Monodisperse Highly Ordered and Polydisperse Biobased Solid Foams

Abstract

The aim of this work was the synthesis of monodisperse highly ordered biobased polymer foams and a comparison with their polydisperse counterparts. We used the biobased and biodegradable polymer chitosan, which we cross-linked with genipin. The polymer foams were synthesised via foam templating, i.e. via a liquid foam whose continuous phase contains a polymer and can xvi Nomenclature w c width of the chip's channel W e Weber number xvii

Fluorocarbon Vapors Slow Down Coalescence in Foams

“…The goal was to minimize the osmotic pressure difference with the exterior, which would lead to a net gas transport into the foam and hence its growth with time. [21] Only a small hole was left in the cover to allow for pressure equilibration. The first measurement was performed to ensure equilibrium conditions while the results of the second to fourth measurements were averaged for foam height and bubble size distributions.…”

Highly Ordered Gelatin Methacryloyl Hydrogel Foams with Tunable Pore Size

“…Thus, the higher the viscosity of the continuous phase, the smaller bubbles are generated for a given set of gas pressures and liquid flow rates. Note that an aqueous 20 wt % solution of GM10 behaves like a Newtonian fluid with a dynamic viscosity of approximately 20 mPa·s at 25 °C at the shear rates occurring in our microfluidic setup . Thus, the obtained calibration curve is expected to be independent of the liquid flow rates if the ratio of gas pressure, liquid flow rate, and viscosity is kept constant.…”

“…For monodisperse chitosan foams, no such material shrinkage was found which can be explained by the low material content of only 1.5 wt % chitosan in these foams. For chitosan foams with a polymer content of 4 wt %, however, a shrinkage of approximately 35% was observed when comparing the bubble size of the liquid foam with the pore size of the cross-linked freeze-dried foam . Costantini et al observed a shrinkage of 40% when comparing the bubble size of liquid dextran-based foams (dextran concentration of 20 wt %) with the corresponding pore size of freeze-dried hydrogel foams .…”

Monodisperse highly ordered chitosan/cellulose nanocomposite foams

“…We are, however, interested in the viscosity of the solutions at the shear rates applied in the chip to fit the microfluidic parameters with the flow properties. For the chip used in this work, the shear rate at the constriction of the T-junction is γ  ~ 850 s -1 (see the calculations in [18]). We list the corresponding viscosities at the T-junction T in Table 1.…”

“…We have shown in our previous work how to generate monodisperse chitosan foams with interesting morphological properties via foam templating [16,17]. However, with an elastic modulus below 100 kPa [18] such foams are too weak to be used as scaffolds for tissue engineering. Following the work of Svagan et al [19], who designed amylopectin/cellulose nanocomposite foams, Wang et al [20] showed that by adding cellulose nanofibres (CNF) to a chitosan-based solution, one obtains improved mechanical properties of the resulting solid foams.…”