Schematic diagram of the Brillouin microscope. A custom heating cell holds the submerged polymer sample, pressed against the glass bottom to eliminate signal due to water only. Backscattered light is split into distinct Raman and Brillouin spectrometer arms using a long pass filter, LPF. A quartz cell filled with Rubidium vapor (“Rb Cell”) is used to filter elastically scattered light to improve the SNR of the Brillouin signal. A VIPA etalon disperses the Brillouin component spectrally across an sCMOS detector array. PBS is a polarizing beam splitter, and $λ4$ is a quarter-wave plate.