SOME EMERGING TECHNIQUES IN POLYMER MWD CHARACTERIZATION

Routine MW analysis of polymers is generally performed in solution by Gel Permeation Chromatography. The technique, however, presents increa sing difficulties in the ultra-high and ultra-low MW range. Moreover, GPC is not applicable to most fluorinated and ''high performance'' the rmoplastics which require dissolution temperatures close to the polyme r melting point. In response to these challenges, polymer scientists h ave developed new methods of MWD determination. Although these methods have not yet reached the versatility of GPC, they present potential f or further development and are interesting as complementary techniques to GPC. For sparingly soluble polymers, melt viscoelastic properties have been used to obtain information on polymer MWD. Flow birefringenc e, based on the orientation and extension of long flexible molecular c hains in a shear field, has been applied to the characterization of ul tra-high MW polymers. For low MW polymers and oligomers, the MALDI mas s spectrometry technique, with its unique capabilities to resolve indi vidual oligomers within a MWD, proves to be an interesting alternative to conventional GPC characterization.