Rigid backbone polymers. X. Transitions in bulk polyisocyanates

Data obtained by hot‐stage cross‐polarized light microscopy and thermogravimetric analysis were used to plot a transition map for the poly(n‐alkylisocyanate) homologous family. Most members had a low‐temperature transition (or relaxation). The middle members of the family, with side‐chain length of 4 ≤ n < 13 carbon atoms, exhibit a mesomorphic range of temperatures. Members with sidechains of n ≥ 13 in length, go directly from the low‐temperature transition to the melting point without passage through a liquid crystalline state. A transition map for two homopolymers and a series of their copolymers, poly[x mol% n‐butyl + (100‐x)mol% p‐anisole‐3‐propyl]isocyanate, was also prepared. The range of mesomorphicity as a function of composition and temperature is clearly indicated.