This is how frogs in shallow pond-bottoms can freeze solid during the winter and then thaw out in spring. The formation of ice crystals is what damages the organ. But glutaraldehyde is highly cytotoxic, and the brain cells are killed, along with anything else, so your brain won't ever be thawed. They will use ion beams to shave off very thin layers of your brain and use a scanning electron microscope to image it, all while still frozen.
This is the same process, in finer detail, that occurs for detail 3-d imagery of plastinated organs and entire organisms. The crosslinking and heat generated during the curing process of most epoxy resins will destroy the finer structures in the brain as it preserves the macro-structure, so no, you couldn't use the same types of plastic typically used to preserve anatomy specimens. Instead of a microtome, the top layer is ablated with ion beams. Instead of an optical microscope, an electron microscope is used.
You can't currently get a more detailed 3-d image than this. The ion beam can strip away one layer of atoms at a time, and the electron microscope can identify the positions of all the atoms in the next layer.
But imagine the size of that data set. Imaging a volume of about 1500 mL, at a detail level of 1 nm, is 1.5e24 voxels. Even at one bit per voxel, for filled/empty, that's in the yottabyte range. A trillion 1 terabyte hard drives. The gap junction of an electrical synapse is about 3.5 nm, and chemical synapses are 20-40 nm apart. so if you image at a resolution of 3.5nm, you're still talking at least a zettabyte, but at least that's just under half the maximum file size of UFS, at around 2^75 bits.
Better hope those cryo-coolers don't fail before we can store that much data and reduce it all to a neuro-map.