The dynamics of the polymer matrix in filled rubbers is modified by the presence of solid particles. We used low-field proton NMR to investigate model filled samples consisting of a dispersion of grafted silica particles into an elastomeric matrix. Exploiting magic-sandwich echo experiments, we were able to determine the fraction of polymer with slower dynamics and to correlate it to the silica specific surface. The presence of immobilized polymer;most probably due to a gradient of glass transition temperature around the solid particles;is detected whether there is a covalent bond between the filler and the matrix or not. Moreover, the fraction of immobilized polymer decreases in similar ways with either an increase of the temperature or the addition of solvent. In the case of covalent bonds between the silica and the polymer, multiple-quantum experiments reveal that the cross-link density of the elastomer matrix is locally increased in the vicinity of the particles. This is an observation that was not made in any conventional filled elastomer system and it can be attributed to the good particle dispersion and the covalent links in our model samples.

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Using simple and cheap low-field (1)H NMR methods such as the magic sandwich echo technique and FID component analysis, we determine jump rates for 180° chain flips in poly(ethylene) (PE) crystallites, which are comparable to literature data obtained from advanced, complex, and time-consuming (13)C-based NMR methods. In the investigated temperature range, we find similar jump rates for the local chain flip process in a melt-crystallized sample containing lamellar crystals with disordered fold surface and in reactor powder samples having a rather adjacent-reentry-like structure. Previous NMR studies of Yao et al. revealed different chain diffusion coefficients for the resulting long-range chain diffusion between amorphous and crystalline regions in melt- vs solution-crystallized (adjacent reentry) samples. From our results, we conclude that, in the investigated temperature range, the fold surface, which presumably influences the effective chain transport, does not have a strong effect on the time scale of the local chain flip process. We confirm an Arrhenius temperature dependence of the jump rate for the local flip process and calculate activation energies which show a slight trend toward smaller values for the reactor powders (~76 kJ/mol) in comparison to the melt-crystallized sample (~103 kJ/mol).

We report on the investigation of cyclic and comparable linear poly(εcaprolactone)s (PεCL) with molecular weight between 50 and 80 kg/mol with regard to chain mobility in the melt and crystallinity using low-field solid-state 1 H NMR. Our results from NMR Hahn echo and more advanced multiquantum measurements demonstrate a higher segmental mobility of cyclics in the melt as compared to their linear counterparts. Rheological experiments indicate that the cyclics are less viscous than the linear analogues by about a factor of 2, confirming the NMR results. FID component analysis shows higher crystallinities of the cyclic samples by some percent under the condition of isothermal crystallization at 48 °C, suggesting that due to their enhanced overall mobility in the melt, the cyclics reach a more perfect morphology leading to higher crystallinity. We compare this finding with results from DSC measurements obtained under identical conditions and critically evaluate the applicability of polymer crystallinity determination from nonisothermal crystallization investigations by DSC. We further highlight the use of nucleating agents to investigate the particular effect of crystal growth on (nonisothermal) crystallization, separated from the influence of nucleation. These experiments indicate a faster crystal growth for cyclic samples.

We investigate the molecular dynamics within the crystallites of poly(εcaprolactone), PCL, crystallized from the melt by means of high-field 13 C and low-field 1 H NMR spectroscopy, addressing the question of whether it can be classified as a "crystal-fixed" polymer without chain motion through the crystallites. We address fast, slow, and intermediateregime (microseconds to milliseconds time scale) motions by means of high-resolution of 13 C DIPSHIFT and CODEX MAS experiments as well as low-resolution static 1 H FID and MSE measurements over a range of temperatures. The DIPSHIFT data provide information on motionally averaged 13 C− 1 H dipole−dipole couplings and indicate the presence of fast (≤1 μs) methylene group librational motions within the crystalline phase, where the amplitudes increase with increasing distance from the rather rigid ester groups. The CODEX experiments, addressing slow (≥ms) local rotations of the chemical-shift anisotropy tensors, suggest the absence of slow intracrystallite chain dynamics. 1 H second-moment and MSE signal loss data of the crystalline fraction, along with the DIPSHIFT and CODEX data, indicate that intermediate-regime chain motions do not take place in PCL crystallites.