G. M. Guzmán

Melting point depression in poly (ethylene oxide)-poly (methyl methacrylate) blends

Thermo-optical analysis of solution cast mixtures of poly (ethylene oxide) (POE) and poly (methyl methacrylate) (PMMA) has been carried out. Melting point depression was observed for increasing proportion of PMMA in the mixture. An analytical expression appropriate to the crystallineamorphous polymer pair has been applied to explain the melting point depression in terms of thermodynamic quantities. From this expression, the interaction parameter for the mixture has been evaluated. The influence of Mw of POE on the binary interaction parameter has been studied.

Spherulitic crystallization in blends of poly(ethylene oxide) and poly(methyl methacrylate)

Abstract The crystallization kinetics of binary blends of poly(ethylene oxide) and poly(methyl methacrylate) were investigated. The isothermal spherulitic growth rates were measured by means of a polarized light microscope. The temperature and composition dependence on the growth rates have been analysed. The temperature range studied was from 44° to 58°C. The introduction of poly(methyl methacrylate) into poly(ethylene oxide) resulted in a reduction of the spherulitic growth rate as the proportion of poly(methyl methacrylate) was increased from zero to 40% by weight. Results have been analysed using the theoretical equations of Boon and Azcue for the growth rate of polymer-diluent mixtures. The experimental results are in good agreement with this equation. The temperature coefficient is negative as is the case in the crystallization of bulk homopolymers.

Determination of the solubility parameter of poly(ethylene oxide) at 25°C by gas-liquid chromatography

Abstract The solubility parameter of poly(ethylene oxide) at 25°C has been determined using the method developed by DiPaola-Baranyi and Guillet, by the extrapolation of the values of the interaction parameter χ, at high temperatures, ranging from 70°–90°, 90°–110° and 110°–130°C down to 25°C. The values of the solubility parameter obtained, depending on the temperature ranges employed, are 9.8, 9.9 and 10.1, respectively.

Graft copolymerization of hydroxylic methacrylates and ethyl acrylate onto amylopectin

Abstract In order to achieve new biocompatible materials, graft copolymerization of mixtures of hydroxyethyl methacrylate/ethyl acrylate (HEMA/EA) and hydroxypropyl methacrylate/ethyl acrylate (HPMA/EA) onto amylopectin by ceric ammonium nitrate initiation was carried out. The influence of feed composition was studied with respect to the characteristic grafting reaction yields. Homopolymer formation decreases as the per cent of HEMA monomer increases in the feed and increases as the per cent of HPMA monomer increases in the feed. The values obtained for the percentage grafting were quite high for all the feed compositions.

Synthesis of graft copolymers of acrylic monomers on amylose: Effect of reaction time

Abstract A study has been carried out on the graft copolymerization of methyl acrylate, ethyl acrylate, ethyl methacrylate and n -butyl methacrylate on the linear fraction of starch (amylose), initiated by ceric ammonium nitrate; the results are compared with those obtained previously for methyl methacrylate and butyl acrylate. We obtained the following maximum grafting efficiency = 99% for poly(methyl acrylate), percent grafting = 338% for poly(ethyl methacrylate) and percent total conversion = 97% for poly( n -butyl methacrylate). The results are discussed.

Calorimetric evidence of the interchange reactions in phenoxy/poly(butylene terephthalate) blends

Abstract Interchange reactions taking place at high temperatures in phenoxy/poly(butylene terephthalate) blends have been studied by differential scanning calorimetry. Results show the influence that these types of reactions have on the thermal transitions of the blends. These results may be explained on the basis of a reaction between hydroxyl groups in phenoxy and ester groups of poly(butylene terephthalate), causing the formation of grafted and crosslinked copolymers.

13C n.m.r. study of the graft copolymerization of a mixture of methyl methacrylate with ethyl acrylate on amylose

Abstract The study of the simultaneous grafting of ethyl acrylate with methyl methacrylate onto amylose with Ce(IV) ammonium nitrate as initiator was attempted. Grafting yields obtained using gravimetric and 13C n.m.r. spectroscopic methods were compared and similar results were obtained. A study of the microstructure of the grafted products obtained involving either the quantitative determination of the grafted copolymer composition or the qualitative study of the sequence distribution and the stereochemical configuration of grafted copolymer sequences has been carried out. The α-methyl group carbon, the quaternary carbon and the carbonyl group carbon have been found to be sensitive to the relative stereochemical configuration of the chain segments.

Graft copolymerization of 4-vinylpyridine onto cellulosics. effect of temperature

Abstract Graft copolymerization of 4-vinylpyridine (4-VP) was carried out on unmodified cotton and partially carboxymethylated cotton (PCMC), using ceric ammonium nitrate as initiator. The grafting parameters were studied as a function of temperature and amount of cellulose. With unmodified cotton, the graft yield increased up to 40° and then decreased on increasing temperature. Graft yields for PCMC increased with increasing temperature and reached a constant value beyond 30°. Carboxymethyl groups attached to cellulose enhanced both graft yield and grafting efficiency as well as the ceric ion consumption. The molecular weight of grafted poly(4-VP) was obtained viscometrically after hydrolysing away the cellulose backbone, and it was found to decrease while the graft frequency increased with temperature. The activation energies were found to be 32.6 and 8.7 kJ/mol for PCMC and unmodified cotton respectively. The weight increase of cellulose due to grafting increased with increasing content of cellulose in the reaction mixture. The presence of occluded air in the grafting system caused a decrease in graft yield.

Stereoregularity of various polyacrylates obtained from graft copolymers onto starch

Abstract 13 C nuclear magnetic resonance spectra of poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(butyl acrylate) (PBA), obtained from graft copolymers onto amylose or amylopectin, have been studied. The spectra of the polymers were recorded with a 75 MHz spectrometer and were analysed by triad, tetrad, pentad or hexad placements. All of them follow Bernoullian statistics, with an isotactic parameter of 0.51, 0.44 and 0.43 for PMA, PEA and PBA respectively. By comparison with other values found in the literature it can be asserted that the presence of the carbohydrate has no effect on the tacticity of the grafted polymer.

Ternary blends containing polyarylate, polycarbonate and poly(butylene terephthalate)

Abstract Binary and ternary blends containing a polyarylate, bisphenol-A polycarbonate and poly(butylene terephthalate) have been studied by differential scanning calorimetry. The polyarylate/poly(butylene terephthalate) blend is fully miscible; the two other binary mixtures show partial miscibility which is greater in the polycarbonate/poly(butylene terephthalate) case. The ternary blends show behaviour depending on the blend composition. It appears that poly(butylene terephthalate) is capable of miscibilizing the polyarylate/polycarbonate blends in some cases.