Polyion Complex Films with Multi-bilayer Structure and Structure of Ionic Polymers Emplo y ed

Abstract

Polyion-complex-type multi-bilayer films were prepared by solvent cast method from cationic bilayer-forming amphiphiles, [CH₃(CH₂)_n-1]₂N⁺(CH₃)₂Br- (2 C_nN, η=14, 16, 18) and various anionic polymers. To clarify the effects of the polymer chains on the bilayer structure in the film, phase transition temperatures (T _c) from solid to liquid-crystalline state of the bilayers, modulus of elasticity of the films, and ESR spectra of the films labeled with a spin probe on the polymer chain, were measured. Disordering effect of polymer chain was observed in the film of the amphiphile with short alkyl chain (2 C₁₄N), resulted in lowerings of T_c, and enthalpy change (The effect was largest in the film prepared from poly (styrene sulfonate)(PSS)). Elasticity of the film mainly depended on the phase of the bilayer matrix (thermal movement of amphiphile molecules). Modulus of elasticity was large below T_c, regardless of the polymer used (Fig.1, 200∼400 MPa). Above T_e, all the films became extremely soft (fluid) not to be measured, though the film prepared from PSS showed the elasticity around 10 MPa (Fig.1). Below T_c, the extrema separation (W) of the ESR spectra was large (more than 6 mT) because of the low thermal movement of the polymer chain, and did not depend on the structure of polymer. On the contrary, aboveT_c, W value (below 5.5 mT) of the film prepared from PSS was larger than that of acrylic polymer (Fig.3). The large disordering effect of PSS on the bilayer, a lack of fluidity of the film in the liquid-crystalline state, and relative large W value in the liquid-crystalline state, were explained on the basis of rigidity of the polymer chain of PSS.