Quantification of evaporatively purified polystyrene oligomers

We present a detailed study of the dependence of glass transition temperature on actual molecular weight for extremely monodisperse polymeric/oligomeric samples. Any synthetic polymerisation process leads to a final sample with an unavoidable degree of polydispersity. For example even with living polymerisation, this intrinsic polydispersity gives rise to a polymer/oligomer with nominally 8 repeat units (N = 8) that contains a non negligible fraction of chains with lengths N = 3 to 13. By employing vacuum distillation on commercially available “standard” polymer, we are able to obtain samples with a much sharper molecular weight profile. These samples (before and after distillation) are compared with MALDI-TOF spectroscopy as well as differential scanning calorimetry. Purified polymers are shown to have a polydispersity index lower than 1.005. We compare calorimetric glass transitions of the polymer standards with the behavior of purified samples.