Determination of solvent-independent polymer-polymer interaction parameterby an improved inverse gas chromatographic approach

The solvent-dependence problem generally observed in the determination of p olymer-polymer interaction parameters from inverse gas chromatography (IGC) measurements has been examined and resolved. The problem is mainly attribu ted to the use of different reference volumes in the calculations of chi (1 2), chi (13), and chi (1(23)) from the raw IGC data for different solvents. Upon selection of a common reference volume for all the solvents used, IGC data were found to be well described by the ternary version of the Flory-H uggins lattice theory; unique solvent-independent chi (23) values were obta ined. Our data on blends of high-density polyethylene (HDPE) and low-densit y polyethylene (LDPE) have also confirmed the validity of the zero Delta ch i criterion suggested by Su and Patterson twenty odd years ago (Macromolecu les, 10 (1977) 708) so long as a common reference volume is used in the dat a analysis. If the latter criterion is not satisfied, measured chi (23) val ues still vary with the solvent used. However, it is uncertain whether the present approach can be applied to the situation in which the solvents used do not meet the zero Delta chi criterion. The chi (23) values obtained in the present work suggest that HDPE/LDPE blends may exhibit a closed-loop ph ase behavior. (C) 2000 Elsevier Science Ltd. All rights reserved.