Morphology Modulation Of Polymer Multilayer Films

The Layer-by-Layer (LbL) self-assembly technique has attracted wideattention because of its simplicity, versatility, and great potential application infabricating thin film materials and devices. Besides the direct application of theLbL films, the post-treatment of LbL films has become an important method forfabricating functional thin film materials. Many post-treatment methods areavailable, including annealing, cross-linking, surface patterning, electrochemicaldeposition and acid/basic solution immersion, etc., which attributes to providingdiverse and feasible methods for fabricating thin films that have differentproperties and functions. Among these methods, solution post-treatment ishighlighted because of its simplicity, noticeable effects and reliability. A typicalapplication example of solution post-treatment is the fabrication of microporousfilms. Microporous films have great application values in many fields, such as thecontrol of some surface properties, optical devices, separation membranes, drugdelivery and sensors. Because hydrogen bonding as a kind of weak interaction isnot very stable, some hydrogen-bonding-directed LbL films, such aspoly(4-vinylpyridine)(PVP)/poly(acrylic acid)(PAA) LbL films, can yieldmicroporous morphology after immersion in basic solution, which has provided agood example for fabricating microporous films. Surrounding the basic solutionpost-treatment of PVP/PAA LbL films, our investigations in this thesis focus onthe effects of electrostatic interaction and substrates on microporous morphologyvariation. In Chapter 2, two kinds of partially quaternized poly(4-vinylpyridine)(PVPQn) with different charge ratios were synthesized and assembled with PAAinto LbL films, and then the morphology variation of these films and PVP/PAALbL films in basic solution was comparatively investigated. We discovered thatvery low charge ratio led to slower microporous morphology variation and highercharge ratio even totally inhibited the formation of microporous morphology.These results showed that electrostatic interaction had a great effect onmicroporous morphology variation. Electrostatic repulsion obstructs or inhibitsthe reconformation/aggregation of PVP chains, leading to the difference ofmicroporous morphology variation. In Chapter 3, PVP/PAA films were prepared on four kinds of differentsubstrates and their morphology variation in basic solution was comparativelystudied. It is discovered that the microporous morphology variation of the filmson hydroxyl-tailored substrates was much faster than on amino-tailored substrates.Similarly, the films on carboxyl-tailored substrates could more easily yieldmicroporous morphology than those on amino-tailored substrates. All indicatedthat substrates played a critical role in the formation and variation process ofmicroporous morphology. The investigation results in this thesis not only have provided a feasible...