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The Phase behavior of PS-b-P4VP(PDP)x

Voortman, T.P. (2012) The Phase behavior of PS-b-P4VP(PDP)x. Master's Thesis / Essay, Chemistry.

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The gyroid network morphology has been subject of many studies to implement it in a wide range of nano-scale applications. A comprehensive study of the phase behavior of the supramolecular complex of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) mixed with 3-pentadecylphenol (PDP) was conducted, in order to develop a simple route to its double gyroid network morphology. Films were prepared from a wide range of PS-b-P4VP compositions and PDP concentrations. Our approach does not require time consuming syntheses of block copolymers (BCPs) with several compositions in search for different morphologies; by simply increasing or decreasing the PDP concentration to a specific PS-b-P4VP BCP, the morphology can be altered. PDP can be removed by immersion in ethanol resulting in the collapse of the P4VP chains onto the PS phase to produce nanoporous polymer templates. Analysis of the morphologies by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) revealed that with increasing volume fraction of the comb block, first lamellae, then gyroid, and finally cylinders are found. Furthermore, the gyroid region contracts with increasing degree of polymerization (N) of the starting BCP and above a critical value the gyroid morphology is no longer observed. Biphasic morphologies were also observed where the gyroid morphology was found along with lamellae or cylinders. By selecting BCPs with a different molecular weight the lattice parameter of the gyroid morphology could be ranged from 71 nm to 127 nm. Furthermore, the gyroid morphology was obtained for different concentrations of PDP, thus, a range of porosities can be chosen after dissolution of PDP. Analysis by DSC of mixtures of PS-b-P4VP with PDP and polystyrene mixed with PDP indicated that, although PDP can migrate into the PS phase, its concentration in the PS phase of the BCP probably remains below 1 wt%. The BCP we used are commercially available, however, we ran out of material of a specific sample and could not order it anymore. Therefore, we used the anionic polymerization technique to synthesize this BCP. Unfortunately, we have not been able to synthesize the BCP with the required composition as was determined by proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). Future work could include back-filling of an empty gyroid template with an inorganic material, for instance, metal alloy by electroless plating in order to achieve a hierarchically porous nanofoam, after etching away the polymer and the less noble metal.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Chemistry
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:50
Last Modified: 15 Feb 2018 07:50

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