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Polyurethane (PU) foams are the most widely used polymer foams [1][2][3][4][5] with a production of millions of tons every year. [4] Ranging from flexible to rigid and from open to closed-cell foams, PU foams span a particularly wide range of uses from seating applications to thermal and acoustic insulation. The PU industry now masters very well the PU chemistry, providing explicit and fine control over the involved reactions and the final polymer properties. However, two important challenges remain in the optimization of the foaming processes: 1) explicit control over pore sizes, pore size distribution, and pore arrangement. 2) explicit control over the degree of the pore connectivity (open vs. closed cells);This missing control results from a threefold complexity:1) complexity of the commonly employed foaming techniques (chemical or physical blowing) which provide large bubble size distributions; 2) complex polyurethane (PU) chemistry with a number of side reaction, especially in the presence of water; 3) complex interplay between the chemistry and the physics of the liquid foam before and during solidification.Moreover, these three aspects are strongly coupled. [2,3,6] Decades of experience provide now reasonable control of these processes within certain parameter ranges which allow the adaptation of different foam types to applications. [1][2][3] In parallel, 3D-imaging and computational techniques evolve rapidly to characterize the structural parameters of PU foams and to predict their properties. [1] However, an experimental technique which provides explicit and fine-control over foam morphology, density, pore connectivity, and polymer properties is still to be found. [1,7] Goal of this work is therefore to propose a simple approach to the generation of PU foams, which keeps the complexity of the involved chemical reactions at a minimum and which allows the generation of foams composed of equal-volume pores with well-controlled spatial organization ( Figure 1). For this purpose, we reduce the PU chemistry to its most basic ingredients: one polyol, one isocyanate, one catalyst and one foam stabilizer. These are physically foamed by a well-controlled bubbling process, in which an inert gas is injected bubble by bubble into the PU mixture in the liquid state. All processing parameters are optimized in such a way that a sufficiently stable liquid foam is obtained at the outset in which the bubbles have time to find their equilibrium positions. As such, we can directly build on an available vast experience concerning the control and description of structural properties of liquid foams in equilibrium. [8][9][10][11] Once the desired foam properties are obtained, the liquid foam is solidified in situ in such a way that the foam structure remains unchanged. In this process, fine-tuning of the system parameters also provides explicit control over the rupture of the thin films separating neighboring bubbles and therefore over the final poreconnectivity of the foams.For the implementation of this approach, we use mill...

A new class of viscoelastic surfactants for chemical enhanced oil recovery is presented. The triphenoxmethanes (TPM) show promise under harsh conditions of high salinity and high temperatures. The TPM's are viscoelastic at low concentrations (<0.5%w/w), show good stability in highly saline brine (18.6% TDS) that contains high concentrations of divalent cations at elevated temperatures (>70°C). Static adsorption measurements show acceptable values for the harsh conditions under study. Rheological measurements demonstrate that the viscoelasticity is not from formation of wormlike micelles and displays non-Maxwell behavior. We propose a novel supramolecular structure that explains the laboratory and rheological observations to date. The compounds show good injectivity into 2 Darcy Gildehaus sandstone The development of this class of compounds combines the efforts of a team comprised of synthesis, analytics, rheology, core lab and computational chemistry. The goal is to develop an understanding the system's behavior from the molecular level in-silico via computational chemistry, through coreflood tests -and beyond- for a future field pilot. The structure- property-relationships that are being developed will lead to further refinement and targeted development of next generation molecules with improved properties.

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We present a comprehensive micro- and macrorheological study of the effect of weak depletion attraction (Ψdep ≈ 1–10 kBT) on dense colloidal suspensions stabilized by short-range repulsive interactions. We used aqueous polymer dispersions as model system and demonstrated the unique capabilities of multiple particle tracking (MPT) to disclose structural changes in such technically important systems exhibiting many characteristic features of hard sphere systems. Below the hard sphere freezing point ϕc, viscosity increases monotonically with increasing Ψdep due to the transition from a fluid to a fluid/crystalline and finally to a gel state. Above ϕc, increasing attraction strength first results in a viscosity reduction corresponding to the formation of large, permeable crystals and then in a viscosity increase when a network of dense, small crystals forms. The fraction of the fluid and crystal phase, particle concentration in each phase as well as the modulus of the micro-crystals are obtained, the latter decreases with Ψdep. Above the colloidal glass transition strong heterogeneities and different local particle mobility in the repulsive and attractive arrested states are found. Particles are trapped in the cage of neighboring particles rather than in an attractive potential well. The intermediate ergodic state exhibits uniform tracer diffusivity.