Dimethylsiloxane Chains Research Articles

Formation of a planar biomimetic membrane with a novel zwitterionic polymer for nanopore sequencing.

Biological membranes containing transmembrane channels play a crucial role in numerous cellular processes, and mimicking of cell membranes has garnered significant interest in various biomedical applications, particularly nanopore sequencing technology, where remarkable progress has been made with nanopore membranes. Considering the fragility of biomimetic membranes formed by artificial lipids and the limited mimicry of those formed by common block copolymers, this study developed a novel amphiphilic polymer by covalently linking hydrophilic heads of phospholipids to the ends of hydrophobic poly(dimethyl siloxane) (PDMS) chains. The absence of hydrophilic blocks allowed for good control over the polydispersity of this polymer within a narrow range. The high flexibility of PDMS chains, combined with relatively uniform molecular weights, would confer enhanced stability and robustness to polymeric membranes. Dynamic light scattering measurements and microdroplet formation tests demonstrated good amphipathic properties of these novel polymers when maintaining an appropriate hydrophilic-hydrophobic ratio. Moreover, the high similarity between the hydrophilic heads and natural phospholipids makes this polymer more compatible with biomolecules. A successful protein insertion experiment confirmed both the stability of this polymeric membrane and its compatibility with membrane proteins. As a result, this novel amphiphilic polymer exhibits great potential for biomembrane mimicking and paves a new path for material design in biomedical applications.

Control of the Organization of 4,4′-bis(carbazole)-1,1′-biphenyl (CBP) Molecular Materials through Siloxane Functionalization

We show that through the introduction of short dimethylsiloxane chains, it was possible to suppress the crystalline state of CBP in favor of various types of organization, transitioning from a soft crystal to a fluid liquid crystal mesophase, then to a liquid state. Characterized by X-ray scattering, all organizations reveal a similar layered configuration in which layers of edge-on lying CBP cores alternate with siloxane. The difference between all CBP organizations essentially lay on the regularity of the molecular packing that modulates the interactions of neighboring conjugated cores. As a result, the materials show quite different thin film absorption and emission properties, which could be correlated to the features of the chemical architectures and the molecular organizations.

Fabrication of ultra-smooth hybrid thin coatings towards robust, highly transparent, liquid-repellent and antismudge coatings

Liquid-repellent and anti-smudge coatings have a wide range of applications on the surface of materials. In this work, a novel liquid-repellent anti-smudge hybrid coating was in situ fabricated by using tetraethyl orthosilicate (TEOS) and dimethoxydimethylsilane (DMDEOS) under acid catalysis. The resulting coatings had a high transmittance of 3–4% higher than that of blank glass. The superior smoothness and high mobility of generated poly(dimethyl siloxane) (PDMS) chains on the surface resulted in low sliding angles of 4.5° (water) and 2.8° (n-hexadecane), and a high water sliding velocity of 15.6 cm s−1 at a tilting angle of 70°. In addition, the hybrid coatings could repel both ink and dust contaminations and hinder bacteria adhesion. What’s more, the anti-smudge coatings demonstrated excellent durability and mechanical properties of 8H pencil hardness and 5A adhesion grade. Thus, a new perspective is provided for the preparation of anti-smudge coatings. The simple preparation method would bring a breakthrough in the development and application of anti-smudge materials.

Fluorene-based chromophore for degradation-recoverable solid-state dye laser

We developed a new fluorene-based chromophore for a degradation-recoverable polydimethylsiloxane (PDMS) dye laser. The chromophore has dimethylsiloxane chains to enhance its solubility in the PDMS matrix. The spectroscopic and mobile characteristics were evaluated, and the attaching of the siloxane/silyl chains improved solubility in PDMS without influencing the laser property. It extended the durability by a factor of 20 for shots in an index-type Bragg grating/PDMS complex laser waveguide compared with a similar fluorene-based chromophore in PMMA laser waveguides. This molecular diffusion not only increased durability but also provided detailed information about dye degradation in waveguides.

Preparation, hybrid formation with single-walled carbon nanotube, and film morphology of pyrene-containing polysiloxanes

Palladium-catalyzed coupling reactions of bis(tributylstannyl)pyrene and diethynylpyrene with α,ω-di(bromothienyl)oligo(dimethylsiloxane) gave the corresponding polymers whose backbones were composed of pyrene-containing π-conjugated units and oligo(dimethylsiloxane) chains. These polymers exhibited red-shifted photoluminescence bands in solutions, probably due to the intramolecular stacking of the π-conjugated chromophores. Ball milling of the polymers with single-walled carbon nanotube (SWNT) afforded the soluble polymer-SWNT hybrid substances. Film morphology of the polymers was investigated by atomic force microscopy, showing the microphase-separated structure.

용매 어닐링에 의한 박막에서 Polystyrene-Poly(1,4-butadiene) 블록공중합체의 모폴로지 전이

본 연구에서는 용매 증기 하에서 박막으로 제조된 polystyrene-poly(1,4-butadiene) 블록공중합체(PS-b-PBD)의 모폴로지 형성과 특성이 원자주사현미경(AFM)을 사용하여 연구되었다. 사이클로헥산으로만 용매 어닐링된 박막의 경우 폴리스티렌의 매트릭스 내부에 PBD가 미세상을 형성하는 perforated lamellae가 형성되었지만, n-헥산만으로 용매 어닐링 된 박막은 불규칙한 패턴만이 관측되었다. 그러나 사이클로헥산과 n-헥산의 혼합 용매를 사용하여 용 매 어닐링할 경우 기질에 수직으로 배향된 라멜라가 관측되었다. 이러한 모폴로지 전이는 혼합 용매의 혼합비에 의 해 조절되며 n-헥산의 양이 증가하면서 라멜라의 형성이 뚜렷이 관측되었다. 그러나 용매 어닐링에 사용된 혼합 용 매 중 n-헥산의 주요 성분이 될 경우 n-헥산의 PBD로의 용매 친화력에 의해 모폴로지 형성이 오히려 지연되는 것을 확인하였다. 이러한 사이클로헥산과 n-헥산의 혼합비에 따른 모폴로지 전이는 블록공중합체에 대한 두 용매들의 친화력과 관련 있으며, 이를 이해하기 위해 이들의 용해도 상수 및 Flory 상호인력 인자들이 고려되었다. 또한 본 연구로부터 얻어진 두 가지 모폴로지를 이용하여 실리카 나노 패턴의 제조를 위한 템플레이트로 활용하였다.

Novel stabilisers acting simultaneously as molecular-weight regulators in soluble elastomeric polyurethanes

Three new low-molecular-weight stabilisers, bearing in their molecules a tri(dimethylsiloxane) chain, end-capped with primary OH groups, have been synthesised and characterised. One is based on a sterically hindered phenolic antioxidant, the others on sterically hindered piperidines (HALS-type). When added to the reaction mixture for the preparation of model soluble elastomeric polyurethanes (containing a polybutadiene α,ω-diol, a diisocyanate and a catalyst), each of these stabilisers, due to the presence of the OH group, is joined by a covalent bond at one or both chain ends of the polyurethane formed, and acts simultaneously as a molecular-weight regulator. Thermoanalytical methods revealed that the stabilising efficiency of these polymer-bound structures is comparable with that of their low-molecular-weight analogues, physically admixed with the polyurethane. The advantage of these chemically fixed stabilisers lies in the fact that they remain in the matrix and cannot be evaporated nor washed out.

Controlled Stepwise Growth of Siloxane Chains Using Bivalent Building Units With Different Functionalities

AbstractOrganic/inorganic hybrids of silicon and their subsequent chemical modification are of interest for tailoring and structuring surfaces on the nanoscale. The formation of monolayers on hydroxylated silicon surfaces was employed to synthesize molecular dimethylsiloxane chains by wet-chemical condensation reactions, using dimethylmonochlorosilane as the precursor. The SiH group of the resulting dimethylsilyl termination could be selectively oxidized to the SiOH group, which opened the possibility of bonding another species. By repeating the condensation and oxidation cycle the stepwise growth of one-dimensional dimethylsiloxane chains was achieved. The ongoing chain growth was characterized by attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and determination of the surface energy by contact-angle experiments.

Molecular structure and morphology of membrane-forming copolymers of tolylene diurea and poly(dimethylsiloxane)

The molecular structure of tolylene diurea and poly(dimethylsiloxane) copolymers has been studied by the methods of mechanical and dielectric losses, photoelasticity, and X-ray analysis. The above copolymers are found to experience microphase separation. The radius of gyration of domains formed by the hard blocks based on tolylene diurea was estimated as R ≈ 30 A. Hard blocks connected by the hydrogen bonds in domains are shown to be perpendicular to directions of the maximum extension of domains. The proposed molecular model of a membrane based on the above copolymer includes a molecular network composed of flexible poly(dimethylsiloxane) chains connected by physical junctions; the above physical junctions are domains formed by the thermodynamically hard blocks of tolylene diurea.

Thermally initiated cationic polymerization and properties of epoxy siloxane

AbstractDifunctional epoxy siloxane monomers containing disiloxane, trisiloxane, and tetrasiloxane were prepared by hydrosilylation of an α,ω‐difunctional SiH‐terminated siloxane with a vinyl‐functional epoxide. Cationic polymerization of these monomers using 3‐methyl‐2‐butenyltetramethylenesulfonium hexafluoroantimonate and their reactivities were examined. The reactivity order was disiloxane > trisiloxane > tetrasiloxane. Thermal discoloration of these polymers increased with catalyst concentration and also with the length of dimethyl siloxane. UV discoloration was also accelerated by catalyst. From the thermo gravimetric analysis, it was found that the thermal stabilities of polymers increased with increasing the length of dimethyl siloxane chain. Mechanical properties of polymers were also tested by thermal mechanical analysis and dynamic mechanical analysis, and it was found that the flexibility of polymers was increased with increasing siloxane chain length. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2010–2019, 2006

Synthesis and investigation of properties of silaoxadihydrophenanthrene‐diphenylsiloxane fragments containing block copolymers

AbstractThe reaction of heterofunctional condensation of 1,1‐dichloro‐1‐sila‐2‐oxadihydrophenanthrene with dihydroxydiphenylsilane at various ratios of initial compounds in the presence of pyridine is investigated. α,ω‐Dihydroxysilaoxadihydrophenanthrene‐diphenylsiloxane oligomers with various degrees of condensation are obtained. Organosiloxane block copolymers with the regular arrangement of silaoxadihydrophenanthrene‐diphenylsiloxanes fragments in the main linear dimethylsiloxane chain are produced by the reaction of heterofunctional condensation of α,ω‐dihydroxysilaoxadihydrophenanthrene‐diphenylsiloxanes with α,ω‐dichlorodimethylsiloxanes in the presence of anhydrous pyridine, as an acceptor of hydrochloric acid. Thermogravimetry, differential scanning calorimetry, gel permeation chromatography, and wide‐angle X‐ray analysis are carried out on the synthesized block copolymers. The microheterogeneous structure of block copolymers is observed at definite values of the length of the flexible dimethylsiloxane chain by DSC and X‐ray investigation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 9–16, 2002; DOI 10.1002/app.10045

Card-type Organosiloxane Copolymers with Silaoxaphenantrene Fragments in Dimethylsiloxane Chain

The reaction of heterofunctional condensation of 1,1-dichloro-1-sila-2-oxaphenantrene with α,ω-dihydroxydimethylsiloxane in the presence of pyridine has been investigated and card-type organosiloxane copolymers with regular arrangement of silaoxaphenantrene fragments in dimethylsiloxane chain has been obtained. It is shown, that at small length of linear dimethylsiloxane chain, besides the reaction of intermolecular condensation, intramolecular cyclization takes place with formation of bicyclic compounds. Thermogravimetric, DSC, GPC and X-ray analysis of the synthesised copolymers have been carried out.

Some Attempts to Force Poly(Dimethylsiloxane) Chains through Zeolite Cavities to Improve Elastomer Reinforcement

Abstract The reinforcing effects of zeolites in poly(dimethylsiloxane) (PDMS) elastomers were characterized using two preparative approaches. In the first, end-functionalized polymer chains were blended into the zeolite, and were then endlinked into the required network structure. The second approach represented an attempt to force some chains through the cavities, by blending the monomer itself into the zeolite and then polymerizing it to obtain the PDMS elastomer. The two types of zeolite-filled PDMS were characterized using stress-strain measurements in elongation, equilibrium swelling, and small-angle X-ray scattering. The second synthetic approach did seem to give improvements in mechanical properties, particularly when the average cavity size of the zeolite particles was relatively large. Ascribing the observed improvements in reinforcement at least partly to the threading of some PDMS chains through the zeolites was supported by the results obtained in the swelling and scattering experiments.

Synthesis of novel block siloxane polymers for the removal of butanols from aqueous feed solutions

The design and synthesis of novel siloxane–urea block polymers has been carried out from amino end-capped dimethylsiloxane chains, and their separation properties in pervaporation have been investigated. Using fluorinated chain extenders, new urea copolymers have been prepared; combining polar and apolar blocks, these soluble materials have excellent film forming ability and their good mechanical properties allowed their use in membrane separation technology. Their chemical nature has been characterized by FTIR and their phase-separated microstructure by DSC. Applied to the separation of butanol isomers from water, it has been shown that these alcohols can be separated easily from their diluted aqueous solutions, with normalized fluxes reaching 0.5 kg h −1 m −2 and a selectivity as high as 37 for a 0.1 feed activity. In isothermal sorption of pure water, the data revealed the masking effect of the polar urea junction in the polymer containing bulky methyl groups next to it. Referring to the sorption–diffusion model, the pervaporation results demonstrated that the materials are endowed with organic selective properties due to the higher interactions of the copolymers for the butanol isomers, resulting from the combined sorption and diffusion steps.

Monolayer Behavior of Poly(amic acid) Alkylamine Salts Containing the Dimethylsiloxane Structure and Their Langmuir−Blodgett Films

The behavior of monolayers of poly(amic acid) alkylamine salts containing different dimethylsiloxane chain lengths at the air−water interface was investigated. The limiting areas estimated from surface pressure−area isotherms were much larger than those calculated from both the alkyl chain number per repeating unit and the cross-sectional area of the alkyl chain. The direct observation of monolayers was carried out by Brewster angle microscopy (BAM). The BAM observation was affected by the length of the dimethylsiloxane chain in the poly(amic acid)s. The layered structure of the LB films of poly(amic acid) alkylamine salts with multichains was investigated by X-ray diffraction, Fourier transform infrared−reflection absorption spectroscopy, and X-ray photoelectron spectroscopy. Consequently, it was found that the LB films consist of bilayer (Y-type) structures in which the alkyl chains are appreciably tilted from the normal direction and that the long dimethylsiloxane chain is concentrated in the outer surface of the LB films.

Poly(dimethylsiloxane) Chains Cross-Linked at Random. Percolation and NMR Approaches

The formation of network structures associated with randomly cross-linked polydimethylsiloxane chains is analyzed as a function of time. A cross-linking reaction between the methyl groups and the v...

Thermodynamics of linear dimethylsiloxane–perfluoroalkane mixtures Part 1.—Liquid–liquid coexistence curves for hexamethyldisiloxane–, octamethyltrisiloxane– or decamethyltetrasiloxane–tetradecafluorohexane near the upper critical endpoint and upper coexistence temperatures for 21 other dimethylsiloxane–perfluoroalkane mixtures

Measurements of the liquidliquid coexistence curve for hexamethyldisiloxane, octamethyltrisiloxane or decamethyltetrasiloxanetetradecafluorohexane near the upper critical endpoint and of the upper coexistence temperatures T UCX for equivolume mixtures of 21 other mixtures of this kind confirm the basic similarity of the thermodynamics of such mixtures to those of alkaneperfluoroalkane mixtures. The upper critical solution temperatures T UCS increase linearly within the range studied with perfluoroalkane chain length and nearly so with dimethylsiloxane chain length. The coexistence curves have been fitted to Wegner extended-scaling expressions in order to investigate the universality of the shape. The temperaturevolume-fraction (T−φ) representation is more symmetrical than that in mole fraction and with a reduced temperature =(T/T UCS ), withthe upper critical solution temperature T UCS as the reduction factor, the (−φ) representation is universal for all threemixtures as well as nearly so for the comparison mixture C 6 H 14 C 6 F 14 . T UCS (C 6 H 14 C 6 F 14 )=295.80 K and T UCS (hexamethyldisiloxaneC 6 F 14 )=296.95 K are unsurprisingly close, in view of the near-equal temperature reduction factors of hexamethyldisiloxane and hexane. The effect of this correspondence is extended to the analysis of the T UCX of the other mixtures. The results are discussed in terms of the solubility parameter version of the regular solution theory incorporating the Flory–Huggins entropy of mixing term. With a correction of nearly 10% on the geometric-mean combining rule for the cohesive energy density T UCS is reasonably well predicted. For these mixtures, the critical mole fraction is also surprisingly well predicted from the ratio of component molar volumes.

Copolymers with 1,3-diorgano-1,3-disila-2-oxaindane fragments in the dimethyl siloxane chain

Siloxane copolymers with disilaindane cycles in the main chain have been synthetized by heterofunctional polycondensation of 1,3-dichloro-1,3-diorgano-1,3-disilia-2-oxaindanes with α-ω-dihydroxydimethl-siloxanes in presence of pyridine and their thermomechanical, thermogravimetric and radiographic investigations undertaken.

Thermodynamics and structure in nonelectrolyte solutions

Abstract

Pervaporation of ethanol-water mixture by plasma films prepared from hexamethyldisiloxane

The plasma polymerization process was investigated to obtain plasma films like poly(dimethylsiloxane), and the formed films were applied as membranes for pervaporation of ethanol-water solution. A reaction chamber which had the triode electrode structure for initiation of a glow discharge was provided for preparation of films like poly(dimethylsiloxane) by plasma polymerization. Films plasma-polymerized from hexamethyldisiloxane (HMDSO) resembled poly(dimethylsiloxane) in spectroscopic view and were composed of dimethylsiloxane chains with branches of trimethylsilyl groups. The surface energy for the films was 19.6 mN/m. The films deposited from HMDSO on Nuclepore membrane showed good ethanol-selectivity in pervaporation of ethanol-water solution. The separation factor depended on the film thickness as well as the feed composition. The film-thickness effect was maximized at 34 nm thick, and the separation factor reached 4.5. A model for the separation process using our composite membrane was discussed.