The reaction products from the radically initiated grafting of specifically 13 C-enriched maleic anhydride ([2,3-13 C2]MA) onto polyethene, isotactic polypropene and ethene-propene copolymers in the melt and in solution are investigated using noise-decoupled and 1D inadequate 13 C NMR spectroscopy. The sites of attachment and the structures of the grafts depend on (co)polymer composition. In random EPM, MA attaches to methylene and methine carbons in the backbone. In alternating EPM, MA attaches solely to polymer methines, indicating that (CH2)m sequences with m > 3 are needed for MA attachment to backbone methylene carbons. In the copolymers and in IPP, grafts are single succinic anhydride rings; in HDPE and LDPE short MA oligomers are also present. In polyolefins containing polypropene sequences, chain scission can yield structures in which the anhydride ring is attached to the chain terminus via a fully substituted double bond.

A pulse sequence has been implemented for the determination of domain sizes in 13 C enriched organic materials with two-dimensional high-resolution magic angle spinning (MAS) NMR correlation spectroscopy. The method integrates the high resolution of 13 C MAS for selection and detection with an efficient polarization transfer across domain boundaries via strong 1 H dipolar interactions. A one-dimensional version with spectral editing allows for improved efficiency with respect to measurement time. With this MAS NMR and labeling approach heterogeneity at length scales from 1 to 100 nm can be determined for systems without long-range order. As an example, proton spin diffusion times up to 500 ms were used to study the morphology of a phase-separated semi-interpenetrating network of poly(styrene-co-acrylonitrile) and cross-linked poly(styrene-co-maleic anhydride). From the spin diffusion behavior a characteristic domain diameter d ) 63 ( 4 nm was calculated.

Accelerated-sulfur-vulcanized 13 C-labeled EPDM with and without carbon black and extender oil was analyzed using 13 C solid-state NMR to determine the chemical structure of the network. Highresolution solid-state 13 C NMR reveals that sulfur cross-linking takes place at the allylic positions of the ENB independent of the presence of carbon black and oil. From the integrated intensities of the 13 C signals, the conversion of ENB into a cross-link can be quantitatively determined during the vulcanization process. The ENB conversion for gumstock EPDM is ∼10% after 10 min of vulcanization at 150 °C, which is a typical optimum vulcanization time in commercial applications. In the presence of carbon black the ENB conversion is marginally faster and reaches ∼12% in 10 min, while a maximum conversion of ∼20% was obtained. The efficiency of the ENB conversion was ∼20% less at 150 °C and ∼30% less at 180 °C in the compound with carbon black and oil compared to the compound without carbon black and oil. The substitution at the 9-position of ENB is always preferred over each of the two 3-positions. In turn, the substitution on the 3-exo position is always preferred over the 3-endo position, which is different from earlier model studies. When the material is heated for extended periods (10-20 min), oxidation and reversion of the cross-links starts to occur. Reversion is enhanced upon a temperature increase to 180 °C and yields a 4,5,6,7-tetrahydro-4,7-methanobenzo[b]thiophene compound. The length of the sulfur bridge in compound A and B is rather short, i.e., 1 or 2.

The aromatic odd‐alternant phenalenyl anion and a number of its derivatives were prepared in order to study the perturbation of this conjugated anion by methyl and methoxy groups. The conjugated anions were studied by means of 1H and 13C NMR spectrometry, alkylation experiments and semi‐empirical calculations. It was found that a substituent at a charged carbon atom perturbs the entire conjugated system, whereas substituents at inactive (uncharged) carbon atoms have a large effect on the positions ortho to the substituent.

Site-directed isotopic enrichment and solid-state 13 C spin-diffusion NMR techniques were employed to characterize miscibility at the molecular level and phase separation in blends of amorphous polymers. Using 2D proton-driven spin-diffusion techniques on a mixture of 13 C-labeled poly(styreneco-maleic anhydride), [ 13 CH2, 13 CO]SMA (27 wt % MA, Mw ∼ 4 × 10 4 g mol -1 ), and poly(styrene-coacrylonitrile), [ 13 CN]SAN (27 wt % ACN, Mw ) 1.3 × 10 5 g mol -1 ), it is demonstrated that SMA and SAN are miscible on the molecular level. However, a specific orientation of the nitrile moieties in SAN with respect to the carbonyl groups in SMA is unlikely. This suggests that the miscibility of SAN and SMA copolymers is associated mainly with a decrease of intramolecular repulsion upon mixing, as opposed to a specific exothermic binary interaction. In addition, spin-diffusion experiments show that upon selective cross-linking of the SMA phase semi-interpenetrating networks are formed. Increasing the degree of cross-linking results in increasing degrees of phase separation.