mass-%. With increasing content of oligo(Omega-hydroxypentadecanoate) the elastic modulus as well as the tensile strength of the mix-IPN in tensile tests at 70°C are increased. The polymer networks show good to excellent shape memory properties in cyclic thermomechanical tensile tests between 0°C and 70°C, combining a good fixability of the temporary shape, fast attainment of a stable themomechanical behavior and only little loss of the permanent shape in the first cycles. Networks containing exclusively covalent crosslinking show an almost ideal-elastic behavior and reach back their original permanent shape completely under the experimental conditions. In hydrolytic degradation experiments at pH 7.0 and 37°C or 70°C it is shown that the materials show a slow degradation. The presence of the new comonomer accelerates the course of hydrolytic chain scission and mass loss, and in contrast to this, the presence of butyl acrylate decreases the degradation rate. The course of the mechanical properties at 37°C with hydrolysis is determined by the crystallinity of the materials at this temperature. It can be shown, that materials that show a low crystallinity at 37°C get softer with degradation time. One of the networks is investigated for its cytotoxicity. Agarose diffusion tests are performed on samples that are sterilized by ethylene oxide or low temperature plasma sterilization. The samples have been partially degraded in cell culture medium for a period between 0 and 28 days prior to testing. No sign for cytotoxicity is found for all samples according to ASTM standard F-895-84.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2002

Author dc:creator

• Schmidt, Annette M.

Contributors dc:contributor

• Höcker, Hartwig

• info:eu-repo/classification/ddc/660
• Technische Chemie

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-208188%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61530