The effect of block copolymer morphology on polymer crystallization and water sorption was investigated using two amphiphilic block copolymers with minority hydrophilic phase. Such polymers have many potential membrane applications, including CO2capture and water purification. A model block copolymer chemistry comprising polystyrene and poly(ethylene oxide) (PEO) is used in this work. Both block copolymers have strongly phase-separated order, one with lamellar morphology and another with cylindrical morphology. In addition to the block copolymer structure, the PEO phase is semicrystalline at room temperature. The block copolymer structure has dramatic consequences for the degree of PEO crystallinity even in the absence of water. Furthermore, the crystallinity is affected by water sorption. PEO melting and degree of crystallinity were determined as a function of water content. Water solubility was measured between 35 and 75 °C. Interestingly, water sorption properties are dictated almost exclusively by the amorphous PEO volume fraction, being low in the semicrystalline state (below 55 °C) and higher in the amorphous state (above 55 °C). At 55 °C, crystallite dissolution is observed with increasing water solubility. Water diffusion coefficient was also measured; it decreases monotonically with increasing water content. This concentration dependence of diffusion is explained by water clustering, which increases with increasing water content. In addition to block copolymer morphology playing a major role in PEO crystallinity, it has a significant effect on water diffusion in the amorphous polymers and is of practical importance as investigations at elevated temperature are not possible with homopolymer PEO.
Oparaji, O., Minelli, M., Zhu, C., Schaible, E., Hexemer, A., Hallinan, D.T. (2017). Effect of block copolymer morphology on crystallization and water transport. POLYMER, 120, 209-216 [10.1016/j.polymer.2017.05.055].
Effect of block copolymer morphology on crystallization and water transport
Minelli, Matteo;
2017
Abstract
The effect of block copolymer morphology on polymer crystallization and water sorption was investigated using two amphiphilic block copolymers with minority hydrophilic phase. Such polymers have many potential membrane applications, including CO2capture and water purification. A model block copolymer chemistry comprising polystyrene and poly(ethylene oxide) (PEO) is used in this work. Both block copolymers have strongly phase-separated order, one with lamellar morphology and another with cylindrical morphology. In addition to the block copolymer structure, the PEO phase is semicrystalline at room temperature. The block copolymer structure has dramatic consequences for the degree of PEO crystallinity even in the absence of water. Furthermore, the crystallinity is affected by water sorption. PEO melting and degree of crystallinity were determined as a function of water content. Water solubility was measured between 35 and 75 °C. Interestingly, water sorption properties are dictated almost exclusively by the amorphous PEO volume fraction, being low in the semicrystalline state (below 55 °C) and higher in the amorphous state (above 55 °C). At 55 °C, crystallite dissolution is observed with increasing water solubility. Water diffusion coefficient was also measured; it decreases monotonically with increasing water content. This concentration dependence of diffusion is explained by water clustering, which increases with increasing water content. In addition to block copolymer morphology playing a major role in PEO crystallinity, it has a significant effect on water diffusion in the amorphous polymers and is of practical importance as investigations at elevated temperature are not possible with homopolymer PEO.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
