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Copolymer analysis copolymers

In analysis of homopolymers the critical interpretation problems are calibration of retention time for molecular weight and allowance for the imperfect re >lution of the GPC. In copolymer analysis these interpretation problems remain but are ven added dimensions by the simultaneous presence of molecular weight distribution, copolymer composition distribution and monomer sequence length distribution. Since, the GPC usu y separates on the basis of "molecular size" in solution and not on the basB of any one of these particular properties, this means that at any retention time there can be distributions of all three. The usual GPC chromatogram then represents a r onse to the concentration of some avera of e h of these properties at each retention time. [Pg.149]

In homopolymer analysis this meant a closer study of the accuracy and reproducibility of data from GPC to see how resolution correction techniques could be either circumvented or practically applied. In copolymer analysis the limitation of conventional molecular size fractionation emerged as the fundamental difficulty. An orthogonal coupling of GPCs operated so as to achieve the desired cross fractionation before detection is presented as a novel approach with considerable potential. [Pg.150]

From the axial dispersion viewpoint alone there is no doubt that the experimental reduction of dispersion or its conation would be preferable to assuming it negligible. Either of these options require a simple method for the assessment of axial dispersion which does not depend upon absolute molecular weight averages or assumption of distribution functions (5, Such a method will be shown in Section 3 of this report. However, first the problem of copolymer analysis which led to this method as a byproduct win be examined. [Pg.159]

Garcia-Rubio, L.H., MacGregor, J.F., Hamielec, A.E., "Copolymer Analysis Using GPC with Multiple Detectors , presented at the Symposium on Recent Developments in Size Exclusion Chromatography , 178th ACS National Meeting, Washington, D.C., September 9-14, 1979. [Pg.182]

Branching in the polymer chain affects the relationship between retention and molecular weight.83 Universal calibration has been used with some success in branched polymers, but there are also pitfalls. Viscosimetry84-91 and other instrumental methods have proved to be useful. A computer simulation of the effects of branching on hydrodynamic volume and the detailed effects observable in GPC is available in the literature.92 93 In copolymer analysis, retention may be different for block and random copolymers, so universal calibration may be difficult. However, a UV-VIS detector, followed by a low-angle light-scattering (LALLS) detector and a differential... [Pg.330]

Mori, S., Copolymer analysis, in Size Exclusion Chromatography, Hunt, B. J. and Holding, S. R., Eds., Blackie, Glasgow, 1989, chap. 5. [Pg.368]

Mori, S., Wada, A., Kaneuchi, F., Ikeda, A., Watanabe, M., and Mochizuki, K., Design of a highly sensitive infrared detector and application to a high-performance size exclusion chromatography for copolymer analysis, /. Chromatogr., 246, 215, 1982. [Pg.370]

A number of 2DLC applications have attempted to use liquid chromatography at critical conditions (LCCC) and are discussed in Chapter 17. This mode of operation is useful for copolymer analysis when one of the functional groups has no retention in a very narrow range of the solvent mixture. However, determining the critical solvent composition is problematic as it is very sensitive to small changes in composition. [Pg.135]

GTP was employed for the synthesis of block copolymers with the first block PDMAEMA and the second PDEAEMA, poly[2-(diisopropylamino)e-thyl methacrylate], PDIPAEMA or poly[2-(N-morpholino)ethyl methacrylate], PM EM A (Scheme 33) [87]. The reactions took place under an inert atmosphere in THF at room temperature with l-methoxy-l-trimethylsiloxy-2-methyl-1-propane, MTS, as the initiator and tetra-n-butyl ammonium bibenzoate, TBABB, as the catalyst. Little or no homopolymer contamination was evidenced by SEC analysis. Copolymers in high yields with controlled molecular weights and narrow molecular weight distributions were obtained in all cases. The micellar properties of these materials were studied in aqueous solutions. [Pg.51]

Copolymerization reactions Copolymerization experiments with styrene and MMA employed molar fractions of 20, 40, 60, and 80% comonomers, which were reacted in ethanol 1,2-dichIorethane 60 40 (by volume) mixtures and benzoyl peroxide as catalyst. Polymerizations were carried out at 70°C. The reactions were quenched by the addition of methanol as non-solvent, and the copolymer was isolated by centrifugation. Copolymer analysis employed UV spectroscopy for copolymers with MMA, and methoxyl content determination according to a procedure by Hodges et al. (16) in the case of styrene copolymers. Reactivity ratios were determined in accordance with the method by Kelen-Tiidos (17) and that by Yezrielev-Brokhina-Roskin (YBR) (18). Experimental details and results are presented elsewhere (15). [Pg.516]

There are many problems associated with copolymer analysis which require a whole variety of techniques for solution. Isotopic tracers can play their own small part by establishing the exact composition in terms of relative amounts of the monomeric constituents. Consider the following examples ... [Pg.136]

Table 5. Copolymer analysis using labelled monomers... Table 5. Copolymer analysis using labelled monomers...
Beginning in the late forties, copolymers were fractionated by adsorption chromatography poly (butadiene-co-styrene)32 34), poly(butadiene-co-acrylonitrile)32), polystyrene- -vinyl acetate)35), poly(styrene-h-ethylene oxide)36) and poly(styrene-co-acrylonitrile) 37). HPLC adsorption chromatography was first applied to copolymer analysis by Teramachi et al. in 1979 38>. [Pg.174]

The same conclusion is found when the copolymer is prepared using large quantities of dichloroethane and the precipitation step occurs for higher n value. Consequently we must deduce, in such cases, that added PVC is different from PVC contained in the copolymer. One is justified in concluding that PVC is grafted by butadiene copolymer, (analysis verifies this) and that all PVC chains are grafted in the samples prepared with high dichloroethane ratios. [Pg.307]

Characterization of the Copolymer. The copolymer composition was analyzed by elementary analysis and NMR. NMR spectra were run at 70°C. on a JNM-C-60 high resolution spectrometer at 60 Me. in CC14. [Pg.373]

The copolymer composition can be estimated usefully in many cases from the composition of unreacted monomers, as measured by gas-liquid chromatography. Analytical errors are reduced if the reaction is carried to as high a conversion as possible, since the content of a given monomer in the copolymer equals the difference between its initial and final measured contents in the feed mixture. The uncertainty in the copolymer analysis is thus a smaller proportion of the estimated quantity, the greater the magnitude of the decrease in the monomer concentration in the feed. It may seem appropriate under these circumstances to estimate reactivity ratios by fitting the data to an integrated form of the copolymer equation. [Pg.256]

The extensive reactivity ratio data in the literature exhibit a wide scatter for many monomer pairs. This is partly due to errors in copolymer analysis and computational methods that result in larger uncertainties in n and Z2 than was realized when the results were reported. Another factor reflects the frequent reliance on an inadequate number of data points because copolymerization experiments lend to be tedious and time consuming. [Pg.272]

Table I shows these different approaches and their requirements, benefits, and limitations of chromatographic copolymer analysis. Table I shows these different approaches and their requirements, benefits, and limitations of chromatographic copolymer analysis.
In this kind of calculation the absence of segment-segment interactions and chemically monodisperse SEC fractions has to be assumed. The main benefits of this approach is ordinary SEC equipment is used and the copolymer analysis is done with the same injection without additional sample preparation. [Pg.229]

Thermal analysis are widely used for polymers and copolymers analysis. Glass transitions, melting, and decomposition processes are analyzed. Since the glass transition temperature Tg is marked by changes in the thermal capacity, expansion coefficient, and rigidity, TMA technique as well as DSC may be used. Tg increases with molecular mass up to certain values. Plasticizers and water depress this temperature. Thermal stability and influence of antioxidants and fillers may be analyzed by TG or DSC, under oxygen. [Pg.3742]

Copolymer Analysis by LC Methods, Including Two-Dimensional Chrome Peter Kilz... [Pg.19]

R. O. Bielsa and G. R. Meira, Linear copolymer analysis with dual-detection size exclusion chromatography Correction for instrumental broadening, /. Appl. Polym. Sci. 46 835 (1992). [Pg.208]


See other pages where Copolymer analysis copolymers is mentioned: [Pg.368]    [Pg.150]    [Pg.159]    [Pg.180]    [Pg.10]    [Pg.335]    [Pg.331]    [Pg.94]    [Pg.52]    [Pg.480]    [Pg.481]    [Pg.128]    [Pg.136]    [Pg.368]    [Pg.109]    [Pg.396]    [Pg.197]    [Pg.224]    [Pg.441]    [Pg.444]    [Pg.446]    [Pg.447]   
See also in sourсe #XX -- [ Pg.156 ]




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