Topochemical polymerisation of a diacetylene: Studies of lattice parameters and thermal expansion coefficients

The solid‐state polymerisation of the disubstituted diacetylene, 2,4‐hexadiynylene bis( p ‐toluene sulphonate). has been studied by x‐ray diffraction in the temperature range 223 to 295 K. The variation in lattice parameters is shown to be similar to that reported in previous less extensive studies. This data is used to determine the behaviour of the thermal expansion coefficients as a function of polymer content. The relevance of these results to the question of polymer chain lengths at low conversion is discussed.