Multiscale Porous Polymer Films and Their Applications
Reverse osmosis (RO) is one of the most common technologies to purify water in locations where potable water is scarce. RO is the dominant production process for ocean water desalination and is also used in the production of bottled mineral water and boiler water purification in power plants. Thin-film composite membranes are the heart of this technology. These membranes consist of a polyamide layer on top of a polysulfone layer on top of a nonwoven fabric (polyester). The filtration is done primarily by the polyamide layer with a pore size ranging from 0.1nm-5 µm. Although RO is extremely efficient (up to 99% removal of salts) and many advances in membrane technology have been made, the need for high pressures to reverse natural osmotic flow still remains the costly process element. New membranes that allow lower operating pressure or increased flux are needed to reduce the energy cost.
Polyelectrolytes have been used to create a new class of material known as polyelectrolyte multilayers/membranes (PEMs). These thin films are constructed using a layer-by-layer (LbL) deposition technique. During LbL deposition, a charged growth substrate is dipped back and forth between baths of positively and negatively charged polyelectrolyte solutions often taking 10 or more minutes per dip. During each dip a small amount of polyelectrolyte is adsorbed and the surface charge is reversed, allowing the gradual and controlled build-up of polycation-polyanion layers. Each PEM requires several dips and post-dip processing which all together can take several hours. The conventional LbL process is extremely time consuming to fabricate a PEM film of desired thickness. Although the process was developed over 10 years ago with extensive research since then, LbL has not been widely accepted in industries. The main inhibition to adopting is this technology is its time intensive processing.
Description of Technology
This technology is a new methodology for LbL manufacturing with drastically reduced processing time. This technology can have dip times as short as 10 s compared to a typical average of 10 min. By varying the polycation/anion molecular weights and dipping time, pore sizes can be varied (25nm-10µm) and nano-pore layers can be stacked on micro-pore layers and vice versa. Ref: TEC2015-0046.
- Faster layer-by-layer processing time
- Higher yield in reverse osmosis water purification
- One method to create PEM
- Flexible drug release timing
- Lower fouling rates
- Controlled layering with different pore sizes
- Reverse osmosis water purification
- Power plant boiler water, Desalination stations, Bottled water production
- Increasing lower-end/cheaper membrane performance
- Drug delivery
- Fuel cells
Ilsoon Lee, Jing Yu, Oishi Sanyal
For Information, Contact:
Michigan State University