1. The molecules of a block copolymer consist of a central block of butadiene
units, with end blocks of polystyrene units. The average degree of
polymerization is 2000for the central block and 150 for each of the end
blocks. In the solid material, the polystyrene chains form a separate phase,
which is seen in the electron microscope as spheres approx 25nm in diameter.
Calculate the wt fraction of styrene in the block copolymer, and estimate the
number of polystyrene chains in each sphere. The density of PS is 1050kgm-3

2. Why it is harder to maker very long polymer chains using the condensation
polymerization method than by using addition?

3. What is crazing?

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