Search results for "Silo"

Polydimethylsiloxanes with amylose side chains by enzymatic polymerization

1996

Maltoheptaonamide modified polydimethylsiloxane was prepared applying a simplified synthetic pathway in the derivatization sequence of the carbohydrate. The products were characterized by 13C NMR and FT-IR spectroscopy. The glucan side chains of these “sweet siloxanes” were elongated by enzymatic catalysis with potato phosphorylase.

Superhydrophobic TiO2/Fluorinated Polysiloxane Hybrid Coatings with Controlled Morphology for Solar Photocatalysis

2021

Abstract Technological applications of polysiloxane coatings have been influenced by their intrinsic low surface energy, which increases their water repellence. Accurate control of composition and interfacial properties through the introduction of perfluorinated moieties further lowers the polysiloxane surface energy, while mixing with metal oxide nanoparticles enhances roughness, resulting in a great potential in the development of superhydrophobic materials for photocatalysis. Herein, a series of hydrophobic and superhydrophobic hybrid coatings were prepared by dehydrocoupling and hydrosilylation reactions of polymethylhydrosiloxane with 1H,1H,2H,2H‐perfluorooctyltriethoxysilane and 1,3-d…

Dimesogenic liquid crystalline oligosiloxanes

1995

Abstract In this paper, the syntheses, phase properties and ferroelectric properties of new liquid crystalline oligosiloxane dimesogens are described. Smectic phases are dominant in this class of materials. Spontaneous polarizations are in the range of 10 to approximately 100 nCcm−2. The materials show interesting properties for display applications. Although offering higher mechanical stability than low molar mass materials, their switching is significantly faster (switching times in the range of some 10−5s) than is the case for similar side group polymers (typically some 10−3s). Therefore these new oligosiloxane derivatives may be ideal for building flexible displays. In addition, mixture…

Are polymers suitable rock analogs?

2002

To evaluate if a polymer is suitable for analog modeling, it is essential to know the rheological properties of the material. Polymers used in analog modeling exhibit a complex rheological behavior; only part of which has been taken into account in most modeling studies. The mechanical behavior is strongly dependent on strain rate and temperature, and is characterized by specific dependencies of the storage and loss moduli, related to the elasticity and viscosity, on the deformation rate (frequency). We have measured the storage and loss moduli at a broad range of strain rates and strains, using an oscillatory parallel-disk rheometer. Investigated materials are polydimethylsiloxane (PDMS), …

1983

The synthesis and the phase behaviour of liquid crystalline main chain polymers are described. In these poly- and copolyesters the mesogenic units are linked by highly flexible oligodimethylsiloxane spacers. The comparison of their phase behaviour with that of polyesters known from the literature shows that dimethylsiloxane spacers as a replacement for alkyl spacers are leading to a drastic decrease of the transition temperatures. Depending on the length of the spacer glass transitions as low as −111°C can be achieved. The widths of the liquid crystalline phases thereby are retained up to a spacerlength of 13 oxydimethylsilanediyl (dimethylsiloxane) units. The homopolyesters mainly show sme…

Synthesis of aldonamide siloxanes by hydrosilylation

1998

Abstract The synthesis of hydrophobic/hydrophilic hybrid polymers based on polydimethylsiloxanes (PDMS) and carbohydrate derivatives involving a hydrosilylation step is reported. Starting with poly(dimethyl- co -hydromethyl)siloxanes (PDMS- co -HMS), O -acetylated N -allylaldonamides of various sugars can be attached to the siloxane backbone using platinum catalysts. The characteristics of different transition metal complexes in the polymer-analogous formation of SiC bonds are investigated. A generalized reaction pathway applicable to several reducing carbohydrates is established to synthesize aldonamide siloxanes in a broad variety of molecular weight and composition. The products obtaine…

Chemical structure and internal diffusion within polymer chains in the melt

1985

The single chain dynamics of polydimethylsiloxane in the melt is studied by means of quasielastic neutron scattering. For this polymer the wave vector range 0.03 A−1≦q≦0.30 A−1 covers the regime of universal modes as well as local diffusive processes. A model is described which incorporates the specific chemical structure of the macromolecule and allows to interpret our data in the full wave vector regime. The only parameter which enters the model, the monomer diffusion constantDm, is found to be (1.2±0.2)·10−5 cm2s−1.

Interfacial tension of demixed polymer solutions: augmentation by polymer additives

1997

The interfacial tension between phase separated polymer solutions increases pronouncedly upon the addition of asmall amounts of incompatible polymers. This feature is demonstrated by means of measurements with solutions of polystyrene in cyclohexane and the folloowing additives: poly(styrene-block-dimethylsiloxane), polyisobutylene and polydimethylsiloxane. Theoretical considerations based on a correlation between the lenth of the tie lines and the corresponding interfacial tension corroborates this finding

Biological Activities of Natural Sesquiterpene Lactones and the Effect of Synthetic Sesquiterpene Derivatives on Insect Juvenile Hormone Biosynthesis

1998

Three natural sesquiterpene lactones have been assayed for their biological activity on locust (Locusta migratoria) nymphs. Since results obtained in vivo pointed to disruptions on juvenile hormone (JH)-regulated physiology, we tested the sesquiterpene lactones and a family of synthetic sesquiterpene derivatives for their ability to disturb the rate of JH biosynthesis by locust corpora allata (CA) in vitro. All the active compounds in vitro share a basic sesquiterpene double-ring structure as well as substituents with different chemical complexities. Compounds that shared an eudesmane base with different oxidation states on C3 and C12 carbon atoms were tested as JH biosynthesis inhibitors. …

Polyethylene composites filled with n‐alkyl‐functionalized siloxane‐silsesquioxane resins and sol‐gel silicas

2019

High‐density polyethylene (HDPE) composites filled with silicon‐based fillers were prepared by melt blending. The use of non‐functionalized and n‐octyl‐functionalized siloxane‐silsesquioxane resins and the sol‐gel silicas as fillers allowed us to evaluate the influence of functionalization of the fillers on the properties of the composites. The melting and crystallization temperatures of the composites were found to be only slightly affected by the addition of the silicon‐based fillers. In turn, the crystallization degree values were increased, in particular for the materials containing non‐functionalized fillers. The free‐volume properties of the composites did not change significantly in …