Evaluation of compatibility of methacrylic copolymers by capillary viscometry

The estimation of the compatibility of different pairs of polymers can, be based on capillary viscometry data for ternary polymer-polymer-solvent syst ems using mathematical models based on the slope of the Huggins equation (D elta b) and Huggins constant (Delta k'), In this study, the compatibility o f binary mixtures of six types of methacrylic copolymers with similar molec ular weights but different functional groups [one characterized by amine gr oups (EuE), two by ammonium groups (EuRL EuRS), two by carboxylic groups (E uL EuS), and one without charge (EuNE)] was evaluated using these methods. On the basis of Huggins and Kraemer constants, acetone and tetrahydrofurane were selected as good solvents for the programmed blends. Cationic copolym ers mixed with anionic copolymers showed the formation of visible aggregate s. The study performed on the other blends showed that EuRL and EuRS could be considered compatible with EuE; EuNE was incompatible with both EuL and EuE, EuL and EuS were incompatible between them. EuRL and EuRS could be con sidered compatible even if the weight ratio seems to influence the behavior of the two copolymers. The Delta k' approach seems to be more robust than the Delta b model. The compatibility of different pairs of methacrylic copo lymers with similar molecular weights could be evaluated using capillary vi scometry, (C) 2000 John Wiley & Sons, Inc.