Microdomain scale organization and scattering patterns of associating polymer melts

A microscopic theory of the structure of compressible associating AB regula r heteropolymer fluids is proposed based on polymer integral equation metho ds. The theory is employed to systematically explore, as a function of temp erature, the influence of sticky group attractive energy, concentration, de gree of blockiness, and global architecture (telechelic, surfactant, multib lock) on self-assembly and microdomain formation as encoded in small-angle partial scattering structure factors. Characteristic apparent spinodal and order-disorder temperatures are estimated, and strong composition fluctuati on effects are always present. The evolution of collective properties deriv ed from scattering profiles such as microdomain period, intermultiplet cohe rence length, degree of Porodlike scattering, and modification of wide-angl e intensity, with polymer structure and thermodynamic state are established . At fixed bare (chemical) driving force, end-functionalized architectures are found to form more ordered microphase-separated fluids than the multibl ock analogues. Increasing sequence length also enhances self-assembly even at fixed global sticky group composition. Significant differences between t elechelics composed of unimer sticky groups vs mini-triblocks are found, wi th the former displaying many self-assembly features not in accord with cla ssic block copolymer behavior. Semiquantitative comparisons with small-angl e X-ray scattering experiments suggest the theory provides a realistic desc ription of self-assembly in ionomer melts, and failure of incompressible ra ndom phase approximation approaches for many properties is documented. Pred ictions for the majority (nonpolar) monomer density fluctuations, and cross -correlations, are obtained. Subtle, but systematic structural changes are induced by the minority group self-assembly process which may be amenable t o direct measurement using small-angle neutron scattering and are possibly of mechanical property relevance.