This work reports the first instance of self-organized thermoset blends containing diblock copolymers with a crystallizable thermoset-immiscible block. Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and a low-molecular-weight (M n ) 1400) amphiphilic polyethylene-block-poly-(ethylene oxide) (EEO) symmetric diblock copolymer were prepared using 4,4′-methylenedianiline (MDA) as curing agent and were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC). All the MDA-cured ER/EEO blends do not show macroscopic phase separation but exhibit microstructures. The ER selectively mixes with the epoxy-miscible PEO block in the EEO diblock copolymer whereas the crystallizable PE blocks that are immiscible with ER form separate microdomains at nanoscales in the blends. The PE crystals with size on nanoscales are formed and restricted within the individual spherical micelles in the nanostructured ER/EEO blends with EEO content up to 30 wt %. The spherical micelles are highly aggregated in the blends containing 40 and 50 wt % EEO. The PE dentritic crystallites exist in the blend containing 50 wt % EEO whereas the blends with even higher EEO content are completely volume-filled with PE spherulites. The semicrystalline microphase-separated lamellae in the symmetric EEO diblock copolymer are swollen in the blend with decreasing EEO content, followed by a structural transition to aggregated spherical micellar phase morphology and, eventually, spherical micellar phase morphology at the lowest EEO contents. Three morphological regimes are identified, corresponding precisely to the three regimes of crystallization kinetics of the PE blocks. The nanoscale confinement effect on the crystallization kinetics in nanostructured thermoset blends is revealed for the first time. This new phenomenon is explained on the basis of homogeneous nucleation controlled crystallization within nanoscale confined environments in the block copolymer/thermoset blends.

We have synthesized a series of liquid crystalline/isotropic block copolymers with narrow molecular weight distribution and with well-defined chemical structure. Block volume fractions were varied systematically. The domain structure of these compounds was determined by means of small-angle X-ray scattering. Spherical, cylindrical, and lamellar morphologies were observed with the liquid crystalline (LC) block in the matrix or in the domain, respectively. The polymers are strongly segregated, and no order-to-disorder transition is found up to 170 °C. DSC and polarized microscopy data reveal that the mesomorphic behavior of LC blocks is only slightly influenced by copolymer composition and is basically characterized by the sequence g/∼35 °C/n/∼120 °C/i. The rotational dynamics over a broad temperature and frequency range was studied using dielectric spectroscopy. The LC block reveals two cooperative modes assigned to the segmental relaxation (α process) and to the side chain rotation as a whole (δ process). A confinement effect is visible in the shift of both relaxation times to lower values for domain sizes less than 20 nm. The effect is stronger for 2D than for 1D confinement geometry. It is small compared to similar effects found for free-standing thin polymer films. For copolymers with alternate lamellae or LC cylindrical microdomains, a Maxwell−Wagner polarization was observed in addition to the α and δ processes.

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The effect of nanoscale confinement on the local polymer dynamics has been studied by means of dielectric spectroscopy in the frequency range from 10 mHz to 1 MHz. We have used microphase-separated PS/LC block copolymers (PS = polystyrene, LC = liquid crystalline). Depending on volume fraction, the LC blocks were confined to a layer with thickness of 21.3 and 11.2 nm (lamellae morphology) or were contained in domains of cylindrical or spherical form with diameter of 12.6 and 9.4 nm, respectively. At lower concentration of PS blocks, the LC copolymer form a continuous LC matrix with cylindrical inclusions of PS component. For all morphologies the LC block reveals two dielectric relaxations related to the local motion of mesogen (β process) and spacer (γ process). The relaxation time as well as the activation energy for the γ process was independent of spatial constraints even for the smallest characteristic length of 9.4 nm. The β relaxation, however, speeds up, and its activation energy decreases for confinement lengths less than 20 nm. The γ process has an essentially noncooperative nature, whereas the β process exhibits a positive apparent activation entropy, reflecting a partial cooperative feature. As a result, the β relaxation is affected by confinement just as the essentially cooperative dynamic glass transition (α relaxation) in polymers.

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