The synthesis of the metal-free and the dihydroxysilicon derivatives of tetrakis[4',5'-bis(decoxy)benzo-18-crown-6]phthalocyanine is described. The metal-free phthalocyanine is liquid crystalline and exhibits a crystalline phase to mesophase transition at 148 °C. The structures of the crystalline phase and the mesophase are determined by X-ray measurements. The metal-free compound strongly aggregates in chloroform solution to form a gel. Electron micrographs show that this gel contains a network of fibers, each of which is built up of parallel strands of supermolecules having the thickness of one molecule and a length of several micrometers. The strands are formed by a process of self-assembly involving up to 104 molecules. They can be considered as being molecular cables, containing a central electron wire, four ion channels, and a surrounding insulating hydrocarbon mantle. The silicon derivative contains two axial hydroxy groups which prevent the molecule from aggregating. This compound is not liquid crystalline. It forms a stable monolayer at the air-water interface. In this layer, the phthalocyanine planes are oriented parallel to the water surface. The monolayers can be transferred onto glass substrates by a Y-type deposition. The resulting Langmuir-Blodgett film is built up of bilayers containing slipped face-to-face phthalocyanine dimers. The monolayer is capable of binding alkali metal ions from the subphase, as is concluded from surface area-surface pressure isotherms. The binding constant for potassium ions has been determined by analyzing the isotherms as a function of the concentration of this metal ion. The dihydroxysilicon phthalocyanine can be polymerized to form a polysiloxane.

Stamm, M. (1997). Grafting of polypeptides on solid substrates by initiation of N-carboxyanhydride polymerization by aminoterminated self-assembled monolayers. Langmuir, 13(4), 723-728. DOI: 10.1021/la960467g Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Volker Erb and Manfred StammMax-Plank-Institut fü r Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany Received May 13, 1996. In Final Form: December 9, 1996 A series of mixed self-assembled monolayers of functionalized (Br(CH2)11SiCl3) and unfunctionalized (CH3(CH2)10SiCl3) alkyltrichlorosilanes of different compositions have been prepared on bulk silicon substrates. By in situ modification of these monolayers the bromo end groups were transformed to amino end groups as shown by X-ray photoelectron spectroscopy measurements. The change of hydrophilicity was monitored by water contact angle measurements, showing the expected decrease of contact angles with increase amino group content on the surface. These substrates were used to initiate Ncarboxyanhydrides in dioxane to yield R-helical polypeptides grafted from the surface. The thicknesses of the obtained polymer layers were measured with ellipsometry and X-ray reflectometry. Fourier transform infrared measurements confirm that the grafted polymers are in the R-helical conformation.

Grafting of poly(methyl methacrylate) (PMMA) on microparticulate silica was achieved by initiating the polymerization of MMA by 4,4'-azobis(4-cyanopentanoic acid) that was covalently bound to the silica surface. The initiator seems to be destabilized upon binding it to the silica surface. The kinetics of the graft polymerization are described and are largely affected by the Trommsdorff effect, which makes it possible to graft a high amount of PMMA on silica.

account for the large magnitude of the acoustic signal seen in the cvlindrical exci-" tation geometry, the audible sound, and the failure of both of these signals to disappear at low temuerature. T h e reaction of carbon with water takes place at temperatures o n the order of hundreds of degrees Celsius;

Polyurethanes based on poly(epsilon-caprolactone) (PCL) (750-2800 g/mol) and 1,4-butane diisocyanate (BDI) with different soft segment lengths and constant uniform hard segment length were synthesized in absence of catalysts for the production of a degradable meniscus scaffold. First the polyesterdiols were endcapped with BDI yielding a macrodiisocyanate with a minimal amount of side reactions and a functionality of 2.0. Subsequently, the macrodiisocyanates were extended with 1,4-butanediol in order to obtain the corresponding polyurethane. The polyurethanes had molecular weights between 78 and 160 kg/mol. Above molar masses of 1900 g/mol of the polyesterdiol crystalline PCL was found while the hard segment showed an increase in melting point from 78 to 122 degrees C with increasing hard segment content. It was estimated that the percentage crystallinity of the hard segment varied between 92 and 26%. The Young's modulus varied between 30 and 264 MPa, the strain at break varied between 870 and 1200% and tear strengths varied between 97 and 237 kJ/m2.

Electromechanical properties of an ultrathin layer of directionally aligned helical polypeptides Jaworek, T.; Neher, D.; Wegner, G.; Wieringa, R.H.; Schouten, A.J.

In an attempt to study which factors determine the transferability of monolayers of preformed polymers from the air-water interface onto substrates we investigated flexible polymers (poly(octadecylmethacrylates) (PODMAs)) and 0t-helical polymers (polyglutamates). Pressure-area isotherms show the formation of a liquid-analogous state which depends on temperature and side chain "impurity". Ymode Langmuir-Blodgett multilayers of these polymers can be formed with a constant transfer ratio under conditions at which a more or less liquid-analogous state exists. Polarized IR spectra suggest that the polyglutamate a helices in the multilayer are oriented with the main axis parallel to the transfer direction and that carbon Side chains are practically randomly oriented around the a-helical cylinder. In PODMA multilayers the side chains are perpendicular to the film. In both cases the sidechains seem to interdigitate.

The monomer conversion dependence of the formation of the various types of defect structures in radical suspension polymerization of vinyl chloride was examined via both 1H and 13C NMR spectrometry. The rate coefficients for model propagation and intra- and intermolecular hydrogen abstraction reactions were obtained via high-level ab initio molecular orbital calculations. An enormous increase in the formation of both branched and internal unsaturated structures was observed at conversions above 85%, and this is mirrored by a sudden decrease in stability of the resulting PVC polymer. Above this threshold-conversion, the monomer is depleted from the polymer-rich phase, and the propagation rate is thus substantially reduced, thereby allowing the chain-transfer processes to compete more effectively. In contrast to the other defects, the chloroallylic end groups were found to decrease at high conversions. On the basis of the theoretical and experimental data obtained in this study, this decrease was attributed to copolymerization and abstraction reactions that are expected to be favored at high monomer conversions. Finally, a surprising increase in the concentration of the methyl branches was reported. Although a definitive explanation for this behavior is yet to be obtained, the involvement of transfer reactions of an intra- or intermolecular nature seems likely, and (in the latter case) these could lead to the presence of tertiary chlorine in these defects.