首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Poly(pyridine ether)s were prepared in two ways: the polycondensation of silylated 1,1,1‐tris(4‐hydroxyphenyl)ethane (THPE) with 2,6‐difluoropyridine (method A) and the polycondensation of free THPE with 2,6‐dichloropyridine (method B). With method A, the THPE/difluoropyridine feed ratio was varied from 1.0:1.0 to 1.0:1.6. Cycles, bicycles, and multicycles were the main reaction products, and crosslinking was never observed. When ideal stoichiometry was used exclusively, multicycles free of functional groups were obtained. These multicycles were detectable in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra up to B38C76 with a mass of approximately 32,000 Da. With method B, the reaction conditions were varied at a fixed feed ratio to achieve an optimum for the preparation of multicyclic polyethers, but because of the lower reactivity of 2,6‐dichloropyridine, a quantitative conversion was not achieved. The reaction products were characterized with MALDI‐TOF mass spectrometry, viscosity measurements, and size exclusion chromatography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5725–5735, 2004  相似文献   

2.
1,1,1‐Tris(4‐trimethylsiloxyphenyl)ethane, (silylated THPE), was polycondensed with 2,4‐difluoroacetophenone and 2,4‐difluorobenzophenone. All polycondensations were performed in N‐methylpyrrolidone with K2CO3 as promotor. The feed ratio THPE/difluoroaromat was varied from 1.0:1.3 to 1.0:1.5. Instead of hyperbranched polymers or gels, soluble multicyclic oligo‐ and polyethers were identified as main reaction products by MALDI‐TOF mass spectrometry in all experiments. At feed ratios around 1.0:1.5 multicycles free of functional group were the main products. However, when isomeric a2‐monomers such as 2,6‐difluoroacetophenone, 2,6‐difluorobenzophenone (or 2,6‐difluorodiphenylsulfone) were used, gelation occurred at feed ratios as low as 1.0:1.1. An explanation of the different cyclization tendencies on the basis of different conformations is discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6233–6246, 2005  相似文献   

3.
Matrix‐assisted laser desorption ionization time of flight mass spectrometry (MALDI‐TOF‐MS) was utilized for the analysis of polymers obtained by the living cationic polymerization of isobutyl vinyl ether (IBVE) with the HCl‐VE adduct/SnCl4/n‐Bu4NCl initiating system in CH2Cl2 at −78 °C. Under optimized analysis conditions, well‐resolved spectra were obtained for samples with number‐average molecular weights of ≤104 with the use of 1,8‐dihydroxy‐9(10H)‐anthracenone (dithranol) as a matrix and sodium trifluoroacetate as an added salt. The MS spectra showed only one series of peaks separated exactly by the mass of the IBVE. The observed mass of each peak was in good agreement with the theoretical one, which possesses one initiator fragment at the α end and one methoxy group originated from quenching with methanol at the ω end. Thus, detailed end group analysis is possible for poly(VE). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4023–4031, 2000  相似文献   

4.
Isosorbide, succinyl chloride and isophthaloyl chloride are polycondensed under various reaction conditions. The heating in bulk with or without catalysts as well in an aromatic solvent without catalyst, and polycondensation with the addition of pyridine only yield low molar mass copolyesters. However, heating in chlorobenzene with addition of SnCl2 or ZnCl2 produces satisfactory molar masses. The number average molecular weights (Mn) of most copolyesters fall into the range of 7000–15,000 Da with polydispersities (PD) in the range of 3–9. The MALDI‐TOF mass spectra almost exclusively displayed peaks of cyclics indicating that the chain growth was mainly limited by cyclization and not by side reactions, stoichiometric imbalance or incomplete conversion. The glass‐transition temperatures increased with the content of isophthalic acid from 75 to 180 °C and the thermo‐stabilities also followed this trend. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2464–2471  相似文献   

5.
Oligomer samples obtained by the anionic copolymerization of a bis(γ‐lactone), 2,8‐dioxa‐1‐methylbicyclo[3.3.0]octane‐3,7‐dione ( 1 ), and glycidyl phenyl ether with potassium tert‐butoxide have been analyzed by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. The MALDI‐TOF mass spectra of these cooligomers show well‐resolved signals that can be reliably assigned to linear, alternating cooligomers that have carboxylate chain ends or alkoxide chain ends and cyclic ones. The formation of these three series of cooligomers suggests that the polymerization process involves concomitant intermolecular transesterification and intramolecular back‐biting. The intramolecular back‐biting reaction causes the formation of cyclic cooligomers, whereas the intermolecular transesterification causes the reduction of the molecular weight and the transformation of the alkoxide active chain end into a carboxylate chain end. The MALDI‐TOF mass spectrometry study has shown that an excess of monomer 1 enhances the selectivity of propagation by increasing the probability of the attack of the alkoxide chain end to 1 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2643–2649, 2005  相似文献   

6.
3‐Ethyl‐3‐hydroxymethyloxetane (EOX) polymerizes readily to branched multihydroxyl polyethers. Molecular weights of the polymers are, however, limited, and macromolecules are predominantly cyclic. This indicates that intramolecular chain transfer to polymer (back‐biting) proceeds in the system. Repeating units in poly‐EOX contain two nucleophilic sites that may participate in back‐biting, namely ether groups and hydroxyl groups. Analysis of matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra of poly‐EOX prepared in the presence of analogous polyether that does not contain HO? groups (poly(3,3‐dimethyloxetane)‐poly‐DMOX) shows that the ether group in the repeating unit of poly‐DMOX does not participate in chain transfer to the polymer. However, when DMOX was polymerized in the presence of poly‐EOX, clear evidence of participation of HO? groups in intramolecular chain transfer was obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 245–252, 2004  相似文献   

7.
Living cationic polymerization of a vinyl ether with a naphthyl group [2‐(2‐naphthoxy)ethyl vinyl ether, βNpOVE] was achieved using base‐assisting initiating systems with a Lewis acid. The Et1.5AlCl1.5/1,4‐dioxane or ethyl acetate system induced the living cationic polymerization of βNpOVE in toluene at 0 °C. The living nature of this reaction was confirmed by a monomer addition experiment, followed by 1H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) analyses. In contrast, the polymerization of αNpOVE was not fully controlled; under similar conditions, it produced polymers with broad molecular weight distributions. The 1H NMR and MALDI‐TOF‐MS spectra of the resultant poly(αNpOVE) revealed that the products had undesirable structures derived from Friedel–Crafts alkylation. The higher reactivity of αNpOVE in electrophilic substitution reactions, such as the Friedel–Crafts reaction, was attributable to the greater electron density of the naphthyl ring, which was calculated based on frontier orbital theory. The naphthyl groups significantly affected the properties of the resultant polymer. For example, the glass transition temperatures (Tg) of poly(NpOVE)s are higher by approximately 40 °C than that of poly(2‐phenoxyethyl vinyl ether). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

8.
Bisphenol A was polycondensed with 2,6‐dichlorobenzonitrile, 2,6‐difluorobenzonitrile, 2,4‐difluorobenzonitrile, and 3,5‐difluorobenzonitrile in sulfolane. With 2,6‐and 2,4‐difluorobenzonitrile, quantitative conversions were achieved, and matrix‐assisted laser desorption/time‐of‐flight mass spectra revealed a nearly quantitative formation of cyclic oligoethers and polyethers. Furthermore, O,O′‐bistrimethylsilyl bisphenol A was polycondensed with the aforementioned dihalobenzonitriles in dry N‐methylpyrrolidone (promoted by potassium carbonate). Both the temperature and time were optimized. Only with 2,6‐difluorobenzonitrile were nearly quantitative conversions achieved, and this resulted in high molecular weights and high cycle contents. Size exclusion chromatography elution curves exhibited a tendency toward a bimodal character when larger fractions of cycles were present. Calibration with polystyrene standards indicated number‐average molecular weights of up to 105 Da and weight‐average molecular weights of up to 2.3 × 105 Da. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3838–3846, 2003  相似文献   

9.
New aromatic diamines were prepared in two steps from 4,5‐dichlorophthalic anhydride and primary amines. The resulting 4,5‐dichlorophthalimide was reacted with 4‐mercaptoaniline, so that the chloroatoms were substituted by the mercapto groups (via the sulfide anions). The new diamines were polycondensed either with the diphenyl ether 3,3′,4,4′‐tetracarboxylic anhydride or with bicyclooctane tetracarboxylic anhydride. These polycondensations were conducted in boiling m‐cresol with azeotropic removal of water. The isolated polyimides were characterized by viscosity measurement, IR‐spectroscopy, elemental analyses, and MALDI‐TOF mass spectrometry. The mass spectra evidenced a high content of cyclic polyimides, indicating nearly perfect reaction conditions. The mass spectra also proved the formation of copolymers containing one diamine with a trialkylamine group in the side chain. High glass transition temperatures but a low crystallization tendency were found by DSC measurements. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6272–6281, 2005  相似文献   

10.
Molecular weights of seven poly(phenylene ethynylene)‐based water‐soluble conjugated polyelectrolytes (CPEs) obtained through Sonogashira coupling are determined by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). A standard sample preparation protocol is developed to characterize the seven CPEs using 2,5‐dihydroxybenzoic acid as the matrix (M) and AgTFA as the cationization reagent (CR). High‐quality MALDI mass spectra are obtained at volume mixing ratios (CPE/M/CR) of 5/5/1 for anionic polymers (P1–P4) and 5/50/1 for cationic polymers (P5–P7). Molecular weight, molecular weight distribution, and end‐group information are analyzed. The effects of molecular weight of CPEs on optical and quenching properties are also studied. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2537–2543  相似文献   

11.
Dicyanotetrafluorobenzene was polycondensed with bisphenol‐P, bisphenol‐M, or 1,4‐bis(4‐hydroxyphenoxy)butane in DMF. Either K2CO3 and ethyldiisopropylamine (EDPA) or tetramethyl piperidine (TMPD) was used as catalysts and HF acceptors. Regardless of base and concentration, all polycondensations of bisphenol‐P or 1,4‐bis(4‐hydroxyphenoxy)butane yielded more or less crosslinked polyethers. In the case of bisphenol‐M, all polycondensations conducted with K2CO3 and 0.4, 0.2, or 0.1 M monomer concentrations resulted again in gelation. Gels were also obtained when polycondensations of 0.4 M monomer solutions were catalyzed with EDPA or TMPD. Yet, at a concentration of 0.2 M, the amines yielded completely soluble polyethers, which were characterized by elemental analyses, inherent viscosities, MALDI‐TOF mass spectrometry, and DSC measurements. The mass spectra revealed that the soluble polyethers mainly consisted of cycles containing two C? F bonds per repeat unit. Nearly quantitative substitution of the C? F groups with 4‐chlorothiophenol, 4‐bromophenol, 4‐aminophenol, and 4‐phenyl azophenol proved successful, so that a broad variety of multifunctional polyethers was obtained, but in the case of 4‐chloro thiophenol cleavage of the polyether chain also occurred. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 543–551, 2008  相似文献   

12.
The polycondensation of potassium 5‐cyano‐4‐fluoro‐2‐octylphenolate ( 1b ) was carried out in the presence of 4‐fluoro‐4′‐trifluoromethylbenzophenone ( 2 ) as an initiator for chain‐growth polycondensation in a variety of solvents, and the chain‐growth nature of this polymerization was found to depend on the kind of solvent. In the polycondensation of 1b with 2 in sulfolane at 150 °C, the MALDI‐TOF mass spectra of poly 1b showed only one series of peaks due to poly 1b attached with the initiator 2 unit, and the 19F NMR spectra indicated that the ratios of the initiator unit to the end group were 1.0. Therefore, chain‐growth polycondensation occured in this condition. On the other hand, the polycondensation in THF, quinoline, DMI, tetraglyme at 150 °C gave poly 1b with broad molecular weight distributions, and the MALDI‐TOF mass spectra showed two series of peaks resulting from both chain‐growth and step‐growth polycondensations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1198–1207, 2004  相似文献   

13.
Linear–hyperbranched hybrid poly(butylene adipate) (HPBA) copolymers were synthesized through a branching reaction between the linear tailored prepolymer terminated with methyl ester groups and different mol percents of the 1,1,1‐tris(hydroxymethyl) propane (TMP) as branching agent, using the titanium(IV) isopropoxide as catalyst, at 180 °C under vacuum for different times. All samples were characterized by NMR and matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF MS). In particular, MALDI‐TOF mass spectra of the unfractionated and size exclusion chromatography (SEC)‐fractionated hyperbranched (HB) samples gave information on their composition, on the end groups as well as on the TMP units present in each family of HB macromolecules. HB chains containing cyclic branches and ether bonds formed by intermolecular transesterification and intramolecular and intermolecular transetherification side reactions, respectively, were also revealed by MALDI‐TOF MS analysis. All samples were also investigated by SEC. The average molar masses (MMs) evaluated by SEC calibrated with the polystyrene (PS) narrow standards were overestimated with respect to those calculated by the SEC/MALDI‐TOF MS self‐ calibration method, which gave reliable values. Moreover, it also showed that the hydrodynamic volume of the HPBA polymers was higher than that of the linear PSs with similar MMs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

14.
The synthesis of low‐molecular‐weight (weight‐average molecular weight < 45,000 g/mol) lactic acid polymers through the dehydropolycondensation of L ‐lactic acid was investigated. Polymerizations were carried out in solution with solvents (xylene, mesitylene, and decalin), without a solvent using different Lewis acid catalysts (tetraphenyl tin and tetra‐n‐butyldichlorodistannoxane), and at three different polymerization temperatures (143, 165, and 190 °C). The products were characterized with differential scanning calorimetry, size exclusion chromatography, vapor pressure osmometry, 13C NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF). The resulting polymers contained less than 1 mol % lactide, as shown by NMR. The number‐average molecular weights were calculated from the ratio of the area peaks of ester carbonyl and carboxylic acid end groups via 13C NMR. The stereosequences were analyzed by 13C NMR spectroscopy on the basis of triad effects. Tetraphenyl tin was an effective transesterification catalyst, and the randomization of the stereosequence at 190 °C was observed. In contrast, the distannoxane catalyst caused comparatively less transesterification reaction, and the randomization of the stereosequences was slow even at 190 °C. The L ‐lactic acid and D ‐lactic acid isomers were added to the polymer chain in a small, blocky fashion. The MALDI‐TOF spectra of poly(L ‐lactic acid) (PLA) chains doped with Na+ and K+ cations showed that the PLA chains had the expected end groups. The MALDI‐TOF analysis also enabled the simultaneous detection of the cyclic oligomers of PLA present in these samples, and this led to the full structural characterization of the molecular species in PLA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2164–2177, 2005  相似文献   

15.
Functionalizations of poly(styryl)lithium (PSLi), poly(butadienyl)lithium (PBDLi), and poly(isoprenyl)lithium (PILi) with formaldehyde were investigated in benzene solutions at room temperature. Dimer and unfunctionalized products, in addition to the expected products, were found in the PSLi functionalization with formaldehyde. The byproducts were analyzed by 1H NMR, 13C NMR, size exclusion chromatography (SEC), and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) and showed evidence for Cannizzaro reactions and electron‐transfer reactions. A molecular weight dependence of the dimer formation was found for PSLi functionalizations for number‐average molecular weights of less than 20,000; the dimer formation decreased as the molecular weight increased. Changing the reaction conditions did not eliminate dimer formation in the PSLi functionalization. The reactions of PBDLi and PILi with formaldehyde effected quantitative functionalizations, as determined by SEC, 1H NMR, 13C NMR, MALDI‐TOF MS, quantitative column chromatography, and end‐group titration. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2435–2453, 2003  相似文献   

16.
Bisphenol M was subjected to interfacial polycondensations in an NaOH/CH2Cl2 system with triethylamine as a catalyst. Regardless of the catalyst concentration, similar molecular weights were obtained, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra exclusively displayed mass peaks of cycles (detectable up to 15,000 Da). With triethyl benzyl ammonium chloride as a catalyst, linear chains became the main products, but the contents of the cycles and the molecular weights strongly increased with higher catalyst/bisphenol ratios. When the pseudo‐high‐dilution method was applied, both diphosgene and triphosgene yielded cyclic polycarbonates of low or moderate molecular weights. Size exclusion chromatography measurements, evaluated with the triple‐detection method, yielded bimodal mass distribution curves with polydispersities of 5–12. Furthermore, a Mark–Houwink equation was elaborated, and it indicated that the hydrodynamic volume of poly(bisphenol M carbonate) was quite similar to that of poly(bisphenol A carbonate)s with similar concentrations of cyclic species. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1248–1254, 2005  相似文献   

17.
A two‐step route to an AB2 monomer that underwent polymerization via nucleophilic aromatic substitution to afford hyperbranched poly(arylene ether sulfone)s (HB PAES) was developed. The synthesis of 3,5‐difluoro‐4′‐hydroxydiphenyl sulfone ( 4 ) was accomplished by the reaction of 3,5‐difluorophenylmagnesium bromide with 4‐methoxyphenylsulfonyl chloride, followed by deprotection of the phenol group with HBr in acetic acid. The polymerization of 4 in the presence of 3,4,5‐trifluorophenylsulfonyl benzene or tris(3,4,5‐trifluorophenyl)phosphine oxide as a core molecule afforded HB PAES with number‐average molecular weights ranging from 3400 to 8400 Da and polydispersity index values ranging from 1.5 to 4.8. The presence of cyclic oligomeric species, formed by an intramolecular cyclization process, was a contributing factor to the relatively low molecular weights. The degree of branching (DB) of the HB PAES samples was estimated by a comparison of the 19F NMR spectra of the polymer samples with those of a series of model compounds, and DB values ranging from 0.51 to 0.70 were determined. The glass‐transition temperatures for the HB PAES samples were in the range of 205–222 °C, as determined by differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3178–3187, 2005  相似文献   

18.
Effective cationic addition polymerization of 1,4‐dioxene, a six‐membered cyclic olefin with two oxygen atoms adjacent to the double bond, was performed using a simple metal halide catalyst system in dichloromethane. The polymerization was controlled when the reaction was conducted using GaCl3 in conjunction with an isobutyl vinyl ether–HCl adduct as a cationogen at –78°C to give polymers with predetermined molecular weights and relatively narrow molecular weight distributions. The long‐lived properties of the propagating species were further confirmed by a monomer addition experiment and the analyses of the product polymers by 1H NMR and MALDI–TOF–MS. Although highly clean propagation proceeded, the apparent rate constant changed during the controlled cationic polymerization of 1,4‐dioxene. The reason for the change was discussed based on polymerization results under various conditions. The obtained poly(1,4‐dioxene) exhibited a very high glass transition temperature (Tg) of 217°C and unique solubility. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

19.
We prepared 2,2‐dibutyl‐2‐stanna‐1,3‐dithiacycloalkanes from dibutyltin oxide and α,ω‐dimercaptoalkanes. Heterocycles with five‐, six‐, seven‐, or nine‐ring members were used as bifunctional monomers for polycondensations with aliphatic dicarboxylic acid chlorides. These polycondensations conducted in bulk were highly exothermic and yielded poly(thio ester)s with number average molecular weights (Mn's) in the range of 5000–30,000 Da. These poly(thio ester)s proved to be rapidly crystallizing materials with melting temperatures in the range of 90–150 °C. In addition to the success of the new synthetic approach, two interesting and unpredictable results were obtained. All volatile species detectable by matrix assisted laser desorption induced‐time of flight (MALDI‐TOF) mass spectrometry were cyclic oligo‐ and poly(thio ester)s. Second, several polyesters showed a reversible first‐order change of the crystal modification as identified by differential scanning calorimetry measurements and X‐ray scattering with variation of the temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3656–3664, 2000  相似文献   

20.
The present article deals with the synthesis and characterization of some sulfonated copolyethersulfones. The synthetic approach differs from the post sulfonation approach traditionally reported in the literature. The synthetic procedure is based on the use of sulfonated monomers which are then reacted with previously synthesized telechelic hydoxy‐ended poly (ether sulpnone)s. Combining the MALDI‐TOF MS and 1H NMR analyses, with SEC‐Viscometry and TGA measurements, we demonstrate a powerful tool for characterizing the chemical composition, end chains, degree of sulfonation (DS) and molecular mass distribution (MMD) of disulfonated poly(arylene ether‐sulfone) copolymers. The characterization techniques allowed to determine the exact nature of the copolymers synthesized and to reveal some interesting features about the reaction. DMA data show that the glass transition temperature of sulfonated copolymers with similar DS increase as raise their MMD. Copolymers with a DS of 10–11 mol % reach a Tg of 244–246 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3010–3023, 2010  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号