Real space structure of associating polymer melts

Microscopic polymer integral equation theory is employed to investigate the real space collective density fluctuations and interchain radial distribution function of melts of associating AB heteropolymers of various global architectures (telechelic, multiblock). The correlation functions are analyzed in detail to extract four characteristic collective structural length scales (local, intermediate, and global) which emerge due to aggregation of the minority sticky groups: multiplet size, diffuse cluster radius, microdomain period, and intermultiplet coherence length. The dependence of such quantities on temperature, chain architectures, sticky group concentration (f) and blockiness, chain stiffness, and monomer volume mismatch are systematically studied, and various apparent power law dependencies on temperature and f are deduced. A global real space scenario for self-assembly is constructed describing the emergence and thermal evolution of each structural feature in a cooling experiment. Length scale dependent effective compositions and densities surrounding a tagged minority or majority monomer are computed, and their possible relevance to multiple glass transition phenomenon in ionomer melts is discussed. Monomer volume mismatch is always found to inhibit the microphase separation process due to steric constraints which frustrate tight sticky group packing. Comparisons with scattering experiments suggest the theory provides a reliable qualitative and, sometimes, quantitative description of real space correlations in ionomer melts. Connections between the detailed predictions and qualitative physical picture provided by the microscopic theory with the phenomenological 'modified hard sphere model' of ionomer melts are established.