Preparation and properties of block copolymers with two stat-copoly(oxyethylene/oxypropylene) blocks

✍ Scribed by Yulin Deng; Colin Price; Colin Booth

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 877 KB
• Volume: 30
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(94)90239-9

✦ Synopsis

Diblock copolymers, each with two stat-copoly(oxyethylene/oxypropylene) blocks, were prepared by sequential anionic copolymerization in the presence of a crown ether, and characterized by gel permeation chromatography and NMR spectroscopy. Aqueous solutions of the copolymers were investigated by static and dynamic light scattering and differential scanning calorimetry. Standard thermodynamic micellization functions were derived from critical micelle temperatures determined by static light scattering for solutions covering a range of concentrations. The lower and upper temperature boundaries of the gel regions were determined and the standard thermodynamic gelation functions derived. Typical values obtained for the standard enthalpies were +360 kJ (mol of chains)-~ for micellization, +20 kJ (tool of micelles)-i for gelation at the lower temperature boundary, and -15 kJ (mol of micelles)-~ for gelation at the upper temperature boundary: the latter quantities corresponding roughly to + I or -1 kJ (mol of chains)-l respectively. Gelation in aqueous ethanol solution was also investigated.