Polymethylene-block-poly(dimethyl siloxane)-block-polymethylene nanoaggregates in toluene at room temperature

Aggregates of a polymethylene-block-poly(dimethyl siloxane)-block-polymethylene (PM-PDMS-PM) sample were prepared in toluene by cooling down a toluene solution of the sample slowly from 105 °C to room temperature. Atomic force microscopic (AFM) and electron microscopic (EM) studies revealed that the aggregates included triblock crystal plates with sizes of upto tens of micrometers and PM-PDMS-PM nanodiscs. Surprisingly and interestingly, we discovered that the topographic images of the nanodiscs obtained by tapping-mode AFM changed from nanodiscs at light tapping to strikingly beautiful nanodonuts at moderate tapping and then filled nanodonuts at heavy tapping. Justification for such observations is provided.