Functional Membranes Enabled By P H-controlled Complexation Of Weak Polyelectrolyte

Polyelectrolytes undergo electrostatic complexation with oppositely charged building blocks,with important implications in functional materials such as membranes,gels and fibers.However,the ultra-fast kinetics of polyelectrolyte complexation is hard-to-control,limiting the materials’processability and functionality engineering of polyelectrolyte complexes(PECs).To tackle this challenge,a new method such as interfacial polyelectrolyte complexation was proposed to improve the control in polyelectrolyte complexation.High performance pervaporation dehydration membranes and hydro-voltaic membranes were prepared.First,solution p H was tuned to inhibit the ionization of carboxylate groups in sodium carboxymethyl cellulose(CMCNa),which was complexed with a poly(ionic liquid)(PIL)featuring strong electrostatic complexation with CMCNa.Poly(ionic liquid)complexes(PILCs)and their homogeneous membranes(PILCMs)were prepared,which were advantageous in dehydrating acidic organics compared to pristine CMCNa membranes.At70℃,the water in permeate of PILCM was 99.5±0.3 wt%in dehydrating 90 wt%isopropanol-water mixture(p H=1-7),while the flux was stable at 1.1±0.1 kg/m~2h.Moreover,the pervaporation performance of PILCM was stable in dehydrating feed solution at p H 2.On basis of the“partial inhibition of ionization”strategy in the first chapter,we further established the“complete inhibition of ionization”strategy to build an intermediate dormant state between PSSNa and PEI by reducing the solution p H.Interestingly,the PSSNa-PEI solution droplets could spread spontaneously on surfaces of acidic water(p H=1-2.25)despite of miscibility of two of the original solutions.This discovery leads to the one-step preparation of PEC membranes through the interfacial polyelectrolyte complexation.It was found that the surface spreading and polyelectrolyte complexation was determined by the p H and surface tension of the underlying water.At the same time,the interfacial hybrid complex film’s functionality in water evaporation driving electricity generation was explored.The hybrid composite film containing 1 wt%CNT(Carbon Nanotubes)can generate a voltage stable at 390±20 mv by means of water evaporation at room temperature.This method not only reduces the processing burden of the material,but also extends the range of film formation at the water/miscible solvent system interface to polyelectrolyte materials that were previously difficult to process.To summary,new methods for controllable complexation were proposed to fine-tune the kinetics,structures and functionality of PEC membranes,exhibiting good performances in dehydration of acidic water-isopropanol mixtures and the electricity generation driven by water evaporation.