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Key Centre for Polymer Colloids Plymer - Chemistry Glossary
Category: Sciences > Polymer
Date & country: 11/09/2007, AUS
Words: 193


Absorption
Not to be confused with adsorption, absorption is one substance is taken up into the interior of another - adsorption with a 'd' is entirely a surface effect. Examples are the swelling of a poly(acrylamide) polymer with aqueous solution (in a disposable nappy) or the dissolution of carbon dioxide in seawater (one of the possible antidotes to global warming that crops up in models of world climate.

Acetaldehyde
Systematic name, ethanal! This is a good example of a case where the IUPAC system may be logical, but can easily engender no end of confusion.

Acid
There are three definitions - Arrhenius, Bronsted, and Lewis Acids. In the Lewis conception, which is the most general and useful, an acid is essentially any compound that needs electrons, and a base is basically any compound that wants to give them away.

Acid anhydride
Take two carboxylic acid molecules - for example, salicylic acid - and remove water to give a molecule containing a -(C=O)-O-(C=O)- link - this molecule will be an acid anhydride. For example: ethanoic anhydride: ethanoic anhydride (a.k.a acetic anhydride)

Acid chloride
Take a carboxylic acid and replace the OH group with a Chlorine atom. What you now have is an acid chloride. Acid chlorides react readily with water to regenerate carboxylic acid + HCl.

Acidic
Forming or containing an acid.

Acrylonitrile
A common monomer used in free-radical polymerisation.

Active Centre
In chain-growth polymerisation, the highly-reactive spot on the growing polymer chain where new monomer is added. The four most common types are a free-radical (atom with an unpaired electron), carbanion (carbon-centred negative ion), carbocation (carbon-centred positive ion) or a metal complex (as in Ziegler-Natta polymerisation).

Addition Polymerisation
Also known as chain-growth polymerisation. The mechanism in which large numbers of usually identical small molecules are joined together to rapidly form a single large molecule. This involves the addition of reactive centre (anion, cation, or unpaired electron) to a multiple bond to form a new bond and a new reactive centre - which reacts with another multiple bond, et cetera... The finished chain then hangs around without reacting while more of the starting material reacts to form new polymer c…

Adsorption
Not to be confused with absorption, adsorption is the build up of a molecule at a surface (such as an oil/water interface). Adsorption generally occurs because different parts of a molecule have an affinity for the two different phase on either side of the interface.

Alcohol
'Any chemical compound where the hydroxy functional group -O-H is bound to an carbon skeleton. You are probably most familiar with the diols (compounds with two hydroxy groups), which are used in the manufacture of polyesters, and the phenols, where an hydroxy group is bound to an arene.

Aldehyde
Any chemical compound containing the functional group -C(O)H. Acrolein, the simplest aldehyde that is also a monomer capable of undergoing addition polymerisation, is responsible for the distinctive sm…'

Amphiphilic
From the greek meaning 'both' (something like amphi) and 'lover' (something like philos). An amphiphile is a molecule that has a strong attraction towards both polar solvents (like a hydrophile) and non-polar solvents (like a hydrophobe) and will end up concentrated at the interface between the two.

Anionic
A negatively charged chemical species, like the hydroxide OH-, carbonate CO32-, or sulphate SO42-, is called an anion. In an electrochemical cell, an anion will move towards the anode to lose its extra electron and generate a current.

Anthropogenic
A fancy way of saying 'man-made' that hides its lack of political correctness in greek. Think of 'anthropoid' and 'genesis'.

Arene
Any carbon compound containing a six membered ring of carbons, each of which forms only one chemical bond outside of the ring. This is called a phenyl ring, and though it looks like it has alternating single and double bonds, all the bonds are actually the same. Benzene is the simplest arene; other examples are toluene, fulvic acid, and trinitrotoluene Benzene

Bacteria
Single-celled organisms that probably provide the bulk of the biomass on our planet. There are more bacterial cells within your body than human cells. One of the most interesting things about bacteria is that our macroscopic concepts of 'species' are rather inappropriate - genetic material can be swapped from one 'species' to another with disturbing ease, leading some scientists to call all bacteria a single 'superorganism'. The fantastic durability and longevity of bacteria (some concentrate pl…

Benzoyl Peroxide
A common initiator used to start chain growth polymerisation. It undergoes a decomposition reaction at the peroxide (O-O) bond. Here is a picture:

Biocompatible
A material may be regarded as biocompatible if it may be put into living organisms without rejection or detrimental effects. Materials may also be considered to be bioinert if they do not interact with the body at all (like titanium knee implants).

Biodegradable
Capable of being eaten or otherwise decomposed by some kind of living creature. Bacteria and fungi are the main culprits; we usually use the word edible for things that can be eaten by animals. It is important to consider the timescale involved - paper is biodegradable, but can kick around for a very long time before succumbing. Most synthetic polymers are not particularly biodegradable (poly(acrylamide) is a rare example of one that is readily degraded), but many are susceptible to breakdown by…

Biopolymer
A polymer produced by a living plant, animal fungus, bacterium, or other biological entity.

Biosynthesis
The production of a chemical by bacteria or other living organisms.

Boiling Point
The temperature at which the pressure exerted by molecules leaving a liquid equals the pressure exerted by the molecules in the air above it. A free-for-all of molecules leaving the liquid then ensues.

Butadiene
Common monomer in chain-growth polymerisation; an important constituent of ABS rubber. Here is a picture:

Calorimetry
Calorimetry is a technique for measuring the heat generated or lost in a chemical reaction. The reaction is carried out in such a way that as much as possible of the heat change is transferred to another material, raising its temperature. The heat generated can then be calculated from the amount of the material heated and its specific heat.

Carbanion
An anion where the negative charge is localised on a carbon atom is imaginatively called a carbanion. The best way to generate a carbanion is to remove a H+ ion from a hydrocarbon. Since carbanions are conjugate bases to very very very weak acids indeed, they are fiendishly reactive bases.

Carbenium
If a negatively charged hyride (H-) ion is removed from a hydrocarbon, what is left is a positively charged carbenium ion, a form of carbocation.

Carbocation
A positively-charged chemical species where the positive charge is localised on a carbon atom. Both carbenium ions (which have three bonds to a positively charged carbon) and carbonium ions (which may have five or more bonds to a positively charged carbon) are examples of carbocations.

Carbocation Carbon
compound with a positive charge localised on a carbon atom.

Carbonium
If there are five or more bonds to a single carbon atoms, it will be short of electrons and have a positive charge - this species is called a carbonium ion, a form of carbocation. The easiest way to make one is to add a hydrogen ion (H+).

Carboxylate group
When a carboxylic (alkanoic) acid is deprotonated (i.e., loses a H+ ion) what is left is a negatively-charged carboxylate ion.

Carboxylic Acid
Any carbon compound containing the functional group -C(O)OH. Formic acid (HCOOH) gives the distinctive smell of crushed ants, while acetic acid (CH3COOH) gives VB its distinctive odour and taste.

Carothers
Wallace Hume Carrothers (1896-1937) carried out the key early experiments that led to commercial polyesters, nylons, and neoprene while working for the DuPont corporation and almost single-handedly created the polymer industry in the United States. His amazing scientific achievements did not bring him happiness, and he tragically committed suicide by taking cyanide.

Catalyst
Compound that accelerates the rate of a chemical reaction, and is not itself consumed in the reaction.

Catalytic Cracking
A method of cracking that uses a catalyst to convert hydrocarbons to positively charged carbocations, which then break down into smaller molecules. This can be carried out at much lower temperatures than thermal cracking - still hot, 500-600°C as compared to around 700°C, but that difference adds up to a lot of $$$.

Cationic cation
A positively charged chemical species, like the ammonium NH4+ and scandium Sc4+ ions, is called a cation. In an electrochemical cell, a cation will move towards the cathode to gain an electron to remove its excess positive charge.

Caustic Soda
When used in industrial processes, sodium hydroxide is often known as caustic soda.

Ceiling Temperature
Above a certain temperature, monomers can no longer be persuaded to form polymers by chain polymerisation. This occurs when the loss in entropy arising from joining many molecules into one outweighs the energetic benefit of converting double bonds to single bonds. A chain-growth polymer raised above the ceiling temperature will degrade, or depolymerise.

Cellulase
No, not a misspelling of cellulose... Cellulase is an enzyme capable of depolymerising cellulose to form glucose. Chemists like these sort of words - see if your teacher can tell you the definitions of 'filtrate' and 'filtrant' without having to think about it for a couple of minutes... And if they get that one right, test them out on 'carbenium' and 'carbonium' ions!

Cellulose
Cellulose is a large component of the biomass of plants and the main source of food energy for the world's termite population. It can be considered to be a condensation polymer of glucose, like starch, but the links between the glucose monomers are slightly different.

Chain Reaction
A mechanism that has no reason to stop, since the product is just as reactive as the reactants.

Coagulation
Coagulation and coalescence are both words that are used to describe what happens when small particles in a dispersion combine together to form large ones. One example is what happens to milk (a nice disperse emulsion) if it is leftat the back of the fridge too long. Coagulation is used when the particles that are combining are more or less solids, and coalescnce is usually restricted to droplets of liquid.

Cohesion
Cohesion just means 'sticking together' and cohesive forces are the forces that enable something to stick to itself. For example, if you glue two objects together and then break them apart, a cohesive failure is where the glue itself breaks, as opposed to an adhesive failure where the break is at the join between the glue and one of the objects.

Colloid
If the size of a particle is of the order 10 nm to 1 micron (10-8 to 10-6 metres), then a mixture of these particles with a continuous phase (e. g., tiny particles of dust in air or polymer in water) will have properties that are intermediate between those of a true solution and a mixture of largish particles in a substance.

Comonomer
A monomer that is polymerised along with one or more other monomers to make a copolymer. All the different comonomers used in a copolymerisation are incorporated into each chain.

Condensation Polymerisation
Also known as Step-Growth Polymerisation. A way of makiing polymers in which every polymer chain grows continuously through the course of the reaction, remaining quite small until almost all the monomer has reacted.

Copolymer
A polymer that is made up of more than one monomer unit. A copolymer has each of its comonomers in every chain. There are a number of different types of copolymer which describe the nature of the arrangement of the comonomers within the polymer chain. For the two monomer units A and B we can have:block ...AAAAAABBBBBB... alternating ...ABABABABAB... statistical (or random) ...ABAAABBABBAABBB...

Corrosion inhibition
Corrosion can be defined as the unwanted production of a salt from a metal. Adding acid or oxygen are good ways to do this. The main ways of slowing corrosion down (inhibition) are by providing an impermeable coating to stop the chemical reaction from occuring in the first place, or by providing a more easily attacked metal which will be consumed first (a 'sacrificial anode')

Coulomb
An Amp(ere) of current is what you get one one Coulomb worth of electric charge flows past a point in one second - i.e., 1 A = 1 C/s. One mole of electrons has a charge of 96 500 C, which is called a Farad.

Cracking
The process in which large molecules found in crude oil are broken down into smaller molecules. See Catalytic Cracking and Thermal Cracking

Crude Oil
Tarry goop consisting of mixed carbon compounds with a highly variable composition. Not much to look at, but the basis for the chemical industry, modern transport, and many shopping sprees at Harrods.

Crystal
A large number of objects that are all the same size and shape and are attracted to one another will tend to form repeating three-dimensional structures, instead of lying about randomly. A more complicated crystal will be formed if more than one kind of object is present. You are probably most familiar with crystals of simple covalent solids (like sugar) or ionic solids(like table salt), where the attractive forces between perfectly ordinary molecules and ions line up in an orderly fashion to gi…

Density
To find the density of an object, you measure its mass and its volume, then divide the mass by the volume, giving a density measured in g/cm3 or kg/dm-3. Since all atoms are about the same size, the densest materials are metals like osmium and gold, which are elements with heavy nuclei, and the least dense are the very first elements in the periodic table, the gases hydrogen and helium.

Depolymerisation
The chemical reaction which results in a polymer chain being broken up into monomer units. For most polymers made by addition polymerisation, this is done by heating the polymer above its ceiling temperature in the absence of oxygen. Some polymers, like styrene and vinyl chloride, will be difficult to depolymerise because the bonds between the side-groups (the phenyl ring and chlorine in these examples) are weaker than the C-C bonds between ex-monomers, and the polymer will degrade into differen…

Depropagation
The reaction in which small alkenes are generated from the decompostion of a large alkane radical. This reaction is important in Thermal Cracking, and is responsible for the ceiling temperature, which prohibits chain polymerisation above a certain temperature.

Detergency
Detergency is the property of surfactants that allows them to clean things for us. The surfactants accumulate on the oil/water interface so that when we scrub the oily stain to break it up, the oil drops do not coaleasce.

Detergent
A detergent is a type of surfactant. Essentially, a detergent is any surfactant that is not a soap.

Dibasic
An acid that has two acidic hydrogen atoms that can react with a base is dibasic. An example is the amino acid aspartic acid, which contains two carboxylic acid groups with different reactivities.

Dimer
A dimer is two molecules (of the same type) bonded together. (just as monomer is one (mono) unit (mer) a dimer is two units).

Dipole
If one part of a molecule is more attractive to electrons than another part, it will have a permanent uneven distribution of charge - i.e., one end will be slightly positive and one will be slightly negative. There will be an attraction between two molecules of this substance, since they will turn so that the positive end of one is facing the negative end of the other.

Disaccharide
Just as there are monomers, dimers, trimers, oligomers, and polymers, indicating one, two, three, several, and many identical units joined together in a molecule, the combinations of saccharides (aka sugars) are known as mono-, di-, tri-, oligo- and polysaccharides. An example of a disaccharide is sucrose, composed of the simple sugars glucose and fructose joined by an ether linkage. An example of a polysaccharide is chitin, a nitrogen-containing polymer of modified glucose units that makes up t…

Dispersion
Two substances mixed together such that one is not dissolved in the other. For example, milk, a dispersion of globules of fat in water; latex paint, a dispersion of polymer particles in water; smoke, a dispersion of carbon particles in air.

Dispersion Forces
Since electrons move around, even a molecule with no permanent separation of charge will have negative and positively charged bits from one instant to another. These imperfections generate an overall attractive force even between molecules as unreactive as N2. Since this explanation is already too complicated for anyone to understand, I may as well go on to say that they are called Dispersion Forces because they are related to a quantity called the dispersion of a substance, which is the rate of…

Distillation
Separation of two liquid compounds by boiling point. For example, a mixture of two hydrocarbons can be heated so that the lower molecular weight hydrocarbon evaporates - if the vapour is not allowed to escape, but taken around the corner and cooled down, it can be extracted as a pure liquid.

Elastomer
A polymer that, when deformed (stretched, twisted, spindled, mutilated, etc.) springs back into its original shape. The elastomer par excellence is lightly-crosslinked natural rubber.

Electron
A tiny speck of electric charge, so-far impossible to break into smaller pieces, weighing in at 9.109 × 10-31 kg and a charge of 1.602 × 10-19 Coulombs. An electron is so small that its 'size' is a nebulous concept; if it were a little round ball, it would be about 10-15 m across.

Electronegative
The ability of an atom to attract electrons is its electronegativity. Elements that easily form negatively charged ions, such as fluorine and oxygen, have a high electronegativity. Generally speaking, the top right corner of the periodic table is home to the most electronegative elements, while the bottom left is the least electronegative.

Emulsifier
A compound added to a mixture of two immiscible liquids in order to make it an emulsion, and not just two layers of liquid lying on top of each other. An emulsifier will usually be a molecule where one end is highly soluble in water and the other is highly soluble in oil. Sodium dodecyl sulfate, the active ingredient in bubble-blowing mixture, is a surfactant. So is lecithin, found in egg yolk:

Emulsion
A dispersion where a liquid is dispersed in another liquid - for example, mayonnaise is an emulsion of water in oil and milk is an emulsion of oil in water. Strictly speaking, a dispersion is only an emulsion if the dispersed blobs of liquid are of colloidal dimensions.

Entropy
A measure of the number of possible states a group of 'somethings can occupy' - the more possible ways the group can be arranged, the higher the entropy. For example, there are fewer possible configurations of students in chairs in a room where the chairs are bolted to the floor than where the chairs can be moved around - the room with fewer possibilities will have less entropy, and more order... It's also interesting that the entropy of the universe is always increasing, so any process that giv…

Enzyme
A protein that catalyses a biochemical reaction. For example, chemical engineers make nitrogen (N2) into ammonia (NH3) using high temperatures and pressures - generating the power to make fertiliser by this process accounts for about 2% of all anthropogenic greenhouse gas emissions. Bacteria do the same thing at soil temperature and pressure using enzymes to catalyse the reaction.

Ester
Take a carboxylic acid and an alcohol and remove water, so that you are left with two bits linked by a C(O)-O- group - this is an ester. Many of the most important industrial polymers are esters. For example, ethyl acetate:

Ethanol
What most people just call alcohol, ethanol is the alcohol with which most people are most familiar. It's a very useful solvent, antiseptic, cleaner and is also known as a 'social lubricant' due to its physiological effects, which can include death. Most polymer scientists never ever touch the stuff. Honest.

Ethene
Also known as ethylene, ethene is the simplest monomer for use in addition polymerisation reactions. Poly(ethene) (or polyethylene) is well known to you in the form of cling wrap.

Ether
Any carbon compound containing the functional group C-O-C. A commonly used ether is diethyl ether, which used to be used as an anæsthetic.

Eutrophication
Usually, the limiting factor on how many living organisms can grow in a body of water is the supply of nutrient elements such as nitrogen and phosphorus. If these are supplied in overabundance (for example, by pouring fertilizer into the lake), plants and bacteria can multiply to such an extent that the oxygen consumed in their decomposition can exhaust the oxygen available in the lake, causing a loss of species that like oxygen and the multiplication of anaerobic bacteria that generate nasty ch…

Experiment
A controlled environment for the application of common sense. Having observed something interesting in the world of chemistry, we make an educated guess as to what is happening (a 'theory'), then say 'if this explanation is true, we should see such-and-such an effect if we do such-and-such.' Actually doing such-and-such and seeing what happens is called 'doing an experiment'.

Fermentation
The process in which an organic substance is converted into another organic substance and carbon dioxide to generate energy by a (micro)organism in the absence of oxygen. 'Fermentation' comes from the latin word for yeast, a kind of single-celled fungus. The most common fermentation reaction is the one by which glucose is converted into ethanol and carbon dioxide. This series of reactions is made use of humans when they use yeasts to make alcoholic drinks. It is easy to go wrong and make some di…

Fluorescence
If a substance absorbs light at one wavelength and re-radiates it at another wavelength almost immediately, it is fluorescent; this is why many materials glow under ultraviolet light. If the substance keeps re-radiating light over a period of seconds, minutes, or hours, it is called phosphorescent.

Fossil Fuel
A fossil fuel is a fuel such as coal, oil or natural gas that was formed through the decomposition of ancient plant and animal life. Fossil fuels are generally burnt to release the energy stored in the chemical bonds of the hydrocarbons. A side-effect of this combustion is the release of gases such as carbon dioxide, which has been linked to global warming through the Greenhouse Effect. Fossil fuel reserves are also finite and some of them (particularly oil reserves) are likely to run out within…

Fractionation
Separation of a mixture of hydrocarbons into fractions with different boiling point ranges by heating crude oil in a column that is cooler at the top than at the bottom - 'fractions' are removed from the column at different heights where the temperature is different.

Free Radical
A molecule which has an odd number of electrons. The 'unpaired' electron feels lonely and wants to find a friend. If it finds something that might be willing to give it an electron it reacts very quickly with it. Molecules such as other radicals and alkenes turn out to be good things for radicals to attack. The reaction of radicals with the double bonds in alkenes is how some of us earn our living.

Freezing Point
The temperature where a liquid or solution changes from a liquid to a solid. Clearly, one person's Freezing Point will be another's Melting Point. In a solution the freezing point will be reduced by a number that depends on the number of particles in solution delta(T) = Kf × (number of solute molecules per litre) where delta(T) is the reduction in freezing point and Kf is called the 'cryoscopic constant' and varies from one solvent to another.

Functional Group
An atom or group of atoms that has similar chemical behavior, no matter what the rest of the molecule looks like. For example, the hydroxy (OH) group in all alcohols has similar reactivity, as does the thio (SH) group in all thiols.

Fungi
Neither plants nor animals, fungi are eukaryotes (organisms whose cells have nuclei) which are incapable of making their own food by photosynthesis and survive by breaking down chemical compounds made by plants and bacteria to waste products, just like we do.

Giulio Natta
Nobel prize winning chemist (1903-1979) who did a vast quantity of work on the catalysts allowing high density poly(ethene) and poly(propene) to be produced. Most of his work was done in Milan, Italy, for the Montecatini corporation, making him one of the most successful industrial chemists of the 20th century. He was married to Rosita Beati Natta. Like Karl Ziegler, he was a keen mountain climber. A quote: 'What had been exclusively in the power of Nature, namely to join the monomeric units in …

Glass Transition Temperature
The temperature where the molecules of a polymeric solid can begin to move relative to one another, giving a substance that behaves like a rubber, rather than a brittle glass. Alternatively, you can think of it as the temperature where the molecules of a polymeric solid can no longer move relative to one another, giving a substance that behaves like glass, rather than a rubber that can be stretched without breaking. It all depends on which way you are going...

Glossary
A set of definitions of words, such as this one. Not all glossaries are self-referential.

Glucose
A common sugar, one of many with the chemical formula C6O6H12 but different three-dimensional structures. It is not the simplest of all sugars (that honour belongs to glyceraldehyde, C3O3H6), but glucose is the fundamental building block of many biopolymers, including starch and cellulose, and is the starting material for the serious biochemical reactions used to obtain energy in most 'higher' organisms.

Glycerol
Propan-1,2,3-triol, named from the greek word for 'sweet' thanks to its taste. It is the basis for many animal and vegetable fats.

Gutta-percha
While natural rubber from the rubber tree Hevea brasiliensis is cis-poly(isoprene), the Malaysian sapodilla tree Palaquium oblongifolia produces a latex that is trans-poly(isoprene). This material is called guttah-percha and is more brittle and hard than natural rubber.

Halide
The ions of charge -1 of the elements in the next to last column of the periodic table: chloride, fluoride, bromide, iodide (and astatide, but there are only eleven known atoms of astatine, so no one ever counts it).

Halogen
One of the elements in the next-to-last column of the periodic table - fluorine, chlorine, bromine, iodine, and astatine.

Heat of combustion
The amount of heat released in burning completely an amount of substance is its heat of combustion. The amount needed for one mole is naturally called the molar heat of combustion. A general formula for the combustion of any organic compound is:

Heat of vaporisation
The amount of heat energy required to transform an amount of a substance from the liquid phase to the gas phase is its heat of vaporisation. The amount needed for one mole is naturally called the molar heat of vaporisation...

Homo Neanderthalensis
A species of human, now extinct, that was common in Europe and the Mideast about 100 000 years ago. The name comes from Neandertal, meaning 'Neander valley', in northwestern Germany, which was in turn named after the 17th century latin teacher and school principal Joachim Neander, where the first remains of Neandertal man were discovered. Here is more info.

Hydrocarbon
Any chemical compound containing only hydrogen and carbon. We have been unable to determine where the word comes from.

Hydrogen bond
The strongest attraction between two dipoles is when one or both of them involves a bond between hydrogen and a strongly electronegative atom, like oxygen, fluorine, or nitrogen. Because hydrogen only has one electron, if it forms a bond with an element that is very keen to grab an electron, it becomes much more positive than an element that has plenty of other electrons left to hang around the positively charged nucleus. Dipole-dipole interactions between these sort of molecules (like water {H2…

Hydrogen sulfide
'Rotten egg gas', H2S. It is responsible for the distinctive odour of Rotorua, in New Zealand.

Hydrolysis
Hydrolysis is a reaction where water attacks a part of a molecule, usually breaking it up. An example of hydrolysis is the breaking of the ester linkages to form a soap out of an oil. In this reaction, the ester linkage is broken, releasing an alcohol and an acid.