Matrix-assisted laser desorption/ionization mass spectrometry of covalently cationized polyethylene as a function of sample temperature

A pre-charged, low molecular mass, low polydispersity linear polyethylene was analyzed with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry as a function of sample temperature between 25 °C and 150 °C. This temperature range crosses the polyethylene melting temperature. Buckminsterfullerene (C60) was used as MALDI matrix due to the high volatility of typical MALDI matrices making them unsuitable for heating in vacuum. Starting at 90 °C there is an increase in polyethylene ion intensity at fixed laser energy. By 150 °C the integrated total ion intensity had grown by six-fold indicating that melting did indeed increase ion yield. At 150 °C the threshold laser intensity to produce intact polyethylene ions decreased by about 25%. Nevertheless, significant fragmentation accompanied the intact polyethylene ions even at the highest temperatures and the lowest laser energies.