Comprehensive Guide to Addition Polymers: Types, Structures, and Uses

hello everybody in this video we'll be talking about polymers polymers are large organic

molecules that consist of repeating monomers monomers are small

organic molecules that make up the polymer now you can think of the polymer as a

brick that makes up a brick wall which represents the much larger polymer in this video we'll look at different

types and structures of monomers and the polymers that they do make up addition polymers are made

from monomers that contain a carbon to carbon double bond these carbon to carbon double bonds are

reactive and responsible for connecting monomers together to produce a polymer

for example multiple ethereum monomers undergo polymerization to produce polyethylene

in polymer chemistry ethene is typically referred to as ethylene and polyethylene polyethylene i'll be

using these two terms from now on let's have a closer look at how polymerization is achieved

addition polymerization consists of three main stages initiation elongation and termination

initiation begins with the order cleavage of hydrogen peroxide which produces two hydroxyl radical molecules

this is hydrogen peroxide and the bond between the two oxygen atoms is especially weak so what usually

happens in this molecule is that the two electrons will go towards the adjacent oxygen atoms

this produces a molecule that consists of an oxygen and hydrogen where the oxygen atom contains a single

unpaired electron we call this a radical molecule this radical molecule

specifically the unpaired electron is able to react with the double bond from the ethylene monomer the reaction

here produces another organic radical molecule where we again

have a unpaired single electron that is very reactive this is followed by elongation whereby

the organic radical molecule formed from before reacts with another ethylene monomer to

produce a much larger organic radical where we have formed another single

unpaired electron now as you can imagine the larger organic radical molecule from before can

further react with another monomer to produce an even larger molecule as shown below

since this molecule still has an unpaired electron its length will continue to grow by

reacting with a further ethylene monomer hence the name of this stage

is called elongation there's no definitive number of monomers that can be added to this growing molecule

the main factors that influence how long elongation can go on for is the time of reaction

and the number of monomers that has been supplied or are readily available

this is why polymer molecules have different lengths polymerization terminates when

two radical molecules react together to form a final product that does not have an unpaired

electron therefore this final molecule here it is not a radical molecule in this

structural formula of polyethylene the letter n can represent any integer that is a whole number this is because

the number of monomers already added to this growing molecule this is because

the number of monomers added to this growing molecule during the elongation phase is

completely random another way polymerization can terminate is when

two large radical molecules react to form an even larger polymer that no longer

has an unpaired electron to react further again this reinforces the concept that every

polymer molecule is large but has different lengths or sizes

let's summarize how monomers can be added together to produce an addition polymer

in initiation a molecule of hydrogen peroxide decomposes to generate two radical

hydroxyl molecules which reacts with a double bond in the ethereum

monomer to produce another organic radical over here while i use hydrogen peroxide as an example

please keep in mind that there are other compounds that can also be used to produce these radical molecules that

will initiate the polymerization in elongation monomers

are added sequentially to the radical molecule produced initiation this increases the length of the organic

molecule eventually forming a longer polymer finally polymerization terminates

when two radical molecules shown here react together to form a final molecule without an unpaired electron

as a result this molecule will no longer react and becomes a final product of the reaction

in hs chemistry syllabus there are four additional polymers you need to know polyethylene polyvinyl chloride short

for pvc polystyrene and polytetrafluoroethylene short for ptfe

for each polymer we'll discuss the structure properties and uses i'll be using these examples of

polymers to demonstrate how the structure affects the polymers properties

and how the properties plays an important role in determining their uses polyethylene is an addition polymer that

i used to demonstrate the production of addition polymers in another video

polyethylene is formed for the polymerization of ethy which is the monomer shown here there

are two types of polyethylene low density and high density polyethylene short for

ldpe and hdp respectively ldp and hdp have different structures properties and uses high density

polyethylene hdpe consists of polymer chains that are straight and linear

as a result these linear polymer molecules can compact very nicely without creating

much unused space as a result they have high density

and allows for extensive dispersion forces to form between these long linear chains

the extensive dispersion forces gives rise to high melting point as well as a crystalline structure for

the polymer in addition the linear polymer chains causes the polymer to be very rigid as

opposed to being flexible as we'll see in a moment with ldpe some typical uses of hdpe utilizes its

rigid and crystalline structure for example it is found in most plastic utensils

such as calories plastic bottles as you can see in this image here and plus the toys low density

polyethylene ldpe also is formed from ethylene as the monomer but the polymer

chains formed are branched as opposed to linear as we saw before

this diagram here shows a very nice illustration of what branched polyethylene looks like

as a result of the branched structure this type of polyethylene has a lower density as a result there is

a weaker dispersion force between these branched chains as the surface area between polymers

have greatly reduced due to their branched structure so compared to hdpe ldp have a much

lower melting point and it is important to know that they are amorphous that is

the structure can be molded very easily as opposed to the crystalline structure that we saw in http ldp is also soft

and flexible the application of ldpe is quite different to that of hdpe ldp is found

in plastic bags films and plastic packaging it is very important for you to know the

similarities and differences between http and ltp while both of these polymers are

formed from ethylene as the monomer their structure varies

in terms of whether it's linear versus branched for http its linear structure gives rise

to a higher density which allows for stronger dispersion forces a higher melting point

and a crystalline structure as well as a very high rigidity all of these properties are very useful

in its uses as plastic utensils bottles and toys in contrast the branch form of ldpe

has a much weaker dispersion force and therefore has a lower melting point than http and it also has

a amorphous structure which allows for its flexibility again these properties are very useful in its

application in plastic bags packaging and films or which require some degree of

flexibility the next addition polymer is polyvinyl chloride pvc

this polymer is produced by using chloroethylene as the monomer the structure of

chloroethylene is shown here this polymer is very similar to polyethylene

except one of the hydrogen atoms in each monomer is replaced by a chlorine atom as a

result the polymer chains acquire some degree of dipole moment this is why

between polymer chains of pvc we have extensive dispersion forces as well as dipole dipole forces

the extensive dipole dipole forces on top of the dispersion force is the reason why pvc has a higher

melting point than both ldp and htpe some important properties of pvc

include lightweight durable acid resistant that is it doesn't react in the presence of acids

it is electrically insulating that is it doesn't conduct electricity and it can be either made into a rigid

or flexible polymer depending on how pvc is produced for rigid pvc these polymers are

typically found in pipes mainly due to the fact that they are acid resistant

and durable especially resistant to weathering on the other hand flexible pvc are found

in cling wraps cable and wire insulation due to their electrical

installation property and inflatables as they are very flexible and malleable polystyrene

ps for short is made from a styrene monomer the systematic name for styring is ethyl

benzene it's important for you to recognize that benzene is a very common structure in organic

chemistry it is a six carbon membrane with alternating double bonds as shown here

so a staring monomer is a two carbon alkene whereby one of the carbons is attached

to a benzene ring over here polystyrene is a polymer that contains multiple

of these benzene rings which are very very bulky structure this is something that you

need to definitely remember it is very bulky structure the bulky benzene rings in polystyrene

causes a polymer to become very brittle that is it breaks very easily when forces are applied onto it

some other important properties of polystyrene include it is transparent that is see-through it is also very

lightweight and has a low density and furthermore it is both thermally and electrically insulating polystyrene

is used in a variety of applications the most common use is in styrofoam

this is foam in found in food containers and packaging as shown in the picture here this is

mainly due to the fact that polystyrene has a very low cost when it comes to production it is

lightweight and it is thermally insulating so it's good for food storage its transparent and lightweight

properties also enable polystyrene use in cassette cases shown here and furthermore polystyrene's

electrically insulated property allows this usage in the

handle of multiple tools including screwdrivers the last edition polymer that you need

to know is polytetrafluoroethylene ptfe this polymer is produced from a monomer

called tetrafluoroethyne tetrafluoroethene is a two-carbon alkene where all the

hydrogen atoms have been replaced by fluorine so essentially ptfe is exactly the same

as polyethylene but with all the hydrogen atoms being replaced with fluorine atoms the

implication of this structure change is that ptfe contains extensive dispersion

and dipole-dipole forces between polymer chains so ptfe has a relatively high melting

point compared to other polymers furthermore ptfe is also flame resistant acid

resistant and has a low friction the most important use

of ptfe that you need to remember is in teflon found in non-stick frying pans this is

because ptfe has a very high melting point and also it is flame and acid resistance

both of these resistances are very useful in cooking a secondary use of ptfe is in mechanical

components such as gaskets this is because they have a high melting point

and more importantly they have a low friction which is a very useful trait to have when it comes to engineering

let's quickly summarize the different types of addition polymers that we went through and what i want you

to take away for each of the polymers hdpe and ldp are both made from

ethylene as the monomer but hdp is rigid and crystalline found in plastic utensils on the other

hand ldp is more flexible and has an amorphous structure

therefore it is found in plastic bags pvc is a polymer that can be made either as a rigid

structure or a flexible one rigid pvc is found in pipes

whereas flexible pvc is found in cling wraps polyethylene is relatively lightweight and has a low cost

to manufacture it is found in styrofoam such as in containers and packaging ptfe is

chemical resistant and has a high melting point it is found in non-stick frying pans

that concludes the video on addition polymers