Characterization and permeation of microporous poly(ε-caprolactone) films

The porous poly(ε-caprolactone) (PCL) membranes were prepared by solvent-casting-leaching method, and PEG10,000 as well as PEG4000 were used as the pore formers. The properties of membranes were characterized by SEM, DSC, FTIR, 1H NMR, and their thickness as well as porosity. The thickness of membranes were well controlled in the range of 71.0±13.0∼85.0±1.7 μm. From SEM micrographs, the pores formed were spherical and had identical size, and the size of micropores created by PEG4000 was larger than that by PEG10,000. The calculated porosity in membranes increased proportion to the amount of Poly(ethylene glycol) (PEG) blended initially which was irrespective of the molecular weight (Mw) of PEG. The FTIR and DSC data showed that there is no significant interaction between PCL and PEG. In permeation study, theophylline and FITC-dextran were used as the model compounds. Once the porosity increased above the critical value 0.35, reducing the dead-end fraction, resulting in increasing permeability. The permeability of drug from porous membranes formed by PEG4000 was faster than that by PEG10,000. In addition, the permeation rate of theophylline was higher than that of FITC-dextran. This was attributed to smaller hydrodynamic radius of theophylline (0.3 nm) than FITC-dextran (4.7 nm) and the partition of theophylline to the PCL membrane (K=0.095).