Tetrahydrofuran , polystyrene characteristics

The GPC analysis was conducted using a seven column Styragel arrangement with tetrahydrofuran as the carrier solvent. Solution concentrations of 1/8% (w/v) were used. The flow rate was 1 ml min-1. The characteristics of this column arrangement are presented elsewhere (20,21). The Styragel columns were calibrated using eleven polystyrene standards. All of the polystyrenes prepared in this work were analyzed by gel permeation chromatography. Without exception, all samples were found to have values of Mz/Mw<1.07 and values of / . 05. None of... 

Solubility tests permit at least a tentative identification of the components also in polymer blends. Blends of ABS and polycarbonate are soluble in most polar solvents. Solubility in tetrahydrofuran and methyl ethyl ketone demonstrates the absence of polyolefins in such blends and the presence of aromatic polyesters or of polyamides can also be excluded. On the other hand, generally they may contain such highly soluble polymers as polystyrene, PVC, ABS, or polymethacrylates. However, blends that contain polybutylene terephthalate or polyethylene terephthalate do not dissolve in the usual solvents, but require m-cresol, which can he a clear indication that aromatic polyesters are present. Polyolefins dissolve at high temperatures, at least 110 °C, in toluene and p-xylene, and this behavior is characteristic of blends that contain polyethylene or polypropylene. 

Block copolymers consisting of segments with widely separated solubility characteristics have generated considerable interest because of their unusual surfactant properties. In fact, one of the earliest commercial block copolymers were the Wyandotte "Pluronics." These were poly(propylene oxide-b-ethylene oxide) prepared by sequential addition of ethylene oxide to sodium alkoxide initiated propylene oxide (37,38). Szwarc (39) and others (40,41) prepared poly(styrene-b-ethylene oxide) by addition of ethylene oxide to polystyrene anions in tetrahydrofuran. Other syntheses of AB or ABA block copolymers of styrene-ethylene oxide include sequential addition in various solvents, and coupling reactions (42,43). 

Ethylene oxide/styrene block copolymers have been further free-radical copolymerized with other ethylenically unsaturated compounds such as methyl methacrylate and methacrylic acid in benzene, tetrahydrofuran, and dimethylformamide (176). Correlations were made between reactivity ratio and solvent dielectric constant, as well as between solubility parameters of reaction solvent and growing polymer chains with marked effects apparent. Gel permeation chromatography of diblock and triblock copolymers based on polystyrene and poly(ethylene oxide) has revealed interesting molecular characteristics (177). Such block copolymers have an amphiphilic character. In aqueous solution, the polymers form spherical micells with a polystyrene core and a poly(ethylene oxide) outer sheath. The investigations used an aqueous-methanolic solution and were able to ascertain block copolymer structures and to estimate the impurities in the diblock copolymer. 

Triblock copolymers of poly(methyl methacrylate) at terminal ends with side chains containing an average of eight oxyethylene units each and a middle joining block of polystyrene were complexed with lithium perchlorate in tetrahydrofuran and cast into films (167). The polystyrene block markedly improved filmforming characteristics and mechanical properties, but lowered ion conductivity. Addition of methyl tetraethylene glycol increased ion conductivity by a factor of about five. The synthesis and preparation of other polymers useful for complexing cations have been described (168). 

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