Matrix-assisted laser desorption 726 INDEX

The development of mass spectroscopic techniques such as matrix assisted laser desorption (MALDI) and electrospray mass spectrometry has allowed the absolute determination of dendrimer perfection [7,8], For divergent dendrimers such as PAMAM and PPI, single flaws in the chemical structure can be measured as a function of generation to genealogically define an unreacted site of or a side reaction producing a loop at a particular generation level. Mass spectromet-ric results on dendrimers, not only demonstrate the extreme sensitivity of the technique, but also demonstrate the uniformity of the molecular mass. The polydispersity index of Mw/Mn for a G6 PAMAM dendrimer can be 1.0006 which is substantially narrower than that of living polymers of the same molecular mass [7],... 

The polymers were characterised by NMR and matrix assisted laser desorption/ ionisation-time of flight MS (MALDI-TOF MS) [92]. They have variable indices of refraction (from 1.45-1.52), Tg from 265-350 °C, and long-term thermal stability at 623 K. The dependence of refractive index on wavelength were also measured and the constants of copolymerisation reaction were determined [92]. End-group analysis has been a reliable asset in PFCB chemistry and in particular for copolymerisation studies [92]. 

A recently reported off-line procedure to estimate molecular weight averages and MWD index, also for polydisperse polymers, directly from their matrix-assisted laser desorption/ionisation time-of-flight mass spectra (MALDI-TOF) was applied to poly(bisphenol A-carbonate), a poly(ether-sulphone resin) and poly(dimethylphenylene oxide), all having a wide polydispersity index. The molecular weight and MWD obtained values were compared with those determined by GPC or supplied by makers. A structural characterisation of these polymers was also performed by examining their MALDI-TOF mass spectra. 29 refs. 

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