Synthesis and Solution Properties of Carbohydrate‐Modified Polysiloxane Bola Surfactants

Three carbohydrate‐modified polysiloxane bola surfactants (ATPS‐GA) were synthesized using a two‐step method. Their chemical structures were characterized by infrared spectroscopy (FT‐IR) and proton nuclear magnetic resonance spectroscopy (¹H NMR). Their surface properties and aggregation properties in aqueous solution were determined using surface tension measurements and transmission electron microscopy (TEM). Surface tension measurement results indicated that the three bola surfactants are under 25 mN m^?1, and much lower than those of conventional hydrocarbon bola surfactants due to the siloxane moiety at the end of the hydrophobic chains. TEM analysis results indicated that the ATPS‐GA can self‐assemble into spherical micelles with a wide range of average diameters from 100 nm to above 600 nm.     

Synthesis of ferroelectric liquid crystalline polysiloxanes containing (S)-2-methylbutyl 4-alkyloxybiphenyl-4′-carboxylate and (2S, 3S)-2-chloro-3-methylpentyl 4-alkyloxybiphenyl-4′-carboxylate

The synthesis of side-chain liquid crystalline polysiloxanes containing (S)-2-methylbutyl-4-alkyloxybiphenyl and (2S, 3S)-2-chloro-3-methylpentyl 4-alkyloxybiphenyl-4-carboxylate moieties as mesogenic units and aliphatic spacers containing respectively three to eleven methylene units is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements reveal chiral smectic mesomorphism for most of the obtained polymers. Two polysiloxanes that contain respectively three methylene units in their spacers exhibit an enantiotropic smectic A phase or no mesophase. Four polysiloxanes that contain respectively five, six and eleven methylene units in their spacers exhibit enantiotropic smectic A and chiral smectic C phases. The results seem to demonstrate that the tendency toward chiral smectic C mesomorphism increases with increasing spacer length. Incorporation of a chloro-containing chiral end group into the mesogenic core of a polymer will decrease the thermal stability of the mesophase formed.     

改性聚合多元醇水基润滑剂的研究

介绍钻井液用有机硅改性聚合多元醇润滑剂Silicon-1的性能。室内研究表明:Silicon-1具有优良的润滑性,加入1.0%-3.0%Silicon-1使6%膨润土浆的润滑系数(0.358)降低71.51%-83.8%;Silicon-1具有良好的井眼清洁能力,井壁稳定和抑制能力接近油基钻井液水平;无荧光不干扰地质录井,储层保护效果好;对聚合物钻井液常规性能无不良影响,不引起发泡;生物毒性检测结果表明,Silicon-1具有环境可接受性。     

RETRACTED ARTICLE: A correlation between the optical and mechanical properties of novel polysilane/polysiloxane nanocomposites

Poly(di-n-hexyl)silanes (PDNHS), which are σ-conjugated conductive polymers were synthesized by the conventional Wurtz-type coupling reaction. PDNHS were incorporated into polymer networks obtained by cross-linking vinyl terminated poly(dimethyl)siloxanes and methylhydrosiloxane-dimethylsiloxane copolymers. From the UV spectra of polysilane/polysiloxane composites, it can be derived that direct correlations exist between the structure of the polysiloxane matrix and the conformation of small amounts of added polysilanes. The degree of cross-linking plays an important role to understand the structure of the polysiloxane matrix. In addition, rheological measurements indicate that the mechanical properties and the degree of cross-linking in the PDNHS/polysiloxane composites are directly correlated. This implies that the optical properties of small amounts of added PDNHS can be correlated to the mechanical properties of the surrounding polymer matrix. Furthermore, this correlation confirms that PDNHS are suitable to probe the properties of complex polymeric structures.     

有机硅嵌段水性聚氨酯织物整理剂

研究了有机硅嵌段水性聚氨酯织物整理剂的合成、性能及应用。     

Synthesis and characterization of side-chain liquid crystalline polysiloxanes

The synthesis and characterization are described for a series of side-chain liquid crystal polysiloxanes using polyhydrosilylation reaction between a poly(hydrogen methyl-co-dimethylsiloxanes),-(OSiHMe)_x,-(OSiMe2)_y-, where x/y was 13/87, 30/70, 55/45, 73/27 and 98/2, and [4-(allyloxy)benzoyll biphenyl mesogenic group. The side-chain liquid crystal polysiloxanes were characterized by¹H NMR,¹³C NMR, IR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and optical polarizing microscopy. The dimethylsiloxane segment factors governing thermal transition temperatures and activation energy (E_a) of the nematic-to-isotropic phase transition are discussed.     

Synthesis, characterization, and thermal properties of poly(siloxane-carborane)s

Three exactly alternating carborane-siloxane polymers P1, P2, and P3, have been synthesized by the polycondensation of 1,7-bis(dimethylhydroxylsilyl)-m-carborane and cyclotrisilazanes in the presence of (NH₄)₂SO₄. The reaction shows a new and convenient synthesis of poly(carborane-siloxane)s, and the first example of stoichiometric polycondensation of cyclosilazanes with diols. The new polymers P2 and P3 could be converted into thermosets at elevated temperature through the cross-linking of pendant vinyl groups. The structures of the polymers were fully characterized. Thermogravimetric analysis (TGA) showed the superior thermal stability of the polymers and thermosets, with their char yields of over 83% both in air (800 °C) and nitrogen (1000 °C). The microstructure of the chars was studied by scanning electron microscopy (SEM). It was found that the cross-linking of vinyl groups helped in enhancing the thermal stabilities of the polymers and keeping the integrity of the chars. The results suggest their potential utility under severe thermal and/or thermo-oxidative conditions.     

Impact of aluminum oxide nanopowder on thermal,optical and surface properties of polysiloxane-aluminum oxide composites as elastomeric thermal pad for light emitting diode application

ABSTRACT

Virgin polysiloxane and aluminum oxide nanopowder (10%–50%) reinforced polysiloxane composite films were prepared and its thermal, optical, surface properties were investigated. Polysiloxane/aluminum oxide (Al₂O₃) (50%–50%) composite film sample exhibit high thermal conductivity (k – 0.26 W/mK) and UV absorption, decreased junction temperature (ΔT_J = 25.69°C at 700 mA) and thermal resistance (?R_th-tot = 12.41 K/W at 700 mA) compared to virgin polysiloxane film. Overall, the prepared composites can be used as an alternate elastomer thermal pad for efficient thermal management as well as UV blocking encapsulant for future UV-free LED application development.     

Processing and properties of Cfibre/SiCfillers/SiOC composites using solvent free liquid polysiloxane as matrix source

Abstract

Carbon fibre reinforced SiOC composites (denoted as C_fibre/SiC_fillers/SiOC) were prepared by slurry coating and polymer infiltration pyrolysis (PIP) process. Low viscosity liquid polysiloxane (PSO) and SiC powder were combined at a 1∶1 weight ratio to produce a blend (S-PSO), which was employed as matrix source. Heat treated carbon fibre fabric was adopted as the reinforcement. The lamination process was determined on the basis of cure and rheology investigations on S-PSO. The effects of PIP cycles and temperature of heat treatment of the carbon fibre on the mechanical properties of C_fibre/SiC_fillers/SiOC were examined. The results indicate that composites using carbon fibres annealed at 1700°C as reinforcement reached a maximum flexural strength of 300 MPa after six PIP cycles. The resistance of the C_fibre/SiC_fillers/SiOC composite to oxidation was also evaluated. Without any protective coatings, the composite retained 60% of its strength after oxidation at 800°C for 3 h in a static air environment.     

Microstructure and properties of poly(urethane-siloxane)s based on hyperbranched polyester of the fourth pseudo generation

Poly(urethane-siloxane) networks based on hydroxyethoxy propyl terminated poly(dimethylsiloxane) (PDMS) as the soft segment and 4,4′-methylenediphenyl diisocyanate (MDI) and two hyperbranched polyesters with different core as the hard segments were characterized by swelling experiments, thermal analyses (DSC and TG), thermomechanical analysis (DMTA), X-ray scattering studies, SEM and AFM analyses, water contact angle and water absorption measurements, as well as surface free energy determination. From these studies, structure–property relationships were elucidated. Hyperbranched polyesters based on 2,2-bis(hydroxymethyl)propionic acid and ethoxylated pentaerythritol or di-trimethylolpropane as core (BH-40 and HBP-4) were used as crosslinkers for the samples of different series. Both series are composed of samples having different PDMS (i.e., soft segment) content. The crosslinking density and extent of hydrogen bonding showed an influence on the polyurethane (PU) properties. It was found that higher crosslinking density and better thermal stability of PUs based on BH-40 compared to HBP-4 based PUs are due to the less dense structure of BH-40. DMTA experiments revealed that the networks exhibit two glass transition temperatures, of the soft and hard segments, and one secondary relaxation process. The crosslinking density and extent of the microphase separation increased and thermomechanical properties were improved with decreasing content of PDMS. With increasing PDMS content, the surface of the polyurethane networks became more hydrophobic, the surface free energy decreased and thermal stability was improved. The obtained results revealed that synthesized PUs have good thermal and thermomechanical properties, which can be tailored for the potential use in the coating technology by changing the type of hyperbranched polyester or PDMS content.