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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.

The translocation of biologically active macromolecules through cell membranes is of vital importance for cells and is a key process for drug delivery. Proteins exploit specific conformational changes in their secondary structure to facilitate membrane translocation. For the large class of biological and synthetic macromolecules, where such conformational adaptions are not possible, guidelines to tailor the structure of monomers and macromolecules to aid membrane translocation and cross-membrane drug delivery would be highly desirable. Here, we use alternating amphiphilic macromolecules to systematically investigate the relation between polarity, polymer chain length, lipid chain length, polymer concentration, and temperature on membrane partition and translocation rate. We employed pulse field gradient NMR and confocal fluorescence microscopy to determine membrane adsorption and desorption rate constants and partitioning coefficients. We find that translocation is a two-step process involving a fast adsorption and membrane insertion process and a slower desorption process. Membrane insertion is a key step that determines the molecular weight, concentration, and temperature dependences. Passive translocation is possible on time scales from minutes to hours. Macromolecules with different adapted hydrophilic/hydrophobic comonomer sequences show the same translocation rate, indicating that common optimized translocation conditions can be realized with a variety of monomer chemical structures. The investigated copolymers are biocompatible, biodegradable, and capable of transporting a hydrophobic payload through the lipid membrane. This detailed understanding of the macromolecular translocation mechanism enables to better tailor the delivery of active agents using macromolecular carriers.

Amphiphilic polymers show a rich variety of self-assembly behavior in aqueous solutions. In experimental studies, statistical copolymer or block copolymer architectures are usually investigated because of their ease of synthesis or their structural analogy to surfactants. A copolymer structure that links the two architectures is an alternating copolymer, which is easily accessible by polycondensation reactions. Using alternating hydrophilic and hydrophobic building blocks with varying lengths allows a systematic variation between statistical and multiblock architectures. We synthesized alternating amphiphilic copolymers as polyesters using hydrophobic dicarboxylic acids (C4–C20) and hydrophilic poly(ethylene glycol) (PEG) units (EG3–EG1000). Copolymers with long EG units were made accessible with the help of a newly developed esterification process. The solution properties of amphiphilic copolymers feature a lower critical solution temperature (LCST) behavior in water, which can be systematically varied over a wide range from 3 to 83 °C by adjusting the lengths of the Cnand EGmunits. We find that the transition temperature depends linearly on the hydrophobic unit length Cmand logarithmically on the hydrophilic length EGn. In the one-phase region, PEG copolymer coils are more compact compared to the respective PEG homopolymers due to hydrophobic interactions between the hydrophobic units leading to loop formation. For shorter PEG units, the copolymers form micellar structures consisting only of a few copolymer chains. The micellar cores consist of hydrophobic regions containing only a few dicarboxylic acid units embedded in a PEG-rich and water-poor matrix. The cores are surrounded by a diluted corona of PEG chains. Further decreasing the PEG unit length leads to the formation of highly swollen gels consisting of networks of interconnected micelles. These can self-assemble to form highly ordered liquid crystalline cubic phases. The study demonstrates how the structure of alternating amphiphilic copolymers can be systematically varied to adjust the thermal solution properties such as the LCST over a wide range, as well as the self-assembly properties varying between single chains, micelles, gels, and highly ordered lyotropic liquid crystals.

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 investigated the influence of an n-alkyl-PEO polymer on the structure and dynamics of phospholipid vesicles. Multilayer formation and about a 9% increase in the size in vesicles were observed by cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), and small-angle neutron/X-ray scattering (SANS/SAXS). The results indicate a change in the lamellar structure of the vesicles by a partial disruption caused by polymer chains, which seems to correlate with about a 30% reduction in bending rigidity per unit bilayer, as revealed by neutron spin echo (NSE) spectroscopy. Also, a strong change in lipid tail relaxation was observed. Our results point to opportunities using synthetic polymers to control the structure and dynamics of membranes, with possible applications in technical materials and also in drug and nutraceutical delivery.

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 role of poly(ethylene oxide) (PEO) topology in the melt intercalation in graphite oxide (GO)-based materials is investigated. The intercalation of PEO in GO leads to changes in the GO interlayer space and to the suppression of polymer thermal transitions (crystallization and glass transition). Herein, we perform kinetic measurements of the melt intercalation of cyclic and linear PEO (CPEO and LPEO) with Mn= 2–20 kg/mol in different GO-based structures by monitoring the reduction of melting peak areas of PEO. We demonstrate that high sensitivity to PEO topology can be achieved using GO partially pillared with 1,6-hexanediamine. Using only 1 wt % of pillars, the rate constants of cyclic PEO become up to a 100 times smaller than that of linear chains of similar molecular weight. This enormous difference in the intercalation kinetics of topologically different PEO chains cannot be achieved in nonpillared GO, where the rate constants of cyclic PEO presented values that were only up to 4 times smaller than that of their linear analogues. The dramatic reduction in the intercalation rate for CPEO in the presence of pillars indicates that topological constraints (formation of squeezed structures with double folded strand conformations) are the most important factors affecting the melt intercalation kinetics. The results suggest that it is possible to restrict the intercalation of cyclic PEO into partially pillared GO, whilst allowing the linear analogue to diffuse through the GO interlayer space. This important finding could be the basis for developing new methods of purification of cyclic polymers.

The spin relaxation of protons and deuterons was investigated in melts of ring poly(ethylene oxide) (PEO) macromolecules with a molecular mass varying from 5280 to 96,000 Da. Comparison of the frequency dispersion of NMR spin–lattice relaxation rates with corresponding rates in the melts of linear PEO of similar molecular masses shows that there is a significant mutual interpenetration of neighboring ring macromolecules, although less pronounced than in their linear counterparts. The mean-squared displacement of ring segments in the investigated frequency interval corresponding to the time interval 8 × 10–9to 2 × 10–5s depends on time as ⟨rn2(t)⟩ ∝ t0.39, in agreement with neutron spin echo (NSE) results. Decays of the normalized Hahn echo signal in ring macromolecules are exponential within experimental errors, unlike for their linear counterparts where strongly nonexponential behavior is found. This indicates the absence of dynamic heterogeneity of ring segments seen by NMR and associated with the presence of end segments in their linear analogues.

Nanocomposite materials based on highly stable encapsulated superparamagnetic iron oxide nanocrystals (SPIONs) were synthesized and characterized by scattering methods and transmission electron microscopy (TEM). The combination of advanced synthesis and encapsulation techniques using different diblock copolymers and the thiol–ene click reaction for cross-linking the polymeric shell results in uniform hybrid SPIONs homogeneously dispersed in a poly(ethylene oxide) matrix. Small-angle X-ray scattering and TEM investigations demonstrate the presence of mostly single particles and a negligible amount of dyads. Consequently, an efficient control over the encapsulation and synthetic conditions is of paramount importance to minimize the fraction of agglomerates and to obtain uniform hybrid nanomaterials.

Ring polymers have fascinated theorists, simulators, and experimentalists as they are the simplest polymer without ends, giving rise to important topology related properties. We present the state of the art of recent synthetic efforts and investigations into the structure and dynamics of dense nonconcatenated ring polymer systems. Analyzing the existing knowledge, we identify challenges for future research: In the realm of synthesis the creation of well-defined high molecular weight rings based on different monomers are highly desirable. In the field of ring conformations, the existence of double folded structures that are at the basis of many theoretical approaches was severely challenged and further scrutiny is needed. Similarly, the issue of the size dependent transition to mass fractal structures, or the effect of local stiffness on the conformation and dynamics are open questions. The role of ring–ring threading in the terminal dynamics of rings needs to be further elucidated. In particular, the novel proposed topological glass transition for very high molecular weight ring melts awaits experimental verification. Experimentally, ring-linear blends are very seldomly investigated: only a small number of studies on the miscibility and the conformation of rings in such blends are available. Microscopic experiments on the dynamics are nearly entirely missing. Finally, as different theoretical approaches are always backed by corresponding simulations, a crucial task would be to find out how the different approaches connect to each other and which experiments should be performed.

The phase diagram of a series of poly(1,2‐octylene oxide)–poly(ethylene oxide) (POO–PEO) diblock copolymers is determined by small‐angle X‐ray scattering. The Flory–Huggins interaction parameter was measured by small‐angle neutron scattering. The phase diagram is highly asymmetric due to large conformational asymmetry that results from the hexyl side chains in the POO block. Non‐lamellar phases (hexagonal and gyroid) are observed near fPEO= 0.5, and the lamellar phase is observed for fPEO≥ 0.5.

Poly(ethylene carbonate/ethylene oxide) P(EC/EO) copolymer was synthesized from EC monomer as a new matrix component of solid polymer electrolytes (SPEs), and the correlation between polymer dynamics and ionic conductivity in the P(EC/EO)-based SPEs at various lithium salt weight fractions (wLi) was investigated by dielectric spectroscopy, rheology, and molecular dynamics (MD) simulations. With the addition of lithium salt, the molecular motions at various scales (i.e., from local to segmental and global motion scales) were found to change as follows: (i) the local motion of P(EC/EO) was slightly accelerated, and at wLi≥ 0.22, it was separated into two relaxation modes, one faster and the other slower than that of P(EC/EO), (ii) the segmental motion of P(EC/EO) became significantly slower with the addition of lithium salt, and (iii) the global terminal relaxation became slightly slower with the increase of wLi. Thus, the motion of P(EC/EO) at various scales in SPEs changed with different trends with increasing lithium salt. It was also found that the temperature dependence of the ionic conductivity was described by a Vogel–Fulcher–Tammann-type function, which was correlated with the segmental motion, as is known in other SPE systems. Furthermore, from MD simulations, lithium ions are coordinated with the EC units more likely and with a closer distance than EO units in P(EC/EO), and the coordination number of oxygens around one lithium ion was estimated as 6–7 at the distance of 0.30 nm. These results suggest that the coordination structure of the oxygens around the lithium ion is slightly disrupted due to the presence of EC units compared to the chelating structure of pure PEO electrolytes.

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.

Summary: Poly(5-n-hexylnorbornene) (PHNB) was obtained in high molecular weight and high yields by vinyl-type polymerization of 5‐n‐hexyl‐2‐norbornene (endo/exo = 77/23) with [NiBr(NPMe3)]4/B(C6F5)3 as catalyst precursor. The combination of size exclusion chromatography with on‐line light scattering and intrinsic viscosity measurements allowed the Mark‐Houwink expressions to be evaluated in tetrahydrofuran. The unperturbed chain dimensions for poly(5‐n‐hexylnorbornene) were estimated via the extrapolation procedure of Burchard‐Stockmayer‐Fixman. This evaluation of the unperturbed chain dimension in turn permits the calculation of the entanglement molecular weight and the plateau modulus via the packing length model. This allows the determination of rheological properties for these materials where conventional rheology measurements are difficult, or impossible.[η]-M data for PHNB in THF at 35 °C.

Summary:Stepwise anionic polymerization, catalytic hydrogenation, and atom transfer radical polymerization were performed to synthesize an amphiphilic ABC triblock copolymer, poly(ethylene‐alt‐propylene)‐block‐poly(ethylene oxide)‐block‐poly(hexyl methacrylate) (PEP‐b‐PEO‐b‐PHMA), with hydrophilic PEO as the middle block. The resulting block copolymers have well‐defined molecular weights and narrow molecular weight distributions as revealed by 1H NMR spectroscopy and gel permeation chromatography.

Abstract: We present experiments and theory on the diluted melt dynamics of monodisperse entangled polymers of linear, star and H-shaped architecture. Frequency-dependent rheological data on a series of progressively diluted linear, star and H-polymers are in good agreement with a refined tube-model theory that, for H-polymers, combines star polymer melt behaviour at high frequency, with linear polymer reptation behaviour at low frequencies. Taking into account the effect of dilution via some simple scaling relations, mild polydispersity and by incorporating the high frequency Rouse modes, we are able to model quantitatively the entire frequency range. This work suggests a novel rheological route to analysing long chain branching in polymer melts.

A novel method for the simultaneous measurement of small-angle neutron scattering and Fourier transform infrared spectroscopy (SANS/FTIR) has been developed. The method was realized by building a device consisting of a portable FTIR spectrometer and an optical system that allows both a neutron beam and an infrared beam to pass through a sample coaxially. The device was installed on a small-angle neutron diffractometer, KWS2 of the Jülich Centre for Neutron Science (JCNS) outstation at Heinz Maier-Leibnitz Center (MLZ) in Garching, Germany. In order to check the performance of this measuring system, the structural changes in a cocrystal of syndiotactic polystyrene with triethylene glycol dimethyl ether, were followed during the course of heating.

Cover:The cover shows the molecular architecture of the A block, poly(ethylene‐alt‐propylene), and the AB diblock, poly(ethylene‐alt‐propylene)‐block‐poly(ethylene oxide), leading to the final ABC triblock copolymer, poly(ethylene‐alt‐propylene)‐block‐poly‐(ethylene oxide)‐block‐poly(hexyl methacrylate). Oxygen containing segments are shown in red. The corresponding GPC chromatograms reveal narrow molecular weight distributions for all the species.