Multiply continuous network morphologies were previously identified in
“monodisperse” (polydispersity index (PDI) < ~1.1 in all blocks) poly(isoprene-bstyrene-
b-ethylene oxide) (ISO) triblock terpolymers. This work extends the
investigation of multiply continuous network structures to two other classes of
multiblock terpolymers: i) “monodisperse” OSISO pentablocks and ii) polydisperse ISO
triblocks. The OSISO pentablocks are synthesized using a protected initiation strategy
that required the development of the functional organolithium 3-triisopropylsilyloxy-1-
propyllithium (TIPSOPrLi). TIPSOPrLi may be used to prepare α-hydroxypolystyrene
with narrower molecular weight distributions (PDI ~ 1.1) than are attainable using the
commercially available 3-tert-butyldimethylsilyloxy-1-propyllithium. A telechelic
triblock terpolymer (HO-SIS-OH) with narrow molecular weight distributions in all
blocks is prepared using TIPSOPrLi. A series of OSISO pentablocks is synthesized
from this parent triblock, and a stable region of O70 (the orthorhombic Fddd network) is
identified between two-domain lamellae (LAM2) and three-domain lamellae (LAM3) in
OSISO materials. This sequence of morphologies was previously reported in ISO
triblocks with comparable compositions. Mechanical tensile testing reveals that an
OSISO sample with a lamellar mesostructure fractures in a brittle fashion at a strain of
0.06. An OSISO containing the O70 network, in contrast, has a strain at failure of 1.3,
even though the crystallinity of the terminal blocks is above the brittle threshold
established in other multiblock materials. This improved toughness is attributed to the
combined effects of a triply continuous morphology and an intrinsically tough SIS core.
The ISO triblock studies probe the stability of network morphologies with
respect to polydispersity in the polystyrene and poly(ethylene oxide) chains. Three
series of ISO triblocks with polydisperse (PS PDI = 1.16, 1.31, 1.44) polystyrene blocks
are prepared by anionic polymerization. While the network “window” in the
PS PDI = 1.16 series is comparable in width and location to the window reported in the
“monodisperse” ISO materials, it apparently shrinks for the higher PS PDI values. Only
lamellar mesostructures are reported in the PS PDI = 1.31 materials, and network
morphologies are identified over only a narrow range of compositions in the
PS PDI = 1.44 samples. Polydispersity does not always destabilize network
morphologies, however, as broadening the molecular weight distribution of the terminal
poly(ethylene oxide) block drives a morphological transition from lamellae to the coreshell
gyroid network. This result demonstrates that polydispersity can be used to tune
block terpolymer phase behavior and stabilize technologically useful network
mesostructures. Self-consistent field theory calculations augment the experimental
analysis and offer insight into the physics underlying the polydispersity-driven
University of Minnesota Ph.D. dissertation. February 2009. Major: Chemical Engineering. Advisors: Frank S. Bates and Marc A. Hillmyer. 1 computer file (PDF);xx, 329 pages.
Meuler, Adam James.
Network morphologies in monodisperse and polydisperse multiblock terpolymers..
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