This paper addresses concentration fluctuations in comblike copolymer systems obtained by hydrogen bonding between polymers and end-functionalized oligomers. Monodisperse block copolymer systems in the homogeneous melt exhibit small-angle X-ray scattering peaks at finite nonzero angle due to characteristic correlation hole concentration fluctuations. In comblike copolymer systems obtained by hydrogen bonding, the dominant fluctuations have been found by us to vary experimentally between conventional long wavelength fluctuations (for weak hydrogen bonding) and finite wavelength fluctuations (strong hydrogen bonding). Monte Carlo computer simulations show that both regimes occur in one and the same system depending on the temperature. The transition between both regimes is directly related to the fraction of free oligomers, which depends on the temperature and the interactions. The structure factors are analyzed in terms of the random phase approximation applied to a mixture of free oligomers and comb copolymers, using a uniform distribution of teeth along the polymer chains and a binomial distribution in the number of polymers with a given number of teeth, confirmed numerically, as input. The agreement is excellent at both high and low temperatures.
- MICROPHASE SEPARATION
- MESOMORPHIC STATE