The oxypolymerization reaction of perfluoro olefins is one of the industrial routes for the synthesis of perfluoropolyethers (PFPEs). The distinctive feature of this radically initiated process is that one obtains peroxidic perfluoropolyethers from the oxypolymerization reaction. In the particular case of tetrafluoroethylene (TFE), due to the high reactivity of the olefin, it is possible to obtain peroxidic polymers with variable amounts of peroxide units. It is, therefore of great interest to know in detail the micro structure of this peroxidic polymer with 19F and 13C NMR spectroscopy by far the most suitable techniques for the analysis. A recent investigation on samples with variable peroxide content using a 400 MHz instrument allowed a significant improvement in the analysis of the peroxidic sequences. The results have been discussed in terms of reaction mechanism and kinetics. 相似文献
The oxypolymerization reaction of perfluoro olefins is one of the industrial routes for the synthesis of perfluoropolyethers (PFPEs). The distinctive feature of this radically initiated process is that one obtains peroxidic perfluoropolyethers from the oxypolymerization reaction. In the particular case of tetrafluoroethylene (TFE), due to the high reactivity of the olefin, it is possible to obtain peroxidic polymers with variable amounts of peroxide units. It is, therefore of great interest to know in detail the micro structure of this peroxidic polymer with 19F and 13C NMR spectroscopy by far the most suitable techniques for the analysis. A recent investigation on samples with variable peroxide content using a 400 MHz instrument allowed a significant improvement in the analysis of the peroxidic sequences. The results have been discussed in terms of reaction mechanism and kinetics. 相似文献
A new technological platform, based on the chemistry of the peroxidic perfluoropolyethers, has been recently developed for the synthesis of innovative fluorinated materials. Perfluoropolyether–tetrafluorethylene (PFPE–TFE) copolymers are one of the most representative examples of the potential and the flexibility of this technology. By tuning the reaction parameters, the structure of these copolymers can be easily modulated to obtain products with the desired chemical–physical and rheological properties. Applications are endless, from thin film lubrication to gel based greases, to additives for plastics, rubber and other compounds. This technology will lead to entirely new classes of PFPE materials that will fill many of the gaps existing today in markets not currently served by PFPEs. 相似文献
We have synthesized new poly(arylene ether sulfone) (PAES) and polydimethylsiloxane (PDMS) segmented block copolymers where the PAES segments contain 20–30% of 4,4′-dihydroxyterphenol (DHTP) and 70–80% of bisphenol A (BA) units. The tensile and thermal properties of these new polymeric materials were measured and were compared to those of existing bisphenol A PAES–PDMS segmented block copolymers (BA PAES-b-PDMS). Also, a high molecular weight BA–DHTP PAES random copolymer containing 80% BA and 20% DHTP was prepared and its properties were compared to Udel®, a commercial PAES based on BA. The BA–DHTP PAES random copolymer had a significantly higher modulus, 1800 MPa and a higher Tg, 196 °C when compared to Udel®. In the segmented block copolymer materials, increased modulus and tensile strain at break (elongation) were also found when DHTP was incorporated into the PAES segments. 相似文献
Perfluoropolyethers (PFPEs) are a class of high performance materials used in a wide range of applications (refrigeration, lubrication, semiconductor industry, etc.). PFPEs containing peroxidic units are intermediate materials for the preparation of commercial end products. In this work we study the spectroscopic properties of ether and peroxides linkages in this class of compounds; nuclear magnetic resonance (NMR) spectra are discussed, FT-Raman data presented. Quantum chemical calculations on model molecules were used as a tool for the interpretation of the Raman experimental data and physical-chemical properties. 相似文献
An experimental and theoretical study has been used to investigate gas diffusion and solubility in PEBAX®2533 block copolymer membrane. Molecular simulations using COMPASS force field have been successful in predicting the gas-transport properties of a PEBAX®2533 block copolymer and of a pure PTMO homopolymer. Gusev–Suter transition state theory (TST) and Monte Carlo methods are used for simulating the transport of five permanent gases (He, H2, N2, O2, CO2 and CH4). Theoretical and experimental data have been compared. 相似文献
The block copolymers of chitosan with D,L-lactide are synthesized under UV irradiation of the homogeneous solution of the corresponding homopolymers with the yield of the main product being 96 wt %. The polyblock structure of copolymer chains, in which the size of polylactide blocks is varied in the range of (2.9–22.0) × 103 depending on the synthesis conditions, is demonstrated. The incorporation of polylactide blocks into the structure of chitosan leads to development of the material structure close to the structure of polylactide. The films of the block copolymers containing 16 wt % polylactide and having a molecular mass of its blocks of 22.0 × 103 have increased values of breaking stress (47 MPa) and ultimate strain (20%) compared to chitosan (24 MPa and 1.9%, respectively). The obtained block copolymers possess bactericidal properties. 相似文献
Poly(butylene/diethylene succinate) block copolymers (PBSPDGS), prepared by reactive blending of the parent homopolymers (PBS and PDGS) in the presence of Ti(OBu)4, were analyzed by 1H-NMR, TGA and DSC, in order to investigate the effects of the transesterification reactions on the molecular structure and thermal properties. 1H-NMR analysis evidenced the formation of copolymers whose degree of randomness increases with the mixing time. The thermal analysis of the melt-quenched samples showed that the melting peak, due to the crystalline phase of PBS, tends to disappear with increasing mixing time and therefore with decreasing the block length in the copolymers. As concern miscibility, a single homogeneous amorphous phase always occurred, independently on block length. Nevertheless, a phase separation, due to the tendency of the PBS blocks to crystallize, was evidenced in the copolymers with long butylene succinate sequences. The results obtained indicated that the block size had a fundamental role in determining the crystallizability and, therefore, phase behavior of the block copolymers. 相似文献
In this study, synthesis of poly(epichlorohydrin-g-methyl methacrylate) graft copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization was reported. For this purpose, epichlorohydrin was polymerized by using HNO3 via cationic ring-opening mechanism. A RAFT macroinitiator (macro-RAFT agent) was obtained by the reaction of potassium ethyl xanthogenate and polyepichlorohydrin. The graft copolymers were synthesized using macro-RAFT agent as initiator and methyl methacrylate as monomer. The synthesis of graft copolymers was conducted by changing the time of polymerization and the amount of monomer-initiator concentration that affect the RAFT polymerization. The effects of these parameters on polymerization were evaluated via various analyses. The characterization of the products was determined using 1H-nuclear magnetic resonance (1H-NMR), Fourier-transform infrared spectroscopy, gel-permeation chromatography, thermogravimetric analysis, elemental analysis, and fractional precipitation techniques. The block lengths of the graft copolymers were calculated by using 1H-NMR spectrum. It was observed that the block length could be altered by varying the monomer and initiator concentrations. 相似文献
A practical synthesis of cinacalcet (Sensipar®, Mimpara®) is described. The synthesis starts from readily available starting materials and relies on safe and practical reaction conditions. The sequence comprises three synthetic steps and only one isolation point. The overall yield for the sequence is 85%. 相似文献
Summary: The free‐radical addition of ω‐functional mercaptans to the vinyl double bonds of 1,2‐polybutadiene‐block‐poly(ethylene oxide) copolymers was used for modular synthesis of well‐defined functional block copolymers. The modification reaction proceeds smoothly and yields quantitatively functionalized block copolymers (1H NMR and FT‐IR spectroscopy) without disturbing the molecular‐weight distribution of the parent copolymer (PDI < 1.09, size exclusion chromatography).
The modular synthetic pathway towards the functional block copolymers reported here. 相似文献
The thermogravimetric analysis (TG) of two series
of tri-block copolymers based on poly(L,L-lactide) (PLLA) and poly(ethyleneglycol) (PEG)
segments, having molar mass of 4000 or 600 g mol–1,
respectively, is reported. The prepared block copolymers presented wide range
of molecular masses (800 to 47500 g mol–1)
and compositions (16 to 80 mass% PEG). The thermal stability increased with
the PLLA and/or PEG segment size and the tri-block copolymers prepared from
PEG 4000 started to decompose at higher temperatures compared to those copolymers
from PEG 600. The copolymers compositions were determined by thermogravimetric
analysis and the results were compared to other traditional quantitative spectroscopic
methods, hydrogen nuclear magnetic resonance spectrometry (1HNMR)
and Fourier transform infrared spectrometry (FTIR). The PEG 4000 copolymer
compositions calculated by TG and by 1HNMR, presented
differences of 1%, demonstrating feasibility of using thermogravimetric analysis
for quantitative purposes. 相似文献
Understanding processes resulting in heterogeneous degradation in polymers is of extreme importance for improving their stabilization and minimizing negative impact of photooxidation on the material properties. We adopted modern physical techniques for studies of spatial distribution of intermediates and products of photodegradation during accelerated ageing of four commodity polymers, polypropylene (PP), polyethylene (PE), polystyrene (PS) and poly(ethylene-co-norbornene) (Topas®, TP) stabilized with hindered amine stabilizer (HAS). Concentration profiles of nitroxides inside polymer plaques along the direction perpendicular to their surface were determined by electron spin resonance imaging (ESRI) as a function of the duration of the accelerated photooxidation. We present data characterizing stabilization activity of three alkoxyamine derivatives of HAS (Tinuvin® NOR 123, Tinuvin® NOR 371, Flamestab® NOR 116), Chimasorb® 119 structurally similar to Flamestab® NOR 116, and nitroxide-based HAS Dastib® 1045 and compare them with the data characterizing stabilization activity of the secondary HAS (>NH) Tinuvin® 770. ESRI data are complemented by ATR FTIR spectroscopic detection of oxidation products on the surface and inside the plaques and by data characterizing diffusive optical transmittance of the polymer plaques in the spectral region 280-400 nm (terrestrial range of the solar UV radiation). 相似文献
This paper describes the synthesis and properties of oligomer chains derived from 2-oxazolines. First, poly(styrene-g-N-acetyl-ethylenimine) was prepared, and its hydrolysis gave poly(styrene-g-ethylenimine) which showed good chelating properties. Secondly, ABA type triblock copolymers were prepared in which an N-acylethylenimine chain is used as A block and ethylene oxide chain is employed as B block. These triblock copolymers showed good compatibility with Nylon 6, which were shown to posecess effective anti-electrostatic properties for Nylon 6. Thirdly, AB type block copolymers from 2-oxazolines have been prepared by using living polymerization technique. These block copolymers are soluble in water and showed good surfactant nature as reflected by surface tension (γ), when A block is consisted from N-acetyl- or N-propionylethylenimine chain (hydro-philic) and B block is made of N-tridecanoyl or N-aroylethylenimine chain (lipophilic). Finally, graft copolymers of cellulose diacetate having N-acetylethylenimine chain were prepared. It has been found by using a rheovibron that these graft copolymers are compatible with poly(vinyl chloride). 相似文献
A general thermodynamic equation for the swelling of a cross-linked polymer system in the vapour of a swelling agent has been derived under isothermal and isobaric conditions. The equation is used to describe the equilibrium uptake of water by elastomers Arnitel® (DSM), which are hard-soft-segment block copolymers in which the hard segments poly(butylene terephthalate) crystallise and are responsible for a physical cross-linking. The gravimetrically determined degrees of swelling of different elastomers in water vapour of various partial pressures are analysed and discussed by the application of an extended semi-empirical swelling equation of Flory-Huggins-Staverman-van Santen. 相似文献
Experimental data, which includes catalyst lifetimes, thermal analyses, fractionation by urea complexation, x-ray diffraction, and 13C-NMR spectroscopy, are presented to confirm the successful synthesis of ABA propylene-ethylene block copolymers. A dry catalyst system of DEAC-TiCl3(AA) and a gas-phase polymerization technique was used to prepare the copolymers. PRP-and ERE-type copolymers (P-isotactic polypropylene, E-polyethylene, and R-random propylene-ethylene copolymer block) were prepared. Some preliminary physical property data are given which indicate that PRP-type copolymers can behave as elastomeric fibers. The stress-strain behavior also indicates block copolymer formation. 相似文献