Enhanced polymer blend compatibility through controlled specific interactions

Most multicomponent polymeric systems are immiscible, exhibiting a phase-separated structure with sharp domain interfaces. These materials typically have poor mechanical properties particularly at large strains, and are termed "incompatible". Moderate and high deformation mechanical response could be improved dramatically if interdomain adhesion were enhanced, allowing effective stress transfer across the domain interface. Mixing of components primarily at domain boundaries should augment the interphase, thus ensuring adhesion.; In this work, I have investigated the feasibility of promoting such mixing effects through specific interactions between unlike functional groups on dissimilar polymer chains. Attention was focussed on a model bicomponent polymer system with the components synthesized to contain complementary interacting functional groups at variable levels, in order to alter compatibility in a controlled fashion. The basis of this system was a blend of a rubbery polymer, poly(ethyl acrylate), with a glassy polymer from one of two series of functionalized polystyrenes. The polystyrene component was functionalized at various levels with either phenolic or sulfonic acid groups, both potential hydrogen bond donors. Component mixing was induced via hydrogen bonding between the acrylate carbonyl and the styrene function.; It was demonstrated through various techniques that the degree of mixing in this two-phase system could be varied continuously via systematic control of the polystyrene functionalization level and type. Much of the research focussed on investigating effects of varying interacting group content within blends of fixed component weight fraction. However, at functionalization levels yielding the greatest levels of mixing at the interface consistent with unmixed domain centers, component weight fractions were varied to track the system behavior at optimum compatibility. Thermal, thermomechanical and uniaxial tensile stress-strain analyses were utilized to probe macroscopic effects of enhanced intercomponent adhesion. Small angle x-ray scattering, electron microscopy and mathematical modelling studies were applied to investigate the impact of hydrogen-bond-induced phase mixing on blend microstructure and morphology. These multiple approaches were combined to relate the extent and effects of phase mixing in the model multicomponent materials.