  Gamma-Ray Bursts are among the most powerful events in the Universe. Despite
half a century of observations of these transient sources, many open questions
remain about their nature. Polarization measurements of the GRB prompt emission
have long been theorized to be able to answer most of these questions. With the
aim of characterizing the polarization of these prompt emissions, a compact
Compton polarimeter, called POLAR, has been launched to space in September
2016. Time integrated polarization analysis of the POLAR GRB catalog have shown
that the prompt emission is lowly polarized or fully unpolarized. However, time
resolved analysis depicted strong hints of an evolving polarization angle
within single pulses, washing out the polarization degree in time integrated
analyses. Here we will for the first time present energy resolved polarization
measurements with the POLAR data. The novel analysis, performed on several
GRBs, will provide new insights and alter our understanding of GRB
polarization. The analysis was performed using the 3ML framework to fit
polarization parameters versus energy in parallel to the spectral parameters.
Although limited by statistics, the results could provide a very relevant input
to disentangle between existing theoretical models. In order to gather more
statistics per GRB and perform joint time and energy resolved analysis, a
successor instrument, called POLAR-2, is under development with a launch window
early 2025 to the CSS. After presenting the first energy resolved polarization
results of the POLAR mission, we will present the prospects for such
measurements with the upcoming POLAR-2 mission.
