19095-24-0Relevant articles and documents
Synthesis and Self-Assembly of Discrete Dimethylsiloxane-Lactic Acid Diblock Co-oligomers: The Dononacontamer and Its Shorter Homologues
Van Genabeek, Bas,De Waal, Bas F. M.,Gosens, Mark M. J.,Pitet, Louis M.,Palmans, Anja R. A.,Meijer
, p. 4210 - 4218 (2016)
Most of the theoretical and computational descriptions of the phase behavior of block copolymers describe the chain ensembles of perfect and uniform polymers. In contrast, experimental studies on block copolymers always employ materials with disperse molecular makeup. Although most polymers are so-called monodisperse, they still have a molecular weight dispersity. Here, we describe the synthesis and properties of a series of discrete length diblock co-oligomers, based on oligo-dimethylsiloxane (oDMS) and oligo-lactic acid (oLA), diblock co-oligomers with highly noncompatible blocks. By utilizing an iterative synthetic protocol, co-oligomers with molar masses up to 6901 Da, ultralow molar mass dispersities (D ≤ 1.00002), and unique control over the co-oligomer composition are synthesized and characterized. This specific block co-oligomer required the development of a new divergent strategy for the oDMS structures by which both bis- and monosubstituted oDMS derivatives up to 59 Si-atoms became available. The incompatibility of the two blocks makes the final coupling more demanding the longer the blocks become. These optimized synthetic procedures granted access to multigram quantities of most of the block co-oligomers, useful to study the lower limits of block copolymer phase segregation in detail. Cylindrical, gyroid, and lamellar nanostructures, as revealed by DSC, SAXS, and AFM, were generated. The small oligomeric size of the block co-oligomers resulted in exceptionally small feature sizes (down to 3.4 nm) and long-range organization.
End groups of functionalized siloxane oligomers direct block-copolymeric or liquid-crystalline self-assembly behavior
Zha, R. Helen,De Waal, Bas F.M.,Lutz, Martin,Teunissen, Abraham J.P.,Meijer
, p. 5693 - 5698 (2016)
Monodisperse oligodimethylsiloxanes end-functionalized with the hydrogen-bonding ureidopyrimidinone (UPy) motif undergo phase separation between their aromatic end groups and dimethylsiloxane midblocks to form ordered nanostructures with domain spacings of 1.13 results in disorder, showing importance of molecular monodispersity for ultrasmall ordered phase separation. In contrast, oligodimethylsiloxanes end-functionalized with an O-benzylated UPy derivative self-assemble into lamellar nanostructures regardless of volume fraction because of the strong preference of the end groups to aggregate in a planar geometry. Thus, these molecules display more classically liquid-crystalline self-assembly behavior where the lamellar bilayer thickness is determined by the siloxane midblock. Here the lamellar nanostructure is tolerant to molecular polydispersity. We show the importance of end groups in high χ-low N block molecules, where block-copolymer-like self-assembly in our UPy-functionalized oligodimethylsiloxanes relies upon the dominance of phase separation effects over directional end group aggregation.
Effect of catalyst structure on the reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane
De Vekki,Skvortsov
body text, p. 762 - 777 (2009/09/26)
Reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane in the presence of the complexes of platinum(II), palladium(II) and rhodium(I) is explored. It is established that in the presence of platinum catalyst predominantly occurs hydrosilylation of α-methylstyrene leading to formation of β-adduct, on palladium catalysts proceeds reduction of α-methylstyrene, on rhodium catalysts both the processes take place. In the reaction mixture proceeds disproportion and dehydrocondensation of 1,1,3,3-tetramethyldisiloxane that leads to formation of long chain linear and cyclic siloxanes of general formula HMe2Si(OSiMe2) n H and (-OSiMe2-)m (n = 2-6, m = 3-7), respectively. Platinum catalysts promotes formation of linear siloxanes, while both rhodium and palladium catalysts afford linear and cyclic siloxanes as well. Structure of intermediate metallocomplexes is studied.
Composition for separating mixtures
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Page/Page column 16, (2008/06/13)
Therefore, there is provided herein in one specific embodiment a composition comprising: a) at least one silicone surfactant, and where silicone of silicone surfactant (a) has the general structure of: [in-line-formulae]Ma1Mb2Dc1Dd2Te1Tf2Qg; [/in-line-formulae][in-line-formulae]and, [/in-line-formulae][in-line-formulae]2≦(a+b+c+d+e+f+g)≦100; and, [/in-line-formulae] b) a mixture comprising an aqueous phase, a solid filler phase and optionally an oil phase that is substantially insoluble in said aqueous phase.
PROCESS FOR MAKING SI-H FUNCTIONAL SILOXANE OLIGOMER
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Page/Page column 8-10, (2008/06/13)
The present invention relates to a method of making a Si-H functional siloxane oligomer from the reaction between silicon hydride compounds and cyclic siloxane oligomer in the presence of a Lewis acid that is capable of interacting with the hydrogen of th
A Convenient Synthesis of α,ω-Difunctionalized Linear Dimethylsiloxanes with Definite Chain Lengths
Yoshino, Koji,Kawamata, Akira,Uchida, Hiroaki,Kabe, Yoshio
, p. 2133 - 2136 (2007/10/02)
α,ω-Difunctionalized linear dimethylsiloxanes with definite chain lengths are conveniently prepared by the inorganic-solid-catalyzed ring cleavage of cyclodimethylsiloxanes with dimethylchlorosilane and water under very mild conditions.
