Chemistry: Rare earths, polymers and nanomaterials

Rare earths and critical minerals

The rare-earth group is the 15 lanthanides, atomic numbers 57 (lanthanum) to 71 (lutetium), and yttrium is commonly regarded as one too (USGS Fact Sheet 2014-3078). Despite the name, they are relatively abundant in the Earth’s crust, but minable concentrations are less common than for most other minerals (USGS, Mineral Commodity Summaries 2025). They go into permanent magnets, catalysts, glass and polishing, ceramics and alloys.

UPSC asked why rare earth metals were in short supply: China, the largest producer, imposed some restrictions on their export, and the metals are essential for many electronic items with growing demand. They are found in many countries besides China, Australia, Canada and Chile, including India (Prelims 2012: answer (c), 1 and 3 only).

Some rare earth elements have phosphorescent properties, so they are used as phosphors that glow in colour; this is why some rare earth elements are used in the manufacture of flat television screens and computer monitors. Both statements are correct and Statement II explains Statement I (Prelims 2025: answer (a)).

Source: USGS, Mineral Commodity Summaries 2025, Rare Earths. 2024 production is a USGS estimate; reserves are estimates of economically extractable amounts.

India’s response (official approvals; outlays are planned spending, not results): the National Critical Mineral Mission, approved by the Union Cabinet on 29 Jan 2025, has an outlay of Rs 34,300 crore over seven years, Rs 16,300 crore of government outlay plus an expected Rs 18,000 crore investment by PSUs and others; it covers exploration, mining, processing and recycling (PIB). On 26 Nov 2025 the Cabinet approved a Rs 7,280 crore scheme to set up 6,000 tonnes a year of integrated sintered rare earth permanent magnet (REPM) manufacturing capacity (PIB, 16 Dec 2025).

Polymers, plastics and new materials

Polymers are long chains of small repeating units (monomers). Natural polymers include cellulose, starch and proteins; synthetic polymers include polyethylene, PVC, nylon and polyester. Plastics that soften on heating can be reshaped; thermosets set permanently once cured.

Bisphenol A (BPA) is a chemical produced in large quantities for use primarily in the production of polycarbonate plastics (NIEHS, US National Institutes of Health). It is a structural/key component of polycarbonate, not of polyethylene or PVC (Prelims 2021: answer (b)).

Microbeads are tiny plastic pieces of 5 millimetres or less once added to scrubs and toothpaste. The US Microbead-Free Waters Act of 2015 prohibits making and selling rinse-off cosmetics containing plastic

microbeads, which wash into rivers and seas (US FDA). They are considered harmful to marine ecosystems (Prelims 2019: answer (a)).

Carbon-fibre-reinforced polymer (CFRP) is light, strong and tough, so it is used in components used in automobiles and aircrafts and in spacecraft to cut weight and save fuel. Conventional

CFRPs are difficult to recycle, but they can be recycled: in February 2024, Oak Ridge National Laboratory reported a laboratory process that recovered 100% of the fibre, polymer and crosslinker (ORNL). So only statement 1 is correct (Prelims 2023: answer (a)).

Hydrogels are cross-linked polymer networks that hold large amounts of water while keeping their shape; their mesh can be tuned to release a drug slowly, so they are used for Controlled drug delivery in patients (Li and Mooney, Nature Reviews Materials, 2016, on NIH PubMed Central). UPSC’s answer: only drug delivery, not air-conditioning or lubricants (Prelims 2024: answer (a)).

Carbon allotropes and nanomaterials

Carbon forms different structures called allotropes. In diamond each carbon atom is bonded to four others in a rigid 3-D network, making it the hardest substance known; in graphite each carbon is bonded to three others in flat hexagonal layers that slide, making it smooth, slippery and a good conductor of electricity. Fullerenes such as C-60 (buckminsterfullerene) are football-shaped cages (NCERT Science, Class 10, Chapter 4).

Graphene is a single layer of carbon atoms, a two-dimensional material. The 2010 Physics Nobel went to Andre Geim and Konstantin Novoselov for experiments on it. It is not only the thinnest ever but also the strongest material, conducts electricity as well as copper, and is almost transparent, so it suits transparent touch screens and light panels (nobelprize.org press release). UPSC: graphene is one of the thinnest but strongest materials tested so far and can be used as conducting electrodes; it is made of carbon, not silicon (Prelims 2012: answer (c), 1, 2 and 4).

Carbon nanotubes are graphene-like sheets of carbon rolled into tubes only a few nanometres wide. In UPSC’s 2020 question, the official answer accepted three statements: they can be used as carriers of drugs and antigens in the human body, they can be used in biochemical sensors, and “Carbon nanotubes are biodegradable “; making them into artificial blood capillaries was not accepted (Prelims 2020: answer (c), 1, 3 and 4 only).

A nanometre is one billionth of a metre. At this scale, materials can behave very differently: more surface area per gram, new optical and electrical properties. That is the basis of nanomedicine, nano-sensors and nano-fertilizers (see Fertilizers and Nanotechnology).