Synthetic polymers are ubiquitous — nylon and polyester, Teflon and epoxy, to name just a few. All are made up of long, linear structures that can tangle. Chemists have long dreamed of making polymers with two-dimensional, grid-like formations, but this goal has proven challenging.
The first examples of such structures, now known as covalent organic frameworks (COFs), were discovered in 2005, but their quality has been poor and preparation methods are uncontrolled. Now a Northwestern University research team is the first to produce high-quality versions of these materials, demonstrate their superior properties and control their growth.
The researchers developed a two-step growth process that produces organic polymers with crystalline, two-dimensional structures. The precision of the material’s structure and the empty space in its hexagonal pores provide will allow scientists to design new materials with desirable properties.
Even low-quality COFs have shown preliminary promise for water purification, storing electricity, body armor, and other tough composite materials. Once developed further, higher-quality samples of these materials will enable these applications to be explored more fully.
“These covalent-organic frameworks fill a century-long gap in polymer science,” said William Dichtel, an expert in organic and polymer chemistry who led the study. “Most plastics are long, linear structures that tangle up like spaghetti. We have made ordered two-dimensional polymers where the building blocks are arranged in a perfect grid of repeating hexagons. This gives us precise control of the structure and its properties.”
thumbnail courtesy of northwestern.edu