Sequencing of Monomer Unit in Polymers

A very important aspect of microstructure is the sequence of monomer units in a polymer. This applies whether the polymer is based on a single monomer which is capable of polymerising in different ways, e.g., head-to-head or head-to-tail polymerisation, or whether it is based on two or more different monomers when many variants of monomer sequence are possible. Sequence distribution has an important bearing on the tacticity and other properties of polymers, as will be discussed later. Three major techniques have been used to study sequence problems in polymers, they are pyrolysis-gas chromatography, nnclear magnetic resonance (NMR) and, more recently, secondary ion mass spectrometry (SIMS). 

As might be expected, groups at either end of a polymer chain differ from those in the main polymer chain. Various methods are available for determining low concentrations of such end-groups in polymers. 

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