Thermodynamic Stabilities of the 3 Crystalline Forms of Isotactic Poly-1-butene As A Function of Temperature

Thermodn. stabilities of the 3 cryst. forms of isotactic poly(1-butene) [25036-29-7] as a function of the temp. was evaluated by packing energy calcns. using the values of the axes of the unit cells obtained by x-ray measurements. The lengths of the axes of the unit cells were detd. from x-ray powder spectra at different temps. in a range between 170 K and temps. near the m.p. for each form. The packing energy was calcd. by minimizations performed using the exptl. values of the axes of the unit cells at the various temps. The results showed that form 1 was the most stable form in all the range of temp. and that form 3 was low in energy with resp. to form 2, but the 2 forms became almost isoenergetic at high temps.