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"This process is highly customizable, meaning that we can make adjustments along the way, shaping the material's pore structure and density as it is grown," says Mitchell Anthamatten. "As a result, it will be easier to put foam polymers in hard-to-get-at places, or even on curved surfaces." (Credit: Adam Fenster/University of Rochester)

coatings

Grow foam polymer coatings from gases

Engineers have discovered a new method for creating highly customizable foam polymer coatings directly from gases.

“With this process we can grow polymer coatings in which the density and pore structure varies in space,” says Mitchell Anthamatten, a chemical engineer at the University of Rochester’s Hajim School of Engineering and Applied Science. “My hope is that the research leads to applications in a wide variety of fields, including medical, manufacturing, and high-tech research.”

Polymers are the essential component of plastics. Polymers that are porous are called foam polymers and are especially useful because they combine light weight with rigid mechanical properties.

An initiated chemical vapor deposition (ICVD) system is used to convert a mixture of gases into foam polymer.
An initiated chemical vapor deposition (ICVD) system is used to convert a mixture of gases into foam polymer. (Credit: Adam Fenster/University of Rochester)

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Anthamatten, working closely with graduate student Ran Tao, developed a system in which a mixture of gases is pumped into a low pressure reactor containing a cold surface to encourage condensation. One of the condensed liquids actually forms the polymer material (think of the solid part of a sponge), while the other one temporarily occupies the spaces that become the pores in the foam material (think of the hollow part of a sponge).

But the problem is that the liquids in the film don’t mix well—very much like water and oil. What’s required is to quickly solidify the polymer film, just as the two liquids begin to separate from one another.

By controlling the solidification rate, they could control the size and distribution of the pores; the faster the coating is solidified, the smaller the pores become.

Anthamatten and Tao found the answer by adjusting the rate at which the gases were fed into the system, changing the temperature of the cold surface in the reactor, and using a chemical agent that helps solidify the coating. By adjusting all those factors, they were able to coat foam polymers with different densities, thicknesses, shapes, and hole-sizes.

“This process is highly customizable, meaning that we can make adjustments along the way, shaping the material’s pore structure and density as it is grown,” says Anthamatten. “As a result, it will be easier to put foam polymers in hard-to-get-at places, or even on curved surfaces.”

Anthamatten has worked on the project since 2008 and has received support from the National Science Foundation. His findings were published this week in the journal Macromolecular Rapid Communications.

Source: University of Rochester

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