Synthesis of carbohydrate‐segmented polydimethylsiloxanes by hydrosilylation

Carbohydrate‐modified polysiloxanes have been presented several times within the last decade. In this work, a new route to carbohydrate‐segmented polysiloxanes is presented. A series of allyl‐group‐containing bifunctional carbohydrate derivatives was synthesized and reacted with hydrodimethylsilyl‐terminated polysiloxane in hydrosilylation reactions with Speier's catalyst. The carbohydrate monomers and the resulting materials were fully characterized with ¹H and ¹³C NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3814–3822, 2005     

Oligomerization of Electron‐Deficient Vinyl Monomers Through an Ate‐Complex Mechanism: A New Role for B(C6F5)3 Lewis Acid

The Lewis acid B(C₆F₅)₃ in combination with hydrosilanes exhibits remarkable activity in the oligomerization of sulfone‐ and phosphonate‐based monomers. This process opens new routes to high‐tech silicone‐based materials, i.e., thermoplastic elastomers and heat‐resistant polysiloxanes.

     

Polysiloxane‐Backbone Block Copolymers in a One‐Pot Synthesis: A Silicone Platform for Facile Functionalization

Block copolymers consisting exclusively of a silicon–oxygen backbone are synthesized by sequential anionic ring‐opening polymerization of different cyclic siloxane monomers. After formation of a poly(dimethylsiloxane) (PDMS) block by butyllithium‐initiated polymerization of D3, a functional second block is generated by subsequent addition of tetramethyl tetravinyl cyclotetrasiloxane (D4^V), resulting in diblock copolymers comprised a simple PDMS block and a functional poly(methylvinylsiloxane) (PMVS) block. Polymers of varying block length ratios were obtained and characterized. The vinyl groups of the second block can be easily modified with a variety of side chains using hydrosilylation chemistry to attach compounds with Si—H bond. Conversion of the hydrosilylation used for polymer modification was investigated.     

芳基乙酮酸乙酯的合成新方法

以芳烃和草酰氯单乙酯为原料, 采用Friedel-Crafts酰基化反应合成了8种芳基乙酮酸乙酯, 用IR, 1H NMR, 元素分析确认了合成化合物结构, 并用高效液相色谱法分析了反应的选择性. 此合成方法具有反应条件温和、操作简单、产率高的特点.     

A New Way to Silicone‐Based Peptide Polymers

We describe a new class of silicone‐containing peptide polymers obtained by a straightforward polymerization in water using tailored chlorodimethylsilyl peptide blocks as monomeric units. This general strategy is applicable to any type of peptide sequences, yielding linear or branched polymer chains composed of well‐defined peptide sequences.     

A Primer on the Analytical Aspects of Silicones at Trace Levels-Challenges and Artifacts – A Review

Silicones (polydimethylsiloxanes) find use in a wide variety of industrial and consumer product applications because of their outstanding properties. Potential human exposure to silicones occurs at the work place during manufacturing and product formulation, as well as through the normal use of consumer products containing them.The entry of silicones into various environmental compartments raised health and safety concerns from potential exposure and mandated numerous environmental and toxicological studies. Such studies require qualitative and quantitative determination of silicone species at trace levels. However, the ubiquitous presence of silicones coupled with their unique chemistry renders their analysis at trace levels challenging.This paper provides a consolidated account of various aspects silicones that must be borne in mind to obtain reliable data. The following are some of topics discussed: differences in the chemistry of silicones vs carbon; precautions in sample handling to avoid losses and inadvertent chemical transformation; potential sources for artifacts and interferences that could lead to systematic errors and data misinterpretation; sources for background and the need for matrix matched blank experiments; distinguishing silicones from silicates to avoid overestimation; potential for incorrect structural assignments; preventing inadvertent contamination; questionable claims on the presence of silicones in biological matrices including that of silicone implants.     

Direct Olefination of Fluorinated Benzothiadiazoles: A New Entry to Optoelectronic Materials

Fluorinated olefin‐containing benzothiadiazoles have important applications in optoelectronic materials. Herein, we reported the direct olefination of fluorinated benzothiadiazoles, as catalyzed by palladium. The reaction proceeds under mild reaction conditions and shows high functional‐group compatibility. A preliminary study of the properties of the resulting symmetrical and unsymmetrical olefin‐containing fluorinated benzothiadiazoles in red‐light‐emitting dyes has also been conducted.     

Synthesis of photocrosslinkable fluorinated polydimethylsiloxanes: Direct introduction of acrylic pendant groups via hydrosilylation

The synthesis of photocrosslinkable fluorinated polydimethylsiloxanes was achieved through direct hydrosilylation with copoly(dimethyl)(methyl‐hydrogen) siloxane. First, the hydrosilylation of a fluorinated olefin allowed the introduction of a fluorinated group onto the polysiloxane. Then, a second hydrosilylation of allyl methyl methacrylate led to the polysiloxane bearing both fluorinated and photocrosslinkable groups. This method, compared with a previous method of copolycondensation, is shown to be easier and more efficient. All the new products synthesized were characterized by IR, ¹H NMR, ¹⁹F NMR, and ²⁹Si NMR. A formulation containing the fluorosilicone was crosslinked after being coated on a mesoporous membrane and was evaluated as a vapor permeation membrane. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3722–3728, 2000     

Synthesis and Characterization of Fully-Functionalized Polysilanes for Photorefractive Materials

Photorefractive (PR) polymers have attracted much interest since 1991 1. Furthermore,because fully-functionalized polymeric systems can overcome the shortcomings such asphase-separation and composite sublimation in composite systems they have gainedespecial attention.Polysilanes can be used as novel photoconductors because of a-electionsdelocalization in the polymeric backbone2. Silence3 and Nishida4 have stUdied thepolysilane composite photorefractive materials and found that the response t…     

A Facile Two‐Step Route to Branched Polyisoprenes via ABn‐Macromonomers

A facile two‐step synthesis for branched poly(isoprene)s (PI) based on polyaddition of AB_n‐type macromonomers is described. The synthesis of the macromonomers was achieved by anionic polymerization of isoprene and subsequent end‐capping of the polymers by addition of chlorodimethylsilane to the living carbanions. This led to PI‐based macromonomers with narrow polydispersity ( / < 1.15) and molecular weights in the range of 1 700 – 22 100 g · mol⁻¹. Synthesis of the branched polymers was carried out by a hydrosilylation‐based polymerization of the macromonomers. Characterization via SEC, SEC‐MALLS, coupled SEC‐viscosimetry and ¹H‐NMR‐spectroscopy supported the formation of branched structures. Interestingly, these branched polymers exhibited α‐values that were similar to those reported for hyperbranched polymers based on AB₂‐monomers.

     

超分子聚合物制备新方法:超分子单体的共价聚合

超分子聚合物是超分子化学与高分子化学交叉的前沿研究领域,近年来受到了国内外研究学者的广泛关注.可控制备超分子聚合物对于研究超分子聚合物的结构与性能关系、设计合成特定功能的超分子聚合物具有重要的意义.本文将总结通过超分子单体的共价聚合反应以制备超分子聚合物的方法.不同于传统的制备超分子聚合物的方法,超分子单体的共价聚合方法将不易调控的非共价聚合转化为可控的共价聚合,为实现超分子聚合物的可控制备提供了新思路.     

A Hydrosilylation Approach to Silicon‐Bridged Functional Dipyrromethanes: Introducing Silicon to A New Arena

Two silylene‐spaced ((E)‐vinylsilyl)anthracene‐dipyrromethane dyads have been designed and synthesized by RhCl(PPh₃)₃‐catalyzed hydrosilylation reactions of 5‐methyl‐5′‐(ethynylaryl)dipyrromethanes with (9‐Anthryl)‐dimethylsilane. The complexation studies of dyads toward different anions have also been performed, which reveal that dyads exhibit a highly selective response towards fluoride anion attributable to both hydrogen‐bonding and pentacoordination phenomena. This dual‐mode fluoride recognition event is unprecedented and may pave the way for future developments in the areas of porphyrinoids, organosilicon, polymer, and supramolecular chemistry.     

Direct Synthesis of PVA‐g‐PDMS in Microsuspension

The synthesis of P(VA‐co‐VAc)‐graft‐PDMS copolymers has been achieved in microsuspension by direct reaction between an epoxy‐terminated PDMS and some pendant alcohol groups in P(VA‐co‐VAc). In this synthesis, the copolymer is used both as dispersant and reactant. The hydrophilic/hydrophobic character of the final material can be varied at will by incorporating various contents of epoxy‐functionalized PDMS through optimized reaction conditions. The final composition was determined by TGA and ¹H NMR. Products prepared from monofunctional PDMS were easily redispersed in water whereas a film of crosslinked materials, arising from difunctional PDMS, showed the best waterproofing as shown by contact angle analysis.

     

A General and Selective Rhodium‐Catalyzed Reduction of Amides,N‐Acyl Amino Esters,and Dipeptides Using Phenylsilane

This article describes a selective reduction of functionalized amides, including N‐acyl amino esters and dipeptides, to the corresponding amines using simple [Rh(acac)(cod)]. The catalyst shows excellent chemoselectivity in the presence of different sensitive functional moieties.     

A Plausible Simultaneous Synthesis of Amino Acids and Simple Peptides on the Primordial Earth

Following his seminal work in 1953, Stanley Miller conducted an experiment in 1958 to study the polymerization of amino acids under simulated early Earth conditions. In the experiment, Miller sparked a gas mixture of CH₄, NH₃, and H₂O, while intermittently adding the plausible prebiotic condensing reagent cyanamide. For unknown reasons, an analysis of the samples was not reported. We analyzed the archived samples for amino acids, dipeptides, and diketopiperazines by liquid chromatography, ion mobility spectrometry, and mass spectrometry. A dozen amino acids, 10 glycine‐containing dipeptides, and 3 glycine‐containing diketopiperazines were detected. Miller’s experiment was repeated and similar polymerization products were observed. Aqueous heating experiments indicate that Strecker synthesis intermediates play a key role in facilitating polymerization. These results highlight the potential importance of condensing reagents in generating diversity within the prebiotic chemical inventory.     

Synthesis of Bottlebrush Polystyrenes with Uniform,Alternating, and Gradient Distributions of Brushes Via Living Anionic Polymerization and Hydrosilylation

By combining living anionic polymerization and hydrosilylation, densely grafted bottlebrush polymers with controlled spacing of branch points are prepared. Dimethyl(4‐vinylphenyl)silane and dimethyl(4‐(1‐phenylvinyl)phenyl)silane are anionically (co)polymerized to synthesize uniform, alternating, and gradient in‐chain silyl–hydride (Si–H) functionalized backbones. The spacing of branch points is controlled effectively by regulating the distribution of Si–H groups along the backbones. Three backbones with a similar number of Si–H groups but variable distributions are used to synthesize corresponding bottlebrush polymers via hydrosilylation between the backbones and chain‐end vinyl functionalized polystyrene. The uniformly grafted bottlebrush exhibits the highest hydrodynamic radius (R_h) of 5.6 nm and the lowest T_g of 79 °C which may be attributed to its compact grafted structure. This methodology exhibits high efficiency and convenience for the construction of bottlebrushes with controlled distribution of brushes.