title: Creep-resistant porous structures based on stereo-complex forming triblock copolymers of 1,3-trimethylene carbonate and lactides.
abstract: Stereo-complexes (poly(ST-TMC-ST)) of enantiomeric triblock copolymers based on 1,3-trimethylene carbonate (TMC) and L- or D-lactide (poly(LLA-TMC-LLA) and poly(DLA-TMC-DLA)) were prepared. Films of poly(ST-TMC-ST) could be prepared by solvent casting mixtures of equal amounts of poly(LLA-TMC-LLA) and poly(DLA-TMC-DLA) solutions and by compression moulding co-precipitates. Although compression moulding was performed at 191 degrees C, thermal degradation was not apparent and materials with good tensile properties could be obtained. For compression-moulded poly(ST-TMC-ST) specimens containing approximately 16 mol % lactide, the values for E-modulus, yield stress and elongation at break were respectively 17, 1.7 MPa and 90%. Also a very low long-term creep rate of 2.2 x 10(-7)s(-1) was determined when specimens were loaded to 20% of the yield stress. When compared with compression-moulded poly(TMC), poly(ST-TMC-ST) specimens deform at a rate that is one to two orders of magnitude lower. Furthermore, poly(ST-TMC-ST) specimens showed complete dimensional recovery within 24 h after loading to 20% and 40% of the yield stress for 40 and 5.5 h, respectively. Highly porous poly(TMC) and poly(ST-TMC-ST) structures with interconnected pores were prepared by a method combining co-precipitation, compression moulding and salt leaching. After prolonged compressive deformation, solid and porous poly(ST-TMC-ST) discs showed significantly better recovery behaviour than poly(TMC) discs.
authors.affiliation: Institute for Biomedical Technology (BMTI), Department of Polymer Chemistry and Biomaterials, Faculty of Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Dirk W
authors.initials: DW
authors.lastname: Grijpma
authors.forename: Jan
authors.initials: J
authors.lastname: Feijen
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D004146:Dioxanes / Q000737:chemistry*; D004548:Elasticity; D046911:Macromolecular Substances; D008422:Materials Testing; D008567:Membranes, Artificial; D011091:Polyesters / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D016062:Porosity; D013237:Stereoisomerism; D013499:Surface Properties; D013718:Tensile Strength; D014783:Viscosity
chemical_list: D001672:Biocompatible Materials; D004146:Dioxanes; D046911:Macromolecular Substances; D008567:Membranes, Artificial; D011091:Polyesters; D011108:Polymers; C443643:trimethylene carbonate; C033616:poly(lactide)