All polymer composites containing silica particles had body-temperature mediated thermal transitions, but mechanical properties varied depending on particle size. Composite sealants containing the largest particles tested (P-620) had reduced Young’s modulus and increased failure strain, indicating improved flexibility and crack suppression. Asterisks indicate statistically significant differences (p < 0.01) between the indicated group and all other groups. (A) Modulated differential scanning calorimetry (MDSC) of sealants. Curves have been shifted vertically for clarity. (B) Young’s modulus, (C) failure strain in tensile testing, (D) toughness, and (E) ultimate tensile strength in tensile testing at room temperature and body temperature (37 °C). Composite surgical sealants are denoted “P-X”, where “X” is the diameter of the silica particles incorporated into PLGA/PEG.