Study on Ordered Polymer-based Composite Films

Author:Li Shuang Zuo

Supervisor:feng wei


Degree Year:2017





Lightweight,flexible,and robust anisotropic materials show a great potential for electrodes of field-emission devices,components of electronic skin applications,and thermal interface materials.Such notable in-plane anisotropy in absorbance,refractive index,conductivity,electrical resistivity or tensile strength depends on highly horizontally aligned or ordered structures.High in-plane alignment not only improves the conductance along the preferential uniaxial direction but also provides an opportunity to improve the strength,modulus,wear resistance,tensile properties and quasi-one-dimensional(Q1D)superconductors.In this thesis,a variety of in-plane anisotropic flexible composites have been fabricated by molecular design and microstructure modulation.The flexible and transparent composite films with highly anisotropic structures and related mechanical,thermal,electrical or optical properties were fabricated.A number of alignment techniques have been developed to mediate en masse parallel bulk alignment.The highly aligned templates and linearly polarized light often used to fabricate extremely highly parallelized materials,which resulting in the demonstration of a variety of unique properties.In this paper,the effects of polymer properties(microstructure,thermal conductivity,mechanical properties,photosensitivity)and orientation methods on the anisotropic properties of materials are studied,providing a theoretical basis for subsequent researches.The surface modification of the horizontally aligned carbon nanotubes(HACNTs)improves their interfacial compatibility with the molecular chains of the polymer matrix,which are preferentially oriented along the longitudinal direction of the highly aligned G-HACNTs due to strong interfacial interactions.Transparent,flexible,and robust anisotropic films containing aniline-grafted horizontally aligned carbon nanotube(G-HACNT)based composites have been synthesized.In spite of the extremely small amounts of the G-HACNTs in a polymer matrix,the obtained uniform G-HACNT based composite films are characterized by a variety of excellent anisotropic properties.Additionally,evolution of chirality and orientation from supramolecular self-assembly polymer are materials of emerging interest and challenging.Aim at the difficulty in controlling the stability of molecular orientation,we presented an azobenzene-grafted fluorinated PI assembly via intermolecular H-bonding for 3D helix.The supramolecular assembled Azo/PI shows a long-term polarized light(PL)-induced high molecular alignment due to the limited cis-to-trans reversion in the rigid chains even at high temperature.A 3D macroscopic helical ribbons using highly oriented Azo/PI combines excellent thermal and environmental stability.It has been found that the anisotropic properties of the composites mainly originate from their highly oriented structure and uniform orientation.The ordered structure and highly in-plane anisotropy are controlled by the interaction between the polymer and G-HACNTs or linearly polarized ultraviolet light.Therefore,the electrically conductive,thermally conductive,flexible or chiral composite films with desirable anisotropic properties can be promising candidates for advanced electrochemical devices and aerospace materials.