Preparation of macroporous biodegradable poly(L-lactide-co-ϵ-caprolactone) foams and characterization by mercury intrusion porosimetry, image analysis, and impedance spectroscopy
- 27 June 2003
- journal article
- research article
- Published by Wiley in Journal of Biomedical Materials Research Part A
- Vol. 66A (2), 199-213
- https://doi.org/10.1002/jbm.a.10523
Abstract
Two poly(L-lactide-co-ϵ-caprolactone) random copolymers containing 5 and 40 mol % of ϵ-CL, namely P(LA-co-CL5) and P(LA-co-CL40), respectively, have been made macroporous by freeze-drying solutions in dimethylcarbonate. Most of the freeze-dried foams, prepared by varying polymer concentration and cooling rate, exhibited two main pore populations: (1) longitudinally oriented tube-like macropores with diameters ≥100 μm, and (2) interconnected micropores (10–100 μm). Pore characteristics, including macropore density, mean diameter, and interdistance, as well as micropore density, area, and shape, were determined by image analysis of scanning electron micrographs in order to study the influence of processing and formulation parameters on foam structure and properties. The pore orientation and the 3-D texture also were studied by image analysis and impedance spectroscopy. In the case of the P(LA-co-CL5), the macropore diameter increased with the cooling rate while the micropore diameter decreased. The micropores also became more circular when the cooling rate was increased. The pore size and morphology of the P(LA-co-CL40) were quite unchanged by varying the cooling rate. All the other conditions being the same, the P(LA-co-CL5) foams were better organized than the P(LA-co-CL40) foams, and pore orientation was improved at the higher cooling rate. Pore size and morphology also can be controlled by changing the polymer concentration (Cp), as we showed by studying P(LA-co-CL5) foams prepared by freeze-drying solutions in the 1–10 w/v % Cp range. Macropore density, average diameter, and interdistance of P(LA-co-CL5) foams increased with Cp, but the micropore characteristics remained almost unchanged no matter the Cp. The reliability of the characterization methods has been discussed, with special attention to mercury intrusion porosimetry, which is used primarily for measurement of pore volume and pore size distribution. However, this technique is reported here as a destructive and unreliable method for the characterization of fragile P(LA-co-CL40) foams. This study shows that image analysis and impedance spectroscopy can give reliable information relative to the pore morphology and anisotropy of freeze-dried foams. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A:199–213, 2003Keywords
Funding Information
- J & J Corporate Biomaterials Center (Somerville, NJ)
- Fonds National de la Recherche Scientifique (FNRS)
This publication has 26 references indexed in Scilit:
- Characterization of porous texture of hyperporous materials by mercury porosimetry using densification equationPowder Technology, 2002
- Image analysis, impedance spectroscopy and mercury porosimetry characterisation of freeze-drying porous materialsColloids and Surfaces A: Physicochemical and Engineering Aspects, 2001
- Poly(?,?-lactide) foams modified by poly(ethylene oxide)–block–poly(?,?-lactide) copolymers and a-FGF: in vitro and in vivo evaluation for spinal cord regenerationBiomaterials, 2001
- Characterization of Porous Polylactide Foams by Image Analysis and Impedance SpectroscopyLangmuir, 2000
- Analysis of 3-D microstructure of porous poly(lactide-glycolide) matrices using confocal microscopyJournal of Biomedical Materials Research, 1998
- Interpretation of mercury porosimetry applied to aerogelsJournal of Materials Research, 1995
- Fabrication of Controlled Release Biodegradable Foams by Phase SeparationTissue Engineering, 1995
- Laminated three-dimensional biodegradable foams for use in tissue engineeringBiomaterials, 1993
- Geometric and dielectric characterization of porous mediaPhysical Review B, 1991
- Low-density, microcellular polystyrene foamsPolymer, 1985