Polymer solvent purification

Poly(acylonitrile) is soluble in DMF but not in solvents such as dichloromethane. DMF is not a suitable solvent to use in solvent purification not least because removing it from the final polymer is likely to be difficult. Increasing the 2-vinylpyridine concentration improves solubility in dichloromethane. 

We have investigated the solvolytic stability and reactivity of polymer-bound borohydrides and have evaluated these materials in several applications such as solvent purification, arsine generation, and metal reduction. These polymer-bound borohydrides offer several advantages over sodium or tetraethylammonium borohydride. The primary advantages are the convenience of use and the minimal introduction of ionic species or organic by-products into the treated bulk media. With the polymer-bound borohydrides, the cation is bonded covalently to the insoluble resin while the borohydride anion or its oxidation product (borate) is retained by ionic bonding. Typically, boron at levels of less than 5 ppm is the only impurity introduced into the treated medium. 

The extractive distillation data show that in general, for satisfactory operation, furfural is limited to high solvent-to-C4 feed ratios. The data in Table IV indicate the limiting solvent ratio to be ca. 12 to 1. In addition to its poor selectivity compared with other solvents, furfural reacts with itself to form a polymer (4) and with butadiene to form codimers which have been characterized in detail by Hillyer (5). Solvent losses to polymer and in the associated solvent purification system amount to a considerable yearly operating expense. 

Some of the most successful commercial processes that employ CO2 as a solvent involve polymeric substrates. Recently, SCF have been applied for polymerization, swelling, impregnation (see Chapter 7), fractionation, purification, and formation of powdered polymers. Due to the admittedly weak solvent power of CO2, the general problem of the very low entropy of mixing in polymer/solvent binaries is magnified even more in the case of CO2. However, the resulting poor solubility of most polymers is not a barrier here, as can be seen in the following numerous applications [ ] ... 

Polymeric supports of variable solubility have been investigated as an alternative to insoluble supports used in solid-phase synthesis. Reactions are performed in homogeneous media by choosing an appropriate solvent that solubilizes the polymer, and purification is performed by precipitation. This methodology benefits both solution-phase and solid-phase syntheses. Moreover compound characterization can be easily undertaken at any stage of the synthesis, since the support is soluble in standard spectroscopic solvents. A direct real-time control is possible, whereas a solid-phase protocol relies on a cleave and analyze strategy that consumes compound, imparts delay, and thus can only be accomplished at the end of synthesis. For these reasons soluble polymeric supports are preferred to conventional insoluble supports (resins, plastic pins), and they are compatible with analytical techniques such as NMR and mass spectrometry. 

Use of a single solvent at several different temperatures is economical from the viewpoint of solvent purification, but it is far from obvious that such a scheme can given clean splits between the various polymers. Thus the separ-... 

S. Rajabzadeh, T. Maruyama, T. Sotani, and H. Matsuyama, Preparation of PVDF hollow fibre membrane from a ternary polymer/solvent/nonsolvent system via thermally induced phase separation (TIPS) method. Separation and Purification Technology 63 (2(X)8) 415-123. 

Purification. Unsubstituted di- -xylylene (DPXN) is readily purified by recrystaUization from xylene. It is a colorless, highly crystalline soHd. The principal impurity is polymer, which fortunately is iasoluble ia the recrystaUization solvent and easily removed by hot filtration. 

The gases leaving the purification system are scmbbed with water to recover solvent and a continuous small purge of solvent gets rid of polymers. The acetylene purity resulting from this system is 99%. The main impurities in the acetylene are carbon dioxide, propadiene, and a very small amount of... 

The molecular weight of lignin in the wood, ie, of protolignin, is unknown. In addition to difficulties of isolation and purification, the polymer exhibits strong solvent, ionic, and associative effects in solution. An unequivocal method of measurement has not been developed. The polymer properties of lignin and its derivatives have been discussed (10,16). 

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. 

Unless odierwise specified, all monomers, reactants, and solvents were reagent grade 99+% (from Aldrich or Fluka) and used without further purification. In polymer formulas, n, x, y, and z represent number-average numbers of repeating units. 

Osmosis is the flow of solvent through a semipermeable membrane into a solution the osmotic pressure is proportional to the molar concentration of the solute. Osmometry is used to determine the molar masses of compounds with large molecules, such as polymers reverse osmosis is used in water purification. 

In addition to the insoluble polymers described above, soluble polymers, such as non-cross-linked PS and PEG have proven useful for synthetic applications. However, since synthesis on soluble supports is more difficult to automate, these polymers are not used as extensively as insoluble beads. Soluble polymers offer most of the advantages of both homogeneous-phase chemistry (lack of diffusion phenomena and easy monitoring) and solid-phase techniques (use of excess reagents and ease of isolation and purification of products). Separation of the functionalized matrix is achieved by either precipitation (solvent or heat), membrane filtration, or size-exclusion chromatography [98,99]. 

Soluble support-based synthetic approaches offer the advantages of both homogeneous solution-phase chemistry (high reactivity, ease of analysis) and solid-phase synthesis (large excess of reagents, simple product isolation and purification) [98,99]. As a representative example, PEG, one of the most widely used soluble polymers, has good solubility in most organic solvents (i.e., dichloromethane, acetonitrile, dimethylformamide, and toluene), but it... 

By replacing insoluble cross-linked resins with soluble polymer supports, the well-estabhshed reaction conditions of classical organic chemistry can be more readily apphed, while still fadhtating product purification. However, soluble supports suffer from the hmitation of low loading capacity. The recently introduced fluorous synthesis methodology overcomes many of the drawbacks of both the insoluble beads and the soluble polymers, but the high cost of perfluoroalkane solvents, hmitation in solvent selection, and the need for specialized reagents may hmit its apphcations. 

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