SEGMENTED POLY(TETRAMETHYLENE OXIDE) ZWITTERIONOMERS AND THEIR HOMOLOGOUS IONENES .3. STRUCTURAL STUDY THROUGH SAXS AND SANS MEASUREMENTS

The structure in bulk of a series of segmented poly(tetramethylene oxi de) (PTMO) zwitterionomers of the ammonioalkanesulfonate (N+(CH2)(p)SO 3-, p = 3, 4) or alkoxydicyanoethenolate (N+(CH2)pOCOC(-)(CN)(2), p = 2, 3) type and of their homologous ionenes was analyzed through small angle X-ray and neutron scattering measurements in their amorphous sta te. Segregation of the polar units from the PTMO matrix resulting in s harp interfaces systematically occurs in all the systems. These two-ph ase structures are thermally stable and still persist in the liquid st ate up to at least 140 and 100 degrees C for sulfonates and dicyanoeth enolates, respectively. However, long range order is observed only in the case of zwitterionomers bearing a bifunctional junction, with a ty pical transition from a lamellar structure for the shorter PTMO segmen ts (M(n)(0) similar to (1.8-2.2) x 10(3), high zwitterion density, lam ellar spacings between 7 and 8 nm with a thickness of the zwitterionic layer of about 1 nn) to a hexagonal structure for the longer ones (M( n)(0) > 3.6 x 10(3), low zwitterion density, radius of the zwitterioni c cylinder of about 1.2 nm). In the lamellar structure, supported by t ransmission electron microscopy which shows coherence domains spreadin g over more than 100 nn, the PTMO subchain is extended by about 50% wi th respect to its unperturbed dimensions. Such an extension does not o ccur in the less sterically constraining hexagonal structure. The swel ling of the ammonioethoxydicyanoethenolate zwitterionomers by tetrahyd rofuran, a selective solvent of the PTMO segments, results in physical gels (swelling ratios Q less than or equal to 5) with a progressive l oss of long range order. It involves either an inhomogeneous swelling process or a gradual fragmentation of the zwitterionic microdomains of constant and strongly anisotropic shape.