Introduction :
Several simple organic molecules of one or two types combine with each other by chemical bonds forming macro molecules the product is called a polymer. Simple organic molecules which can form polymers by chemical bonding are called monomers while this process of chemical combination is called polymerisation. In any sample or monomers there are very large number of molecules of lower masses same molecular weights and similar physical and chemical properties.
Molecular mass of Polymers:
Overall molecules of ethene combine with each other by addition reaction and give polyethene. This reaction at the first stage two molecules of ethene monomer combine together giving a dimer. A third molecule of ethene combines with this dimer giving a trimer and a forth molecule combine further gives a tetramer. This way monomer molecules go on joining and chain becomes longer. As result very large chain is former which is called macro molecule or polymer.
CH2 = CH2 `stackrel(CH_2=CH_2)(->)` CH3-CH2-CH = CH2 `stackrel(CH_2=CH_2)(->)`
CH3-CH2-CH2-CH2-CH=CH2 `stackrel(CH_2=CH_2)(->)`
CH3-CH2-CH2-CH2-CH2-CH2-CH=CH2
`stackrel(nCH_2=CH_2)(->)` [-CH2-CH2-]n
The polymer chain can be lengthen upto certain limit at laboratory cantons. The tendency of this long chain then decrease to combine with further monomers. Thus in any condition polymers resulting from monomers do not increase in weight more than a certain limit. Generally any polymer asmple contains varying chain-lengths, its molecular mass is always an average molecular mass. The molecular mass of a polymer is expressed as number average molecular mass `barM_n` or weight average molecular mass `barM_w`.
`barM_n = (sumN_tM_t)/(sum tN_t)`
`barM_w = (sumN_tM^2_t)/(sumtN_tM_t)`
Where Nt = number of molecules
Mt = molecular mass.
Several simple organic molecules of one or two types combine with each other by chemical bonds forming macro molecules the product is called a polymer. Simple organic molecules which can form polymers by chemical bonding are called monomers while this process of chemical combination is called polymerisation. In any sample or monomers there are very large number of molecules of lower masses same molecular weights and similar physical and chemical properties.
Polymers:
Ehereas in polymer sample having same molecular weights the number of molecules are very small. The polymers have comparatively very high molecular weight but all molecules do not have comparatively very high molecular weight but all molecules do not have identical molecular weights. Polymers prepared from the same monomer in different conditions do not have all the properties identical. Depending on reaction conditions polymer products have different proportions of molecules of lower and higher masses.Molecular mass of Polymers:
Overall molecules of ethene combine with each other by addition reaction and give polyethene. This reaction at the first stage two molecules of ethene monomer combine together giving a dimer. A third molecule of ethene combines with this dimer giving a trimer and a forth molecule combine further gives a tetramer. This way monomer molecules go on joining and chain becomes longer. As result very large chain is former which is called macro molecule or polymer.
CH2 = CH2 `stackrel(CH_2=CH_2)(->)` CH3-CH2-CH = CH2 `stackrel(CH_2=CH_2)(->)`
CH3-CH2-CH2-CH2-CH=CH2 `stackrel(CH_2=CH_2)(->)`
CH3-CH2-CH2-CH2-CH2-CH2-CH=CH2
`stackrel(nCH_2=CH_2)(->)` [-CH2-CH2-]n
The polymer chain can be lengthen upto certain limit at laboratory cantons. The tendency of this long chain then decrease to combine with further monomers. Thus in any condition polymers resulting from monomers do not increase in weight more than a certain limit. Generally any polymer asmple contains varying chain-lengths, its molecular mass is always an average molecular mass. The molecular mass of a polymer is expressed as number average molecular mass `barM_n` or weight average molecular mass `barM_w`.
`barM_n = (sumN_tM_t)/(sum tN_t)`
`barM_w = (sumN_tM^2_t)/(sumtN_tM_t)`
Where Nt = number of molecules
Mt = molecular mass.
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