Clara Marize F. Oliveira

Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide) and poly(propylene oxide)

Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide (PEO) and poly(propylene oxide) (PPO) was evaluated by building up temperature-concentration phase diagrams. We have studied bifunctional triblock copolymers (HO-PEO-PPO-PEO-OH) and monofunctional diblock copolymers (R-PEO-PPO-OH and R-PPO-PEO-OH, where R length is linear C 4 and C 12-14 ). The cloud points of the polymer solutions depended on EO/PO ratio, polarity, R length and position of the hydrophilic and hydrophobic segments along the molecule. Such factors influence on the solutions behavior was also analyzed in terms of critical micelle concentration (CMC), which was obtained from surface tension vs. concentration plots. Salts (NaCl and KCl) added into the polymer solutions change the solvent polarity decreasing the cloud points. On the other hand, the cloud points of the polymer solutions increased as a hydrotrope (sodium p-toluenesulfonate) was added.

Properties of poly(methyl methacrylate-g-propylene oxide) in solution

SummaryGraft copolymers of poly(methyl methacrylate) backbone and uniform poly(propylene oxide) branches were synthesized by the macromonomer technique and characterized by VPO, GPC and 1H-NMR. Viscometric investigations of unfractionated samples were carried out at 25°C in chloroform and toluene (non-selective solvents) and in carbon tetrachloride (a selective solvent for the branches). The coefficients of the Huggins, Kraemer, Martin and Schulz-Blaschke equations were calculated. According to the values obtained for the Huggins coefficient, kh, the best solvent for the copolymer seems to be chloroform. The positive values of the Kraemer coefficient, kk, determined in carbon tetrachloride, suggest that the copolymer assumes a star-like conformation in this solvent.

Behavior of aqueous solutions of poly(ethylene oxide‐b‐propylene oxide) copolymers containing a hydrotropic agent

The effect of the hydrotropic agent, sodium p-toluenesulfonate (NaPTS), was evaluated on the micelle formation process and on phase behavior of aqueous solutions containing poly(ethylene oxide-b-propylene oxide) (PEO–PPO) copolymers. We have studied monofunctional diblock copolymers coupled with hydrocarbons groups (R—PEO—PPO—OH and R—PPO—PEO—OH, where R length is linear C4 and C12–14). The critical micelle concentration (CMC) and critical micelle temperature (CMT) values of the aqueous copolymers solutions were obtained from both surface tension versus concentration plots and the dye solubilization method. The influence of the hydrocarbons groups length and PPO segment position in the structure of the copolymers were also analyzed. The same measures were obtained for the aqueous solutions of hydrotropic agent which, in turn, also presented molecular aggregation. The presence of the hydrotropic agent in the aqueous copolymers solutions altered the surface tension of these solutions and the occupied molecular area per copolymer molecule at air–water interface and CMC and CMT values of the copolymers. On the other hand, the aggregation points and the surface tension of the NaPTS solutions were dependent on the copolymer structure and composition.

Rheological properties of blends of polycarbonate with poly(ethylene oxide)

Blends of polycarbonate (PC) and poly(ethylene oxide) (PEO), of composition ranging between 5 and 30% in wt of PEO, have been investigated in order to study the effect of the addition of PEO on the flow properties of PC. The blends were prepared in the mixing chamber of a HAAKE torque rheometer Rheomix 600. An attempt was made to convert data obtained by the torque rheometer to fundamental units, such as apparent viscosity, and compare these results to the Instron 3213 capillary rheometer data. Viscosity values of the blends have been found to decrease with the true shear rate, and the decrease is greater for compositions rich in PEO.

Investigation of PMMA/Polyoxide blends containing graft-copolymer compatibilizers by using NMR, SEM, and thermal analysis

The effects of blend compatibility caused by compatibilizing agents were studied by microscopy, thermal analysis, and nuclear magnetic resonance (NMR) spectroscopy (carbon-13 NMR spectra and proton spin-lattice relaxation time) of homopolymers and polymer blends. In this study the results obtained by all measurements are discussed in terms of molecular mobility and compatibility, as a consequence of changes in the microdomains.

Graft copolymers of poly(methyl methacrylate) backbone and poly(propylene oxide-b-ethylene oxide) branches

SummaryTwo mono-functional macromonomers of poly (propylene oxide-b-ethylene oxide) were synthesized by reaction with methacryloyl chloride. The macromonomers have the same molecular weight and ratio of ethylene oxide and propylene oxide sequences. The reactive methacrylate group can be linked to the ethylene oxide (BuPPOPEO) or to the propylene oxide (BuPEOPPO). These macromonomers showed self-gelling in one week even at low temperature and under a dry atmosphere. Graft copolymers were obtained by reaction of these macromonomers with methyl methacrylate upon free-radical initiation and they were characterized by GPC, VPO, IR and 1H NMR spectra.

Surface segregation of components in poly(vinyl chloride)-polydimethylsiloxane and polystyrene-poly(propylene oxide) solvent-cast blends

X-ray photoelectron spectroscopy and scanning electron microscopy are used to study the surface composition and morphology of poly(vinyl chloride)–polydimethylsiloxane (PVC–PDMS) and polystyrene–poly(propylene oxide) (PS–PPO) solvent-cast blends as a function of the blend composition and constituent molecular weights. The PVC–PDMS blends show a pronounced surface enrichment of PDMS, which is higher the lower the molecular weight of PDMS. The surface behavior ofthe PPO–PS blends is strongly dependent on the solvent used. Despite the much lower surface tension of PPO compared to that of PS, no surface segregation of PPO isobserved in the PPO–PS blends cast from tetrahydrofuran, while the blends cast from chloroform exhibit a high surface enrichment of PPO.

Blends of polyamide 6, polycarbonate, and poly(propylene oxide). I. Reactive compatibilization–morphology relationships

The relationship between reactive compatibilization and morphology of the polyamide 6–polycarbonate (PA6–PC) and polyamide 6–polycarbonate–poly(pro-pylene oxide) (PA6–PC–PPO) blends were investigated by means of torque values, scanning electron microscopy, and Fourier transform infrared spectroscopy. The micrographs show that the blends processed for a long period of time presented a PC domain of smaller size and better adherence between the phases than the blends processed for a short period of time. This fact can be related with the presence of the block copolymer of PA6–PC synthesized in situ by the reaction of PA6 and PC and depend on temperature and mixing time. The presence of PPO does not impede the formation of copolymer but interferes on the size of the domain.

Formation of complexes of crown ethers in the absence of solvent observed by differential thermal analysis

Abstract Differential thermal analysis was employed as a new method to observe the formation of complexes of dibenzo-18-crown-6 polyether and macrocyclic nitro derivatives with potassium iodide. DTA thermograms of polyethers, of solid complexes, and mixtures of polyether and potassium iodide were obtained in an atmosphere of dry nitrogen.

Carbon-13 NMR high-resolution study at solid of polyamide 6/PPO blends containing compatibilizer-block copolymer and polycarbonate

Two types of blends containing polyamide 6 and poly(propylene oxide) (PPO) were prepared. One of them was mixed with polycarbonate (PC) in a Brabender mixer. The other one was prepared in solution with the block copolymer as the interfacial agent. The blends were analyzed by 13C nuclear magnetic resonance techniques at solid state, such as: magic angle spinning (MAS); cross-polarization MAS, and variable contact time experiment. It was observed that the addition of PC in the nylon 6/PPO system causes a hardening of it, which can be attributed to strong links, like a hydrogen bond. The ideal quantity of block copolymer added to a blend to improve the compatibility is between 5 and 10%. An increase of the quantity of this agent probably makes it act as a third component. Therefore, both PC and block copolymer can be used as an interfacial agent for nylon 6/PPO blends in an ideal composition.