Morphology orientation of comb-like polymers with rigid backbones under the influence of shear fields

The influence of shear fields on the packing behavior and morphology orientation arestudied for two comb-like polymers viz. poly(1,4-phenylene-2,5-didecyloxy terephthalate) (PPDOT)and poly(2,5-didecyloxy-1,4-phenylenevinylene) (DOPPV) with different rigid backbones having C =10 alkyl carbons per side chain. Crystallographic analysis based on X-ray diffractometry measurementsshows that both PPDOT and DOPPV exhibit a long-range ordered layered structure with alternatingmain chains and alkyl nanodomains and can be characterized by an orthorhombic and monoclinic unitcell respectively. No measurable influence of processing on the unit cell of the individual polymersis observed comparing diffraction data on isotropic (powder) samples and extruded fibers. The maindifference between the PPDOT and DOPPV is in the molecular orientation of the backbones in shearaligned fibers as observed from the 2D diffraction patterns. While, for PPDOT the polymer backbonesalign along the direction of extrusion (fiber axis), for DOPPV the backbones align perpendicular to theextrusion direction. A possible relation between differences in backbone orientation under influence ofshear fields for DOPPV and PPDOT and differences in the packing state of the side chains, which arein a crystalline state for DOPPV but in a disordered state for PPDOT, is considered.