•Fractionation of impact polypropylene was successfully achieved by TREF.•Molecular structure and properties of each fraction were evaluated.•Direct interface between crystalline iPP and EPR was proven by solid-state NMR.•EPR is located in a layer separating a crystalline PE core from the rigid iPP matrix.•Nanoscopic “islands of rigidity” in the phase-separated softer domains were detected.The phase morphology in impact polypropylene was studied by size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and solid-state nuclear magnetic resonance (NMR). The characterizations of the raw copolymer materials indicate the presence of amorphous and crystalline phases. In order to gain more comprehensive insight in the microstructure of these materials, four different subsamples were prepared by Temperature Rising Elution Fractionation (TREF) and subsequently analyzed by DSC, SEC, analytical TREF and solid state NMR measurements. Fraction 1 consisted of non-crystalline ethylene–propylene random copolymer (EPR). Fraction 2 was composed of intermediate ethylene and propylene segments with different length and capabilities to crystallize. In fraction 3, long propylene segments were the dominating contribution, although some amorphous and crystalline ethylene sequences were detected, which are probably incorporated into the polypropylene main chains, since no soluble component was detected by analytical TREF. Finally, isotactic polypropylene (iPP) was determined to be the unique component of fraction 4. The local molecular mobility in the different phases was analyzed using 2D Wide Line Separation (WISE) NMR, while 13C detected spin diffusion experiments helped to elucidate local morphologies. Scanning Force Microscopy (SFM) studies of the impact polypropylene revealed a semicrystalline iPP matrix with dispersed softer regions, which involve not only soft amorphous elastomeric EPR components, but additional nano-domains with semi-crystalline properties different from the iPP matrix. Combining the SFM and solid state NMR results, a phase model for the EPR regions dispersed in the iPP matrix is proposed.

Solid-state NMR experiments as well as extensive Car–Parrinello Molecular Dynamics simulations are used to study the dependence of supramolecular self-organization of benzene-1,3,5-tricarboxamides (BTA) on the local orientation of the amide functionality. Unlike the known symmetric co-planar helical arrangement of CO-centered BTAs found in supramolecular architectures like supramolecular polymers in gels, N-centered BTAs adopt an asymmetric helical arrangement in the solid-state. The resulting tilt angle between the aromatic cores of neighboring BTA molecules leads to a breaking of the three-fold molecular symmetry and thus causes a splitting of 1H MAS NMR signals. At elevated temperatures, motional averaging of the split 1H MAS NMR signals is observed, which can be attributed to certain dynamics on the ms time scale of individual BTA molecules in the columnar packing arrangement.

Dipolar filters select 1H magnetization according to local dipolar dephasing, which corresponds to site mobility in systems with heterogeneous molecular mobility. Combined with a conventional exchange experiment, it is usually applied to polymeric samples exhibiting structures on the nanometer length scale associated with a strong dynamic contrast. There, the resulting 1H nuclear spin diffusion experiment yields the size of the structure. When the same experiment is applied to homopolymer melts exhibiting a weak dynamic contrast and dynamic heterogeneities on significant shorter length scales, the recorded magnetization decay is in agreement with decays expected from a heterogeneous nanostructure. However, dipolar filters actually can also select mobile parts of the repeat unit, e.g. the end of the alkyl side chains and the subsequent magnetization transfer then can occur via cross relaxation due to non coherent zero-quantum transitions (nuclear Overhauser effect, NOE). The difficulties of distinguishing these two cases are examined and it is demonstrated that NOE experiments exploiting magnetization selection via the dipolar filter allow quantifying the local dynamics of the side chains. This opens new possibilities for measurements of local dynamics in non isotopically labeled homopolymer melts.

In synthetic as well as natural polyamides, hydrogen bonding and conformations of amide motifs are strongly influenced by the presence of ions and their concentration, water molecules, and their structure, as well as the pH of the solution. This concept combined with solubility of synthetic aliphatic polyamides, in particular nylons, in water at elevated temperature and corresponding vapor pressure is evaluated as a new reversible shielding route in the processing of these polymers. So far, reversible shielding has not been feasible due to a lack in controlling desired activation and deactivation of hydrogen bonding at the judicious moments. Here we show that in the presence of large halogen anions, crystallization from the random coil state is suppressed by hydrophobic hydration, where the amorphous state of the fast crystallizing nylons can be maintained even at 20 °C. Small hydrating lithium cations are favored since they strengthen the hydrophobic nature of the anions. Complete deshielding of hydrogen bonding, after processing, is facilitated by simple migration of ions in water that allows recovery of the desired conformation and structure.

Solid-state NMR experiments as well as extensive Car–Parrinello Molecular Dynamics simulations are used to study the dependence of supramolecular self-organization of benzene-1,3,5-tricarboxamides (BTA) on the local orientation of the amide functionality. Unlike the known symmetric co-planar helical arrangement of CO-centered BTAs found in supramolecular architectures like supramolecular polymers in gels, N-centered BTAs adopt an asymmetric helical arrangement in the solid-state. The resulting tilt angle between the aromatic cores of neighboring BTA molecules leads to a breaking of the three-fold molecular symmetry and thus causes a splitting of 1H MAS NMR signals. At elevated temperatures, motional averaging of the split 1H MAS NMR signals is observed, which can be attributed to certain dynamics on the ms time scale of individual BTA molecules in the columnar packing arrangement.