Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO−PPO−PEO) triblock copolymers were successfully prepared. Two samples of PEO−PPO−PEO triblock copolymer with different ethylene oxide (EO) contents, denoted as EO30 with 30 wt % EO content and EO80 with 80 wt % EO content, were used to form the self-organized thermoset blends of varying compositions using 4,4‘-methylenedianiline (MDA) as curing agent. The phase behavior, crystallization, and morphology were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). It was found that macroscopic phase separation took place in the MDA-cured ER/EO30 blends containing 60−80 wt % EO30 triblock copolymer. The MDA-cured ER/EO30 blends with EO30 content up to 50 wt % do not show macroscopic phase separation but exhibit nanostructures on the order of 10−30 nm as revealed by both the TEM and SAXS studies. The AFM study further shows that the ER/EO30 blend at some composition displays structural inhomogeneity at two different nanoscales and is hierarchically nanostructured. The spherical PPO domains with an average size of about 10 nm are uniformly dispersed in the 80/20 ER/EO30 blend; meanwhile, a structural inhomogeneity on the order of 50−200 nm is observed. The ER/EO80 blends are not macroscopically phase-separated over the entire composition range because of the much higher PEO content of the EO80 triblock copolymer. However, the ER/EO80 blends show composition-dependent nanostructures on the order of 10−100 nm. The 80/20 ER/EO80 blend displays hierarchical structures at two different nanoscales, i.e., a bicontinuous microphase structure on the order of about 100 nm and spherical domains of 10−20 nm in diameter uniformly dispersed in both the continuous microphases. The blends with 60 wt % and higher EO80 content are completely volume-filled with spherulites. Bundles of PEO lamellae with spacing of 20−30 nm interwoven with a microphase structure on the order of about 100 nm are revealed by AFM study for the 30/70 ER/EO80 blend.

The segmental orientation of uniaxially strained poly(l,4-butadiene) networks was probed by deuterium magnetic resonance over a wide range of extension ratios. The experiments were performed on homogeneously deuterated networks and on partially deuterated networks with short deuterated segments at network junctions. The analysis of the strain-dependent line shapes of the deuterium resonances is interpreted in terms of a nonaffine deformation mechanism by means of which short elastically effective chains are stretched to a greater extent than long chains. Comparison of homogeneously and junction deuterated networks gives evidence of inhomogeneous deformation of individual chains with an excess orientation near network junctions.

A simplified theoretical model of the structure and dynamics of polymer networks is successfully applied to the transversaland 2H-NMR relaxation in 1,4-cis-polybutadiene networks produced by crosslinking a mix of conventional and partially deuterated chains with thiuram. For both independent relaxation methods the relaxation curves are qualitatively equal and their analysis provides a consistent picture of the characteristic network parameters. Especially, the Afc values, which were determined by both relaxation methods, are in good agreement with one another and with values which were obtained from stress-strain measurements on the same samples. Taking into consideration similar results of our previous papers, the theoretical treatment and comparison of the NMR results to mechanical experiments provide a firm basis for the continuing use of the approach to characterize Mc.

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