# Nano-Fibrous Networks from Co-Assembly of Amphiphilic Peptide and Polyelectrolyte
## 3 Results and Discussion
The kinetic monitoring shows two stages with a first part characterized by a steep increase in moduli following the contacting of the aqueous solutions. It has to be noted that the time, although short, necessary to start the analysis after mixing the solutions does not allow us to observe the initiation of this step. On the other hand, this rapid increase is followed by a quasi-plateau for which the moduli evolve only modestly. This observation is in agreement with the previously cited literature on the rapidity of formation of a solid interface in the case of a strong interaction between the PA and the polymer, which is precisely our case. Conventionally, the membranes are produced by  
Figure 5: (**A**) Storage (G\({}^{\prime}\)) and loss (G\({}^{\prime\prime}\)) modulus of a 10 wt.% solution of C\({}_{16}\)V\({}_{3}\)A\({}_{3}\)K\({}_{3}\)G-NH\({}_{2}\) (black) or C\({}_{16}\)V\({}_{3}\)A\({}_{3}\)K\({}_{3}\)G-NH\({}_{2}\)—PSSNa (red) in water as a function of strain at a constant frequency of 10 rad/s. Aqueous solution mixture between C\({}_{16}\)-V\({}_{3}\)A\({}_{3}\)K\({}_{3}\)G-NH\({}_{2}\) (15 mg in 0.5 mL mQ water) and PSSNa (6 mg in 0.5 mL mQ water) (R\({}_{\pi/-}=1\)) just after complete addition (**B**), after slight hand stirring (**C**), and after vortexing (**D**). Figure 6: (**A**) Viscosity versus shear rate of the PA/PSSNa physical gel. (**B**) Storage (G\({}^{\prime}\)) and loss (G\({}^{\prime\prime}\)) modulus for 10 wt.% solutions of C\({}_{16}\)V\({}_{3}\)A\({}_{3}\)K\({}_{3}\)G-NH\({}_{2}\)–PSSNa in water as a function of frequency at a constant strain of 0.1% and different R\({}_{+/-}\). a phase inversion process in which the polymer in a good solvent is immersed in a non-solvent which allows the appearance of a phase rich in polymer (matrix) and a phase poor in polymer (pores). This technique cannot be carried out here because of the high attraction between the two components, which is moreover a conventional problem with polyelectrolyte layers. In a first attempt, a PSSNa solution was tape-casted onto a glass support, then completely covered with a solution of the PA. After a waiting time of 2 h 30 min, the support is then immersed in a water bath so as to wash off the excess unreacted products. A self-supporting material of about 9 \(\upmu\)m in thickness (as judged by SEM images of the film cross sections) is obtained (Figure 8A) but it was too brittle to withstand water pressure during filtration. Thus, in a second attempt, a supported membrane with a PVDF ultrafiltration membrane as a support layer was developed. For this, the PVDF membrane is first immersed in a solution of PSSNa. The C\({}_{16}\)V\({}_{3}\)A\({}_{3}\)K\({}_{3}\)G-NH\({}_{2}\) solution is then tape-casted on the surface of the impregnated support. After a waiting time of 2h30, the film is immersed in demineralized water. Figure 8C shows an apparent decrease in the surface porosity of the PVDF membrane, compared to the virgin membrane (Figure 8B). However, the coverage is  
Figure 8: SEM pictures of PA-PSSNa films. (**A**) Cross section of the self-standing membrane formed by tape-casting of a PSSNa solution then covered with C\({}_{16}\)V\({}_{3}\)A\({}_{3}\)K\({}_{3}\)G-NH\({}_{2}\) solution; (**B**) Top view of virgin hydrophilic PVDF membrane; (**C**) Top view and (**D**) Cross section SEM images of the film deposited on hydrophilic PVDF by impregnation of PSSNa followed by C\({}_{16}\)V\({}_{3}\)A\({}_{3}\)K\({}_{3}\)G-NH\({}_{2}\) tape-casting. only partial and the presence of this selective layer in the thickness of the material is not observed (Figure 8D). In order to enhance the chance of forming a continuous membrane selective layer rather than randomly distributed inside the PVDF commercial membrane material, spray-coating technique was explored. In a first attempt, a solution of PA was tape-casted on a glass support and then a solution of PSSNa was sprayed on the surface so as to form fine droplets which will coalesce to form a thin layer.