Publication

Abstract : pDilute-solution studies on styrene-acrylonitrile random copolymer (SA2) of molar compositionnbsp;51% acrylonitrile (AN) in ethyl acetate (EAc) revealed that phase separation occurred in high-molecular-weight fractions as the temperature was raised.' This behavior, knownnbsp;asnbsp;the lower-critical-solution phenomenon, was originally reported for certain polar systems and attributed to thenbsp;existence of specific interactions between the polymer and solvent.nbsp;More recently, Rowlinson andnbsp;co-workernbsp;showed that nonpolar systems also undergo phase separation on elevation of thenbsp;temperature, but precipitation occurs well above the boiling point of the solvent, in contrastnbsp;tonbsp;manynbsp;polarnbsp;systems where the polymer usually separates at a temperature below or near the solvent boilingnbsp;point. From measurementsnbsp;atnbsp;elevated temperatures, lower-critical-solution temperatures (LCSTs)nbsp;can be estimated for each fraction, which in the limit of infinite molecular weight is the emO/em temperature./p