Correlation hole effect in comblike copolymer systems obtained by hydrogen bonding between homopolymers 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. Here we will address these fluctuations for comblike copolymer systems obtained by strong association between polymers and end-functionalized oligomers. Experimentally, the dominant fluctuations have been found by us to vary between conventional long wave length fluctuations (for weak hydrogen bonding) as for simple mixtures, and finite wave length fluctuations (strong hydrogen bonding), characteristic for block copolymer systems. Monte Carlo computer simulations show that both regimes will 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 analysed 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 both at high and low temperatures.