Novel Epoxide Initiators for the Carbocationic Polymerization of Isobutylene

Summary: We recently reported the synthesis of polyisobutylene (PIB) via direct initiation by epoxycyclohexyl isobutyl polyhedral oligomeric silsesquioxane (POSS®) (Figure 1 ) in conjunction with titanium tetrachloride (TiCl₄). This system successfully initiated the living carbocationic polymerization of isobutylene (IB) in hexane/methyl chloride (Hx/MeCl -60/40, v/v) at T = −80 °C, yielding an asymmetric telechelic PIB with one POSS® cage head group and one tert-Cl end group. 1 This paper will discuss IB polymerizations initiated by 1,2-epoxycyclohexane and bis[3,4-(epoxycyclohexyl)ethyl]-tetramethyl-disiloxane, in conjunction with TiCl₄.     

Synthesis and UV shielding properties of zinc oxide ultrafine particles modified with silica and trimethyl siloxane

This paper introduces a kind of ZnO ultrafine particles modified with silica and trimethyl siloxane (TMS). Thus zinc carbonate hydroxide (ZCH) as the precursor of ZnO was synthesized using chemical precipitation method, and the precursor was modified in situ with silica and TMS. The modified ZnO ultrafine particles were obtained after calcinating the modified precursors. The surface properties of the modified ZnO ultrafine particles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectra (XPS), scanning electron microscope (SEM), and transmission electron microscopy (TEM). The effects of the modifiers on the photocatalytic activity and UV shielding ability of ZnO ultrafine particles were also investigated and discussed.     

含氢低聚硅氧烷合成工艺及表征

以苯基三甲氧基硅烷和四甲基二氢二硅氧烷为合成原料,合成了高产率、高纯度的含多个活性氢基低聚硅氧烷MH3 Tph,采用粘度、折射率、透光率、及核磁共振氢谱、硅谱对其进行了表征.考察了物料投料摩尔比和滴加蒸馏水耗时在合成工艺中的影响,结果表明合成最佳方案为:以1:2.0的比例投料,在低温15℃环境下,滴加酸催化剂0.05 ...     

用高分子冠醚和高分子液晶混合物作毛细管气相色谱固定液的研究

作为毛细管气相色谱固定液,对高分子液晶和高分子冠醚的共混物和含冠醚的高分子液晶单一固定液进行了比较,结果表明它们具有大致相同的保留性能。     

Silicon‐modified surfactants and wetting: III. The spreading behaviour of equimolar mixtures of nonionic trisiloxane surfactants on a low‐energy solid surface

The spreading behaviour of binary and ternary equimolar mixtures of siloxane surfactants of general formula [(CH₃)₃SiO]₂CH₃Si(CH₂)₃ (OCH₂CH₂) _nOCH₃, n = 3–9, has been investigated. The mixtures show a pronounced temperature dependence on the initial spreading rate. Mixtures imitating the average oligoethylene glycol chain length n = 5 are the fastest spreaders at 15 °C. At 23 °C and 40 °C these mixtures spread fastest sucking n = 6 and n = 8, respectively. For a given average chain length an increasing length difference between the components of the binary mixtures reduces the initial spreading rate. Nevertheless, substantial differences between the phase transition temperature T_c from the lamellar phase (L_α) into the two‐phase state (2Φ) and the actual spreading temperature are tolerated. A clear relation between phase transition temperature T_c and initial spreading rate does not exist. Copyright © 1999 John Wiley & Sons, Ltd.     

Silicon-Modified Carbohydrate Surfactants V: The Wetting Behaviour of Low-Molecular-Weight Siloxane,Carbosilane, Silane and Polysilane Precursors on Low-Energy Surfaces

The surface tensions, wetting tensions, contact angles and solid/liquid interfacial tensions of defined siloxanes as well as those of analogous carbosilanes, polysilanes and neopentyl substituted silanes were determined. The wetting experiments were carried out on a glass plate coated with perfluoroalkyl methacrylate (FC 722^®). The siloxanes possess the lowest surface tensions. Due to the presence of oxygen atoms in the siloxane backbone, a donor–acceptor portion (γ^+/−_lv) of the surface tension of about 1–2 mN/m was determined. The solid/liquid interfacial tension also contains a donor–acceptor portion (γ^+/−_sl). Its value is almost identical to that of γ^+/−_lv. The γ^+/−_sl differences between individual molecules of the same surface tension are responsible for contact angle differences of up to 4°. © 1997 John Wiley & Sons, Ltd.     

Temperature and molecular weight dependence of interfacial tension between immiscible polymer pairs by the square gradient theory combined with the Flory–Orwoll–Vrij equation-of-state theory

Interfacial tension between immiscible polymer pairs was predicted by using a square gradient theory in conjunction with the Flory–Orwoll–Vrij equation-of-state expression for the free energy of mixing. The contact interaction parameter was determined by fitting the equation-of-state theory to experimental cloud points taken from the literature, and the square gradient coefficient was estimated from the relation derived from a scattering function. The modified square gradient theory could successfully predict both the magnitude and temperature dependence of interfacial tension between polystyrene and poly(methyl methacrylate), although no adjustable parameters were used in calculating interfacial tension. The molecular weight dependence of interfacial tension was also successfully predicted. The contribution of free volume on interfacial tension is analyzed for two systems: polystyrene/poly(methyl methacrylate) and polystyrene/poly(dimethyl siloxane) blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2683–2689, 1998     

Mechanical and flame‐retardant properties of biodegradable polylactide composites with hyperbranched silicon‐containing polymer

A hyperbranched polymer (HBP‐B2) containing siloxane chains was synthesized via bulk polymerization of diepoxide with a primary amine in the presence of monoepoxide. The weight‐average molecular weight of the prepared polymers was approximately 9200. Composites of polylactide (PLA) with aluminum trihydroxide (ATH) and the HBP‐B2 were prepared via direct melt compounding using a brabender. The test results showed that the LOI could be raised to 34% for the PLA composite with 25 wt% ATH and 5% HBP‐B2. The surface thermal profile of the composite during UL94 V test was further captured by an infrared camera, which was helpful to understand the flame‐retardant properties of the different samples. A V‐0 rating could be achieved by adding ATH and HBP‐B2 to the PLA matrix. Incorporation of HBP‐B2 as a plasticizer could increase the impact strength of a PLA blend or composite. For example, an addition of 10 wt% of HBP and 20 wt% ATH increased the elongation at break from 5% for neat PLA to 155% for the PLA composite.