I. Vocabulary Practice

Mechanical Force Induces Chemical Reaction

March 2007 By Michael Reilly

A. ______

Self-strengthening plastics and artificial bone made from synthetic polymer may be one step closer to reality thanks to a breakthrough in chemistry that allows mechanical force to induce chemical reactions.

Typically, light, heat, electricity and chemical catalysts are used to activate such reactions. Mechanical force has rarely been used in the past, and primarily to pull apart long chains of polymers. Now a team led by Jeffrey Moore at the University of Illinois at Urbana-Champaign in the US have found that by applying ultrasound to a solution of specially prepared molecules can induce reactions that break apart one atomic bond at a time. The team attached two polymer strands to a molecule called benzocyclobutene (BCB) and bombarded the strands with ultrasound. This generated tensile forces that tugged on the connected molecules and, with the proper amount of ultrasound force, they were able to stretch it until one of its bonds broke, forcing the molecule to reform.

B. ________

BCB has two slightly different flavours - called isomers - that usually reform into different shapes when broken. In their experiment, the researchers were able to make both isomers produce the same shape, a feat previously unattainable. "Before, you could not take and pull a molecule in a very specific way," says Virgil Percec of the University of Pennsylvania, US. "It's a very fundamental discovery. It's chemistry at its best."

When the BCB bonds are broken, they become unstable and cross-link with other similarly broken bonds. This leads the researchers to believe they might ultimately be able to make self-healing materials. Polymer bonds that reform in this way could perhaps repair cracks or breaks, and might be stronger than those of the initial material. The researchers believe it might even be possible to make a polymeric substance that mimics living bone in this way.

C. ________

"The mechanical properties of bone are altered over time depending on use history," says Moore. "They thicken and harden. With polymeric materials we currently have no ability to do that."

Moore also believes he can find ways to make such reactions reversible, so that objects could be made to harden, or become suppler, depending on the stresses placed on them.

Such substances will be years in the making. In the meantime, Moore and his colleagues hope to produce colours using stress-induced reactions, which could be used to warn that an object is weakening. "One obvious example would be a parachute cord that turns red when bonds begin breaking" to warn that the chord is weakening, Moore says.

Retrieved from: http://www.newscientist.com/article/dn11427-mechanical-force-induces-chemical-reaction.html

I. Vocabulary Practice

1. Join the bits to make word combinations. Think of their translation into Russian:

A.

induce

chemical

apply

polymer

mechanical

bombard

tensile

connected

reform

a fundamental

cross-link

make

use

B.

chemical reactions

stress-induced reactions

force

molecules

into different shapes

such reactions reversible

with other broken bonds

strands

with ultrasound

forces

discovery

catalysts

ultrasound

2. Express the same in other words:

ñ cause something (2 variants possible),

ñ separate (2 variants possible),

ñ a single thin piece of something,

ñ pull something by making a short strong movement,

ñ impossible to achieve or obtain,

ñ behave or work in the same way as something else,

ñ one of two or more compounds that have the same chemical formula, but have the atoms in their molecules arranged in a different way and have different properties from each other.

II. Reading

1. Think of the possible titles for paragraphs A, B and C.

2. Say whether the statements are true or false:

ñ Mechanical force has long been used to induce chemical reactions.

ñ Applying ultrasound can result in breaking several bonds at a time.

ñ Breaking atomic bonds can cause the molecule to reform.

ñ A fundamental discovery consists in making both isomers reform into different shapes.

ñ Cross-linking can cause self-healing materials to appear.

ñ According to Moore, changing the colour of the chord can show that an object is hardening.

III. Find the answers to the questions:

What are the typical catalysts used to activate chemical reactions?

What can result from applying ultrasound to a solution of specially prepared molecules?

What exactly made V. Percec say “It's chemistry at its best”?

According to the researchers, how can cross-linking be applied?

What Moore and his colleagues are focusing on at present?

IV. Speaking

1. Think of other possible applications of the discovery apart from parachute chord manufacturing.

2. Write a short abstract for an article about the use of ultrasound force in chemical reactions.

3. You're a journalist interviewing Jeffrey Moore, the University of Illinois, about the discovery.

Date: 2015-12-11; view: 906