Poly standard characterization

A commercially available cationic standard that can be used for the calibration of CATSEC columns is poly(2-vinyl pyridine), or PVP. Cationic PVP can be characterized easily on CATSEC columns over a broad range of molecular weight. DRI chromatograms of two cationic PVP standards using a bank of CATSEC columns (100-, 300-, 1000-, and 4000-A pore size) and a mobile phase of 0.05 N NaNOi/0.1% TFA are shown in Fig. 20.10. 

Characterization. The series of poly(alkyl/arylphosphazenes) (1-6) was studied by a variety of standard dilute solution techniques including viscosity measurements, membrane os-... 

Both vibrational spectroscopies are valuable tools in the characterization of crystalline polymers. The degree of crystallinity is calculated from the ratio of isolated vibrational modes, specific to the crystalline regions, and a mode whose intensity is not influenced by degree of crystallinity and serves as internal standard. A significant number of studies have used both types of spectroscopy for quantitative crystallinity determination in the polyethylenes [38,74-82] and other semi-crystalline polymers such as polyfethylene terephthalate) [83-85], isotactic poly(propylene) [86,87], polyfaryl ether ether ketone) [88], polyftetra-fluoroethylene) [89,90] and bisphenol A polycarbonate [91]. 

As explained in Sections 16.3.4, 6.4.1, and 16.4.2, SEC is a nonabsolute method, which needs calibration. The most popular calibration materials are narrow molar mass distribution polystyrenes (PS). Their molar mass averages are determined by the classical absolute methods—or by SEC applying either the absolute detection or the previously calibrated equipment. The latter approach may bring about the transfer and even the augmentation of errors. Therefore, it is recommended to apply exclusively the certified well-characterized materials for calibrations. These are often called PS calibration standards and are readily available from numerous companies in the molar mass range from about 600 to over 30,000,000g moL. Their prices are reasonable and on average (much) lower than the cost of other narrow MMD polymers. Other available homopolymer calibration materials include various poly(acrylate)s and poly(methacrylate)s. They are, similar to PS, synthesized by anionic polymerization. Some calibration materials are prepared by the methods of preparative fractionation, for example, poly(isobutylene)s and poly(vinylchloride)s. 

According to the standard electrochemical potentials (Table 1), with Cu/Cu2+ and Ru/Ru3+ couples, the amount of ruthenium deposited on metallic copper will be small, whereas the redox reaction carried out in presence of platinum or gold salts will occur to a large extent. On the other hand, for electrodes of first type (metal immersed in a solution of a salt of that metal), the standard electrochemical potentials as defined by thermodynamics are calculated with regard to a poly-crystalline metallic phase of infinite size. However, in the case of small metallic particles, characterized by metallic atoms of different coordination numbers, the notion of a local potential can be introduced. That no-... 

Conventional SEC is the classical method for measuring the MMD of synthetic or natural polymers. Conventional SEC essentially means the use of an on-line single concentration detector - differential refractometer (DRI) or UV. In such SEC systems, the molar mass is calculated by means of a direct or universal calibration applying a set of appropriate narrow and/or broad MMD standards. Unfortunately, classical narrow MMD standards for aqueous SEC mobile phases such as pullulan, poly(ethylene oxide), poly (ethylene glycole), and dextran are not suitable for characterization of HA. The listed SEC standards are neutral molecules existing in solution as flexible random coils, and some of... 

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