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The phase behavior of ion-containing block copolymer membranes in equilibrium with humidified air is studied as a function of the relative humidity (RH) of the surrounding air, ion content of the copolymer, and temperature. Increasing RH at constant temperature results in both disorder-to-order and order-to-order transitions. In-situ small-angle neutron scattering experiments on the open block copolymer system, when combined with water uptake measurement, indicate that the disorder-to-order transition is driven by an increase in the partial molar entropy of the water molecules in the ordered phase relative to that in the disordered phase. This is in contrast to most systems wherein increasing entropy results in stabilization of the disordered phase.

The distribution of an ionic liquid within microphase-separated domains of a block copolymer in mixtures of the two components is studied using contrast-matched small-angle neutron scattering (SANS) and differential scanning calorimetry (DSC). In concentrated mixtures of a poly(styrene-block-2-vinyl pyridine) (S2VP) copolymer in an imidazolium bis(trifluoromethane)sulfonimide ([Im][TFSI]) ionic liquid (block copolymer volume fraction ranging from 0.51 to 0.86), the ionic liquid preferentially pervades the poly(2-vinyl pyridine) (P2VP) blocks. Unexpected differences in the degree of partitioning into P2VP-rich and polystyrene-rich (PS) microphases are observed in mixtures with hydrogenated versus deuterated [Im][TFSI]. In the case of mixtures with hydrogenated [Im][TFSI], the microphase partition coefficient, defined as the ratio of the ionic liquid volume fraction in the PS-rich microphase relative to that in the P2VP-rich microphase, ranges from 0.0 to 0.1. In contrast, the microphase partition coefficient in mixtures with deuterated [Im][TFSI] range from 0.0 to 0.7.

The phase behavior of binary blends of polyolefins is studied using small-angle neutron scattering. Component 1 is polyisobutylene (PIB), and component 2 is deuterated polybutadiene (dPB). Blends of these polymers are known to exhibit lower critical solution temperatures. The scattering intensity profiles from homogeneous PIB/dPB blends are fit to the random phase approximation to determine χ, the Flory−Huggins interaction parameter. We demonstrate that χ depends on temperature, blend composition, and component molecular weights.