We performed an in-depth study of the effect of different reaction parameters on the micromorphology of a polyimide synthesized by hydrothermal polymerization. This dataset contains all scanning electron microscopy (SEM) images taken of the polyimide samples. SEM was carried out with a Quanta 200F FEI microscope. Prior to imaging, samples were loaded onto carbon-tape on steel sample holders and coated by sputtering with a 17 nm thick layer of Au/Pd 60/40 alloy with a Quarum Q105T S sample preparation system. This dataset comprises 437 SEM images. The used file names are organized in the following way: T[°C]_HOAc[0/1]_t[h]_magnification_batch#_area_sequence#. T and t are the reaction conditions temperature (T) and time (t); 0 stands for absence and 1 for presence of acetic acid (HOAc) as promotor; magnification employed when imaging the sample; batch number if more than one sample for the same conditions was analyzed; area on the same sample (a, b, c,...); and sequence number of all images taken from the same sample.