6. Heterocycles, Nucleic Acids and Polymers

Question 1

What is addition polymerisation?

Answer 1

a reaction where many monomers bond together via rearrangement of bonds without the loss of any atom or molecule under specific conditions of heat, pressure, and/or the presence of a catalyst

Question 2

What is an amorphous domain?

Answer 2

without any organised regular repeating pattern

Question 3

What is an antioxidant?

Answer 3

compounds that are used to terminate the oxidation reactions taking place due to different weathering conditions and reduce the degradation of organic materials

Question 4

What is a biodegradable polymer?

Answer 4

a specific type ofpolymerthat breaks down after its intended purpose to result in natural byproducts such as gases (CO2, N2), water, biomass, and inorganic salt

Question 5

What are biopolymers?

Answer 5

a polymeric substance occurring in living organisms, e.g. a protein, cellulose, or DNA.

Question 6

What is cationic polymerisation?

Answer 6

a type of chain growth polymerizationin which acationicinitiator transfers charge to a monomer which then becomes reactive. This reactive monomer goes on to react similarly with other monomers to form apolymer.

Question 7

What is chain-growth polymerisation?

Answer 7

A polymerizationtechnique where unsaturated monomer molecules add onto the active site of a growingpolymer chainone at a time.Growthof thepolymeroccurs only at one (or possibly more) ends. Addition of each monomer unit regenerates the active site

Question 8

What is a chain-transfer reaction?

Answer 8

apolymerization reactionby which the activity of a growing polymer chainis transferred to another molecule. P• + XR’ → PX + R’•Chain transfer reactionsreduce the average molecular weight of the finalpolymer.

Question 9

What is condensation polymerisation?

Answer 9

a reaction in which two molecules combine to form a larger molecule, producing a small molecule such as H2O as a by-product.

Question 10

What are cross-links?

Answer 10

a bond thatlinksonepolymerchain to another. They can be covalent bonds or ionic bonds

Question 11

What is degradation?

Answer 11

a change in the properties—tensile strength, color, shape, etc.—of apolymerorpolymer-based product under the influence of one or more environmental factors such as heat, light or chemicals such as acids, alkalis and some salts

Question 12

What are elastomers?

Answer 12

a natural or synthetic polymer having elastic properties, e.g. rubber.

Question 13

What is high-density polyethylene (HDPE)?

Answer 13

a hydrocarbon polymer prepared from ethylene/petroleum by a catalytic process. It is a kind of thermoplastic which is famous for its tensile strength. Its unique properties can stand high temperatures

Question 14

What is isotactic polypropylene?

Answer 14

a type of polypropylene where all of the side chains are on the same side of the polymer

Question 15

What is low-density polyethylene (LDPE)?

Answer 15

highly branched polyethylene with low crystallinity and melting point, prepared at very high pressures, and is used mainly for sheeting, films and packaging materials

Question 16

What is a monomer?

Answer 16

a molecule that can be bonded to other identical molecules to form a polymer

Question 17

What is natural rubber?

Answer 17

an elastic material obtained from the latex sap of trees that can be vulcanized and finished into a variety of products

Question 18

What is photodegradation?

Answer 18

degradationby means of radiant energy (as light)

Question 19

What is plastic?

Answer 19

a synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon, etc., that can be moulded into shape while soft, and then set into a rigid or slightly elastic form.

Question 20

What are polyamides?

Answer 20

a synthetic polymer of a type made by the linkage of an amino group of one molecule and a carboxylic acid group of another, including many synthetic fibres such as nylon

Question 21

What are polycarbonates?

Answer 21

a synthetic resin in which the polymer units are linked through carbonate groups, including many moulding materials and films.

Question 22

What are polyesters?

Answer 22

a synthetic resin in which the polymer units are linked by ester groups, used chiefly to make synthetic textile fibres.

Question 23

What is a polymer?

Answer 23

a substance which has a molecular structure built up chiefly or completely from a large number of similar units bonded together, e.g. many synthetic organic materials used as plastics and resins

Question 24

What is polymerisation?

Answer 24

a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks

Question 25

What are polyurethanes?

Answer 25

a synthetic resin in which the polymer units are linked by urethane groups, used chiefly as constituents of paints, varnishes, adhesives, and foams

Question 26

What are radicals?

Answer 26

an atom, molecule, or ion that has an unpaired valence electron

Question 27

What is radical-chain growth?

Answer 27

a type of chain-growth polymerisation in which the kinetic-chain carriers areradicals

Question 28

What is step-growth polymerisation?

Answer 28

a type of polymerizationmechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers

Question 29

What are thermoplastics?

Answer 29

denoting substances (especially synthetic resins) that become plastic on heating and harden on cooling, and are able to repeat these processes

Question 30

What are thermosetting plastics?

Answer 30

apolymer that irreversibly becomes rigid when heated

Question 31

What is vulcanisation?

Answer 31

a chemical process for converting natural rubber or related polymers into more durable materials by the addition of sulfur or other equivalent curatives or accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains