Synthesis of new derivatives of cyclotriphosphazene substituted with the salen side groups

The reaction between hexachlorocyclotriphosphazenes (N₃P3Cl6) and three equivalents of bis-salicylidene ethylene diamine (HOC₆H_su4-CH=N-CH_2-)₂ (salen) was investigated in two different experimental conditions. In the presence of anhydrous Na₂CO₃ in stirring tetrahydrofuran (THF) medium, the reaction led to a 50:50 mixture of tris[bis(salicylidene)ethylenediamine] cyclotriphosphazene, spiro-N₃P₃[(OC₆H₄-CH=N-CH_2-)₂]₃ (1) and ansa (2) fully substituted products, whereas, in toluene solution, N₃P₃Cl₆ with salen (3) and Al₂O₃/KOH afforded the spiro (1), as the only isolable compound. The spectroscopic data revealed that the oxygen atoms of salen moieties were selectively bonded to the three phosphorus atoms of the phosphazene ring. The new derivatives of cyclotriphosphazenes were characterized by IR spectrophotometry ¹H NMR, ³1P NMR spectral data and elemental analysis.     

Surface and interfacial segregation in blends of polystyrene with functional end groups and deuterated polystyrene

The effect of chain-end chemistry on surface and interfacial segregation in symmetric blends of polystyrene (hPS)/deuterated polystyrene (dPS) has been investigated by X-ray photoelectron and secondary ion mass spectroscopy in conjunction with neutron reflectivity measurements. Alpha,omega-fluoroalkyl- and alpha,omega-carboxy-terminated polystyrenes (alpha,omega-hPS(Rf)2 and alpha,omega-hPS(COOH)2) were used as end-functionalized polymers; the former possesses chain ends with lower surface energies, and the latter possesses higher surface energies compared with that of the main chain. In the case of an alpha,omega-hPS(Rf)2/dPS blend film, alpha,omega-hPS(Rf)2 was enriched at the surface owing to the surface localization of the Rf groups, although the surface energy of the hPS segments was slightly higher than that of the dPS ones. On the contrary, in the case of an alpha,omega-hPS(COOH)2/dPS blend film, dPS was preferentially segregated at the surface. This may be due to a surface depletion of COOH ends and an apparent molecular weight increase of alpha,omega-hPS(COOH)2 produced by a hydrogen-bonded intermolecular association of COOH ends in addition to the surface energy difference between hPS and dPS segments. Interestingly, both Rf and COOH chain ends were partitioned to the substrate interface for the alpha,omega-hPS(Rf)2/dPS and alpha,omega-hPS(COOH)2/dPS blend films, resulting in the segregation of the hPS component at the substrate interface for both blends. The results presented imply that surface and interfacial segregation in polymer blends could be regulated by incorporating functional groups into the end portions of one component.     

Synthesis of core-shell type polystyrene monodisperse particles with chloromethyl groups

The synthesis of core-shell type polystyrene monodisperse particles with surface chloromethyl groups was carried out by a two-step emulsion polymerization process at different reaction temperatures. In a first step, the core was synthesized at 90 °C by means of batch emulsion polymerization of styrene (St), and in the second step, the shell was polymerized by batch emulsion copolymerization of St and chloromethylstyrene (CMS) using the seed obtained previously. With the aim of optimizing the production of these core-shell type polystyrene monodisperse particles with surface chloromethyl groups, the reaction temperature in the second step, the purification or not of the functionalized monomer (CMS), the amount and type of the redox initiator system used, and the type of addition of the initiator system to the reactor were studied.     

以苯并杂环为端基的非环多醚化合物的合成

本文合成了8种以2(3H)-苯并恶唑酮和苯并三唑为端基的非环多醚化合物. 它们的组成和结构经元素分析,IR,MS和^1H NMR波谱分析得到证实. 初步反应揭示了这些化合物可与UO~2^2^+ 等离子形成稳定的配合物.     

Modification of the halogen end groups of polystyrene prepared by ATRP

The stabilization modification of the halogen end groups of polystyrene prepared by atom transfer radical polymerization (ATRP) has been attempted. The reaction mechanism adopted is radical chain transfer reaction, and iso-propylbenzene is employed as not only the chain transfer agent but also the solvent. Moreover, Cu⁰ is used as the acceptor of the transformed halogen atom in some experiments. As evidenced by ¹H NMR analysis of the modified products, the halogen end group can really be converted into the much more stable carbon-hydrogen structure. When Cu⁰ is not used, the conversion of the halogen end groups rises rapidly during the early stage and the increase rate slows down after about 8 h reaction. In view of the influence of reaction temperature on the modification, the conversion increases almost exponentially with temperature in the range of 80-100 °C, and the increase rate slows down at higher temperature. ¹H NMR and SEC analyses prove that the modification reaction does not destroy the polymer backbone and the molecular weights remain almost the same as those of the unmodified samples. When Cu⁰ is introduced, the modification reaction proceeds much rapidly, the conversion of the halogen end groups rises almost linearly at the early stage and the nearly complete (>95%) dehalogenation of the polymeric chains is observed after only 12 h reaction. However, the molecular weights rise and the polydispersities become wider after the modification, which implies that the modification is accompanied with the couple termination of the polystyrene radicals besides chain transfer reaction. Furthermore, the couple termination can be restrained at some lower catalyst concentration. Indeed, the modified polymers show improved thermal stability, the initial weight loss temperatures is increased from 196 °C to 378 °C for the linear polystyrene and from 203 °C to 261 °C for the hyperbranched polystyrene.     

Synthesis of well-defined azido and amino end-functionalized polystyrene by atom transfer radical polymerization

Mono and difunctional polystyrenes containing active halogenated end groups were prepared by atom transfer radical polymerization (ATRP). Substitution reactions were explored to convert the halogen termini to azido groups, followed by readuction to form the amino functional polymer. Quantitative conversion of the end groups was observed in each transformation reaction. ¹H NMR demonstrated the formation of the azide from the bromide functionality without elimination. The difunctional α,ω-diaminopolystyrene was reacted with terephthaloyl chloride in a condensation process to produce chain-extended polystyrene containing amide bonds along the polymer backbone.     

Synthesis of carbosilane dendrimers with N,N-dimethylaniline as end groups

Carbosilane dendrimers with 4-bromo-N,N-dimethylaniline as end groups were synthesized from methyltrichlorosilane, allyl chloride, magnesium and 4-bromo-N,N-dimethylaniline. All compounds were characterized by 1H NMR, IR, MS.     

Synthesis of maleimide substituted polystyrene–silica hybrid utilizing michael addition reaction

The transparent polymer hybrids were prepared from polystyrene bearing pendant maleimide moieties (16%) and tetraethoxysilane (TEOS) using γ-aminopropyltriethoxysilane (γ-APS) as a crosslinking agent by an in situ sol–gel process by utilizing Michael-addition reaction. Maleimide substituted polystyrene was synthesized by a mild Friedel-Crafts reaction of polystyrene and N-chloromethylmaleimide. Fourier Transform Infrared (FTIR) spectral data confirms the occurrence of Michael-addition reaction between the pendant maleimide moieties of the styrene copolymer and γ-aminopropyltriethoxysilane. The percentage of maleimide substitution was calculated from ¹H NMR spectrum. The transparent hybrid shows high solvent resistance at the boiling point of Tetrahydrofuran (THF) since the polystyrene-substituted-maleimide (PS-s-MA) was covalently bonded with siloxane matrix. Thermal properties of the transparent hybrid materials were investigated by Differential scanning calorimeter (DSC) and Thermo gravimetric analysis (TGA) in order to ascertain their glass transition temperature (Tg) and thermal stability behaviour. Morphology and transparency of the organic–inorganic hybrids were confirmed by Scanning electron microscopy (SEM) and optical images. The homogeneity of the polymer hybrids was also examined by nitrogen porosimetry studies.     

Synthesis of polymers with hydroxyl end groups by atom transfer radical polymerization

Polymers prepared by atom transfer radical polymerization (ATRP) contain end groups defined by the initiator used. Alkyl halides, used as initiators, lead to polymers with an alkyl group at one end and a halide as the other chain end. Using functionalized initiators such as 2‐hydroxyethyl 2‐bromopropionate, hydroxyl groups can be directly incorporated at one polymer chain end while the other end functionality remains a halogen. The direct displacement of the halogen end groups with hydroxyl groups was unsuccessful due to side reactions such as elimination (for polystyrene) or hydrolysis of ester functions (for polyacrylate). Another approach to generate hydroxyl end groups was based on the substitution of the halogen end groups by ethanolamine. This was successful for polystyrene but additional substitution at the backbone esters was observed in polyacrylates. Multiple substitution reactions could be avoided by using 4‐aminobutanol instead of 2‐aminoethanol. Hydroxyl terminated polyacrylates were also obtained by extending the polyacrylate chain end with one allyl alcohol unit in a one‐pot process by adding an excess of allyl alcohol at the end of e polymerization of acrylate.     

Synthesis of well-defined soluble polystyrene supports: Impact of polymer chain on grafted organotin reagent activity

The synthesis of well-defined soluble polystyrene supports bearing tin hydride functionalities has been achieved in two steps. First, a precursor was prepared by copolymerization of styrene and acetoxystyrene using atom transfer radical polymerization. Prior any modification, this precursor was fully characterized to check its structure. Then in a second part, tin hydride functions were introduced by a four step process. The chemical modification was monitored by IR and ¹H NMR spectroscopies. The soluble support was also characterized by triple detection size exclusion chromatography at each step. Two families of supports were synthesized by varying the molecular weight and the degree of functionalization. The effectiveness of these tin hydride supports was tested through the reduction of 6-bromohexene and compared with the small counterpart Bu₃SnH. Measurements of rate constant for hydrogen transfer were also reported.     

Synthesis of a well-defined cyclic polystyrene via α-carboxyl, ω-amino heterodifunctional polystyrene

Living anionic polymerization of styrene was carried out in benzene at room temperature using 1-(3-lithiopropyl)-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane and 2,2,5,5-tetramethyl-1-(3-bromopropyl)-1-aza-2,5-disilacyclopentane as an initiator and terminator, respectively, to obtain α-2,2-bis(hydroxymethyl)propoxycarbonyl, ω-amino heterodifunctional polystyrene. It was hydrolyzed to α-carboxyl, ω-amino heterodifunctional polystyrene which gave a well-defined cyclic polystyrene by the intramolecular cyclization under high dilution conditions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2027–2033, 1999     

Functionalization of single-walled carbon nanotubes with well-defined polystyrene by "click" coupling

Covalent functionalization of alkyne-decorated SWNTs with well-defined, azide-terminated polystyrene polymers was accomplished by the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition. This reaction was found to be extremely efficient in producing organosoluble polymer-nanotube conjugates, even at relatively low reaction temperatures (60 degrees C) and short reaction times (24 h). The reaction was found to be most effective when a CuI catalyst was employed in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene as an additive. IR spectroscopy was utilized to follow the introduction and consumption of alkyne groups on the SWNTs, and Raman spectroscopy evidenced the conversion of a high proportion of sp(2) carbons to sp(3) hybridization during alkyne introduction. Thermogravimetric analysis indicated that the polymer-functionalized SWNTs consisted of 45% polymer, amounting to approximately one polymer chain for every 200-700 carbons of the nanotubes, depending on polymer molecular weight. Transmission electron microscopy and atomic force microscopy were utilized to image polymer-functionalized SWNTs, showing relatively uniform polymer coatings present on the surface of individual, debundled nanotubes.     

Synthesis and comparative characteristic of organophosphorus dendrimers with phenoxy and deuterophenoxy end groups

Two series of generation 0 to 6 phosphorus dendrimers (6 to 384 end groups) are synthesized starting from the cyclotriphosphazene core. The series are distinguished by the type of their terminal groups: O-C₆H₅ in first series and O-C₆D₅ in the other. These functions are chemically analogous, but they give different spectroscopic signatures which afford detailed information about the structure of these dendrimers.     

Preparation of well-defined polystyrene/silica hybrid nanoparticles by ATRP

Immobilization of the atom transfer radical polymerization (ATRP) macroinitiators at the silica nanoparticle surfaces was achieved through surface modification with excess toluene-2,4-diisocynate (TDI), after which the residual isocyanate groups were converted into ATRP macroinitiators. Structurally well-defined polystyrene chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined, densely grafted outer polystyrene by ATRP, which was initiated by the as-synthesized silica-based macroinitiator. FTIR, NMR and gel permeation chro-matography (GPC) were used to characterize the polystyrene/silica hybrid particles.     

Synthesis and characterization of new cyclotriphosphazene compounds

In the present study, spiro (1a), dispiro (1b, 2, 3), per-substituted spermine-bridged (6–9) and dispiroansa spermine (10) derivatives of cyclotriphosphazene have been synthesized. The structures of the novel compounds (1b, 6–10) have been characterized by elemental analysis, FTIR, mass spectrometry, ¹H and ³¹P NMR spectroscopy. The molecular structures of 1b, 2, 8, and 10 were determined by single crystal X-ray crystallography. In order to investigate the anti-tumour properties of the newly synthesized cyclotriphosphazene derivatives, in vitro cytotoxic activity test (MTT assay) has been performed using HT-29 (human colon adenocarcinoma) and Hep2 (human epidermoid larynx carcinoma) cell lines. The result of the MTT assay showed that while compound 1a has cytotoxic effect on both Hep2 and HT-29 cell lines, compound 3 has only cytotoxic effect towards the Hep 2 cells.     

Oligomeric benzimidazoles with reactive end groups

The condensation of aromatic diamines with aromatic dinitriles and the subsequent conversion of the amidines formed to benzimidazole units has been adapted to the preparation of oligomeric benzimidazoles with nitrile and carboxyl end groups. These are promising new dibasic acids for the preparation of heat-stable condensation polymers.