Three types of compositionally symmetric and nearly monodisperse diblo
ck copolymers, poly(1,2-butadiene)-poly(styrene) (1,2-PB-PS), poly(cis
-1,4-isoprene)-poly(styrene) (1,4-PI-PS), and poly(1,4-butadiene)-poly
(styrene) (1,4-PB-PS), were anionically synthesized and subsequently c
atalytically saturated, yielding poly(vinylcyclohexane)-poly(ethylethy
lene) (PVCH-PEE), poly(ethylenepropylene)-poly(vinylcyclohexane) (PEP-
PVCH), and poly(ethylene)-poly(vinylcyclohexane) (PE-PVCH). The order-
disorder transition temperature, T(ODT), was determined for the unsatu
rated and saturated diblock copolymers using dynamic mechanical spectr
oscopy. Changes in T(ODT) with saturation are dependent on the resulti
ng polyolefin microstructure. PVCH-PEE has a much lower T(ODT), while
PEP-PVCH and PE-PVCH display higher ones, relative to the unsaturated
precursor materials. Group contribution analysis qualitatively anticip
ates the PVCH-PEE behavior but fails to account for the PEP-PVCH and P
E-PVCH results. Entropic arguments based on differences in the conform
ational characteristics of each block appear to be correlated with the
associated variations in the segment-segment interaction parameter, c
hi. These findings support earlier speculation regarding the role of c
onformational asymmetry in the thermodynamics of polymer-polymer syste
ms.