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We present a study of the structure and dynamics of long-chain syndiotactic polypropylene (s-PP) melts by small-angle neutron scattering (SANS), rheology, neutron backscattering, and neutron spin echo spectroscopy (NSE). From SANS, we determine the characteristic ratio of C∞= 11.5, which is larger than that obtained from previous experiments but in good agreement with simulation. Concerning dynamics, in the Rouse regime, neutron backscattering and incoherent NSE revealed Rouse rates that very well agree with each other, demonstrating the consistency of measurements in energy and time space. The single-chain dynamic structure factor was also measured by NSE. As none of the conventional data evaluation schemes for local reptation were successfully applicable, we used the novel extended de Gennes dynamic structure factor [Monkenbusch, M.J. Chem. Phys.2023, 159, 034902]. We found that s-PP displays a strongly asymmetric tube with an aspect ratio of about 0.5. Allowing for a small non-Gaussianity improves the fit. The scaling properties of the Monkenbusch dynamic structure factor are well fulfilled also for s-PP. Contrary to intuition, the tube asymmetry appears not to be related to chain stiffness at least not in the range of C∞= 5 (polyisoprene) and 11.5 (s-PP).

We have presented a systematic small angle neutron scattering investigation of ring–linear blends, where we vary either the ring volume fraction for a given ring in a long linear matrix or the matrix length at a low ring fraction. We found that the ring radius of gyration (Rg) shrinks with increasing ring fraction and nearly reaches the Rgof the ring melt at a volume fraction of ϕR= 0.5. At the same time, the fractal dimension, which is close to a Gaussian conformation at low ϕR, decreases to the value of the ring melt. Aside from very short matrices, the ring size is independent of the host length. Following a random phase approximation treatment, the effective Flory–Huggins parameter (χF,RL) is negative and independent of ϕR, signifying ring–linear attraction that leads to ring–ring repulsion. χF,RLdecreases with decreasing ring size, which might be related to the decreasing possibility of threading events, when the ring size becomes smaller. The ϕR-dependent data in the cross-over regime between low QPorod scattering ∼ Q–4and polymer RPA contribution displays an intermediate Q–2regime, the intensity of which increases proportional to ϕR. The origin of this Q–2contribution is not clear but may be related to critical fluctuations or microphase separation induced by a nonlocal positive contribution to χF,RL. The experimental results fit well into the general picture that is mainly based on simulations, even though in detail, quantitative differences are obvious. Finally, our results are in qualitative agreement with earlier studies on polystyrene ring–linear blends.

We present a study on tracer diffusion of short poly(ethylene oxide) (PEO) tracers in a strongly entangled PEO melt. We find that within the entanglement volume, the dynamics of entanglement strands is significantly non-Gaussian. Following theoretical predictions of Guenza [Guenza, M. G.Phys. Rev. E2014, 895052603], we quantify the non-Gaussian correction α2(t) in terms of a logarithmic Gaussian function with a maximum at a time in the order of the Rouse times of different tracers and a width that is independent of the tracer’s length. The strength of the non-Gaussian correction is found to be equal for all tracers providing another proof that tracers mirror the host dynamics, which needs to be independent of the tracer length. As for polyethylene [Zamponi, M.et al. Phys. Rev. Lett.2021, 12618187801], independent of their molecular weight, the tracer’s center-of-mass mean square displacements are subdiffusive at short times until they have reached the size of the reptation tube d; then, a crossover to Fickian diffusion takes place indicating cooperative chain motion within the entanglement volume d3. Thus, the host dynamics within the tube is not only cooperative but also significantly non-Gaussian.

We address the dynamics of isofrictional bimodal polyisoprene (PI) blends and emphasize the effect of concentration and topology of the short component on the dynamics of the long-chain component. The experiments were performed on blends of long well-entangled linear chains with shorter linear and star-branched chains varying systematically the concentration of the short component (additive). Small-angle neutron scattering showed that the conformation of the long chains does not change either with concentration or with the additive topology. Applying different spectroscopic techniques, we studied the terminal times of both the long chain and the additives. Thereby, the dielectric and viscoelastic terminal times for the long-chain dynamics, as well as the diffusion times deduced from pulsed-field-gradient (PFG)-NMR measurements, follow the same scaling behavior as a function of the volume fraction of the long chains (ϕL). For the case of the linear additive, the scaling τL∼ ϕLis observed in the full concentration range covered (0.1 ≤ ϕL≤ 1). In the case of the star additives, deviations from this scaling law are evident at ϕL≲ 0.4. The zero-shear viscosity scales as η0∼ ϕL3for ϕL≳ 0.4. Deviations are observed at lower values of ϕLfor both additive topologies. On the other hand, the terminal relaxation time of the short chain or the arm retraction time for the stars obtained from dielectric spectroscopy (DS) is only weakly affected by blending and stays nearly constant over the full concentration range. However, the diffusion times of both types of additives depend significantly on ϕL. Finally, measuring the dynamic structure factor by neutron spin echo (NSE), we directly observe the process of constraint removal at the molecular scale. These results are discussed in terms of the different theoretical approaches available. Thereby, the nearly quantitative agreement of the rheological results with the Read extension of the Viovy theory for long-chain volume fractions ϕL≥ 0.5 is emphasized. On the other hand, the low ϕLresults cannot be accounted for. Also, predictions of the tension equilibration mechanism leading to an enhanced ϕL-dependence are not supported by our data.

The diffusion of isobutane in silicalite was studied using neutron spin–echo (NSE) experiments and molecular dynamics (MD) simulations between 444 and 550 K. The experimental and simulated diffusion coefficients showed agreement well within an order of magnitude, as did the activation energies of diffusion which agreed to within 3.4 kJ mol–l(∼15%). Jump diffusion was observed by NSE with a jump distance of 10 Å, also observed by the MD simulations showing that the residence time was spent in a small section of the sinusoidal channel, rather than the intersections between channels as reported in previous simulations. The level of sinusoidal trapping diminishes in the simulations with increasing temperature, where the isobutane develops isotropic diffusion through both channel systems, as observed by NSE experiments.

The dynamics of rigid random polymer coils in dilute solution has been investigated by neutron spin-echo (NSE) spectroscopy. The polymers used were polynorbornenes that consist of chains of the bridged norbornene rings with hexyl (PNBH) or propyl (PNBP) side groups. These polymer molecules have large internal rotation barriers that hinder conformational changes and give each chain a kind of individual shape memory. Thereby the chains exhibit a dynamical stiffness that leads to a significantly retarded relaxation as compared to flexible polyisoprene chains (PI). While the latter perfectly match the prediction of the Zimm model, the polynorbornene spectra display the signature of a dynamical stiffness due to the “frozen” coil conformation of the PNBH or PNBP chains.

Random crystalline–amorphous copolymers containing ethylene and butene segments, yielded from dilute‐solution, and self‐assembled to one‐dimensional, needle‐shaped aggregates, can modify wax crystal structures through the cocrystallization of the copolymer and wax molecules into hairy platelets. These copolymers show selectivity in their wax crystal modification capacities that depends on the ethylene content of the backbone. Thus, it has been qualitatively established that a copolymer containing larger crystallizable polyethylene sections [poly(ethylene butene) with 7.5 ethyl branches per 100 backbone carbons (PEB‐7.5)] is very efficient for longer wax molecules (C36), whereas for shorter waxes (C24), its efficacy diminishes. Here we present a quantitative evaluation of the small‐angle neutron scattering results obtained in a complex study of the self‐assembling behavior of PEB‐7.5 and paraffin waxes (C24 and C36) in decane and of cocrystallization for different polymer–paraffin combinations and solution conditions. The richness of the morphologies was evaluated with a contrast variation technique and the application of structural models. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3113–3132, 2004

Neutron scattering accesses the space time evolution of molecular motion on atomistic length and time scales covering all dynamical processes from local relaxations to overall chain diffusion. Using the dynamics of a chain in the melt as an example, we review results obtained by the various high resolution neutron scattering techniques and outline future opportunities.Copyright © 2002 Society of Chemical Industry

Abstract. The time-resolved small-angle X-ray scattering (SAXS) profiles, obtained during the polymerization of perfluorooctyltrimethoxysilane catalyzed by different HCl concentrations, have been analyzed using the unified Guinier/power-law equation introduced by Beaucage. SAXS profiles, time-sliced for the reaction mixture catalyzed by dilute HCl, can be perfectly fitted by a simple Beaucage function with only one step of structural hierarchy. The time-resolved SAXS profiles, obtained from the reaction mixtures catalyzed by more concentrated HCl, have led to the conclusion that the growth process of the polymeric aggregate occurs in two steps. This result was successfully explained by application of the unified equation at two structural levels. This conclusion is now corroborated by application of the unified Beaucage equation to evaluation of the growth process of the polymeric precursors.

We applied these methods of small-angle neutron scattering (SANS) and neutron spin echo (NSE) on a swollen poly ( N -isopropyl acrylamide) (NIPA) gel in order to observe the elastic scattering of frozen concentration fluctuations due to crosslinks. We successfully obtained the structure factor for the frozen concentration fluctuations in a q -domain of q >0.01 A -1 , while in a q -domain of q <0.01 A -1 , this attempt failed due to the limited performance of the q -resolution and the Fourier time t F of the current specifications of the NSE spectrometers. This technical hurdle for the spectrometer should be overcome on an intensified neutron source for the next generation, realizing t F of μs-order and the q -resolution down closer to 0.001 A -1 .

Elastic and quasielastic small angle neutron scattering experiments on low molecular mass isotopic polydimethylsiloxane (PDMS) and polyethylmethylsiloxane (PEMS) blends were performed in order to study the static and dynamic single and many chain behavior in both systems. Within experimental error no differences could be detected with respect to the fundamental chain properties: conformation and type of relaxation. In particular, the latter follows the predictions of the Rouse model up to Q-values of 0.2 Å^–1. However, it was also observed that the relaxation rates are not the same. In both siloxanes single chains relax slightly faster than many chains. The origin of this effect is not known. Despite of these deviations the overall experimental findings favor the hypothesis that the collective or many chain properties of low molecular mass polymer melts can be well modeled by the related single chain behavior.

Tenside anion "doped", highly conducting polypyrroles (PPY) have been grown electrochemical-ly from aqueous electrolytes. The influence of the electrolysis parameters on the conductivity have been investigated. The X-ray diffraction patterns allow to derive a structural model.

The structure of conducting polymers is discussed in comparison to simple, so-called organic metals derived from naphthalene and similar arenes. In this context the conducting polymers are viewed as ion-radical salts of the backbone-units. This view is substantiated by recent results from X-ray investigations on electrochemically oxidized p-quaterphenyl as a model for poly(p-phenylene), poly-pyrrol salts of detergent ions and oxidized, highly oriented polyacetylene.