Morphological changes in poly(ɛ-caprolactone) in dense carbon dioxide

• DOI: 10.1016/j.polymer.2008.02.017
• Publication Date: 2008-02-15T12:44:10Z
• Authors: Erdogan Kiran; Kun Liu; Katrina Ramsdell
• Keywords: 01 natural sciences; 0104 chemical sciences

Abstract Morphological changes that take place in poly(ɛ-caprolactone) upon exposure to carbon dioxide at high pressures have been explored as a function of pressure and temperature. SEM and DSC results point to a competition between CO 2 -modulated crystallization and pressure-induced phase separation which leads to unique morphologies. At 293 K, exposure to CO 2 at pressures up to 45 MPa leads to recrystallization resulting in higher level of crystallinity and higher melting temperatures. Highest crystallinity levels along with distinct crystal morphology were observed after exposure to CO 2 at 308 K and 21 MPa. At a higher pressure at this temperature (308 K/34 MPa) polymer undergoes melting, and foaming is achieved during depressurization prior to solidification. At 323 K, the polymer is found to display unique crystal morphology with concave crystal geometry as well as porous domains. The results are discussed in terms of the crystallization and phase separation paths that are followed during exposure to CO 2 and the depressurization stages.