Deuterium NMR in Rubbery Materials

Deuterium NMR (2H NMR) has been used extensively to study and characterise molecular properties in various complex fluids such as liquid crystals [1, 2, 3] and in polymer systems [4]. 

Rubber materials are soft, elastic solids, made of mobile, flexible polymer chains (with a glass transition temperature (Tg) typically lower than 0 °C) which are linked together to form a three-dimensional network. They are characterised by a low, frequency independent elastic modulus (of the order 105 to 106 Pa) and usually by a large maximum reversible deformation (up to a few hundred per cent). Rubber elasticity is based on the properties of crosslinked polymer chains at large spatial scales, the presence of crosslinks ensures the reversibility of the deformation, while at short scales, mobile polymer chains behave as molecular, entropic springs. 

There are different ways to realise rubber materials with customised properties. The main requirements are usually chemical and mechanical stability over a certain temperature range a given value of the elastic modulus a high maximum deformation and eventually, biocompatibility. 

Amongst the various techniques sensitive to the molecular behaviour, deuterium (2H) nuclear magnetic resonance (NMR) has some properties which make it particularly specific  

The basics of 2H NMR are summarised in Section 15.2. Its potential for the characterisation of molecular motions, are reviewed simply. 

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