V. Balsamo et R. Stadler, Influence of the crystallization temperature on the microphase morphology of a semicrystalline ABC triblock copolymer, MACROMOLEC, 32(12), 1999, pp. 3994-3999
The microphase morphology of a polystyrene-block-polybutadiene-block-poly(e
psilon-caprolactone) SBC triblock copolymer is studied through transmission
electron microscopy. Even though crystallization of the PCL block takes pl
ace well below the PS glass transition, lamellar microphases and the format
ion of well-defined spherulites are observed. The typical long-range order
normally obtained for amorphous triblock copolymers is not obtained in the
SBC triblock copolymer, The morphology of a polystyrene-block-poly(epsilon-
caprolactone) diblock copolymer was also observed and compared with the tri
block copolymer, To investigate whether the crystallization temperature (T-
c) is a parameter influencing the final morphology, samples of the triblock
copolymer were crystallized at 45 and 42 degrees C. This reduction in T-c
results in a morphological transition from a simple lamellar morphology (PS
, PB, and PCL form layers), which we call lamellar-lamellar (ll), to a lame
llar-cylindrical (lc)-morphology with PS and PCL layers and PB cylinders at
the PS/PCL boundary. From these changes, combined with the observation of
well-defined spherulites in both cases, we can deduce the orientation of th
e PCL chains in the crystalline regions as being perpendicular with regard
to the block copolymer interfaces.