Hs. Lee et al., SEGMENTAL ORIENTATION BEHAVIOR OF POLY(BUTYLENE TEREPHTHALATE-CO-TETRAMETHYLENE OXIDE) UPON UNIAXIAL DEFORMATION, Macromolecules, 27(15), 1994, pp. 4364-4370
The segmental orientation behavior of the thermoplastic elastomer [pol
y(butylene terephthalate-co-tetramethyleneoxide)] has been studied wit
h infrared dichroism and polarizing microscopy. The orientation of har
d segments as well as soft segments has been determined as a function
of draw ratio. The difference in the orientation behavior of soft and
hard segments has been associated with the respective glass transition
temperatures. It has been also established that annealing significant
ly affects the deformation behavior. The segmental orientation has bee
n observed to be strongly affected by the addition of small amount of
the asymmetric chain extender. These results indicate that the crystal
line structure of the hard segment can be significantly perturbed by t
he heterogeneity of the chain extender. The birefringence observed usi
ng the polarizing microscopy as a function of draw ratio correlates we
ll with the orientation functions of hard segments rather than those o
f soft segments. It is known that pi electrons in the hard-segment str
ucture affect the refractive index significantly. Thus chemical struct
ure of each segment in phase-separated thermoplastic elastomer should
be considered in order to properly interpret birefringence data.