Cheng-Mei Liu

1D nano- and microbelts self-assembled from the organic-inorganic hybrid molecules: oxadiazole-containing cyclotriphosphazene.

A new oxadiazole-containing cyclotriphosphazene, namely, hexakis-(4-(5-phenyl-1,3,4-oxazodiazol-2-yl)-phenoxy)-cyclotriphosphazene (HPCP) was synthesized. Single-crystal nano- and microbelts of HPCP were self-assembly via two simple solution methods. The shapes of the as-prepared nano- and microstructures can be readily controlled by varying the solvent and aging time in the self-assembly process. A growth mechanism was proposed for the formation of the 1D morphological structures. Crystal structure analysis demonstrated that the overlap between the aryl units attached to the cyclotriphosphazene backbone forms effective intermolecular π-π linking for crystal growth. Electronic and optical properties of the as-prepared nano- and microstructures are investigated.

Phosphorus-containing polymers from tetrakis-(hydroxymethyl)phosphonium sulfate III. A new hydrolysis-resistant tris(allyloxymethyl)phosphine oxide and its thiol-ene reaction under ultraviolet irradiation

Two kinds of new phosphorus-containing crosslinked polymer materials were prepared via thiol-ene photopolymerization and their properties were studied. In order to prepare these crosslinked polymer materials, multifunctional monomer tris(allyloxymethyl)phosphine oxide (TAOPO) was synthesized from an eco-friendly raw material, tetrakis(hydroxymethyl) phosphonium sulfate (THPS). Crosslinked poly(phosphine oxide) networks were then produced by a thiol-ene reaction in which TAOPO reacts with the two kinds of polythiol under ultraviolet (UV) irradiation. The new crosslinked polymers possess long-term hydrolysis-resistance property because the monomer TAOPO contains a phosphorus–carbon bond. The crosslinked polymers have a high gel content, high dielectric constant, low dielectric loss, and excellent transparency with a high refractive index and high Abbe number. DMA and TGA results indicated that all cured poly(phosphine oxide) were uniform networks and exhibited a high thermal stability.

A New Polymer Containing α-Aminophosphonate Unit Used as Reactive, Halogen-Free Flame Retardant for Epoxy Resins

Abstract A new polymer containing α-aminophosphonate unit (PAP) was synthesized through a simple and solvent-free Kabachnik–Fields reaction, and was characterized by NMR, FTIR, and gel permeation chromatography (GPC). This polymer was used as a novel reactive, halogen-free flame retardant. The curing behavior of bisphenol A type epoxy resin with PAP was investigated by differential scanning calorimetry (DSC), and the glass transition temperatures (Tg) of the cured sample were determined by dynamic mechanical analysis. Flammability and thermal stability of the cured epoxy resins with different contents of PAP were investigated by UL-94 test and thermogravimetric analysis (TGA). The results of UL-94 test and TGA show that PAP could improve the flame retardancy and thermal stability of cured epoxy resins. As the content of PAP was more than 20% in weight, the flame retardancy of epoxy resin can pass V-0 rating. GRAPHICAL ABSTRACT

Synthesis of Cyclotriphosphazenes Containing Cyanostilbenes with Different Terminal Substituents

Abstract The synthesis and mesomorphic properties of a class of cyclotriphosphazenes containing cyanostilbene groups with different terminal substituents (-H, -CH3, -OCH3, -CN) are described. All the resulting compounds are characterized by 1 H, 13 C, and 31P NMR, matrix-assisted laser desorption/ionization time of flight, and elemental analysis. The thermal behaviors of cyclotriphosphazene derivatives are studied by the means of differential scanning calorimetry and polarizing optical microscopy. Nematic phases are observed in cyclotriphosphazenes with terminal substituents (-CH3, -OCH3, -CN). GRAPHICAL ABSTRACT

Phosphorus-containing polymers from THPS. VII. Synthesis of phosphorus-containing trialkynes and their metal-free 1,3-dipolar cycloaddition reaction with azidated soybean-oil

A novel hydrolysis-resistant trialkyne, namely tris(prop-2-yn-1-yloxy methyl)phosphane oxide (TPOPO) was prepared from an environmentally friendly tetrakis(hydroxymethyl)phosphonium sulfate (THPS). The chemical structure of TPOPO was characterized by FT-IR, NMR (1H, 13C, 31P) and MS. The TPOPO underwent metal-free and solvent-free 1,3-dipolar cycloaddition reaction with azidated soybean oil (AzSBO) at different alkyne/azide molar ratios. The gel contents of the cured polymers were higher than 95% and the char yields of polymers at 850 °C were over 16.4%. DMA analysis showed that the glass transition temperatures were over 45.9 °C. The cured polymers showed high dielectric constant and dielectric loss due to their high polarity.

Organic-Inorganic Hybrid Materials 8: Stability of Poly (Methyl Methacrylate) in Pmma-SiO2 Hybrids

Abstract Poly(methyl methacrylate) modified silica hybrid materials (PMMA-SiO2 hybrids) were prepared by in situ polycondensation of alkoxysilane in the presence of trialkoxysilane-functional poly(methyl methacrylate), The thermal stabilities and apparent activation energies E a for the thermal and thermo-oxidative degradations of these samples were studied by thermo-gravimetric analysis (TGA), The effects of alkoxysilane content and atmosphere on the stability of the PMMA moiety were investigated in this study. The values of E a were evaluated by van Krevelen method.

Dendritic organic–inorganic hybrid polyphenol and branched benzoxazine monomers with low curing temperature

A novel dendritic organic–inorganic hybrid polyphenol (T2) based on cyclotriphosphazene was synthesized by the condensation reaction of T1 and phenol catalysed by phosphotungstic acid. The dendritic polyphenol T2 comprising twelve phenolic hydroxyl groups exhibited excellent solubility in common organic solvents. Three branched benzoxazine monomers with different oxazine ring content were synthesized via Mannich condensation reaction. These branched benzoxazine monomers showed low initial curing temperature. The properties of corresponding polybenzoxazines, such as thermal stabilities, mechanical properties, dielectric properties and gel contents significantly depended on the oxazine ring content of T3. With the increase of the oxazine ring content for T3, these properties could be greatly improved due to their high crosslinking density.

Synthesis and properties of main-chain oligomeric benzoxazine precursor containing cyclotriphosphazene units

A linear oligobenzoxazine precursor with cyclotriphosphazene ring was prepared through the Schiff base route. The resulting polymers showed higher molecular weight and better thermal stability than those from the traditional Mannich polycondensation method. The oligomeric benzoxazine precursor can form a high-quality transparent yellow film; however, it was fragile after being cured. In order to identify the effect of end groups on the cured polymer, an aniline-capped polymer was prepared by the same Schiff base method and then was changed into a benzoxazine end group. The results indicated that the uncapped polymer exhibited higher stability than the capped polymer. This can be ascribed to different chemical structures resulting from different end groups.

In Vitro Degradation Studies of a Novel Unsaturated Polyphosphoester Based Injectable Bone Repair Material

A novel unsaturated polyphosphoester (UPPE) was synthesized for use as an injectable bone repair material.1 From the point of chemical structure, phosphoester bond in this polymer backbone can be cleaved by water and possibly enzymatic digestion under physiological conditions. In this article in vitro degradation property of the unsaturated polyphosphoester based crosslinked composites2 formed by UPPE, crosslink reagent N-vinyl pyrrolidone (NVP) and β-tricalcium phosphate (β-TCP) was investigated. The results indicated that UPPE/NVP/βTCP crosslinked composites were degradable in phosphate buffered saline. The physical parameters (sample mass, mechanical property, etc.) changed dramatically during the initial stages of degradation and changed gradually due to the slow degradation of crosslinked polymer three dimension network after 48 h. UPPE/NVP ratios were seen to have a significant effect on the mechanical properties and mass remaining of the composites throughout 120 days in vitro degradation. Increasing ratio of PPF/NVP resulted in an improvement in the compressive strength and modulus of composites over this time frame. Surface of samples degraded for 120 days exhibited porous morphology, which will benefit the attachment and growth of the osteoblast cell.

Phosphorus-containing polymers from THPS. IV: Synthesis and properties of phosphorus-containing polybenzoxazines as a green route for recycling toxic phosphine (PH3) tail gas

A convenient route to convert the highly toxic phosphine (PH3) tail gas into high-performance polybenzoxazines was first described in this paper. Two aliphatic polyamines, namely tris(aminomethyl)phosphine oxide and bis(aminomethyl)phenylphosphine oxide, were synthesized from tetrakis(hydroxymethyl)phosphonium sulfate (THPS), a green derivative of PH3 tail gas. And then two novel phosphorus-containing benzoxazine monomers, tris(3,4-dihydro-2H-1,3-benzoxazin-3-yl-methyl)phosphine oxide (TBOz) and benzylbis(3,4-dihydro-2H-1,3-benzoxazin-3-yl-methyl) phosphine oxide (BBOz) were prepared by three-steps procedure. FT-IR and DSC technologies were adopted to study the thermal-initiated polymerization behaviors of two benzoxazine monomers. Thermal properties of these crosslinked polymers were studied by TGA and DMA. The results display that the polybenzoxazines (PTBOz and PBBOz) exhibite good thermal stabilities and high glass transition temperatures. The char yield of polybanzoxazine is high as 47% and indiactes that phosphorus-containing polybenzoxazines show high fire-retardancy. The surface free energies of the PTBOz and PBBOz are 37.1 and 40.4mJm-2 by Owens two-liquid method. The dielectric properties of the PTBOz and PBBOz remaine near constant in the experimental frequency range.