Polymorphism of Poly(butylene terephthalate) Investigated
by Means of Periodic Density Functional Theory Calculations
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Abstract
The conformation and solid state
structure of the two α and
β polymorphs of poly(butylene terephthalate) are here studied
by means of state-of-the-art first principles calculations, carried
out both for the crystals and the infinite one-dimensional chain models.
Focusing in details on the debated β form, induced by mechanical
deformation, we verified the setting on of an all-trans conformation,
as also supported by the simulation of the infrared spectra of the
different polymorphs compared to the available experimental spectra.
The transition from the α to the β form is also simulated
by applying increasing strains to the infinite polymer chain: a peculiar
evolution of the intramolecular structure is indeed predicted, showing
a transition from the GTG′ conformation found for the α
form to the TTT conformation of the strained β form