Self-assembly of high molecular weight polydisperse acrylic block copolymers and their blends is
presented under conditions as close as possible to thermodynamic equilibrium. Di- and triblock copolymers
comprising a poly(butyl acrylate) (PBA) first or middle block, and poly(methyl methacrylate) (PMMA) second
or outer blocks, denoted MBA and MBAM, respectively, are prepared by nitroxide-mediated polymerization
(NMP). Their particularity is that the acrylic block is controlled while the methacrylate block is polymerized via
an uncontrolled radical process under the synthesis conditions used. Overall composition and molecular weight
polydispersities are large. Molecular disorder does not yield macrophase separation, and TEM on solvent cast
films reveals lamellar and poorly ordered bicontinuous, cylindrical, or spherical morphologies. Except for the
lamellar phase, clear multiple orders of diffraction are not visible in SAXS, and scattering profiles instead indicate
a liquidlike order of microdomains. More importantly, morphology boundaries are strongly shifted compared to
those commonly accepted for model monodisperse block copolymers. Hence, symmetric copolymers adopt
morphologies with highly curved interfaces while lamellae are displaced to PMMA-rich compositions. These
results suggest that unbalanced polydispersity between the two blocks can induce interfacial curvature toward to
broadest molecular weight distribution, thereby releasing stretching energy of the whole chain. This effect is
expected to be encountered in radical or hybrid block copolymer syntheses whenever control cannot be optimized
for all blocks.
In supramolecular polymers, directional interactions control the constituting units connectivity, but dispersion forces may conspire to make complex organizations. Here we report on the long-range order and order-disorder transition (ODT) of main-chain supramolecular polymers based on poly(propylene oxide) (PPO) spacers functionalized on both ends with thymine. Below the ODT temperature (T(ODT)), these compounds are semicrystalline with a lamellar structure, showing nanophase separation between crystallized thymine planes and amorphous PPO layers. Above T(ODT), they are amorphous and homogeneous even though their X-ray scattering spectrum reveals a peak. This peak is due to correlation hole effect resulting from contrast between end-functional groups and spacer. Macroscopically, the transition is accompanied by dramatic flow and mechanical properties changes.
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