Determination of Oligomers

Non-MS methods have been described for the determination of oligomers in polyvinylchloride, chlorinated polyethylene [18], styrene [15, 16, 19] and ethylene glycol [20], styrene-methyl methyl methacrylate [21], alkyl/phenol formaldehyde [22], and PET [22], 

A good example of this application is the work of Lyons and co-workers [23] on the use of solvent gradient adsorption LC in a study of interchain compositional inhomogeneities in PS-co-ethylene random copolymers. 

Eluent gradient adsorption chromatography is one of the main HPLC techniques used in polymer fractionation including deposition-dissolution, chromatography under critical conditions, temperature gradient adsorption LC and precipitation dissolution LC [24-30]. 

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Various techniques have been used for the determination of oligomers, including GC [135], HPLC [136-138], TLC for polystyrene and poly a-methyl-styrene [139] and SEC for polyesters [140,141]. GC and PyGC-MS can also profitably be used for the analysis of the compositions of volatile products formed using different flame retardants (FRs). Takeda [142] reported that volumes and compositions of the volatile products and morphology of the char were affected by FRs, polymers (PC, PPE, PBT) and their reactions from 300... 

Off-line coupling of HPLC with FD-MS has been used by several authors [118-121] for the determination of oligomers, oligomeric antioxidants (such as poly-TMDQ), ozonation and vulcanisation products. Pausch [122] reported on rubbers, cyclic polyurethane oligomers, as well as on the determination of the molecular weight distribution (up to 5300 Da) and oligomer analysis of polystyrene. Also the components of an aniline-acetone resin were deduced from FD-MS molecular weights [122]. 

High-field NMR spectral analyses including a variety of two-dimensional techniques are the most powerful tools for the structural determination of oligomers. The H- and C-NMR spectra provide useful information on the nature and number of polyphenolic acyl units, e.g. galloyl, HHDP, DHHDP, valoneoyl units and others, and on the substitution modes of glucose residues. 

Figure 6 Determination of oligomers in a phenol-formaldehyde adhesive. HPM, dihydroxydi-phenyl methane. 

In this chapter, the reported information on different NMR, IR, and NIR spectroscopy techniques on structural characterization and the DA determination of oligomers and polymers of chitin and chitosan have been described. The following conclusions were made from this study (1) NMR and IR are nondestructive and noninvasive methods (2) impurities (minerals, proteins, and pigments) and moisture induce interferences and difficulties to obtain accurate results. To achieve more accurate results, care must be taken to identify the peaks correspond to the impurities (3) IR and NMR... 

Tables 3.3 and 3.4 show the results of the determination of oligomers contained in 0.5 mg/ml sample solutions of PEG 400 and POE(9)D, respectively. Both analyses were carried out in purely methanolic mobile phases. PEG and POE were selected as standards for corresponding oligomer mixtures. values for the POE( )D series are listed in Table 3.4 together with analytical results. Since fCf values generally included approximately 5% relative errors, the concentrations listed in tables show more ambiguity.

Figure 3.7 shows an example of an oligomer separation achieved by this method for various POE-HPLC has also been applied to the determination of oligomers in polyesters [34], alkylphenyl formaldehyde resins [35, 36] and polyethylene terephthalate [37, 38]. 

The technique has also been applied to the determination of oligomers in PET [46, 47]. 

THERMAL STABILITY OF POLYETHYLENE TEREPHTHALATE PACKAGING DETERMINATION OF OLIGOMERS... 

Sun, C., M. Baird, H. A. Anderson, D. L. Brydon, Separation and determination of oligomers and homologs of aliphatic AE in textile lubricants and lubricant emulsions by HPLC, 7. Chro-matogr. A, 1997, 771,145-1545. 

Laser desorption Fourier transform ion cyclotron resonance spectrometry. Laser desorption FTICR-MS looks very promising for the analysis of high ethoxylates, but this technique is still the province of research universities. It has been demonstrated for determination of oligomer distribution of OPE of average degree of ethoxylation of 59 (74). 

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