共查询到20条相似文献,搜索用时 15 毫秒
1.
B. S. Uphade P. S. Patil S. B. Pandit C. R. Rajan V. M. Nadkarni 《Journal of polymer science. Part A, Polymer chemistry》1994,32(11):2003-2010
Kinetics of polyesterification of maleic anhydride with polyethylene glycol (PEG) of varying molecular weights have been evaluated. The investigations have been carried out by employing heating cycles comparable to those employed in industrial processes and under nonisothermal conditions. The rate of reaction was found to decrease with increase in the chain length of the polyether. The energy of activation was estimated as 26.91, 40.25, and 47.30 Kcal/mol for PEG of molecular weights 200, 300, and 400, respectively. © 1994 John Wiley & Sons, Inc. 相似文献
2.
Azadeh S. Hashemi Doulabi Hamid Mirzadeh Mohammad Imani Shahriar Sharifi Mohammad Atai Shahram Mehdipour‐Ataei 《先进技术聚合物》2008,19(9):1199-1208
Biodegradable polymers have currently attracted high interest as ideal carriers in drug delivery and tissue engineering applications. In situ forming devices based on these materials will synergistically provide the advantages of the customary prefabricated devices as well as ease of administration. To acheive these objectives, optically transparent and biodegradable macromers based on poly(ethylene glycol) and fumaric acid copolymers were synthesized using propylene oxide as a different proton scavenger to enhance in situ photocrosslinking capability. The macromers in different compositions were then photocured for 300 sec in the presence of a visible light initiator/accelerator couple and also a reactive diluent. Characterization of the macromers and the resulting networks were performed using different spectroscopic, chromatographic, physical, and thermal analysis techniques. The resulted shrinkage strain of the macromers upon photocuring was studied using the bounded disk technique, and initial shrinkage strain rates were obtained by numerical differentiation. Our results suggest that the compositions based on these unsaturated aliphatic polyesters are potentially useful to develop injectable, in situ photocrosslinkable carriers for drug and cell delivery applications. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
Wally L. Chang Tom Karalis 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):493-504
A series of studies of uncatalyzed and catalyzed polyesterification experiments have been investigated using different glycols at different temperatures. The experimental results for uncatalyzed reactions agreed quite well with the kinetic equation as proposed by P. J. Flory. However, Flory proposed a second-order reaction for an externally added strong acid as a catalyst. In contrast to Flory's theory, a mixed mechanism, based on a combination of carboxylic acid groups from the raw material and an external organotin catalyst, was proposed for the catalyzed reaction. In this article, the reaction rate of catalyzed and uncatalyzed polyesterifications using different glycols was compared, and the effect of different temperatures and catalyst levels was also discussed. The reaction rate constant decreases in the following order for both catalyzed and uncatalyzed polyesterification: 1,6-HD > 1,4-BD > NPG > DEG > EG ? PG. © 1993 John Wiley & Sons, Inc. 相似文献
4.
M. J. Callejo Cudero M. M. C. Lpez-Gonzlez J. M. Barrales-Rienda 《Journal of polymer science. Part A, Polymer chemistry》1996,34(6):1059-1072
Analysis of the polyesterification in bulk without any external catalyst at 200°C of o-phthalic anhydride with neopentyl glycol (2,2-dimethyl-1,3-propanediol) with a mole ratio ([(SINGLE BOND) COOH]/[ (SINGLE BOND) OH]) = 0.7 has been carried out by high resolution 13C nuclear magnetic resonance (13C-NMR). Polyesters can be analyzed by 13C-NMR spectra because of the fact that both o-phthalic acid (o-phthalic anhydride) and neopentyl glycol carbons are sensitive to sequence effects. Spin-lattice relaxation times T1, of quaternary, tertiary and secondary carbons in different structures are in the 0.1–6.5 s range depending on the neighboring residue effects in the polymer chain. © 1996 John Wiley & Sons, Inc. 相似文献
5.
Ioakim K. Spiliopoulos John A. Mikroyannidis 《Journal of polymer science. Part A, Polymer chemistry》1996,34(13):2799-2807
Various unsaturated polyamides and polyesters were prepared from the reactions of 1,4-bis(2-carboxyvinyl)benzene acid chloride with aromatic diamines and bisphenols, respectively. In addition, various unsaturated homo- and copolyesters were synthesized from 4-hydroxycinnamic acid and 4-hydroxybenzoic acid. They were heat-cured to thermally stable resins. The polymers were characterized by inherent viscosity measurements, FT-IR, x-ray, DTA, TMA, TGA, and isothermal gravimetric analysis. The water absorption as well as the solubility behavior of the polymers was also investigated. © 1996 John Wiley & Sons, Inc. 相似文献
6.
7.
Fukuji Higashi Akira Kobayashi Hisashi Shimazaki 《Journal of polymer science. Part A, Polymer chemistry》1993,31(5):1301-1305
The reaction of the N-phosphonium salt of pyridine derived from phosphorus oxychloride in pyridine was successfully used for the preparation of aromatic polyesters with high molecular weight when carried out in the presence of lithium chloride. In the copolycondensations of isophthalic and terephthalic acid with diphenols, the mode of reaction with the diacids was expected to produce several types of the diacid activated intermediates, which might control the sequences of the diacids in the copolymers. The possible variation of the sequences was studied in terms of the mode and copolymer properties such as glass transition temperatures and liquid crystalline transition temperatures. Competitive model reactions were carried out to discuss these relationships. © 1993 John Wiley & Sons, Inc. 相似文献
8.
The influence of chemical modification of unsaturated polyesters on viscoelastic properties and thermal behavior of styrene copolymers 总被引:1,自引:0,他引:1
Marta Worzakowska 《Journal of Thermal Analysis and Calorimetry》2009,96(1):235-241
The influence of chemical modification of unsaturated polyesters on viscoelastic properties and thermal behavior of styrene
copolymers has been investigated by DMA and TG analyses. Chemical modification of unsaturated polyesters obtained in polycondensation
of cyclohex-4-ene-1,2-dicarboxylic anhydride (THPA), maleic anhydride (MA) and suitable glycol: diethylene glycol (DEG) or
triethylene glycol (TEG) was performed using 38–40% peracetic acid. It allowed to selective and successful oxidation of carbon-carbon
double bonds in unsaturated polyesters giving modified unsaturated polyesters/unsaturated epoxypolyesters/containing both
carbon-carbon double bonds in polyester chain and new functional groups-epoxy groups in cycloaliphatic rings. Both unsaturated
polyesters and unsaturated epoxypolyesters were used as a component of styrene copolymers cured with different hardeners.
It has been demonstrated that the use of modified unsaturated polyesters as a component of styrene copolymers allowed obtaining
more stiffness and more cross-linked network structure compared to styrene copolymers based on unmodified polyesters. The
higher values of storage modulus, glass transition temperatures and better thermal stability for styrene copolymers based
on unsaturated epoxypolyesters were obtained. 相似文献
9.
Dafna Knani David H. Kohn 《Journal of polymer science. Part A, Polymer chemistry》1993,31(12):2887-2897
Enzymatic polymerization of hydroxyesters in organic media has been the subject of a previous and ongoing research in our laboratory. As part of that study, four ?-substituted-?-hydroxyesters were synthesized, and then polymerized using crude porcine pancreatic lipase (PPL) in n-hexane. These lateral-substituted hydroxyesters polymerized enantioselectively to produce optically active oligomers and a resolved optically active unreacted monomer. It was found that with increasing bulkiness of the lateral substituent, in the order Me >Et >Ph, the enzymatic reaction becomes slower, yet the enantioselectivity is higher. The lateral-substituted hydroxyesters were also copolymerized enzymatically with the more reactive linear methyl ?-hydroxyhexanoate. Optically active copolymers were obtained, higher in molecular weight than the analogous homopolymers. © 1993 John Wiley & Sons, Inc. 相似文献
10.
11.
Ivan Hevus Dean C. Webster John McNamara Nicole G. Ricapito Stepan Tymoshenko 《Journal of polymer science. Part A, Polymer chemistry》2021,59(8):665-674
The applicability of polyesters across a wide range of fields creates a demand for novel polyester structures that can offer advanced product performance. Two critical factors to the development of unique polymer architectures are the speed at which new polymeric systems can be synthesized and the available selection of monomers from which polymers are designed. Herein, we successfully demonstrate the applicability of a high-throughput (HT) approach to polyesterification reaction between dicarboxylic acids and diols in reaction conditions similar to those used in industry. Furthermore, we apply our HT design to a series of bio-based monomers whose unique structures offer potential for enhanced properties in polyester-based systems. Using a custom-built array of small-scale film reactors, we conducted a parallel screening of 13 bio-based dicarboxylic acids as potential monomers in the synthesis of polyester polyols through copolymerization with 1,6-hexanediol. The polyester polyols were characterized for their molecular weight and thermal properties. Carrying out polyesterification reactions in small-scale film reactors is seen as a quick and powerful tool for screening the effectiveness of a series of potential monomers, as this method offers highly controllable and reproducible reaction conditions in every reactor coupled with the ability to use a minimum amount of reagents. 相似文献
12.
The AB2 type bulk polymerization of 3,5-bis(trimethylsiloxy)benzoyl chloride is studied by the reactive 3d bond fluctuation lattice model (3d-BFLM). Through tuning the reactivity parameters, the experimental data are fitted well via an iterative dichotomy method. By using the optimized reactivity parameters, the number-average degree of polymerization and degree of branching obtained in simulation are very close to experimental data. Meanwhile, the information about the weightaverage degree of polymerization and the polydispersity index is provided, and the internal structural properties of hyperbranched polyesters are investigated. Simulation results demonstrate that the 3d-BFLM can be used to study specific hyperbranched polymerizations semi-quantitatively which is helpful to deep understand the kinetics of reactions and make predictions for specific polymerization systems. 相似文献
13.
Lidia Jasinska Cor E. Koning 《Journal of polymer science. Part A, Polymer chemistry》2010,48(13):2885-2895
Biobased, unsaturated polyesters derived from isosorbide, maleic anhydride, and succinic acid were synthesized and characterized. The presence of maleic anhydride units in the structure of the polyesters allowed converting them into cured coatings by radical copolymerization with crosslinking agents such as 2‐hydroxyethyl methacrylate, N‐vinyl‐2‐pyrrolidinone, acrylic acid or methacrylamide. The investigated polyesters were obtained via bulk polycondensation, catalyzed by titanium(IV) n‐butoxide. 2D NMR and MALDI‐Tof‐MS spectroscopy proved that this polymerization resulted in isomerization of maleic acid units into fumaric ones and in the formation of slightly branched structures by the reaction of isosorbide (end) groups with main chain unsaturated bonds. Moreover, some double bonds proved to have reacted with the condensation by‐product water. The resulting polyesters displayed the expected correlation between variables such as molecular weight and content of unsaturated bonds and their Tg values. Since the thermal properties of the obtained polyesters were appropriate for coating applications, the polymers were crosslinked with unsaturated monomers by radical copolymerization. The crosslinking process was studied using FTIR spectroscopy and by measurements of the soluble part of the cured coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2885–2895, 2010 相似文献
14.
Iulian C. Alupei Valentina Alupei Helmut Ritter 《Macromolecular rapid communications》2003,24(8):527-531
A new method was developed to crosslink water‐soluble unsaturated polyester resins prepared from maleic anhydride and poly(ethylene glycol) in water as the solvent. Crosslinking was carried out with various molar ratios of the host‐guest complex consisting of styrene as the guest and methylated β‐cyclodextrin as the host. Polymerizations were performed in water with K2S2O8/Na2S2O5 as free radical initiator at 25 °C. Thermal properties of the networks obtained depend on the amount of styrene incorporated into the polymer.
15.
Dafna Knani Arie L. Gutman David H. Kohn 《Journal of polymer science. Part A, Polymer chemistry》1993,31(5):1221-1232
With the object to synthesize polyesters by enzymatic catalysis in organic media, two directions have been investigated: (1) the condensation polymerization of linear ω-hydroxyesters and (2) the ring-opening polymerization of lactones. The commercially-available crude porcine pancreatic lipase (PPL), suspended in organic solvents, was the preferred enzyme for the reactions. In order to determine the optimal conditions for the condensation polymerization, the bifunctional methyl 6-hydroxyhexanoate was used as a model compound to study the influence of the following parameters: type of the enzymecatalyst, kind of solvent, concentration, temperature, duration, size of the reaction mixture, and stirring. Film-forming polyesters with a degree of polymerization (DP) up to about 100 were obtained from linear aliphatic hydroxyesters in n-hexane at reflux temperature (69°C). Yet concurrently with the intermolecular condensation polymerization, macrolactones were also formed by intramolecular reaction. Two aromatic hydroxyesters did not react under these conditions. For the ring-opening polymerization of lactones the reaction of ?-caprolactone with methanol as the preferred nucleophile, was studied. Polyesters with a DP of up to 35 were obtained in n-hexane at temperatures between 25 and 40°C. The degrees of polymerization of the polyesters were determined by comparative analyses of the end groups in the 1H-NMR spectra and by determination of molecular weights either by vapor phase osmometry, gel permeation chromatography, or intrinsic viscosity. © 1993 John Wiley & Sons, Inc. 相似文献
16.
Hans R. Kricheldorf Saber Chatti Gert Schwarz Ralf‐P. Krüger 《Journal of polymer science. Part A, Polymer chemistry》2003,41(21):3414-3424
Numerous polycondensations of isosorbide and suberoyl chloride or other aliphatic dicarboxylic acid dichlorides were performed with pyridine as a catalyst and HCl acceptor. The reaction conditions were varied to optimize both the molecular weight and the fraction of cyclic oligo‐ and polyesters. Furthermore, we attempted to obtain the cyclic monomer by catalyzed back‐biting degradation of the molten cyclic polyesters above 220 °C in vacuo. The polyesters were characterized by viscosity and size exclusion chromatographic measurements as well as matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. In selected cases, mixtures of linear and cyclic polyesters were treated with a hot solution of partially methylated β‐cyclodextrin in methanol. This treatment allowed for a selective extraction of the linear chains up to approximately 5000 Da. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3414–3424, 2003 相似文献
18.
A series of aliphatic polyesters has been synthesized starting from 1,12-dodecanedioic acid and aliphatic diols, bearing from 2 to 12 carbon atoms. These polymers, which were fully characterized in terms of chemical structure, molecular weight and thermal behaviour, were obtained as crystalline materials with melting points ranging from 70 to 90 °C and with a relatively high molecular weight. All the monomers used can be obtained from biomasses, as a consequence these materials can be an interesting alternative to synthetic polymers produced from petrochemical processes based on nonrenewable resources. 相似文献
19.
Mónica Lomelí‐Rodríguez Miguel Martín‐Molina María Jiménez‐Pardo Zahara Nasim‐Afzal Solène I. Cauët Thomas E. Davies Martín Rivera‐Toledo Jose A. Lopez‐Sanchez 《Journal of polymer science. Part A, Polymer chemistry》2016,54(18):2876-2887
The biomass‐derived polyesters poly(1,3‐propylene 2,5‐furandicarboxylate) (PPF), poly(1,3‐propylene succinate) (PPS) and poly(1,3‐propylene 2,5‐furandicarboxylate‐co‐1,3‐propylene succinate) (PPFPS) have been synthesized via a two‐step process involving polycondensation and azeotropic distillation. The kinetic parameters were obtained by fitting the experimental data from a batch polymerization reactor to three different kinetic models for polyesterification reactions. The activation energies of the all monomer systems were obtained by Arrhenius plots. Given the increasing availability of biomass‐derived monomers their use in renewable polyesters as substitutes for fossil fuel derived chemicals becomes a distinct possibility. The kinetic modeling of the uncatalyzed polyesterification reactions will enable further integrative process simulation of the studied bioderived polymers and provide a reference for future practical study or industrial applications of catalyzed polyesterification reactions and other bioderived monomer systems. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2876–2887 相似文献
20.
Nobuhiro Kawatsuki Michael Drr Hans-Werner Schmidt 《Journal of polymer science. Part A, Polymer chemistry》1993,31(4):1013-1021
The synthesis, characterization, and structure—property relations of aromatic polyesters with dicyanovinyl substituents is presented. Two comparable series of polyesters based on 3,4-dihydroxybenzylidenemalononitrile and 3,4-dihydroxy-5-methoxybenzylidenemalononitrile were prepared. As aromatic diacid components, terephthalic acid, phenylterephthalic acid, isophthalic acid, and 2-phenylisophthalic acid were used. The polyesters were prepared by solution polycondensation. GPC investigations revealed the existence of substantial amounts of defined cyclic products. These cycles could be isolated by preparative GPC. The polyesters are soluble in common low boiling organic solvents, particularly the phenyl-substituted ones. The polyesters are amorphous and have glass transition temperatures between 140 and 170°C. The absorption maxima are in the 306–322 nm range. The cut-off wavelength is between 400 and 428 nm. The polyesters with methoxy substitutent have generally the absorptions at longer wavelength. The refractive index of thin films of these polyesters were between 1.61 and 1.63 at 632.8 nm. © 1993 John Wiley & Sons, Inc. 相似文献