Polymers acting as molecular sieves seeing an increasing number of applications
Membrane Technology
To survive, living cells need a membrane. This selective barrier filters what enters and leaves the cell. Membrane technology mimics this process with a material separating two phases. A phase could be a mixture of different molecules, one of which we wish to isolate. Depending on the given conditions, selection can be made in relation to size, concentration, electronics, temperature…
Similar to when you drain pasta, the sieve is designed with holes big enough to let only water through, filtering pasta from water.
Polymer chemistry engineers new membrane materials applicable to specific conditions. A polymer is a chain of macromolecules whose structures are composed of repeating subunits.
Polymers of Intrinsic Microporosity (PIMs) were discovered in Manchester in 2004. The distinctive feature of PIMs, are their rigid and contorted structures. The way the long chain folds, unable to pack efficiently, creates small voids – pores, less than 2.0 nm wide, within the structure, maintaining permanent microporosity.
Using membranes for separation and purification processes has shown to be enery saving and cost efficient. In chemistry, many options are available for separation-purification techniques. However, many times these are expensive and lengthy procedures, calling for more chemicals, thus creating more waste. The elegance of a single selective barrier system, which yields favourable results at low-cost, whilst remaining environmentally friendly, is a crucial aspect of PIMs. These polymers can be synthesised in various forms, coupled with many applications.
The elegance of a single selective barrier system, which yields favourable results at low-cost, whilst remaining environmentally friendly, is a crucial aspect of PIMs.
PIMs put into practice
Today, one of the largest polluters is the textile industry. Aside from the working conditions, an increasing concern is their environmental impact. The fast-fashion business has answered a demand for cheap clothes, made with non-recyclable synthetic materials. Vast amounts of clothes are produced each year and disposed of just as quickly by consumers. Parts of the production process which have been marked as most damaging are the dyeing and finishing processes. Factories dump toxic textile dyes into near waters. These chemicals contain solvents, salts, colour, surfactants, heavy metals, which, if left untreated, are harmful to living organisms.
Polymers are essential in this purification process. PIMs in particular are key in the treatment of these textile effluents, interacting with dye molecules. These adsorbents are a solution for an industry that holds the title of one of the worst water polluters in the world. Other applications of PIMs have been found in gas separation. Specific gases can be selected, filtered and recycled. The most common example is CO2 capture. One of the first commercial applications of this polymer was for 3M’s respiratory masks.
Described above is only a brief introduction to the work surrounding PIMs. Increasing applications of these polymers are anticipated, allowing for further design and synthesis.
Sources
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