Synthesis of asymmetric diglycidyl ester compounds. Reaction with aromatic diamines

New diglycidyl esters coming from the corresponding diacids and epichlorohydrin were synthetized using a quaternary ammonium salt as a catalyst. The new asymmetric compounds were characterized by spectroscopic methods and employed as starting monomers in a crosslinking process. The course of the reactions was followed by IR spectroscopy. Some intermediate species were identified in the onset of the reactions by recording ¹³C-NMR spectra until the products became insoluble in the usual deuterated solvents. The thermal behaviour of these cured epoxy resins was also studied.     

N,N'-Diglycidylimides and their polymers

At first new epoxy derivatives, namely glycidylimide compounds, have been prepared using benzyltrimethylammonium chloride as catalyst and epichlorohydrin in excess. Their chemical and physical properties were studied. Spectral data confirmed these new structures. Afterwards new epoxy resins have been synthesized by the reaction of diimides and their glycidyl derivatives in N,N-dimethylformamide. The physical characteristics of the obtained polymers and also their solubilities are reported. Their IR, ¹H- and ¹³C-NMR spectra allowed to confirm the polymer structure. Thermal analysis of these compounds showed their good thermal properties.     

Crosslinking of trimellitimide glycidyl ester derivatives

The cure reaction of diglycidyl trimellitimide esters with 4‐dimethylaminopyridine, diaminodiphenylmethane, and dicyandiamide as hardener was studied by differential scanning calorimetry (DSC). Isoconversional kinetic analysis was applied to nonisothermal DSC data and the dependences of activation energies on conversion degrees were obtained. Differences in the shape of these plots were found in accordance to the different kinetic schemes of the curing agents. The thermal properties of the final products evaluated by thermogravimetry do not show noteworthy differences. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 537–542, 1999     

Cationic curing of diglycidyl ether of bisphenol A and 2,2,5,5‐tetramethyl‐4,6‐dioxo‐1,3‐dioxane and degradation of the thermosets obtained

Ytterbium and lanthanum triflates were used as cationic initiators to cure mixtures of diglycidyl ether of bisphenol A and 2,2,5,5‐tetramethyl‐4,6‐dioxo‐1,3‐dioxane in several proportions. The evolution of the epoxy and lactone during curing and the linear ester groups in the final materials were evaluated with Fourier transform infrared in the attenuated total reflection mode. The shrinkage after curing and the thermal degradability of the materials with variations in the comonomer ratios and initiator used were evaluated and related to the chemical structure of the final network. The expandable character of 2,2,5,5‐tetramethyl‐4,6‐dioxo‐1,3‐dioxane was confirmed. The obtained materials were more degradable than conventional epoxy resins because of the tertiary ester groups incorporated into the network by copolymerization. The kinetic parameters of the curing and degradation processes were calculated with differential scanning calorimetry and thermogravimetric analysis, respectively, with isoconversional procedures applied in both cases. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

An unexpected structure in the preparation of new epoxy resins

Spectroscopic data of epoxy resins, derivatives of pyromellitimide, have shown two types of attack on the two carbons of the oxirane group, giving rise to normal and abnormal opening of the ring. Thus, primary and secondary hydroxy groups were obtained. The physical characteristics of the obtained new polymers and also their solubilities are reported. Thermal analysis of these epoxy polyesterimides showed their good thermal properties.     

Cardiac tamponade as a clinical symptom of systemic lupus erythematosus

Upper lid closure in facial nerve paresis induced lagophthalmos is often improved by implantation of gold weights. However, the tolerability of gold implants has not always met expectations. We therefore investigated whether results could be improved by implantation of well-tolerated platinum implants. PATIENTS AND METHODS: Three patients with lagophthalmos received pretarsal platinum-iridium implants in the upper lid. The implants were primary in two patients and secondary in one. In this patient, the previous gold implant had led to marked swelling and redness of the upper lid 6 weeks after surgery. The platinum implants were prefabricated with a radius of 20 mm and weighed between 1.3 and 1.4 g. During implantation, they were individually contoured to fit lidcurvature and attached pretarsally with nonresorbable thread. RESULTS: Postoperatively, the upper lid of all three patients could be closed completely. The implants healed without irritation. No lid swelling occurred during 2-to 6-month follow-up. Because platinum-iridium alloys have a higher specific gravity (Ptlr 90/10 = 21.65 g/cm3) than gold (18.43 g/cm3), they can attain equal weight at smaller size. CONCLUSIONS: Our first results show that platinum implants are a feasible alternative to gold implants in treating lagophthalmos due to better biocompatibility and higher specific gravity.     

Synthesis,characterization, and thermal behaviour of new epoxy polyesterimides

New epoxy resins have been synthesized by the reaction of diimide-diacids trimellitimide derivatives containing different aliphatic and aromatic fragments in N-methyl pyrrolidone (NMP) with their corresponding diglycidylesters, using several molar ratios. The polymer composition has been determinated by chemical and elemental analyses. Their IR, ¹H, and ¹³C NMR spectral data allowed to confirm the structural unit. Epoxy polyesterimides are soluble in polar organic solvents and show good thermal resistance. Differences on the basis of the introduced aliphatic or aromatic fragments were observed.     

Curing of new trimellitimide glycidyl ester derivatives with aromatic diamines

The cure behaviour of new epoxy resins containing a preformed imide ring with m-phenylenediamine (mPDA) and diaminodiphenylmethane (DDM) was investigated. The progress of polymerization was followed by recording IR and ¹³C-NMR spectra at time intervals. The curing proceeded mainly by chain extension at low temperatures, the reaction being not very fast, whereas crosslinking occurred as the gel point was reached (about 15 h at 60°C) by reaction of secondary amino groups with epoxides. Impurities influence, playing the part of catalysts, could be determined from the reaction rate of glycidyl and amino groups. So a kinetic study was made. The thermal behaviour of these cured epoxy resins was also studied.