A typical hBN composite was prepared using the following procedure. First, 1.9 g of pristine hBN (UK10 or UK5) was loaded into a 300 mL beaker, followed by the addition of 100 mL of styrene, 10 mL of divinyl benzene (not added for samples for phase diagrams or acoustic spectroscopy), and 100 mL of DI water. The sample was then homogenized with a Silverson LSM-A homogenizer for 5 min, with either 210 mg of BPO, 140 mg of AIBN, or 235 mg of KPS added after four minutes of sonication, for a 1:500 molar ratio of radical to monomer. The mixture was then transferred into a 200 mL jar and placed in a convection oven (BlueM Oven) at 70 °C, typically for 48 h. Finally, to dry the outer portion of the sample, they were placed in the Petri dishes inside the convection oven at 70 °C.