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Understanding polymer gelation over multiple length‐scales is crucial to develop advanced materials. An experimental setup is developed that combines rheological measurements with simultaneous time‐domain 1H NMR relaxometry (TD‐NMR) techniques, which are used to study molecular motion (<10 nm) in soft matter. This so‐called low‐field RheoNMR setup is used to study the impact of varying degrees of crosslinking (DC) on the gelation kinetics of acrylic acid (AAc) and N,N′‐methylene bisacrylamide (MBA) free radical crosslinking copolymerization. A stretched exponential function describes the T2 relaxation curves throughout the gelation process. The stretching exponent β decreases from 0.90 to 0.67 as a function of increasing DC, suggesting an increase in network heterogeneity with a broad T2 distribution at higher DC. The inverse correlation of the elastic modulus G′ with T2 relaxation times reveals a pronounced molecular rigidity for higher DC at early gelation times, indicating the formation of inelastic, rigid domains such as crosslinking clusters. The authors further correlate G′ with the polymer concentration during gelation using a T1 filter for solvent suppression. A characteristic scaling exponent of 2.3 is found, which is in agreement with theoretical predictions of G′ based on the confining tube model in semi‐dilute entangled polymer solutions. [ABSTRACT FROM AUTHOR]

Abstract Background Ultrasonographically guided punctures of the liver represent a decisive tool in the diagnosis of many diseases of the liver. Objective of the study was to determine the extent to which the complication rate for ultrasonographically guided punctures of the liver is affected by less comprehensively studied risk factors. Methods A total of 2,229 liver biopsies were performed in 1,961 patients (55.5% males; 44.5% females). We recorded actual complications and assessed the following risk factors: needle gauge, puncture technique, examiner experience, coagulation status, puncture target (focal lesion versus parenchyma), lesion size, patient sex and age. Results he rate of complications stood at 1.2% (n = 27), of which 0.5% (n = 12) were major and 0.7% (n = 15) minor complications. A significant increase in complications involving bleeding was observed with larger-gauge needles compared with smaller-gauge needles and for cutting biopsy punctures compared with aspiration biopsies (Menghini technique). In the bivariate analysis complications were 2.7 times more frequent in procedures performed by experienced examiners compared with those with comparatively less experience. Lower values for Quick’s test and higher partial thromboplastin times were associated with a higher rate of bleeding. Neither the puncture target, lesion size or patient sex exerted any measurable influence on the puncture risk. Advanced patient age was associated with a higher rate of complications involving bleeding. Conclusions Our study helps to establish the importance of potential and less comprehensively studied risk factors and may contribute to further reduction in complications rates in routine clinical practice.

Bound and free water within dough strongly affect its rheological behavior and processability, as well as its gluten network. Depending on its total content and on the characteristics of flour constituents, water can be both bound to components and free in the dough. The equilibrium between bound and free water directly impacts the elasticity and extensibility of dough and therefore controls the texture of final products. In this study, Nuclear Magnetic Resonance (NMR) was used to assess the relaxation behavior with the focus on water. The proton spin-spin relaxation measurements were carried out at 20 MHz with a Bruker Minispec mq20 NMR spectrometer (Bruker, Rheinstetten, Germany). The transverse relaxation time in a spin locking field (T1?) was determined at 25°C following the Carr-Purcell-Meiboom-Gill (CPMG) sequence. The data were analyzed by the continuous distribution model. The dough was prepared with commercial semolina, which was mixed with water in a Brabender Mixer 350 (Brabender® GmbH, Duisburg, Germany) to reach three different levels of water content (30, 50, and 70%, based on semolina weight) and to study the water distribution as a function of the water total content. The dough characterization was carried out also comparing the T1? distribution of semolina dough with that of starch-water and gluten-water mixtures and also of pure starch and gluten to assess the role of each flour component. Additionally, the semolina dough sample was compared with a sample prepared with pastry flour, with a lower content of proteins, to investigate the different behavior as a function of the gluten amount. It was found that the dough presents three relaxation processes: one, very fast, is related to crystalline starch, while the other two are characteristic of two water populations, water in intragranular and in extragranular regions of starch, respectively. The comparison with pastry flour showed that the dough prepared with the latter one was less homogenous than the semolina one, with a clear distinction between free and bound water, while the semolina dough seemed to contain several water populations differently bounded, that were responsible for a broader peak at medium water content (around 50%). [ABSTRACT FROM AUTHOR]

Different physicochemical phenomena are involved in breadmaking, which produce perceptible changes in the rheological properties of dough. In this regard, the kneading phase is crucial for the assessment of the quality of the final product. Indeed, the determination of the optimal time in the mixing process allows to optimize the rheological properties of the dough and the energy consumption. In this work, torque measurements were carried out on durum wheat commercial semolina using a Brabender Mixer 350 (Brabender® GmbH, Duisburg, D) where semolina was mixed with water in different amounts (from 40% to 60% of semolina weight). Each sample was mixed for 20 minutes. The salt effect was instead investigated by adding a variable amount of salt (from 0% to 2.5% of semolina weight). The optimal mixing time value, which occurs at the maximum torque value, was determined and studied with respect to salt and water quantity. Additionally, spectrograms of the torque time series data were computed in order to provide the magnitude (and frequency) of the torque oscillations with time. The results showed a significant influence of water amount on the torque maximum value and on the mixing time, with the latter that linearly depends on water amount. Also, the amplitude oscillations resulted to be related to the water amount, as their amplitude decreases when the water amount increases. On the other hand, the salt effect is less evident but an influence on optimal mixing time is however detected. [ABSTRACT FROM AUTHOR]

A Capillary Break-up Extensional Rheometer (CaBER) was modified to enable measurements of the axial force in combination with the related displacement. This makes it possible to determine the separation energy W s e p N , the tackiness, of a polymer solution between two parallel plates with the CaBER. Separation energies of solutions of linear polystyrene, comb polystyrene and linear poly(methyl methacrylate) in dimethylformamide were measured as model systems. For linear polymers at a critical polymer concentration, there was a drastic change in slope of the separation energy W s e p N c . This critical concentration was shown to be the minimum concentration at which continuous bead-free fibers could be electrospun. [ABSTRACT FROM AUTHOR]

A series of poly(sodium methacrylate) hydrogels, also called superabsorbents, having a theoretical degree of neutralization of 100 mol%, and degree of crosslinking varying from 0.6 to 20 mol%, are synthesized via conventional free radical polymerization. The networks are characterized in detail by inverse size‐exclusion chromatography and 1H‐NMR relaxometry in order to place particular emphasis on the investigation of the pore size distribution (PSD) and the chain mobility, respectively. The two previously mentioned parameters are compared to understand the correlation between the elastic chain mobilities and the average pore size of the hydrogel. From the resulting data, a new empirical equation is proposed, which is valid under the given experimental conditions and permits a rough estimation of the average PSD from the relaxation data. Thus, the equation permits to reduce the number of analytical techniques needed for the characterization of complex systems such as polymer networks. [ABSTRACT FROM AUTHOR]

Cellulose composites with polyethylene (PE) permit to reinforce this commodity polymer, while at the same time introducing renewable content and thus minimizing the use of petroleum‐based feedstocks. Herein, we report on two fully renewably sourced and sustainably synthesized compatibilisers based on amylose and starch, which allow for such cellulose dispersion in low‐density PE (LDPE). These compatibilisers advantageously combine the hydrophilicity of carbohydrates with the hydrophobicity of fatty acids. Upon extrusion of cellulose, LDPE, and the compatibilisers, a significantly improved dispersion of cellulose within LDPE was observed using rheology at loadings of 10 wt % cellulose and 5–15 wt % compatibiliser. Moreover, an improved interfacial adhesion was observed using scanning electron microscopy and was also confirmed by the mechanical properties, notably the Young's modulus, as a result of the good stress transfer between filler and matrix material. This study highlights the potential of fully renewable compatibilisers for the preparation of composites of cellulose and the commodity plastic LDPE. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48744. [ABSTRACT FROM AUTHOR]