INTRINSIC VISCOSITIES AND HUGGINS CONSTANT FOR ETHYLENE-PROPYLENE COPOLYMERS .2. EFFECT OF THE STERIC HINDRANCE OF THE SOLVENT ON THE SOLVENT QUALITY - VISCOSITIES IN BRANCHED ALKANES, CYCLOALKANES, TETRAALKYLTIN COMPOUNDS, CIS-BICYCLO[4.4.0]DECANE AND TRANS-BICYCLO[4.4.0]DECANE, AND TETRAHYDRONAPHTHALENE

The intrinsic viscosities of three ethylene-propylene copolymers (33, 63, 75%, mole percent of ethylene) have been measured in branched alkanes, cycloalkanes, cis- and trans-bicyclo[4.4.0] decane, tetrahydronaphthalene, and the SnR4 (R = alkyl group) compounds. The solvents chosen represent striking examples of the large differences of steric hindrance among compounds of apparent similarity. The macromolecules were used as models of linear and branched alkanes to investigate the effect of the steric hindrance character of the solvent on the free energy of mixing. Steric hindrance is known to give an exothermic contribution to the heats and is found here to increase considerably the quality of the solvent. For example, with 2, 4-dimethylpentane [η] = 1.73 whereas it is 2.37 dL/g-1 for the sterically hindered 2, 3-dimethylpentane. Cyclopentane is recognized as being by far the best solvent for two samples. The Huggins’ constant diminishes from 0.5 to 0.2 when the solvent quality increases. Large variations of k’ in moderately bad solvents seem to reflect differences in shape and steric hindrance of the solvent. Due to its low cost in time and in the amount of material required, intrinsic viscosity measurements of EP copolymers may be a convenient way to study some properties of linear and branched alkanes. © 1979, American Chemical Society. All rights reserved.