Effects of the degree of polymerization on the free volume structure of linear amphiphilic poly(isobutylene)-poly(methyl vinyl ether) diblock copolymers

The free volume was studied in different poly(isobutylene)/poly(methyl vinyl ether) diblock copolymers by positron annihilation spectroscopy. The degree of polymerization of both constituents was varied in the work. The addition of further monomer units was found to increase the size of free volume holes continuously. However, the observed effect was much smaller than the size of monomer units. According to Doppler-broadening measurements, the structure of blocks changes with their size.