Thin films of gutta percha have been examined by means of electron diffraction, and shown to exist in three distinct crystalline forms, termed the α, β and γ modifications, whereas prior to this work only two forms had been recognized.
The conditions necessary for the occurrrence of the different forms are considered and probable unit cells are suggested for two of them. These have the dimensions:
β form: a=7.83 Å, b=11.87 Å, c=4.75 Å, α=β=γ=90°.
γ form: a=5.9 Å, b= 7 9 Å, c=9.2 Å, α=β=90°, γ=94°.
Data from the α modification were insufficient to provide the full set of lattice constants but the identity period along the chain axis was found to be 8.76 Å.
The β form which provides the most data has received much, previous study and the present figures show broad agreement with those of previous workers.
The three identity periods of 8.76 Å, 4 75 Å, and 9 2 Å are in close agreement with those predicted by C. W. Bunn on the basis of theoretical considerations of the possible configurations of a transpolyisoprene chain