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Styrene-4-vinylpyridinium ionomers of different architectures, random and ABA blocks, were synthesized and their thermal and dynamic mechanical properties investigated. / The Tg's of the random ionomers were found to increase regularly with increasing ion content, at a rate of about 3.5(DEGREES)C per mole % of ions. In contrast with other ionomeric systems studied before, however, these materials showed only one peak in their tan delta curves, associated with the Tg of the matrix. The absence of a second, high temperature peak suggests the absence of clusters in these vinylpyridinium ionomers, at least at temperatures above their Tg. The storage modulus curves were in agreement with this conclusion. / An elaborate polymerization line was constructed for the production of the block copolymers by living anionic polymerization; a basic design was modified considerably and two new units were completely designed in this laboratory. Only one Tg, associated with the Tg of the polystyrene phase, was observed in DSC measurements for the resulting ionomers. The glass transition of the ionic domains was detected in dynamic mechanical measurements as a shoulder on the low temperature side of the polystyrene transition. This unexpected low value for the Tg of the ionic domains was attributed to plasticization by water.

The magnetic properties, crystal and magnetic structures of Nd5 SixGe4-x were investigated by ac susceptibility and high resolution neutron powder diffraction. The magnetic and crystalline phase diagrams were derived. Four distinct structures exist in the Nd 5SixGe4-x system: Gd5Ge 4-type [O(II)], Gd5Si2Ge2-type (M), Gd5Si4-type [O(I)], and Zr5Si4-type (T). The refinements of the neutron powder diffraction patterns revealed that the Nd5SixGe4-x compounds exhibit mixed ferro-antiferromagnetic structures. The ac susceptibility measurements showed that the magnetic ordering temperature of Nd5SixGe 4-x increases slightly with increasing silicon content, except that it increases by a factor of 2 in the orthorhombic Gd5Si 4-type [O(I)] phase region. The abrupt change of the magnetic ordering temperature between x = 2.25 and x = 2.5, where the monoclinic Gd5Si 2Ge2-type (M) structure changes to the orthorhombic Gd 5Si4-type [O(I)] structure, suggested that a first order magnetostructural transition likely takes place in this narrow composition range (2.25 < x < 2.5). The investigation of Nd5Si2.335 Ge1.665 revealed that Nd5Si2.335Ge 1.665 adopts the Gd5Si2Ge2-type (M) structure and undergoes a first order magnetostructural transition from the paramagnetic-monoclinic Gd5Si2Ge2-type (M) structure to the orthorhombic Gd5Si4-type [O(I)] structure upon cooling. The T1-T1 bonds increases by ∼1 A when the the Gd 5Si4-type [O(I)] structure (10 K) transforms to the Gd 5Si2Ge2-type (M) structure (140 K). The giant magnetocaloric effect is not observed in Nd5Si2.335Ge 1.665 probably due to the co-existence of the M phase and the O(I) phase. The maximum magnetic entropy change in Nd5Si2.335Ge 1.665 is 7.3 J/kg K for magnetic field change from 0 to 7 Tesla, which is similar to that obtained in Nd5Si1.5Ge2.5, the neighboring phase O(I).

Structural effects in hydrogen and non-hydrogen bonded liquids and their mixtures have been studied using several experimental techniques and theoretical approaches. Apparent heat capacities and volumes of linear alcohols in hydrocarbons were determined at very low alcohol concentrations and their self-association in solution discussed in terms of the Treszczanowicz-Kehiaian theory. An extension of this theory was used to describe cholesterol self-association and its interactions with tripalmitin and lecithin. Heat capacities of water-organic mixtures are reported. It is found that water behaves as a lower alcohol at the organic-rich concentration range. At the water-rich end, Shinoda's views on water structuring around hydrophobes are supported. Thermal pressure coefficients of cyclohexane + normal and branched alkanes are consistent with the presence of orientational order in the long pure n-alkanes. Excess volumes for mixtures of alkanes with liquids of different internal pressures are predicted using Flory theory. The anomalous thermodynamic behaviour of cyclopentane mixed with cyclic and branched alkanes has been studied through the measurement of cyclopentane spin-lattice relaxation times in these mixtures. An extension of Sanchez-Lacombe theory for pure liquids is described and the molecular parameters obtained for sixty common substances. An equation of state for pure n-alkanes with correlations of molecular orientations is presented.

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