AMM Project "Organic Materials": a "Hands-on" Laboratory Course
This Lab course aims to broaden the knowledge of students in the areas of polymer synthesis, polymer characterization, and processing. The course illustrates structure-property relations in polymeric materials, i.e. how polymer chain characteristics and composition influence macroscopic properties.
The following topics are included:
1. Thin polymer films as separation media.
Polyimides, especially aromatic polyimides, are gaining importance in membrane-based gas separation due to their outstanding thermal and chemical stability and good mechanical properties. Tailored polyimide membranes can separate commercially important gas pairs such as O2/N2, CO2/N2, and CO2/CH4. In this experiment, an alcohol-soluble polyimide will be synthesized by condensation polymerization. Molecular characterization will be performed using Gel Permeation Chromatography (GPC),
1H NMR spectrometry and FTIR. Subsequently, the polyimide will be employed to fabricate a membrane for gas separation.
Fabrication and performance of a polyimide gas separation membrane. At the MTG group, a gas separation membrane will be fabricated from the synthesized condensation polymer and its gas separation characteristics will be studied.
2. Polymer characterization in solution.
Polymer properties depend strongly on characteristics such as molar mass, polydispersity, and chain composition. In this experiment, a Gel Permeation Chromatography measurement will be performed on polymer samples to study their molar mass characteristics and to familiarize the students with relative and universal calibration methods. In addition, the molar mass of polystyrene standards with narrow molar mass distribution will be determined by solution viscometry, using an Ubbelohde viscometer (Images from Schott-Geräte and from Viscotek).
3. Designer surfaces by polymer grafting.
The decoration of substrates with surface-initiated polymer brushes has become an important way of modifying surfaces with chemically and mechanically robust thin polymer films. When stimulus-responsive polymers are used, brushes with switchable properties result, with tremendous application potential in the biomedical field, for creating sensors, supporting catalysts, etc. In this experiment, pH-responsive poly(methacrylic acid) brushes will be grown from initiator molecules, anchored to a silicon substrate, by controlled radical polymerization (ATRP). The brushes will be characterized by FTIR measurements as a function of pH, and by contact angle measurements.
4. Smart materials
Polymer-based smart hydrogels, which can change their volume and porous structure under an external stimulus such as temperature, pH value, light, electric field, and chemical environment, have attracted great interest in materials science, polymer science, and biomedicine. Responsive hydrogels have potential applications in the fields of biology and medicine for gene and drug delivery, as biochemical sensor, biocatalysts and in size-dependent separation processes. Poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) based hydrogels have been studied the most. Stimulus-responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogels will be formed by photopolymerization. In water, PNIPAM networks show an interesting temperature-responsive behavior which will be studied in this course by means of turbidity measurements, dynamic mechanical measurements and differential scanning calorimetry.
5. Micro / nanofabrication with polymers.
Elastomeric stamps based on crosslinked poly(dimethylsiloxane) (PDMS) have found widespread use in the fabrication of functional, micrometer-sized (down to sub-micrometer) patterns on solid substrates. The stamps allow the transfer of surface-reactive molecules of choice, such as alkanethiols or chlorosilanes, to e.g. gold substrates or silicon surfaces, respectively, in a process known as microcontact printing. Surfaces decorated with functional patterns are of interest for instance in sensor applications. In this experiment, a hydrophilicized PDMS stamp will be used to locally transfer polar molecules, in this case acids such as methanesulphonic acid, to spin-coated films of poly(tert-butyl methacrylate) on silicon wafers. The locally introduced acid converts, upon heating, the tert-butyl ester groups into carboxylic acid groups, thus creating a poly(methacrylic acid) pattern that corresponds to the stamp pattern. The quality of the obtained patterns will be analyzed by Optical Microscopy and Atomic Force Microscopy (AFM) measurements, and related to the hydrophilicity of the stamps.
