Ferdinand Männle

Oxygen Transport in Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes (POSS)

The transport properties of oxygen in three amino-functionalized cubic polyhedral oligomeric silsesquioxanes (POSS) have been studied using classical molecular dynamics (MD) simulations over a timescale long enough to reach the Fickian regime for diffusion. An amount of O2 corresponding to an applied pressure of 3 bars was inserted into molecular models of hybrid organic/inorganic POSS with the chemical composition (RSiO3/2)8, which differed by the end-groups of their organic pendant chains, that is, R = −(CH2)3−NH−CO−X with X = −C6H4OH, −C6H5 or −C6H11. The oxygen … POSS energies were found to be small with respect to the POSS… POSS interactions. The O2 molecules permeate the organic phase and move through combinations of oscillations within available free volumes in the matrices and occasional jumping events. Gas mobility was more restricted in the system with the salicylic end-group and the largest hydrogen-bond network, whereas it was enhanced in the system with the cyclohexyl end-group. The most energetically-favorable sites for O2 insertion were either in the vicinity of the silica cages or close to the rings of the chain end-groups. On the other hand, the amide and hydroxyls groups engaging in H-bonds were less energetically favorable. This confirms that H-bonding networks are a hindrance for O2 transport in such systems.

New Method for Improving Properties of Polymer Composites by Using Organic Inorganic Hybrid Polymers

Polymer materials are utilized in an increasing number of categories of products, such as components for cars, boats, airplanes, within the electronics industry and other advanced industry as well as in paints and other coatings, for special packaging etc. The uses of polymer materials in new categories of products are only limited by the product properties. It is thus a continuous need for developing polymer products with improved properties like increased scratch resistance, improved weather resistance, increased UV resistance, chemical resistance and antioxidation. In addition to pure polymer materials, new products based on hybrid organic inorganic materials involving macromolecules with inorganic core and organic branches have been developed. In this paper, organic inorganic hybrid polymers (HP) are prepared based on a new technology and applied as additives for polymer products like thermoset plastics and in lacquers and other types of coatings for surface protection. Used in appropriate amounts and with suitable particle size, such hybrid polymers contribute to a significant improvement of the properties of the plastic material or the lacquer, hereunder an increased wear resistance/scratch resistance and/or weather resistance. It is shown that HP additives are suitable for a number of applications within organic chemistry and in particular within polymer chemistry and can be used as a stabilizer for thermoplastics with a broader range of utility than known mono-functional stabilizers.

The Stability of Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes in Water

Octa(aminopropylsilsesquioxane) Si8O12[(CH2)3NH2]8 is a very important precursor for many other hybrid organic/inorganic polyhedral oligomeric silsesquioxanes (POSS) because of the reactivity of its primary amine groups. Unfortunately, it is unstable in water, which can lead to the cleavage of its siloxane cage. In the present work, such a degradation was confirmed using solid-state (29)Si NMR spectroscopy, and the molecular features at the basis of this instability were studied using molecular dynamics simulations (MD). It was also investigated whether replacing the primary amine end groups by secondary amines or by amides with long aliphatic chains could lead to an improvement in the water stability of the Si/O framework. In the pure bulk models, all POSS interdigitate with their pendant organic arms intertwined. Upon insertion of isolated molecules into water, the dimensions of the primary amine POSS remain close to those of the bulk, while the secondary amine and the amide POSS favor conformations that optimize the intramolecular chain-chain interactions. When there are several POSS molecules in water, they cluster with each other through both intra- and intermolecular chain-chain interactions. This tendency for the organic chains to intertwine whenever possible provides some protection to the siloxane cages from water, but also leaves some of the siloxane O exposed. As such, the latter are accessible to form transient hydrogen bonds with the water molecules, which could be a precursor step to hydrolysis and thus cage breakage. In the molecular models, a better protection was obtained in the amide POSS for two reasons: its chains tended to wrap efficiently around its cage, and its ketone O kept water from getting close to the siloxanes. The molecular modeling characterizations were found to agree very well with experimental evidence.

Increased Performance of Thermoplastic Packaging Materials by Using a Mild Oxidizing Biobased Additive

Green additives such as prodegradants based on natural fatty acids and iron can improve the environmental profile of thermoplastic packaging materials. We present two studies in which this is demonstrated. In the first study, the addition of a green prodegradant to a 5-layer gas barrier laminate during processing provided a laminate with significantly reduced oxygen transmission due to the resulting oxygen-consuming degradation process. The result shows that material reduction and cost efficiency of packaging laminates can be combined, since 5-layer laminates with reduced oxygen barrier layer thickness and retained gas barrier properties are feasible. The products are interesting from an ecological and economic aspect. In the second study, the addition of a green prodegradant to several qualities of polypropylene that are used in packaging applications leads to materials that are readily degraded in accelerated weathering. The molecular weight of the modified polypropylenes after 830 hours of accelerated weathering is reduced from typically 80.000 g/mole to 1.500–2.500 g/mole. At such molecular weight levels, digestion by microorganisms is feasible. The mild prodegradant used in the study does not lead to degradation during processing. Thermoplastics containing such additives are therefore fully recyclable provided that they have not been exposed to a long period of weathering.