Cross-polarized Light Microscopy Research Articles

Rigid backbone polymers: 6. Ternary phase relationships of polyisocyanates

The ternary systems poly(n-hexyl isocyanate) (PHIC)/poly-(n-octyl isocyanate) (POIC)/tetrachloroethane (TCE), POIC/polystyrene (PS)/TCE, poly(50% n-butyl + 50% p-anisole-2-ethyl) isocyanate (PBAEIC)/PS/TCE, and POIC/PBAEIC/TCE, were studied by means of cross-polarized light microscopy and proton nuclear magnetic resonance (n.m.r.) observations. The system PHIC/POIC/TCE had a polymer concentration range in which a single anisotropic phase was observed over all polymer/polymer ratios. The system POIC/PBAEIC/TCE suggested a similar behaviour. Lower polymer concentrations exhibited an anisotropic/isotropic biphasic concentration interval, and even lower concentrations produced a single isotropic solution. In the systems POIC/PS/TCE and PBAEIC/PS/TCE a single anisotropic phase existed in the high concentration region only where the amount of PS was negligible. In the presence of substantial amounts of PS the systems were either biphasic or isotropic, depending on the polymer/polymer ratio and the concentration of polymer in TCE. The above is in agreement with Flory's recent theory 1–7 concerning the behaviour of mixtures of rod-like particles and mixtures of rods with flexible coils.