6. Heterocycles, Nucleic Acids and Polymers Flashcards
What is addition polymerisation?
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
What is an amorphous domain?
without any organised regular repeating pattern
What is an antioxidant?
compounds that are used to terminate the oxidation reactions taking place due to different weathering conditions and reduce the degradation of organic materials
What is a biodegradable polymer?
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
What are biopolymers?
a polymeric substance occurring in living organisms, e.g. a protein, cellulose, or DNA.
What is cationic polymerisation?
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.
What is chain-growth polymerisation?
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
What is a chain-transfer reaction?
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.
What is condensation polymerisation?
a reaction in which two molecules combine to form a larger molecule, producing a small molecule such as H2O as a by-product.
What are cross-links?
a bond thatlinksonepolymerchain to another. They can be covalent bonds or ionic bonds
What is degradation?
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
What are elastomers?
a natural or synthetic polymer having elastic properties, e.g. rubber.
What is high-density polyethylene (HDPE)?
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
What is isotactic polypropylene?
a type of polypropylene where all of the side chains are on the same side of the polymer
What is low-density polyethylene (LDPE)?
highly branched polyethylene with low crystallinity and melting point, prepared at very high pressures, and is used mainly for sheeting, films and packaging materials
What is a monomer?
a molecule that can be bonded to other identical molecules to form a polymer
What is natural rubber?
an elastic material obtained from the latex sap of trees that can be vulcanized and finished into a variety of products
What is photodegradation?
degradationby means of radiant energy (as light)
What is plastic?
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.
What are polyamides?
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
What are polycarbonates?
a synthetic resin in which the polymer units are linked through carbonate groups, including many moulding materials and films.
What are polyesters?
a synthetic resin in which the polymer units are linked by ester groups, used chiefly to make synthetic textile fibres.
What is a polymer?
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
What is polymerisation?
a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks
What are polyurethanes?
a synthetic resin in which the polymer units are linked by urethane groups, used chiefly as constituents of paints, varnishes, adhesives, and foams
What are radicals?
an atom, molecule, or ion that has an unpaired valence electron
What is radical-chain growth?
a type of chain-growth polymerisation in which the kinetic-chain carriers areradicals
What is step-growth polymerisation?
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
What are thermoplastics?
denoting substances (especially synthetic resins) that become plastic on heating and harden on cooling, and are able to repeat these processes
What are thermosetting plastics?
apolymer that irreversibly becomes rigid when heated
What is vulcanisation?
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
