Comparison of chromatographic ion-exchange resins. III. Strong cation-exchange resins

A comparative study was performed on strong cation-exchangers to investigate the pH dependence, efficiency, binding strength, particle size distribution, static and dynamic capacity, and SEM pictures of chromatographic resins. The resins tested included: SP Sepharose XL, Poros 50 HS, Toyopearl SP 550c, SP Sepharose BB, Source 30S, TSKGel SP-5PW-HR20, and Toyopearl SP 650c. Testing was performed with four different proteins: anti-FVII Mab (IgG), aprotinin, lysozyme, and myoglobin. Dependence of pH on retention was generally very low for proteins with high pI. An unexpected binding at pH 7.5 of anti-FVII Mab with pI < 7.5 was observed on several resins. Efficiency results show the expected trend of higher dependence of the plate height with increasing flow rate of soft resins compared to resins for medium and high-pressure operation. Determination of particle size distribution by two independent methods, Coulter counting and SEM, was in very good agreement. The mono-dispersed nature of Source 30S was confirmed. Binding to cation-exchange resins as a function of ionic strength varies depending on the specific protein. Generally, binding and elution at high salt concentration may be performed with Toyopearl SP 550c and Poros 50 HS, while binding and elution at low salt concentration may be performed with Toyopearl SP 650c. A very high binding capacity was obtained with SP Sepharose XL. Comparison of static capacity and dynamic capacity at 10% break-through shows in general approximately 50-80% utilisation of the total available capacity during chromatographic operation. A general good agreement was obtained between this study and data obtained by others. The results of this study may be used for selection of resins for testing in process development. The validity of experiments and results with model proteins were tested using human insulin precursor in pure state and in real feed-stock on Toyopearl SP 550c, SP Sepharose BB, and Toyopearl SP 650c. Results showed good agreement with experiments with model proteins.     

Thermal behaviour of ethynyl and ethenyl terminated imide resins

A series of ethynyl and ethenyl end-capped imide resins were synthesised by the reaction of 9,9-bis(4-aminophenyl) fluorene (BAF) with pyromellitic dianhydride (PMDA)3/3′, 4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxy phenyl) hexafluoropropane dianhydride (6F) and 3-ethynyl aniline/maleic anhydride. Structural characterisation was done by infra red and elemental analysis. Thermal characterisation was done by differential scanning calorimetry and thermogravimetric analysis. The decomposition temperatures of cured resins were above 200°C in nitrogen atmosphere. Char yield at 800°C ranged from 59–65.5%.     

Synthesis and characterization of imide ring and siloxane-containing cycloaliphatic epoxy resins

A novel imide ring and siloxane-containing cycloaliphatic epoxy compound 1,3-bis[3-(4,5-epoxy-1,2,3,6-tetrahydrophthalimido)propyl]tetramethyldisiloxane (BISE) was synthesized from 1,3-bis(3-aminopropyl)tetramethyldisiloxane and tetrahydrophthalic anhydride by a two-step procedure, which was then thermally cured with alicyclic anhydrides hexahydro-4-methylphthalic anhydride (HMPA) and hexahydrophthalic anhydride (HHPA), respectively. As comparison, a commercial available cycloaliphatic epoxy 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ERL-4221) cured with the same curing agents was also investigated. The experimental results indicated that the BISE gave the exothermic starting temperature higher than ERL-4221 no mater what kind of curing agents applied, implying the reactivity of the former is lower than the latter. The fully cured BISE epoxy resins have good thermal stability with thermal decomposition temperature at 5% weight loss of 346-348 °C in nitrogen, although they gave the relatively low glass transition temperatures due to the presence of flexible propyl and siloxane segments in the epoxy backbone. The BISE epoxy resins exhibited good mechanical and dielectric properties as well as low water absorption. The improved dielectric properties and the reduced water absorption of BISE epoxy resins are attributed to the low polarity as well as the hydrophobic nature of siloxane segment in the epoxy backbone.     

High-strength fire- and heat-resistant imide resins containing cyclotriphosphazene and hexafluoroisopropylidene groups

High-strength fire- and heat-resistant polymers were obtained by the thermally induced melt-polymerization of maleimido-phenoxy cyclotriphosphazenes linked by hexafluoroisopropyliden-ediphthalimide groups. These polymers show good thermal stability and high char yields: 78–80% at 800°C in nitrogen and 60–68% in air at 700°C. Graphite-fabric laminates did not burn in pure oxygen, even at 300°C (LOI = 100%), and were tested for shear, flexural, and tensile strengths. Two monomers were synthesized by reacting tris(4-aminophenoxy)-tris(phenoxy) cyclotriphosphazene with maleic anhydride and hexafluoroisopropylidenediphthalic anhydride. The triamine was synthesized by a stepwise reaction of hexachlorocyclotriphosphazene with phenol and 4-nitrophenol to give tris(4-nitrophenoxy)-tris(phenoxy)cyclotriphosphazene and reducing the nitro groups. The structures of cyclic phosphazene-trimeric precursors and the polymers were characterized by FT-IR, ¹H-NMR, ³¹P-NMR, and mass spectroscopy. The curing behaviors of polymer precursors were evaluated by differential scanning calorimetry and thermogravimetric analyses.     

Syntheses and characterizations of thermally degradable epoxy resins. III

In flip‐chip technology, the development of reworkable underfill materials has been one of the keys to the recovery of highly integrated and expensive board assembly designs through the replacement of defective chips. This article reports the syntheses, formulations, and characterizations of two new diepoxides, one containing secondary ester linkages and the other containing tertiary ester linkages, that are thermally degradable below 300 °C. The secondary and tertiary ester diepoxides were synthesized in three and two steps, respectively. Both compounds were characterized with NMR and Fourier transform infrared spectroscopy and formulated into underfill materials with an anhydride as the hardener and an imidazole as the catalyst. A dual‐epoxy system was also formulated containing the tertiary ester diepoxide and a conventional aliphatic diepoxide, 3,4‐epoxy cyclohexyl methyl‐3,4‐epoxycyclohexyl carboxylate (ERL‐4221E), with the same hardener and catalyst. The curing kinetics of the formulas were studied with differential scanning calorimetry (DSC). Thermal properties of cured samples were characterized with DSC, thermogravimetric analysis, and thermomechanical analysis. The dual‐epoxy system showed a viscosity of 18.7 and 0.87 P at 25 and 100 °C, respectively. The cured secondary, tertiary, and dual‐epoxy formulas showed decomposition temperatures around 265, 190, and 220 °C, glass‐transition temperatures around 120–140, 110–157, and 140–157 °C, and coefficients of thermal expansion of 70, 72, and 64 ppm/°C below their glass‐transition temperatures, respectively. The shear strength of the cured dual‐epoxy system decreased quickly with aging at 230 °C. The reworkability test showed that the removal of a chip underfilled with this material from the board was quite easy, and the residue on the board could be thoroughly removed with a mechanical brush without obvious damage to the solder mask. In summary, the synthesized tertiary epoxide can be used as a reworkable underfill for flip‐chip applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1796–1807, 2002     

Phosphorus-containing podands

A number of monopodands havingo-diphenylphosphinyl terminal groups were synthesized by alkylating sodium derivatives of oligoethylene glycols witho-(bromomethyl)phenyldiphenylphosphine. The stability constants of the complexes of these ligands with alkali metal cations at 25 °C were determined conductometrically in a THF—chloroform solution (41, v/v). The complexing ability of monopodands with respect to the cations studied increases monotonically as the number of electron-donating sites increases (from 3 to 8) for all of the cations except Li⁺ and, to some extent, Na⁺. In the case of Li⁺ a smooth decrease in the stability of the complexes is observed. The monopodands obtained in this work differ drastically in this regard from their structural isomers, bis[o-(diphenylphosphinylmethyl)phenyl] ethers of oligoethylene glycols, which had been studied previously.For part 10, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 952–956, May, 1993.     

Phosphorus-containing polyurethans

Phosphorus-containing polyurethans of the formula were prepared by interfacial polymerization of 1,4-butanebischloroformate and p-xylylene-α, α-bischloroformate with bis(m-aminophenyl)alkylphosphine oxides. The polymers had number average molecular weights up to 8600. A test of the stability to alkali of one of the polymers (R?CH₃, X?1,4-C₆H₄) showed it to be as resistant as nonphosphorus analogs, and a film of this polymer exhibited self-extinguishing properties. Thermal degradation of the phosphorus polymers, which began at approximately 230°C, occurred by an initial first-order process, releasing chiefly carbon dioxide. The energies of activation for the maximum rates of weight loss were 31–37 kcal/mole.     

Phosphorus-containing podands

An improved preparative method for the synthesis of oligo(ethylene glycol) bis[2-(diphenylphosphinoyl)ethyl] ethers has been developed. The complex-forming ability of these ligands toward alkali-metal cations has been studied by conductometry in anhydrous MeCN at 25°C. Ligands of this type have been shown to be highly efficient and selective complexing agents with respect to the Li⁺ cation. The stability series of the complexes M⁺L has the form Li > Na > K > Rb in all cases. The complexing properties and selectivity displayed by these new monopodands in MeCN have been compared with those in the THF-CHCl₃ (41) system studied previously.For a preliminary communication, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 518–522, March, 1993.     

Macroreticular resins. III. Formation of macroreticular styrene–divinylbenzene copolymers

Experimental evidence is presented that describes the mechanism of formation of macroreticular styrene–divinylbenzene copolymers in which phase separation occurs during a suspension polymerization. The mode of formation of the macroreticular structure is described as a three-stage process in which each droplet of the organic phase behaves as an individual in a bulk polymerization that results in a bead of copolymer. Macroreticular structure formation is described by changes in copolymer swelling ratios, infrared absorption spectra of vinyl groups pendent to the polymeric matrices, surface area, total porosity, and pore-size distribution. The proposed mechanism of formation is also substantiated by electron micrographs of the copolymers during various stages of the copolymerization.     

Phenolic resins for solid-phase peptide synthesis. III. Copolymerization of acrylonitrile and p-acetoxystyrene and comparison of reactivity with styrene-based resins

The copolymerization of acrylonitrile (r₁) and p-acetoxystyrene (r₂) in bulk yields reactivity ratios r₁ = 0.08 and r₂ = 0.42. Crosslinked resins are readily obtained by a new type of precipitation copolymerization of acrylonitrile, p-acetoxystyrene, and divinylbenzene. After deacetylation, the phenolic groups afford useful attachment sites for protected amino acids as a first stage in solid-phase peptide synthesis. Reactivity of typical 10% functionalized polyacrylonitrile-based resins is comparable to that of the more usual polystyrene-based equivalents, although swelling characteristics of the two types of resin are very different.     

Aromatic polyethers,polysulfones, and polyketones as laminating resins. III

4,4′-Diphenoxydiphenylsulfone was polymerized with isophthaloyl chloride and terephthaloyl chloride in Friedel-Crafts polymerizations. These polymers had 5-cyanoisophthaloyl units in the backbone obtained either by using 1,3-bis(p-phenoxybenzoyl)-5-cyanobenzene or 5-cyanoisophthaloyl chloride as part of the acid chloride monomer. A terpolymer having 22 wt-% 5-cyanoisophthaloyl unit was also prepared from the Friedel-Crafts polymerization of 1,3-bis(p-phenoxybenzenesulfonyl)benzene and 5-cyanoisophthaloyl chloride. These terpolymers were crosslinked through heating to give insoluble products which proved to be thermally less stable than the uncrosslinked polymers.     

Urea-formaldehyde resins. III. Constitutional characterization by 13C fourier transform NMR spectroscopy

¹³C Fourier transform NMR has been used to characterize a random chemical structure of ureaformaldehyde resins. By comparison of ¹³C chemical shifts with synthesized standard derivatives from urea and formaldehyde the analysis of reacted formaldehyde was completed. In a ¹³C spectrum of resin each signal due to reacted formaldehyde (e.g., methylol group, methylene group, and dimethylene ether group) was isolated. Measurement of a ¹³C spectrum of resin by the gated decoupling of proton without nuclear Overhauser effect made a quantitative analysis of reacted formaldehyde possible. In this quantitative analysis a ¹³C quantity of carbonyl groups in urea residue can be directly compared with that of each combined formaldehyde.     

Phosphorus-containing uracil analogs

We have synthesized phosphorus analogs of 6-methyluracil by cyclization of alkylphosphoric acid diamides of the ROP(O)(NH₂)₂ type by the method proposed for the cyclization of phenylphosphoric acid diamide [1].     

Blends of bisphenol-A polycarbonate and acrylic polymers: III. Effect of imide concentration on compatibility

Imide units copolymerized with MMA units have been selected in order to improve compatibility between PC and acrylics through specific interaction or internal repulsion. Good dispersion of acrylic inside a PC matrix has been observed upon melt mixing, which can be partially explained by the good rheological agreement between these two polymers. Transmission electron microscopy has shown that the system remains phase separated from 5 to 95 wt % of PC. Phase diagrams for three different imide concentrations have been drawn. Results obtained by DSC (conventional and with enthalpy relaxation) are similar to those obtained by optical cloud point detection. The phase diagrams show the raise of the PC/PMMA demixtion curve (LCST type) when percentage of imide increases in the acrylic phase. Theoretical calculations on binary interaction energy density show a slight improvement of the interaction between acrylic and PC when imide percentage increases. Cloud point measurements on 50/50 PC/acrylic blends varying the imide concentration show that the improvement of compatibility deduced from the raise of the demixtion curve (LCST type) is more related to a kinetic effect (the high T_g of imidized samples is reducing macromolecule mobility) than specific interactions. The calculated favorable interactions are probably too weak to be detected with cloud point measurements. The microstructures obtained after crystallization of the PC phase under solvent vapors in phase separated PC/acrylics blends can also be explained by T_g effects. Moreover, solvent vapor exposure could be a powerful tool to determine the real thermodynamic behavior of the blends at room temperature. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 749–761, 1997