Polyphosphazenes are a class of hybrid organic-inorganic macromolecules with high thermo-oxidative stability and good solubility in many solvents. Fluoroalkoxy phosphazene polymers also have high surface hydrophobicity. A method is described to tune this surface property while maintaining the advantageous bulk materials characteristics. The polyphosphazene single-substituent polymer, poly[bis(2,2,2-trifluoroethoxy)phosphazene], with flat film, fiber mat, or bead mat morphology was surface functionalized using an atmospheric plasma treatment with oxygen, nitrogen, methane, or tetrafluoromethane/hydrogen gases. Surface chemistry changes were detected by static water contact angle (WCA) measurements as well as X-ray photon spectroscopy (XPS). It was found that changes in the WCA of as much as 150 degrees occurred, accompanied by shifts in the ratio of elements on the polymer surface as detected by XPS. Overall this plasma technique provides a convenient method for the generation of specific surface characteristics while maintaining the hydrophobicity of the bulk material. 相似文献
In this paper we highlighted the synthesis, characterization, and practical exploitation of different types of polyphosphazenes substituted with fluorinated groups. There are several ways in which fluorine atoms can be inserted into polyphosphazenes, all of which leading to different polymers showing a wide range of characteristics. In general it is true that the insertion of fluorine atoms into phosphazene macromolecules leads to an enhancement of the thermal stability, flame resistance, low-temperature elastomericity, and chemical inertness of the phosphazenes obtained. The contribution of Italian research groups to the preparation and exploitation of organic commercial macromolecules grafted onto fluorinated polyphosphazenes is also reviewed. 相似文献
Abstract In this paper the light-induced grafting reaction of dimethyl maleate, diethyl maleate, dibutyl maleate and diethyl fumarate, onto aryloxysubstituted phosphazene polymers, to form polyphosphazene copolymers containing grafted succinate groups, is investigated by means of IR spectroscopy and the equilibrium swelling technique of polyphosphazene films. The importance of several different experimental factors that can influence the final succinate grafting yields is discussed, i.e. the type and concentration of the polyphosphazenes and of the unsaturated products, reaction time, the absence or presence of molecular oxygen or of the 1-vinyl-2-pyrrolidone monomer, and the concentration of the benzoin ethyl ether photoinitiator. Furthermore, it is shown that the overall efficiency of the lightinduced grafting process is lower than that previously measured for the reaction initiated thermally using peroxide species, and that the photochemical grafting reaction always occurs with no degradation of the phosphazene macromolecules. The possibility of exploiting these new phosphazene substrates in blend technology has been considered. 相似文献
The synthesis of a series of Polybis(arylamino)phosphazenes is described. The polymers usually were prepared by treatment of polydichlorophosphazene in benzene–tetrahydrofuran with arylamines/triethylamine at reflux for 48–144 hr. The polymers, having viscosities of 0.3–1.4dl/g, are essentially free of active chlorine sites, as shown by elemental analysis and their longterm hydrolytic stability. Thermal analysis revealed glass transition temperatures between 53 and 105°C and decomposition temperatures between 243 and 266°C. Analysis by differential scanning calorimetry revealed no first-order endothermic transitions. For comparison with the arylamino polymers, polydiethylaminophenylaminophosphazene, polybis(benzylamino)phosphazene, and polybis(β-phenethylamino)phosphazene were prepared and are described. 相似文献
A new superbase, the cyclic trimeric phosphazene base (CTPB), was prepared with high yield and purity. In the presence of alcohol, the CTPB serves as a highly efficient organocatalyst for ring‐opening polymerization of the “non‐polymerizable” γ‐butyrolactone to offer well‐defined poly(γ‐butyrolactone) with high conversions (up to 98 %) at −60 °C. The produced polymers have high molecular weights (up to 22.9 kg mol−1) and low polydispersity distributions (1.27–1.50). NMR analysis of initiation process and the structural analysis of resulting polymers by MALDI‐TOF suggest a mechanism involving an activating initiator which leads only to linear polymers with BnO/H chain ends. 相似文献
Methods of the preparation of anthracene-containing monomers and polymers have been developed. They are based on the ability of 9-anthryldiazomethane to react with carboxylic groups of macromolecules and unsaturated carboxylic acids, to co-polymerize with diazoalkanes, and to generate 9-anthrylcarbene. These methods are used to obtain: (1) polymers with a low content (< 0.1 mole %) and different arrangement of anthracene groups in macromolecules (i. e., polymers with luminescent marks used to investigate macromolecules by luminescent methods) and (2) polymers with a high content (up to 100%) of anthracene-containing units, (which imparts to polymers specific photophysical and photochemical properties). 相似文献
A new synthetic procedure is described for the preparation of poly(organo)phosphazenes with star‐branched and star dendritic molecular brush type structures, thus describing the first time it has been possible to prepare controlled, highly branched architectures for this type of polymer. Furthermore, as a result of the extremely high‐arm density generated by the phosphazene repeat unit, the second‐generation structures represent quite unique architectures for any type of polymer. Using two relativity straight forward iterative syntheses it is possible to prepare globular highly branched polymers with up to 30 000 functional end groups, while keeping relatively narrow polydispersities (1.2–1.6). Phosphine mediated polymerization of chlorophosphoranimine is first used to prepare three‐arm star polymers. Subsequent substitution with diphenylphosphine moieties gives poly(organo)phosphazenes to function as multifunctional macroinitiators for the growth of a second generation of polyphosphazene arms. Macrosubstitution with Jeffamine oligomers gives a series of large, water soluble branched macromolecules with high‐arm density and hydrodynamic diameters between 10 and 70 nm.
Phosphazene-containing porous materials are of a great interest due to their unique properties, caused by the synergetic presence of nitrogen and phosphorus atoms, and have found applications as adsorbents, basic catalysts, etc. On the other hand, cage-like silsesquioxanes are ideal building blocks for the preparation of covalently-linked porous materials. Here two new phosphazene-functionalized organosilsesquioxane cage-based porous polymers were synthesized successively by a Friedel-Crafts reaction of hexapyrrolylcyclotriphosphazene with octavinylsilsesquioxane in the presence of AlCl3 and CF3SO3H as catalysts. The nature of acid catalysts barely influenced the character of pores due to the interaction of catalysts with basic nitrogen atoms of phosphazene units. The obtained polymers exhibited high efficiency as metal-free catalysts for the Knoevenagel reaction. This work opens new perspectives in the use of porous polymers based on cage-like organosiloxane compounds as basic catalysts for various reactions. 相似文献
When heated above the melting point, a thermodynamic equilibrium mesophase of conformationally disordered crystal type (so-called condis state) has been found in some flexible-chain polymers (not containing mesogenic groups) dispersed in a matrix of another polymer. Typical organic and inorganic polymers such as polyethylene (PE) and poly[bis (2, 2, 2-trifluoroethoxy) phosphazene] (PPh) were taken as main components of the polymer blends under investigation. The most interesting situation is realized if two mesophase polymers are used in the same binary blend. 相似文献
The gaseous products of high temperature pyrolysis (300℃ to 960℃) of aerylonitrile polymers were measured continuously under nitrogen atmosphere by on-line Fourier Transform Infrared Spectroscopic method (FTIR). From the variations of characteristic peaks it was found that the nitrogen of macromolecules evolved were mainly in the form of hydrogen cyanide and ammonia. During the pyrolysis amorphous carbonaceous element was formed, and crosslinked to form network structure. Three kinds of samples were used for comparison. The experimental results show that the gaseous products of volatile small molecules were HCN, NH_3, CH_4, C_2H_6 and cyanide. CO and CO_2 were also formed when copolymers of PAN were thermally pyrolyzed. 相似文献
Ultra-high-pressure liquid chromatography (UHPLC) using columns packed with sub-2 μm particles has great potential for separations of many types of complex samples, including polymers. However, the application of UHPLC for the analysis of polymers meets some fundamental obstacles. Small particles and narrow bore tubing in combination with high pressures generate significant shear and extensional forces in UHPLC systems, which may affect polymer chains. At high stress conditions flexible macromolecules may become extended and eventually the chemical bonds in the molecules can break. Deformation and degradation of macromolecules will affect the peak retention and the peak shape in the chromatogram, which may cause errors in the obtained results (e.g. the calculated molecular-weight distributions). In the present work we explored the limitations of UHPLC for the analysis of polymers. Degradation and deformation of macromolecules were studied by collecting and re-injecting polymer peaks and by off-line two-dimensional liquid chromatography. Polystyrene standards with molecular weight of 4 MDa and larger were found to degrade at UHPLC conditions. However, for most polymers degradation could be avoided by using low linear velocities. No degradation of 3-MDa PS (and smaller) was observed at linear velocities up to 7 mm/s. The column frits were implicated as the main sources of polymer degradation. The extent of degradation was found to depend on the type of the column and on the column history. At high flow rates degradation was observed without a column being installed. We demonstrated that polymer deformation preceded degradation. Stretched polymers eluted from the column in slalom chromatography mode (elution order opposite to that in SEC or HDC). Under certain conditions we observed co-elution of large and small PS molecules though a convolution of slalom chromatography and hydrodynamic chromatography. 相似文献
Linear organic chains and their architectural derivatives such as branched and crosslinked macromolecules have been the main focus of polymer science for many decades. A new direction which should be pursued in the field is the exploration of polymers as “nanostructures”. This exploration would study synthetic polymers as shape invariant objects with nanoscale dimensions which resemble the folded proteins of nature. Such synthetic macromolecules would have well defined shapes which may even include topographical features. Ideally, the definition of shape could include well defined dimensions as well, but molecular objects of common shape but varying dimensions could also exhibit interesting properties. One could for example envision polymers as flat plates (two-dimensional polymers), discs, ellipsoids, spheres with cavities, parallelepipeds, among many other possible shapes. Such objects must have fairly high molar masses, possibly in the range of hundreds to thousands of kilodaltons, and would therefore not be accessible as chemical compounds synthesized by conventional methods. At the same time, the prospects of learning “folding rules” for synthetic chemical sequences in a biomimetic approach to molecular nanostructures seems to be an extremely difficult goal at the present time. This is suggested given our contemporary difficulties in understanding the protein folding problem. 相似文献
The synthesis of novel benzimidazole-2-yl-substited polybenzimidazoles and initial compounds has been described. The polymers are studied by FTIR spectroscopy, TGA, and TMA. The hydrodynamic properties of macromolecules are investigated by translational diffusion and viscometry in 96% H2SO4; the molecular characteristics of the polymers are determined. Positive temperature dependences for intrinsic viscosities of the polymers are obtained. The polymers under study possess high hydrolytic stability with respect to sulfuric acid solutions up to 150°C and high thermal stability in the bulk. The TGA data correlate with the chemical structure of the polymers. The new polybenzimidazoles may be used as materials for the production of medium-temperature proton-conducting membranes. 相似文献