Polymer resolving agents

The six-position may be functionalized by electrophilic aromatic substitution. Either bromination (Br2/CH2Cl2/-5°) acetylation (acetyl chloride, aluminum chloride, nitrobenzene) " or chloromethylation (chloromethyl methyl ether, stannic chloride, -60°) " affords the 6,6 -disubstituted product. It should also be noted that treatment of the acetyl derivative with KOBr in THF affords the carboxylic acid in 84% yield. The brominated crown may then be metallated (n-BuLi) and treated with an electrophile to form a chain-extender. To this end, Cram has utilized both ethylene oxide " and dichlorodimethyl-silane in the conversion of bis-binaphthyl crowns into polymer-bound resolving agents. The acetylation/oxidation sequence is illustrated in Eq. (3.54). 

Occasionally there is the need for simultaneous determination of MW, MWD of polymers and identifica-tion/quantilication of additives [38]. This was the case for polymer and additive analysis of SBR/(softeners, flavour agents, stabilisers) (chewing gum) [41]. The many constituents of the SBR portion of the sample were not resolved, since adjacent components were similar in size. It should be stressed, however, that the need for simultaneous determination of the molecular weight of polymers and the identification/quantification of additives is exceptional rather than the rule. The determination of molecular weight distributions by SEC has indicated that oligomer fractions analysed by dissolution and (Soxhlet) extraction methods may differ essentially [42],... 

The sequence includes several synthetic steps over polymer-supported catalysts in directly coupled commercially available Omnifit glass reaction columns [41] using a Syrris Africa microreactor system [14], Thales H-Cube flow hydrogenator [32] and a microfluidic chip. The process affords the alkaloid in 90% purity after solvent evaporation, but in a moderate 40% yield. After a closer investigation it was concluded that this is due to the poor yield of 50% in the phenolic oxidation step. On condition that this is resolved with the use of a more effective supported agent, the route would provide satisfactory yields and purities of the product. 

There may be occasions when it is difficult to decide whether a polymerization is anionic or cationic. The question can readily be resolved by the use of labelled quench agents (77, 78). In particular the use of a doubly labelled methanol (14CH3OT) will yield the information in one experiment. Thus, with anionic polymerization, tritium would combine with the polymer (Reaction 11) while with cationic polymerization, carbon-14 would be combined (Reaction 12). 

Methods have been developed for the analysis of hydrocarbon polymers (e.g. styrene, butadiene and isoprene) by MALDI-TOF-MS, through the attachment of Ag(acac) to matrices of tran5-3-indoleacrylic acid or l,4-bis(2-(5-phenyloxazolyl))benzene . SUver-cationized molecular ions were produced for polymers of styrene, butadiene and isoprene up to mass 125,000 Da. For lower-mass styrene polymers, the resolved oligomer molecular ions provide information concerning the end group. This technique permits the analysis of many commercially important materials such as acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile, styrene-methyl methacrylate and styrene-isoprene copolymers. The use of the salts of transition metals other than Ag, Cu or Pd as the cationizing agents fails to cationize polystyrenes in MALDI. The ability of MALDI to reduce metals to the oxidation state 4-1 is critically important to polystyrene cationization, as without this reduction MALDI tends to fail to form polystyrene-metal cations. Cu(acac)2 was used for the verification of the above . 

The transport of a swelling agent during swelling/shrinking or the diffusion of substances into a swollen gel can be followed in real time by time-resolved measurements. The method provides information about the nature of diffusion processes into a polymer matrix on a spatially resolved level with a lateral resolution of about 50... 100 pm. 

Colloid Polymer Science 278, No.10. Oct.2000, p.946-53 TIME-RESOLVED NEAR-INFRARED AND TWO-DIMENSIONAL NEAR-EVFRARED CORRELATION SPECTROSCOPIC STUDIES ON POLYMERIZATION OF THE SILANE COUPLING AGENT... 

The flame-retardance of polyamides, therefore, has not yet been completely resolved. The compromise in selection of the agent is governed by the target of application of the polymer. 

Polymer composites represent materials of great and of continuously growing importance. Their potential for application appears to be limitless. They have been the subject of numerous studies both at academic and industrial levels. Much progress has been made in the incisive formulation of composites sophisticated methods of property evaluation have been developed in the past decade and many, largely empirical solutions have been proposed to resolve the problem of their long-term performance under typical conditions of use (i.e. the use of silane or titane coupling agents to enhance adhesion within composite materials). 

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