Polyesterification and isomerization of maleic anhydride and 1,6-hexane diol as studied by 1H and 13C n.m.r.

The polyesterification and isomerization reaction of 1,6-hexane diol and maleic anydride in a melt without catalyst was studied by ¹³C and ¹H n.m.r. spectroscopy. The structure and concentration of oligoester species during the polyesterification and isomerization were determined depending on the reaction temperature and time. According to the number and configuration of repeating units determined from ¹H n.m.r. spectra kinetics of both reactions were also considered. The degree of isomerization is continuously increasing in the investigated reaction range.     

Low‐temperature synthesis of uranium monocarbide by a Pechini‐type in situ polymerizable complex method

Uranium monocarbide (UC) was successfully synthesized by the Pechini‐type in situ polymerizable complex technique (IPC) with the organic matter as the only carbon source. In the aqueous process, a mixture of citric acid (CA) and mannitol with was polymerized to form a spongy‐like organic polymeric precursor without any precipitations. The structural evolution and formation mechanism of the precursor were investigated using XRD, DSC‐TG, SEM (EDX), TEM, and FT‐IR. XRD results demonstrated that UC was obtained with the /mannitol/CA molar ratios of 1.0/0.3/1.0 at a low temperature of 1400°C. SEM and TEM analyses revealed that the UO₂ nanoparticles were uniformly distributed in the carbon matrix to form UO₂/C nanocomposites, and submicrometer‐sized ellipsoidal UC particles cemented together. FT‐IR showed that a ‐CA chelated structure was firstly obtained, achieving the molecular scale mixing of uranium and C. Then the in situ charring guaranteed the intimate contact of UO₂ and C, leading to a low reaction temperature in carbothermal reduction owing to a short diffusion distance.     

Synthesis of polyesters as binders for deinkable inks. II. Kinetics and mechanism of polyesterification between o-phthalic anhydride and neopentyl glycol in bulk at 200°C

The kinetics of the polyesterification in bulk at 200°C between o-phthalic anhydride and neopentyl glycol (2,2-dimethyl-1,3-propanediol) in a nonequimolecular ratio and in the absence of an external catalyst was investigated. The formation of the monoester and two dimeric compounds by uncatalyzed heating of o-phthalic anhydride with neopentyl glycol was virtually complete after dissolution of the anhydride. The data were analyzed statistically by a mathematical method due to Fradet and Maréchal for the estimation of the orders of reaction. This statistical adjustment of the data analysis supports the assumption that the kinetics of polyesterification in the absence of both the solvent and catalyst may be fitted to several orders of reaction over all the conversion. At first, our experimental data may be fitted to 3, or , or 2, etc., overall orders. The results establish that the overall kinetic order of the polyesterification depend upon the goodness of the experimental results and cannot be only selected by means of a correlation coefficient. If this last criterium is adopted, the polyesterification at low, medium, as well as at high conversions may be 3 as the most probable one, order one with respect to acid group concentration, and order two with respect to alcoholic group concentration, in agreement with Flory's predictions. A mechanism consistent with the most plausible kinetic results (I_m,n = 0.9990 and m, n = 1, 2) is proposed. It consists of a dimerization of the alcoholic groups followed by an attack of the acid to the dimer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2409–2431, 1997     

Synthesis of polyesters as binders for deinkable inks. V. Structural analysis of the polyesterification between o-phthalic anhydride and trimethylolpropane in bulk at 165°C by high resolution 13C and 1H nuclear magnetic resonance

Structural analysis of the polyesterification in bulk without external catalyst at 165°C between o-phthalic anhydride (P) and trimethylolpropane (1,1, 1-tri(hydroxymethyl)propane) (T) with a mole ratio ([−COOH]/[−OH])=0·70 has been carried out by high resolution ¹³C nuclear magnetic resonance (¹³C NMR) in DMSO-d₆ and CDCl₃ solutions and by ¹H nuclear magnetic resonance (¹H NMR) in CDCl₃ solution. The use of CDCl₃ as NMR solvent has allowed us to identify several signals, which have been assigned to trimethylolpropane monoesters with different esterification degree in the o-phthalate residue. Identically, we have detected signals assignable to chain-end monoesters in structures with different chain lengths. These monoesterified structures have also been confirmed by analysing, by the same procedures, samples modified by diazomethane addition to the samples in chloroformic solution. These modified samples have also been used to determine free acid groups as their methoxylic derivatives by ¹H NMR in CDCl₃ solution. The values compare very well with those obtained by ¹³C and ¹H NMR spectro-scopies in both solvents in some other regions of the spectra. It has been found that NMR allows quantitative determination as a function of the reaction time, of the conversion of acid P and alcohol T functions, as well as monoester and diester of P distributions and those of free, mono- di- and tri-esterified T. We have not observed any detectable signs of gelation. ©1997 SCI     

邻苯二甲酸酐与二甘醇的聚酯化动力学研究

对邻苯二甲酸酐和二甘醇的聚酯化动力学进行了研究。根据前人所推导的采用质量浓度单位(mol.kg-1)、消除反应体系排除水影响的总包聚酯化反应方程,对Flory和Lin的动力学方程进行了修正。考察了反应温度、反应时间等参数与聚酯化反应速率的关系。结果表明,在温度220~240℃范围内,邻苯二甲酸酐与二甘醇的反应规律符合校正水体积影响之后的Lin所提出的动力学方程,而不遵循Flory所提出的动力学模型,反应活化能为33.70 kJ/mol,频率因子为8.5659 mol.kg-1.min-1,邻苯二甲酸酐和二甘醇的最适宜酯化反应温度为240℃,在不加催化剂的条件下反应240 min,反应程度达到94.7%。     

双(对-羧苯基)苯基氧化膦与乙二醇的自催化聚酯化反?…EI

在不同的恒定反应温度和不同的初始摩尔比下，进行了双苯基氧化膦（ＢＣＰＰＯ）与乙二醇的自催化聚酯化反应。这两个速率方程与实验结果相一致，并计算得到了该反应的速率常数和活化能。     

新戊二醇／顺酐／邻酐体系自催化缩聚反应的动力学研究

采用顺酐／苯酐／新戊二醇三元反应体系，周Hu-Wang的推导方法对Lih-Hsieh提出的动力学方程（考虑水的排除）进行了修正，得到了该反应的总包动力学方程，此方程对于水的排除给动力学分析所带来的影响已被全部消除，以此总包动力学方程得出的动力学参数更接近真实值。     

Development of Green Dual Polymers for Antibacterial Applications

In this article, we report on the antibacterial properties of a novel antimicrobial poly(citric acid-co-curcumin) polymer system that was prepared by a catalyst–free polyesterification process. The dual polymer of poly(citric acid-co-curcumin) was synthesized by varying the weight ratio of citric acid and curcumin monomers. Details of the synthesis, spectral (Fourier transform infrared, ultraviolet), thermal stability (Thermogravimetric analyses), and the morphological (Scanning electron microscopy/energy dispersive spectroscopy) characterization of dual polymers are presented in this scientific article. The UV–visible spectrometry was used to confirm the copolymerization of curcumin dispersion in the dual polymer systems. The presence of functional groups of copolymers was confirmed by Fourier transform infrared spectroscopy. The thermogravimetric analysis results indicated that poly(citric acid-co-curcumin) have a thermal stability up to 225°C. The ratios used were 1:0.25, 1:0.5, 1:0.75, and 1:1 and their antibacterial properties were studied with respect to their activity on gram-positive and gram-negative bacteria. This dual polymer was inoculated onto a Petri dish and its ability to inhibit the growth of Escherichia coli, Staphylococcus, Bacillus subtilis, Candida albicans (fungus), and Micrococcus luteus was evaluated using the bacterial disc method. Results indicated inhibition properties to increase with increasing curcumin content and the dual polymer with highest curcumin content showed excellent antimicrobial activities against both gram-negative and gram-positive microorganisms. Hence, it was clear that the developed dual polymers may be effectively used for antibacterial applications such as wound dressing.     

DSC curing study of catalytically synthesized maleic‐acid‐based unsaturated polyesters

Unsaturated polyesters were synthesized based on ethylene glycol and maleic acid as unsaturated dicarboxylic acid, using a variety of saturated acids in the initial acid mixture, without or with different catalysts. The curing of the polyesters produced with styrene was studied using differential scanning calorimetry (DSC) under dynamic‐ and isothermal‐heating conditions. The FTIR spectra of the initial polyesters and cured polyesters were also determined. Curing is not complete at the end of DSC scan and the unreacted bonds were quantitatively determined from the FTIR spectra and by estimation based on literature data. The value of the mean degree of conversion (α) of all double bonds (styrene unit and maleate unit) was approximately α = 0.40. Using an appropriate kinetic model for the curing exotherm of polyesters, the activation energy (E_a), the reaction order (x) and the frequency factor (k_o) were determined. Because the kinetic parameters (ie E_a, k, x) affect the kinetics in various different ways, the curves of degree of conversion versus time at various isothermal conditions are more useful to compare and characterize the curing of polyesters. The kinetic parameters are mainly influenced by the proportion of maleic acid in the polyesterification reaction mixture and secondarily by the residual polyesterification catalyst. The degree of conversion of already crosslinked polyesters is greatly increased by post‐curing them at elevated temperature and for a prolonged time. © 2002 Society of Chemical Industry     

13C and 1H n.m.r. study of the polyesterification of maleic anhydride and 1,2-propylene glycol

The reaction steps of the polyesterification of maleic anhydride and 1,2-propylene glycol were followed by ¹³C and ¹H n.m.r. spectroscopy. The number and structure of mono- and diesters of both maleates and fumarates in the reaction mixture are determined by the possible glycol unit configurations. The structure of the growing polyester chain reflects a statistical distribution of approximately equal numbers of symmetric and asymmetric arrangements of the polymer sequences.