Damping modulus studies of poly(dimethylsiloxane)-bisphenol-a-polycarbonate block copolymers

Random multiblock copolymers of bisphenol‐A‐polycarbonate and poly(dimethylsiloxane) were hot‐pressed or solvent cast into films which were studied by dynamic mechanical methods over the range 11 to 110 hertz (Hz) and 100 to more than 2200 Hz, respectively. The samples were studied also by differential‐scanning calorimetry. The two phases are separated well in spite of the low‐molecular weights of the blocks. This separation is altered by thermal history and by the solvent medium when solvent casting is used to prepare the films. The damping properties do not vary greatly with frequency. Damping is greatest near the glass‐transition temperatures of the two components. The expansion of the block copolymer with heat appears to be retarded by the polycarbonate phase until the glass transition of that phase is approached.