EFFECT OF SOME FACTORS ON FABRICATION OF POLY(L-LACTIC ACID) MICROPOROUS FOAMS BY THERMALLY INDUCED PHASE SEPARATION USINGN,N-DIMETHYLACETAMIDE AS SOLVENT

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Abstract
Biocompatible, highly interconnected microporous poly(L-lactic acid) (PLLA) foams or scaffolds with nano-fibrous structure, containing pores with diameters of 0.1–3.5 μm and fibers with diameters of 300–700 nm scale, were prepared through the thermally induced liquid–liquid phase separation (TIPS) method using N,N′-dimethyl acetamide (DMAc) as solvent. Various foam morphologies were obtained by changing parameters involved in the TIPS process, such as polymer concentration, solvent composition, and quenching temperatures. The morphology of different foams was examined by scanning electron microscopy, whereas the pore size and the pore size distribution were calculated. The results showed that most porous foams presented nano-fibrous structure with interconnected open pores. In the case of using DMAc as solvent, with increasing polymer concentration, either the average pore diameter or the pore size distribution exhibited a maximum value at 0.05 g/mL polymer concentration and quenching temperature of −30°C. It was found that all the pore size distribution fit the F-distribution equation. With increasing the quenching temperature from −30°C to −10°C, the maximum average pore diameter of the foams decreased and the pore size distribution became narrower, whereas the polymer concentration exhibiting the maximum pore size and widest pore size distribution increased from 0.05 g/mL to 0.07 g/mL. In the case of using the mixed solvent of DMAc/DOX (1,4-dioxane) from 9/1 to 7/3 (v/v) there appeared a maximum value of average pore diameter and a widest pore size distribution all at 0.05 g/mL PLLA concentration and quenching temperature of −30°C. The maximum pore size tends to increase with increasing DOX content.

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