The Miscibility of Novel Bisphenol-Propylene Epoxy Resin With Liquid NBR

A novel kind of bisphenol-type epoxy resin with a vinyl side-chain was developed and its miscibility behavior with liquid nitrile-butadiene rubber (NBR) was investigated. The diglycidyl ether of bisphenol propylene (DGEBP) was prepared by the condensation of phenol with acrolein in the presence of an acid catalyst and the subsequent epoxidization with epichlorohydrin (ECH). The structures of the bisphenol and corresponding epoxy resin were characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectral analyses and the epoxy value was determined to be 0.34 mol/100 g by titration. The mixture of DGEBP with the liquid NBR containing diglycidyl ether of bisphenol acetone (DGEBA) was prepared and cured with diaminodiphenylmethane (DDM). The miscibility and morphology of the mixture system were studied by dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM), respectively. The cured mixture of DGEBP/NBR/DDM exhibited good miscibility and, therefore, no separation, along with a transparent appearance at rubber contents of 10 wt% and 30 wt%. For cured DGEBP/DGEBA/NBR/DDM systems at 20 wt% rubber content, the dispersed rubber phase and rubber particles were not observed by DMTA or TEM at DGEBP content above 40 wt%. The DMTA plot showed a single peak related to the glass transition temperature (T _g) which decreased with increasing DGEBP content. The appearance of the system varied from transparent to opaque and the rubber separated from the epoxy matrix to form two phases when the DGEBP content decreased. The T _g values of the rubber- and epoxy-rich phases were strongly dependent on the DGEBP content in the mixed system. The miscibility of epoxy resin with liquid NBR can be altered by varying the ratio of DGEBP to DGEBA.     

Behaviour of the miscibility of poly(ethylene oxide)/liquid crystal blends

The microscopic behaviour of blends of poly(ethylene oxide) with two different low molecular weight liquid crystals (LC) was studied in order to evaluate miscibility. One of the liquid crystal components had a phase transition temperature lower than the melting temperature of poly(ethylene oxide) (PEO), and the other a higher value. The low molecular weight liquid crystal components were 4-cyano-4′-n-heptylbiphenyl (7CB) and p-cyanophenyl p-pentyloxybenzoate (pCP). Thermal analysis and polarized optical and scanning electron microscopy were employed. The melting temperature (T_m) depression of PEO increased with LC content in the blend, suggesting that the PEO was miscible with both liquid crystals in the isotropic phase. The spherulitic structural morphology of the semicrystalline components is affected by the presence of liquid crystals. © 1998 SCI.     

Removal of H2S using a new Ce(IV) redox mediator by a mediated electrochemical oxidation process

BACKGROUND: Hydrogen sulfide (H₂S) from industrial activities and anaerobic manure decomposition in commercial livestock animal operations is an offensive malodorous and toxic gas even in small concentrations, causing serious discomfort and health and social problems. The objective of this study was to employ for the first time a novel, attractive, low cost, environmentally benign mediated electrochemical oxidation (MEO) process with Ce(IV) as the redox catalyst for H₂S gas removal from an H₂S–air feed mixture. RESULTS: The influence of liquid flow rate (Q_L) from 2–4 L min^?1, gas flow rate (Q_G) from 30–70 L min^?1, H₂S concentration in the H₂S–air feed mixture from 5–15 ppm, and Ce(III) pre‐mediator concentration in the electrochemical cell from 0.1–1 mol L^?1 on H₂S removal efficiency were investigated. Both liquid and gas flow rates influenced the removal efficiencies, but in opposite directions. Nearly 98% H₂S removal was achieved when the concentration of Ce(IV) mediator ion in the flowing scrubbing liquid reached 0.08 mol L^?1. CONCLUSIONS: The new MEO method proved promising for H₂S removal, achieving high removal efficiency. Integration of the electrochemical cell with the scrubber set‐up ensured continuous regeneration of the mediator and its repeated reuse for H₂S removal, avoiding use of additional chemicals. Since the process works at room temperature and atmospheric pressure utilizing conventional transition metal oxide electrodes more commonly used in industrial applications, it is also safe and economical. Copyright © 2008 Society of Chemical Industry     

The glass transition,crystallization, and melting characteristics of a class of polyester ionomers

The glass transition temperature (T_g), crystallization, and melting character of a class of random polyester ionomers (polymer containing < 10 mol % ionic groups) were investigated. The nonlinear change of the T_g and crystallization and melting behavior were characterized using differential scanning colorimetry (DSC). The ionomers are derived from polyethylene terephathalate (PET) modified through copolycondensation with a fully neutralized sulfonate moiety (sodiosulfo) isophthalate (Na‐SIP). Significant and systematic changes in the glass transition temperature and thermal characteristics upon addition of Na‐SIP on the PET backbone were observed, indicating strong association and interaction on the ionic species. At Na‐SIP levels ≥ 4 mol %, the turn of the the glass transition temperature was found, and the same results were obtained for the samples treated either by quenching or dissolution, suggesting the presence of reversible crosslink and aggregation of the ionic species within the organic matrix. When crystallized from the healing or cooling the samples during the DSC nonisothermal crystallization run at a 10°C/min, the enthalpy of the cold crystallization and melting showed an obvious decrease with the increase of Na‐SIP content, and changes of the crystal temperature had an analogy to those of the T_g. A tune of the crystal temperature was found at Na‐SIP levels ≥ 3 mol % (see Figs. 4 , 5 , and 7 ). The experimental data were discussed in the context of the restricted mobility model of the aggregation in the ionomers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3660–3666, 2002     

Destabilizing effects of fructose-1,6-bisphosphate on membrane bilayers

Fructose-1,6-bisphosphate (FBP) is a high-energy glycolytic intermediate that decreases the effects of ischemia; it has been used successfully in organ perfusion and preservation. How the cells utilize external FBP to increase energy production and the mechanism by which the molecule crosses the membrane bilayer are unclear. This study examined the effects of FBP on membrane bilayer permeability, membrane fluidity, phospholipid packing, and membrane potential to determine how FBP crosses the membrane bilayer. Large unilamellar vesicles composed of egg phosphatidylcholine (Egg PC) were made and incubated with 50 mM FBP spiked with ¹⁴C-FBP at 30°C. Uptake of FBP was significant (P<0.05) and dependent on the lipid concentration, suggesting that FBP affects membrane, bilayer permeability. With added calcium (10 mM), FBP uptake by lipid vesicles decreased significantly (P<0.05). Addition of either 5 or 50 mM FBP led to a significant increase (P<0.05) in Egg PC carboxyfluorescein leakage. We hypothesized that the membrane-permeabilizing effects of FBP may be due to a destabilization of the membrane bilayer. Small unilamellar vesicles composed of dipalmitoyl pC (DPPC) were made containing either diphenyl-1,3,5-hexatriene (DPH) or trimethylammmonia-DPH (TMA-DPH) and the effects of FBP on the fluorescence anisotropy (FA) of the fluorescent labels examined. FBP caused a significant decrease in the FA of DPH in the liquid crystalline state of DPPC (P<0.05), had no effect on FA of TMA-DPH in the liquid crystalline state of DPPC, but increased the FA of TMA-DPH in the gel state of DPPC. From phase transition measurements with DPPC/DPH or TMA-DPH, we calculated the slope of the phase transition as an indicator of the cooperativity of the DPPC molecules. FBP significantly decreased the slope, suggesting a decrease in fatty acyl chain interaction (P<0.05). The addition of 50 mM FBP caused a significant decrease (P<0.05) in the liquid crystalline/gel state fluorescence ratio of merocyanine 540, indicating increased head-group packing. To determine what effects these changes would have on cellular membranes, we labeled human endothelial cells with the membrane potential probe 3,3′-dipropylthiacarbocyanine iodide (DiSC₃) and then added FBP. FBP caused a significant, dose-dependent decrease in DiSC₃ fluorescence, indicating membrane depolarization. We suggest that FBP destabilizes membrane bilayers by decreasing fatty acyl chain interaction, leading to significant increases in membrane permeability that allow FBP to diffuse into the cell where it can be used as a glycolytic intermediate.     

Miscibility and morphology of poly(vinylidene fluoride)/poly[(vinylidene fluoride)‐ran‐trifluorethylene] blends

This study presents an investigation of the effect of the different crystalline phases of each blend component on miscibility when blending poly(vinylidene fluoride) (PVDF) and its copolymer poly[(vinylidene fluoride)‐ran‐trifluorethylene] [P(VDF–TrFE)] containing 72 mol % of VDF. It was found that, when both components crystallized in their ferroelectric phase, the PVDF showed a strong effect on the crystallinity and phase‐transition temperature of the copolymer, indicating partial miscibility in the crystalline state. On the other hand, immiscibility was observed when both components, after melting, were crystallized in their paraelectric phase. In this case, however, a decrease in crystallization temperatures suggested a strong interaction between monomers in the liquid state. Blend morphologies indicated that, in spite of the lack of miscibility in the crystalline state, there is at least miscibility between PVDF and P(VDF–TrFE) in the liquid state, and that a very intimate mixture of the two phases on the lamellar level can be maintained upon crystallization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1362–1369, 2002     

Effects of nematic coupling on the phase behaviour of nematogen mixtures

The phase behaviour of binary nematogen mixtures of side‐chain liquid crystal crosslinked polymers and low molecular weight liquid crystals is investigated with particular emphasis on the effects of nematic coupling. The cross nematic quadrupole parameter ν₁₂ is assumed to be proportional to the geometric average of ν₁₁ and ν₂₂ characteristic of single nematogens. In the weak coupling limit, the proportionality constant is lower than 1, and the phase diagram exhibits a reduced miscibility of the nematogens. In the case of strong coupling, the proportionality constant exceeds 1 resulting in higher miscibility. This is characterized by a nematic order that extends to temperatures above the upper nematic–isotropic transition temperature. A wide region of miscibility emerges showing a single nematic phase. Nematogens having similar nematic–isotropic transition temperatures exhibit different phase properties from systems with widely separated transition temperatures. Effects of the polymer volume fraction at crosslinking, rubber elasticity parameters of the network, and the Flory–Huggins interaction parameter on the equilibrium phase diagram of these systems are discussed. © 2001 Society of Chemical Industry     

Morphology and thermal properties of two polymethacrylates modified by a polymer liquid crystal

We have studied blends of a polymer liquid crystal (PLC) with poly(cyclohexylethyl methacrylate) (PCHEMA) or poly(cyclohexylpropyl methacrylate) (PCHPMA). The PLC is PET/0.6PHB where PET = poly(ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of the latter in the copolymer. The microstructure was studied by scanning electron microscopy (SEM). PCHEMA + PLC (20 wt% of the latter, blend E) has a fine texture with LC islands evenly distributed in the matrix and good adhesion between the phases resulting from their partial miscibility. The PCHPMA + PLC (20 wt% of the latter, blend P) shows only limited compatibility. The SEM results are confirmed by values of the glass transition temperatures T_g determined via thermal mechanical analysis. The T_g value of the blend E is shifted towards the T_g of PLC; T_g of blend P is practically equal to that of PCHPMA. The linear isobaric expansivity α_L values for both blends are lower than the respective values for pure PCHPMA and PCHEMA. Thermal stabilities of the blends determined by thermogravimetry are also better than those of pure polymethacrylates. The temperature of 50% weight degradation for blend E is higher than that for pure PCHEMA by more than 60 K Copyright © 2004 Society of Chemical Industry     

Action of cobra venom phospholipase A2 on large unilamellar vesicles: Comparison with small unilamellar vesicles and multibilayers

Phospholipase A₂ (Naja naja naja) catalyzes the hydrolysis of dipalmitoyl phosphatidylcholine in small unilamellar vesicles (SUVs) with a faster initial rate than in large unilamellar vesicles (LUVs) and multilamellar vesicles (MLVs). For the SUVs, the hydrolysis was initially faster for gel phase than liquid crystalline phase phospholipid. For both LUVs and MLVs, hydrolysis was low except in a small temperature range around the thermotropic phase transition of the phospholipid. In this temperature range, the reaction time course of phospholipase action on dipalmitoyl phosphatidylcholine in LUVs and MLVs included a lag period. With SUVs, a lag period also was observed above the phase transition temperature, but it was not observed below it.     

Synthesis and aggregation behavior of an amphiphilic cobalt (III) complex that coordinates higher diacylglyceryldiamine ligands

An amphiphilic cobalt complex that coordinates a higher diacylglycerylethylenediamino group was prepared. They extensively aggregated in aqueous solution upon ultrasonication. Electron microscopy indicated formation of stable bilayer structures, which further formed vesicles and fibrous aggregates. We observed an intermediate state that led to a network morphology in the fusion process of small unilamellar vesicles. Differential scanning calorimetry experiments establiched the presence of the phase transition from gel to liquid crystal for all probes in which a C₁₄ to C₁₈ acyl group was bound. The phase-transition temperature was elevated with increasing carbon numbers of the acyl group.     

Synthesis and characterization of side-chain liquid crystalline polysiloxanes

The synthesis and characterization are described for a series of side-chain liquid crystal polysiloxanes using polyhydrosilylation reaction between a poly(hydrogen methyl-co-dimethylsiloxanes),-(OSiHMe)_x,-(OSiMe2)_y-, where x/y was 13/87, 30/70, 55/45, 73/27 and 98/2, and [4-(allyloxy)benzoyll biphenyl mesogenic group. The side-chain liquid crystal polysiloxanes were characterized by¹H NMR,¹³C NMR, IR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and optical polarizing microscopy. The dimethylsiloxane segment factors governing thermal transition temperatures and activation energy (E_a) of the nematic-to-isotropic phase transition are discussed.     

The effect of 60Co γ‐rays on the crystal structure,melting and crystallization behavior of poly(butylene succinate)

The results obtained for poly(butylene succinate) (PBS) after ⁶⁰Co γ‐ray irradiation, studied by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimeter (DSC) and polarizing optical microscopy (POM), revealed that the degree of crystallinity, melting temperature and enthalpy decreased with increasing irradiation dose, but that the crystal structure of PBS did not vary when compared to non‐irradiated PBS. By using Scherrer equation, small changes occurred in the crystal sizes of L₀₂₀, L₁₁₀ and L₁₁₁. The spherulitic morphology of PBS was strongly dependent on irradiation dose and changed significantly at higher irradiation dosages. The crystallization kinetics of PBS indicated that the Avrami exponent (n) for irradiated PBS was reduced to 2.3, when compared to non‐irradiated PBS (3.3). Copyright © 2004 Society of Chemical Industry     

Preparation and study of a thermo-responsive membrane using binary liquid crystal mixtures of cholesteryl cetyl ether and cholesteryl oleyl carbonate

A facile method for the synthesis of thermotropic liquid crystalline cholesteryl cetyl ether (CCE) was carried out from cholesterol and cetyl alcohol using montmorillonite K-10 as an acid catalyst. The aim of this study was to investigate the use of liquid crystalline blends of CCE and cholesteryl oleyl carbonate (COC) with appropriate crystal to smectic phase temperature (T _c?Cs) just above body temperature as a temperature-modulated drug permeation system. Using 30/70?mol ratio of COC/CCE, a mixture of desirable phase transition temperature was obtained. The phase transition behavior of COC/CCE binary liquid crystalline mixture was established by differential scanning calorimetry and polarizing optical microsopy. The COC/CCE-embedded cellulose nitrate membrane was used by an in vitro drug penetration studies. Paracetamol and mesalazine were chosen as hydrophobic and hydrophilic drug models, respectively. Paracetamol permeability through the membrane was higher at temperatures above the phase transition of liquid crystal (LC) blends (39?°C) than its permeability below the phase transition temperature of liquid crystal blends (30?°C). The drug penetration through LC-embedded cellulose membrane was influenced by the pore size of the membrane and therefore the adsorbed amount of LC. There was no penetration of mesalazine through that membrane presumably, due to the differences in hydrophilicity of LC-embedded membrane and permeated drug.     

Effect of water on the solubilities and mass transfer coefficients of gases in a heavy fraction of fischer-tropsch products

The effects of water on the solubilities, C^*, and volumetric mass transfer coefficients, k_La, for CO, H₂, CH₄ and CO₂ in a heavy fraction of Fischer-Tropsch liquid were examined at elevated pressures and temperatures at different mixing power inputs. For these gases, higher solubilities were measured in the hydrocarbon mixture saturated with water than those obtained in the hydrocarbon free of water. The k_La values for the four gases were slightly affected by the presence of dissolved water in the hydrocarbon mixture; and they were strongly dependent on the power input per unit liquid volume. Two empirical correlations for k_La as a function of turbine speed and pressure are proposed.     

Thermal expansivity and thermal conductivity of amorphous thermoplastic polyimide and polymer liquid crystal blends

Linear thermal expansivities α_L and thermal conductivities of polyimide (TPI) and polymer liquid crystal (PLC) blends were studied. The glass transition temperatures T_g of our amorphous TPI and the PLC are, respectively, 240 and 220°C. The addition of the PLC induces orientation through the channeling process, as predicted by an extension of the Flory statistical‐mechanical theory of PLCs (27). Channeling was observed at PLC concentrations as low as 5 wt%. Thermal conductivity decreases with the addition of the PLC to the TPI. The anisotropic expansivity of the blends shows a strong dependence on PLC concentration and orientation direction. The pure PLC shows a maximum on the along‐the‐flow expansivity vs. temperature curves and also negative α_L values. TPI addition moves the expansivities to positive values, but the maximum persists, even for 5% PLC only.     

Miscibility of blends of epoxidized natural rubber and poly(ethylene-co-acrylic acid)

The blends of epoxidized natural rubber (50 mol %) (ENR) and poly(ethylene-co-acrylic acid) (PEA) (6 wt %) are demonstrated to be partially miscible up to 50% by weight of PEA and completely miscible beyond this proportion. The miscibility has been confirmed by a DSC study which exhibits a single second-order transition (T_g) for the 30 : 70 and 50 : 50 (ENR : PEA) blends. For the 70 : 30 (ENR : PEA) blend, the T_g's shift toward an intermediate value but do not merge to form a single T_g, making the blend partially miscible. The miscibility has been assigned to the esterification reaction between – OH groups formed in situ during melt blending of ENR and – COOH groups of PEA. The occurrence of such reactions have been confirmed by UV and IR spectroscopic studies. The existence of a single phase of the blends beyond 50 wt % of PEA has been shown by SEM studies. © 1995 John Wiley & Sons, Inc.     

Poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene blends: thermodynamic interactions from glass transition data

Summary The glass transition temperatures of several blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene have been measured by DSC, and the T _g -composition data have been described on the basis of a thermodynamic treatment. A negative enthalpy of mixing and a positive entropy of mixing have been found, in agreement with the well known miscibility of the blend. The presence of a singolarity point in the T _g -composition plot has been evidenced and considered at the light of a theoretical treatment recently proposed. Received: 27 November 1998/Accepted: 13 March 1999     

Kinetically Stable Bicelles with Dilution Tolerance,Size Tunability,and Thermoresponsiveness for Drug Delivery Applications

Mixtures of a phospholipid (1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphatidylcholine, DPPC) and a sodium‐cholate‐derived surfactant (SC‐C₅) at room temperature formed phospholipid bilayer fragments that were edge‐stabilized by SC‐C₅: so‐called “bicelles”. Because the bilayer melting point of DPPC (41 °C) is above room temperature and because SC‐C₅ has an exceptionally low critical micelle concentration (<0.5 mm ), the bicelles are kinetically frozen at room temperature. Consequently, they exist even when the mixture is diluted to a concentration of 0.04 wt %. In addition, the lateral size of the bicelles can be fine‐tuned by altering the molar ratio of DPPC to SC‐C₅. On heating to ≈37 °C, the bicelles transformed into micelles composed of DPPC and SC‐C₅. By taking advantage of the dilution tolerance, size tunability, and thermoresponsiveness, we demonstrated in vitro drug delivery based on use of the bicelles as carriers, which suggests their potential utility in transdermal drug delivery.     

Thermodynamic, morphological, mechanical and fracture properties of poly(methyl methacrylate)(PMMA) modified divinylester(DVE)/styrene(St) thermosets

Modified St/DVE cured materials were formulated with a commercial DVE_C (M_n=1015 g/mol) and a synthesized (583 g/mol) DVE_L resins and styrene, adding a high molecular weight PMMA as modifier. A thermodynamic analysis of the initial miscibility for the St-PMMA and DVE-PMMA quasibinary systems was realized using the experimental cloud-point curves (CPC), in order to determine the binary interaction parameters. Calculated CPC for the quasiternary St/DVE/PMMA at 25 °C showed that St/DVE_L/PMMA is miscible in the whole concentration range, while the St/DVE_C/PMMA becomes partially miscible almost at the start of curing reaction (very low conversions). This miscibility behavior originates quite different morphologies in the systems cured at room temperature. Final materials with DVE_L showed typical nodular microphase morphologies generated by polymerization induced phase separation (PIPS) mechanism. Materials with DVE_C showed typical macrophase morphologies characterized by droplets-like domains, with secondary phase separation inside the droplets and in the mother phase. These morphological structures were directly related to the thermal and mechanical properties of the final systems. The low molecular weight resin generates a thermoset of higher glass transition temperature, bending modulus, and compression yield stress, but lower fracture resistance than the high molecular weight commercial resin. The addition of a thermoplastic modifier allowed to improve the fracture resistance without the unwanted reduction in modulus, which is inevitable when using elastomeric additives. The reason for the existence of an optimum modifier concentration is also discussed.     

Novel aprotic polar polymers 2. Miscibility of aliphatic polysulfoxides

Summary Miscibility of aliphatic polysulfoxides (1, 2) with other commodity polymers was examined by comparing glass transition temperature(s) (T_gs) of the mixture of these polymers with T_gs of the original polymers by differential scanning calorimetry. It was found that the aliphatic polysulfoxides had good miscibility with poly(2-methyl-2-oxazoline) or/and poly(N-vinylpyrrolidone). Received: 25 December 1997/Revised version: 23 February 1998/Accepted: 25 February 1998