Thermal properties, rheology and foams of polystyrene-block-poly(4-vinylpyridine) diblock copolymers

Abstract

of the original manuscript:Schulze, M.; Handge, U.A.; Rangou, S.; Lillepaerg, J.; Abetz, V.: Thermal properties, rheology and foams of polystyrene-blockpoly(4-vinylpyridine) diblock copolymers AbstractIn this study, the thermal and rheological properties of polystyrene-block-poly(4-vinylpyridine)(PS-b-P4VP) diblock copolymers are investigated in order to get information about the optimum foaming temperature. Foams of these diblock copolymers were prepared using the technique of batch foaming with carbon dioxide as environmentally-benign blowing agent. The tailored PS-b-P4VP diblock copolymers with different molecular weights and a cylindrical morphology were prepared and analysed regarding their thermal stability. High-pressure differential scanning calorimetry exposes the plasticising effect of the blowing agent which yields a decrease of the glass transition temperature of the polystyrene and the poly(4-vinylpyridine) blocks. Sorption measurements were performed in order to measure the uptake of carbon dioxide in the diblock copolymer. Additionally, rheological experiments in the oscillatory mode were conducted which confirmed a microphase-separated structure of the PS-b-P4VP diblock copolymers by a plateau of the storage and loss moduli in the temperature range of processing. In shear and melt elongation, the transient shear viscosity and the transient elongational viscosity were much smaller than the linear viscoelastic prediction. The analysis of the foam morphology revealed that the foam density of the diblock copolymers as measured via Archimedes` principle exhibits the lowest foam density at a molecular weight in the order of 160 kg mol -1 .

Architectures and Mechanical Properties of Drugs and Complexes of Surface-Active Compounds at Air-Water and Oil-Water Interfaces

“…Notably, in the surface shear data, the interfacial viscosity of the mixed system is higher than that of either the pure drug or pure polymer and much greater than that of LPC. A significant change in interfacial structuring [3,33,49,52] and the magnitude of lateral interactions between adjacent adsorbed molecular species of the polymer adsorbed layer can be inferred from this rheological data involving inclusion of the drug. Fig.…”

“…The Part shows the ease of adsorbed layer disruption using the sharp-edge of an interfacial rheometer bicone to the two-dimensional "gelled" adsorbed layer formed by 67 kDa BSA, ovotransferrin and Tween20:BSA at a molar ratio of R = 0.9. The plot shows how the network formed by both protein only systems, resists the effect of shearing at low rates of deformation, largely as a result of inter-molecular interactions and crosslinking of material adsorbed in the plane of the interface [28,32,42], possibly compounded by the formation of multiple layers as seen with BSA on metal nanoparticles [29], and finally being broken at much higher shear rates [34,48,49]. The mix of protein and surfactant data is more complex in some sense, as initial deformation is permitted to much higher shear rates but at very high shear rate this appears to cause interfacial friction between "interfacial aggregates" and increase in measured shear stress.…”

“…Very noticeably, addition of the crosslinker causes the surface tension to decrease and better residence of protein at the interface, and bearing in mind the system contains competing surfactant that disrupts the protein-protein interactions [3,40,42]. The adsorption of a mixture of protein, Tween, protein-Tween complex, protein-IH and IH is manifested as an increase in both surface elasticity and viscosity [26,43,49]. This aging process is revealed even over the short timeframe of the measurement but noted to take place to a much greater degree on longer timed study described by Gao et al [30].…”

“…Such complex component mixtures with varying interfacial compositions and architectures [19,20,22,55] of rafts, suprastructure and channels are not only pre-requisites of therapeutic efficacy but also of suitability, compatibility and quality [1,2,9,11,17,35] with features that aid active sequestering and encapsulation. Architectures can be made to be 'trigger' release or activation of a drug as a result of local conditions, such as by chemical modification, thus possessing sensitivity or responsiveness to temperature [22,45,49] or pH changes as seen with polysiloxanes [21]. Fig.…”

Open-Celled Foams from Polyethersulfone/Poly(Ethylene Glycol) Blends Using Foam Extrusion

“…The densities of the flat sheet samples were estimated with the buoyancy method using an Excellence XP105DR analytical balance (Mettler Toledo, Gießen, Germany) and auxiliary liquid FC-770 (3M, Saint Paul, MN, USA), as described elsewhere [ 51 ]. The measurement protocol for the sorption experiments and the interpretation of the results were undertaken following previous studies [ 51 , 52 , 53 ]. All samples were dried in a vacuum for 48 h. A CO 2 pressure of 50 bar was applied and samples of selected polymers were measured at 35 °C, 50 °C and 75 °C.…”