Multiphase‐Assembly of Siloxane Oligomers with Improved Mechanical Strength and Water‐Enhanced Healing

Healable silicone materials have great technical impact in coatings, smart actuators, and flexible electronics, however, current healable silicone materials lack mechanical tunability. Herein, we designed and synthesized a new type of healable silicone through hydrogen‐bond assisted multiphase assembly of siloxane oligomers. Besides the enhanced mechanical strength, unique water‐enhanced healing was observed in the polymer network which is due to the reversible dissociation/association of multivalent hydrogen bonds in the presence of water.     

Preparation and characterization of silicone rubber through the reaction between γ‐chloropropyl and amino groups with siloxane polyamidoamine dendrimers as cross‐linkers

A novel heat‐curable silicone rubber (MCSR/Si‐PAMAM) was prepared by using siloxane polyamidoamine (Si‐PAMAM) dendrimers as cross‐linkers and polysiloxane containing γ‐chloropropyl groups as gums. The chemical cross‐linking occurs through the reaction between Si‐PAMAM dendrimers and polysiloxane containing γ‐chloropropyl groups. The effect of various amounts of cross‐linkers on mechanical properties of MCSR/Si‐PAMAM was discussed in this paper. MCSR/Si‐PAMAM exhibits favorable mechanical properties with a tensile strength of 10.06 MPa and a tear strength of 47.9 kN/m when the molar ratio r of [N‐H]/[CH₂CH₂CH₂Cl] is 1:1. These excellent mechanical properties can be attributed to the formation of concentrative cross‐linking from Si‐PAMAM dendrimers in the cross‐linking networks, along with the introduction of Si–O–Si units in the internal structure of dendrimers. The introduction of Si–O–Si units reduces the steric hindrance of molecular structure, which facilitates the N–H bonds in the interior layers of dendrimers to react with γ‐chloropropyl groups. In addition, thermogravimetric analysis results indicate that MCSR/Si‐PAMAM is thermally stable even at high temperatures in a nitrogen atmosphere. Differential scanning calorimetry analysis reveals that the glass transition peak of MCSR/Si‐PAMAM is not identified in the temperature range −150 to −30°C, only a melting endothermic peak at −40°C.     

Sol-gel derived Li+-doped poly(ε-caprolactone)/siloxane biohybrid electrolytes

Electrolytes based on a poly(ε-caprolactone) (PCL)/siloxane organic/inorganic host framework doped with lithium triflate (LiCF₃SO₃) were synthesised through the sol-gel process. In this biohybrid matrix short PCL chains are covalently bonded via urethane linkages to the siliceous network. Samples with salt composition n (molar ratio of PCL repeat units per Li⁺ ion) ranging from ∞ to 0.5 were investigated. All the ormolyte materials analyzed are amorphous. Xerogels with n > 0.5 are thermally stable up to about 300°C. The most conducting ormolyte of the series is that with n = 0.5 (1.6×10⁻⁷ and 3.2×10⁻⁵ Ω⁻¹ cm⁻¹ at 25 and 100°C, respectively). This sample is electrochemically stable between −1 and 6 V versus Li⁺.     

SINGLE-ION CONDUCTIVITY IN POLY (LITHIUM PROPIONATE METHYL SILOXANE)

Poly(lithium propionate methyl siloxane )as a single-ion carrier source was synthesized. The crosslinked film showed lower lithium ionic conductivity at room temperature (about 10~(-10) S/cm). However,the lithium ionic conductivity was obviously increased by blending with high polar polymers such as polyethylene oxide, poly (methylsiloxane - co- ethylene oxide) and poly (methylsiloxane- g- ethylene oxide). In the blend system a high conductivity of 10~(-7)-10~(-5) Scm~(-1) at room temperature was obtained and the single-ion conductivity was deeply influenced by the content of the poly (lithium propionate methyl siioxane). The dc ionic conductivity of the flexible crosslinked films is more stable over time.     

高分子冠醚毛细管柱的性能研究

本文报道了3种新的聚硅氧烷侧链冠醚作气相色谱固定液,并涂渍成弹性石英毛细管柱,这种毛细管柱具有优良的色谱性能,它们具有柱效高,热稳定性好,选择性强的特点,适于分离各种异构体。     

（PSF—PDMS—PHS）n／PSF共混物的相容性及表面组成

利用ＤＳＣ、ＤＭＡ、ＴＥＭ和ＸＰＳ对［ＰＳＦ－ＰＤＭＳ－ＰＨＳ］ｎ／ＰＳＦ共混物的相容性及表面组成进行了研究．结果表明，ＰＤＭＳ在共混物表面的富集与ＰＳＦ均聚物和［ＰＳＦ－ＰＤＭＳ－ＰＨＳ］ｎ中硬段的相容性有关；ＰＤＭＳ在相容的共混物体系表面的富集与对应的多嵌段共聚物组成基本相近；不相容共混物体系表面ＰＤＭＳ的富集程度相对较高，当共混物本体中有机硅含量从１％增至５％，表面层ＰＤＭＳ的含量迅速增加，可达到嵌段共聚物中ＰＤＭＳ的含量．     

Study of structure and polymerization of epitaxially grown SiPc(OH)2 thin films by high-resolution electron microscopy

Thin films of SiPc(OH)₂ (Pc = phthalocyanine) were formed epitaxially on the (001) surface of mica by vacuum deposition and were then polymerized by heat treatment. The molecular packing of the SiPc(OH)₂ was determined by electron diffraction and high-resolution electron microscopy as triclinic${\rm P\bar 1} $ having dimensions a = 0.727, b = 1.307, c = 0.688 nm, α = 102.5, β = 104.2, and γ = 97.4°. This monomer crystal grows with its c-axis parallel to the a-axis of the substrate mica and its bc-plane parallel to the (001) surface of mica. By heat treatment at 320°C, the SiPc(OH)₂ polymerized with the c-axis of the polymer parallel to the c-axis of the monomer. At 420°C, the c-axis of the polymer became parallel to the a*-axis of the monomer (i.e., perpendicular to the film surface). From high-resolution electron microscopy of partially polymerized specimens, the polymerization was shown to start at the edges of small monomer crystals. This may be considered to be due to the volume expansion during the polymerization. © 1993 John Wiley & Sons, Inc.     

Thermal redistribution reactions in crosslinked polysiloxanes

The thermolysis under argon of various polysiloxane resins containing D, T, D^H, or T^H units was investigated using thermogravimetric analysis combined with mass spectroscopy (TG/MS analysis) and solid-state ²⁹Si-NMR. Redistribution reactions involving the exchange of Si? C/Si? O bonds or Si? H/Si? O bonds were evidenced in addition to the exchange of Si? O/Si? O bonds reported to date. These reactions significantly modify the initial siloxane units and lead to an escape of volatile silanes or siloxanes. The exchange of Si? H/Si? O bonds takes place at lower temperatures (300°C) than the exchange of Si? C/Si? O bonds (500°C).     

Hydrogen Bonding Interaction of Formic Acid-, Formaldehyde-, Formylfluoride-Nitrosyl Hydride： Theoretical Study on the Geometries, Interaction Energies and Blue- or Red-Shifted Hydrogen Bonds

The hydrogen bonding interaction of formic acid-, formaldehyde-, formylfluoride-nitrosyl hydride complexes was investigated by the density functional theory （DFT） and ab inito method in conjunction with 6-311＋＋G（2d,2p） basis set. The geometries, vibrational frequencies and interaction energies of the complexes were calculated by both standard and CP-corrected methods respectively. Moreover, G3B3 method was employed to estimate the interaction energies. There are C--H…O, N--H…O, N--H…F blue-shifted H-bonds and red-shifted O----H…O H-bond in the complexes. Electron density redistribution and rehybridization contribute to the N--H and C--H blue shifts. All geometric reorganizations contribute to the N--H blue shifts and partial geometric reorganizations contribute to the C--H blue shifts. The geometric reorganizations of the complex C except ZH（5）-O（4）-C（1） contribute to the O----H red shift. For the N--H blue shifts, the effect of r（N--O） variation on the N--H blue shifts is larger than that of ZH-N-O variation. Rehybridization plays a dominant role in the degree of N--H blue shifts, whereas the electron density redistribution contributes more to the degree of C--H blue shifts than the other effects do.     

Theoretical study of the red‐ and blue‐shifted hydrogen bonds of nitroxyl and acetylene dimers

Ab initio molecular orbital and density functional theory (DFT) in conjunction with different basis sets calculations were performed to study the C? H…O red‐shifted and N? H…π blue‐shifted hydrogen bonds in HNO? C₂H₂ dimers. The geometric structures, vibrational frequencies and interaction energies were calculated by both standard and counterpoise (CP)‐corrected methods. In addition, the G3B3 method was employed to calculate the interaction energies. The topological and natural bond orbital (NBO) analysis were investigated the origin of N? H…π blue‐shifted hydrogen bond. From the NBO analysis, the electron density decrease in the σ* (N? H) is due to the significant electron density redistribution effect. The blue shifts of the N? H stretching frequency are attributed to a cooperative effect between the rehybridization and electron density redistribution. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006