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We detail the influence of tapered interfaces on the nanoscale morphologies of ion-doped poly(styrene-b-oligo-oxyethylene methacrylate) block polymers (BPs). Most significantly, the location of double-gyroid network phase window was found in ion-doped normal-tapered materials, and a similar window was not detectable in the corresponding non-tapered and inverse-tapered BPs. Additionally, the effective interaction parameters, χeff, were reduced substantially in the tapered materials in comparison with their non-tapered counterparts. Overall, this work demonstrates that tapering between polymer blocks provides unique control over BP morphologies and improves the material processability (due to lower χeff), potentially facilitating the development of future ion-conducting devices.

Our previous study presented up to 20% power conversion efficiency (PCE) enhancement of poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) solar cells under the Fe3O4 nanoparticles (NPs) self-assembly (SA) effect by spin coating. Fe3O4 NPs (about 11 nm hydrodynamic diameter) form a thin layer at the top interface of the light absorbing active layer, which results in the generation of PCBM rich region improving the charge transport (Zhang et al. Sol Energ Mat Sol C 160:126–133, 2017). In order to investigate the feasibility of this Fe3O4 NPs SA effect under large-scale production condition, a smooth rod was implemented to mimic roll-to-roll coating technique and yield active layers having about the same thickness as the spin-coated ones. Small angle neutron scattering and grazing incidence X-ray diffraction were employed finding out similar morphologies of the active layers by these two coating techniques. However, rod-coated solar cell’s PCE decreases with the addition of Fe3O4 NPs compared with the one without them. This is because PCBM rich region is not created at the top interface of the active layer due to the absence of Fe3O4 NPs, which is attributed to the weak convective flow and low diffusion rate. Moreover, in the rod-coated solar cells, the presence of Fe3O4 NPs causes decrease in P3HT crystallinity, thus the charge transport and the device performance. Our study confirms the role of spin coating in the Fe3O4 NPs SA effect and enables researchers to explore this finding in other polymer nanocomposite systems.

An excess of elemental sulfur is generated annually from hydrodesulfurization in petroleum refining processes; however, it has a limited number of uses, of which one example is the production of sulfuric acid. Despite this excess, the development of synthetic and processing methods to convert elemental sulfur into useful chemical substances has not been investigated widely. Here we report a facile method (termed ‘inverse vulcanization’) to prepare chemically stable and processable polymeric materials through the direct copolymerization of elemental sulfur with vinylic monomers. This methodology enabled the modification of sulfur into processable copolymer forms with tunable thermomechanical properties, which leads to well-defined sulfur-rich micropatterned films created by imprint lithography. We also demonstrate that these copolymers exhibit comparable electrochemical properties to elemental sulfur and could serve as the active material in Li–S batteries, exhibiting high specific capacity (823 mA h g−1 at 100 cycles) and enhanced capacity retention. A polymerization method for converting elemental sulfur into a chemically stable, processable and electrochemically active copolymer has been described. This methodology — termed inverse vulcanization — is conducted by a one-step process using liquid sulfur, as both reaction medium and reactant, and vinylic comonomers to form polymeric materials with a high content of sulfur (50–90 wt%).

Addition of fullerenes (C60 or buckyballs) to a linear polymer has been found to eliminate dewetting when a thin (∼50 nm) film is exposed to solvent vapor. Based on neutron reflectivity measurements, it is found that the fullerenes form a coherent layer approximately 2 nm thick at the substrate – polymer film interface during the spin-coating process. The thickness and relative fullerene concentration (∼29 vol%) is not altered during solvent vapor annealing and it is thought this layer forms a solid-like buffer shielding the adverse van der Waals forces promoted by the underlying substrate. Several polymer films produced by spin- or spray-coating were tested on both silicon wafers and live surface acoustic wave sensors demonstrating fullerenes stabilize many different polymer types, prepared by different procedures and on various surfaces. Further, the fullerenes drastically improve sensor performance since dewetted films produce a sensor that is effectively inoperable.

Mackay et al. (1995) have presented an approximate technique to determine the elongation viscosity from pressure drop measurements in a simple stagnation flow device. In the present paper we describe experiments using a high viscosity Newtonian oil, aimed at probing some of the assumptions made by Mackay et al. We find that Trouton ratios calculated using the original analysis are well above the value of three expected for Newtonian fluids. Finite element simulations of the flow field show this is due to the net pressure drop having a substantial shear contribution, which should be corrected for before the Trouton ratios are evaluated. Interestingly, most of the shear correction is due to shear on the inside of the orifice near the exit from the central flow region. The shear contribution to the pressure drop occurs for all flow rates, however, at large flow rates there is also an inertial correction to the pressure drop. In this paper we describe an approximate method that corrects for both shear and inertial effects. With these effects recognised and corrected for, the measured Trouton ratios are reduced to around three.

A newly designed oven for rheological characterisation of polymer melts is presented which relies upon conduction and radiation rather than convection to heat the polymer. The design involves three concentric heating elements, all controlled independently to ensure a stable thermal atmosphere. The overshoot on heating is minimal (10 K, and this was due to opening the oven for sample trimming; the overshoot is 3 K if the oven is not opened) and the results of a typical dynamic shear test show that rheological properties attain their equilibrium values very rapidly (25 min after start-up of the oven fro room temperature, and 15 min after the sample was placed in the rheometer). The temperature of the sample was maintained at ±0.5 K, thus, a stable thermal environment was successfully attained.

Stress jumps occur in fluids that possess a viscous contribution to their total stress. On cessation of shear, such a fluid will show an instantaneous loss of stress, while some of the stress will remain and subsequently decay in some manner, either exponential or otherwise. The results in this paper show that filtering, present in most rheometers, will eliminate the stress jump and not allow its measurement. The torque head inertia for a spring-type torque measuring system is found to greatly influence the measurements and a stress jump is not seen. In fact, the material's true stress relaxation behaviour is far from that measured. The force rebalance torque measuring system is found to accurately measure stress jumps.

A comparison is made between elongational properties predicted by the FENE-P dumbbell rheological equation of state for fibre spinning and true values obtained from pure elongation. True values are found by using a constant elongation rate in the model and calculating the steady state values of the stresses. Two new averaging procedures are suggested for extracting elongational properties from fibre spinning experiments. It is suggested that a variety of flow conditions be used and care be taken when determining these properties. The rheological model is found to predict adequately shear and elongational flow properties of the polyacrylamide-type of Boger or ideal elastic fluid.