A sterol-polyether conjugate, 5-androstene3j3,17j3-bis[(oxycarbonyl)hexaethylene glycol] (l), has been synthesized via condensation of the bis-chloroformate derivative of 5-androstene-3j3,17j3-diol with hexaethylene glycol mono(triphenylmethy1 ether), followed by deprotection. This conjugate, which is composed of a long and rigid hydrophobic unit, two flexible hydrophilic chains that are linked to the hydrophobic unit, and a pendant polar head group, was designed as a prototype for new classes of compounds that are intended to serve as functional equivalents of the polyene macrolide antibiotic amphotericin B. Analysis of the surface pressurearea isotherm of 1, generated at the air-water interface, indicates a limiting area of ca. 60 A2 per molecule. This value is fully consistent with a model in which the sterol nucleus (ca. 40 A2) and one pendant polyether chain (ca. 20 A2) define the collisional area of the surfactant; that is, it supports the existence of a 'folded" conformation at the air-water interface. Incorporation of 1 into egg PC vesicular membranes leads to ion channel formation, as demonstrated by 23Na NMR spectroscopy. Operationally, 1 has been found to have an ionophoric activity that is very similar to that found for a synthetic "bouquet" molecule, but significantly less than amphotericin B, itself.

The study of a series of molecularly uniform poly(N-alkylurethanes) with a systematically varied and tailored chain architecture has shown that the packing and superstructure can be controlled by the primary structure of the urethane chain and reversibly altered by the sample treatment, respectively. Depending on the conformation or the stereogeometry of the constitutive unit built in the middle of the otherwise symmetrical oligourethane, chain-extended and/or chainfolded crystallization of the urethane chain can occur. The packing order, i. e., adjacent reentry chain-folding or chain-extended crystallization, and the thermal properties of the oligourethanes are related to the chemical structure of the central constitutive unit.

Segmented polyurethanes with a regular chain architecture exhibit very specific self -organizing properties, often leading to multiphase systems with special phase structures. The study of a series of relatively stiff, monodisperse polyurethane model compounds of various molecularly engineered structures and also multiblock copolymers consisting of an alternating sequence of highly flexible polyether and the above polyurethane segment has shown that extended chain crystallization and chain folding of hard segments and thus the size, shape and ordering of the hard domains can be created and rearranged at will. The molecular design, which can also be applied to graft copolymers, predetermines the possibilities of supramolecular organization. These thermoplastic elastomers exhibit very special properties which correlate systematically with the supramolecular structure.Paper presented at the meeting of the GDCh-Fachgruppe "Makromolekulare Chemie" on "Kautschukelastische

Multiphase polymer systems with special phase structures and properties can be achieved by the proper design of the polymer constitution and the appropriate sample treatment. Multiblock copolymers consisting of molecularly uniform polyurethane segments of various molecularly engineered structures and connected by highly flexible polyether segments have been synthesized. The segregation of the hard segments and the size, shape and perfection of the hard domains can be controlled by the hard segment's architecture in that either extended chain crystallization or chain folding occurs. The same superstructure and properties as of the above multiblock copolymers can be mimicked by specially designed graft copolymers with polyether backbone and polyurethane branches, again uniform and molecularly engineered. This study has shown that the morphology and superstructure of macromolecular systems can be precisely controlled by the molecularly designed chain architecture and the sample history, and is correlated with special material properties.

The study of a series of segmented poly(ether-urethanes) with highly flexible poly(oxytetramethylene) soft segments and especially designed, molecularly uniform poly(Na1kylurethane) hard segments based on piperazine and 1,4-butanediol bischloroformate has shown that size, shape and perfection of the hard domains can be varied by both the primary structure of the urethane chain and the sample history. Depending on the conformation or the stereogeometry of the built-in central constitutive hard segment unit, chain-extended or chain-folded hard segment crystallization, i. e., the formation of cylindrical or lamellar shaped hard domains can be achieved. These thermoplastic elastomers exhibit distinctly different properties which correlate systematically with the supermolecular structure and the corresponding hard segment architecture, respectively.