Calibration poly

Fig. 4. Calibration curves for columns of PLaquagel-OH, designated 30 (A), 40 (A), 50 (O), 60 ( ), and Mixed ( ), for aqueous SEC at ambient temperature. Eluent water, flow rate 1 mL/min, calibrants poly(ethylene oxide/glycol) standards.

Figure 9.17 Plot of log [i ]M versus retention volume for various polymers, showing how different systems are represented by a single calibration curve when data are represented in this manner. The polymers used include linear and branched polystyrene, poly(methyl methacrylate), poly(vinyl chloride), poly(phenyl siloxane), polybutadiene, and branched, block, and graft copolymers of styrene and methyl methacrylate. [From Z. Grubisec, P. Rempp, and H. Benoit, Polym. Lett. 5 753 (1967), used with permission of Wiley.]...

FIGURE 9.28 Room temperature analysis of poly(amide-6). Columns PSS PFG 100 + 1000. Eluent TFE + 0.1 M NatFat. Temp 2S°C. Detection Rl. Calibration PSS PA-6 standards (broad). 

As stated in Section I, columns should be selected so the low molar mass portions of the samples in question can be sufficiently separated from the elution interval of the system peaks. This task cannot always be accomplished, e.g., dimethylacetamide often replaces dimethylformamide as a GPC eluent the analyzed, mostly polar, samples require a neutral salt (e.g., FiBr) (7). The calibration is usually carried out with poly(methylmethacrylate) standards... 

Water-soluble polymers obtained through a radical polymerization [e.g., poly(acrylic acid) PAA] often contain sodium sulfate Na2S04 as a decomposition product of the initiator. The peak of Na2S04 is eluted before the dimer. In the interpretation of the chromatogram, a typical GPC program has to be truncated before the Na2S04 peak, or at a Mpaa value of about 200. The calibration curve in this region can be flattened by an additive small pore column as well, but the principle problem remains unsolved. 

PMMA, on the unmodified porous glass and silica gel, and the universal calibration curves for polystyrenes and poly(methyl methacrylates) did not coincide (10,12,19). 

Commercial grades of PVP, K-15, K-30, K-90, and K-120 and the quaternized copolymer of vinylpyrrolidone and dimthylaminoethylmethacrylate (poly-VP/ DMAEMA) made by International Specialty Products (ISP) were used in this study. PEO standard calibration kits were purchased from Polymer Laboratories Ltd. (PL), American Polymer Standards Corporation (APSC), Polymer Standards Service (PSS), and Tosoh Corporation (TSK). In addition, two narrow NIST standards, 1923 and 1924, were used to evaluate commercial PEO standards. Deionized, filtered water, and high-performance liquid chromatography grade methanol purchased from Aldrich or Fischer Scientific were used in this study. Lithium nitrate (LiN03) from Aldrich was the salt added to the mobile phases to control for polyelectrolyte effects. 

Commercial narrow standards [such as poly(ethylene glycol) (pEG), polystyrene sulfonate, pAA, poly w-vinyl pyrrolidinone, dextrans] are available from American Polymer Standards Corporation, Polymer Laboratories, Polymer Standards Service USA, Toyo Soda, and others. While these standards are often not as narrow as pSty or pMMA that has been anionically polymerized, they are acceptable for narrow standard calibrations. 

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. 

Values of are obtained partly by previous calibration using a series of standard light scatterers whose Rayleigh ratios have been precisely determined. Typical standards used in practice are poly(methyl methacrylate) blocks, colloidal silica suspensions, or tungsto-silicic acid, H4SiW 2O40-... 

Figure 3, HDC universal calibration curve (eluant ionic strength L29rriM. AM A monodisperse lattices (O) polystyrene polyvinyl chloride ( ) poly (styrene-...

Upon applying the calibration constants obtained from the data of one sample to evaluate the SEC data of the other samples, the calculated Mn and values correspond fairly well (within 10-20%) with the absolute MW parameters of the samples. This agreement also suggests that the samples probably have similar chain structures. The distribution functions for samples PN-1 and IL-22 are plotted in Figures 4 and 5. The molecular weight distributions of both polymers are similar to distribution curves reported for derivatized poly(organo)phosphazenes (4-10). 

Figure 5. Calibration curve obtained with relatively narrow molecular weight samples of poly(dichlorophosphazene)...

Figure 4.24 Calibration curves for LiChrospher colunn. Calibration standards poly(styrene) and mobile phase tetrahydrofuran.

For some polymers, like polystyrene or poly(methyl methacrylate), narrow standards of known molar mass and small polydispersity are commercially available, which can be used for calibration. Unfortunately, such standards are not available for all polymers and then the obtained true molar masses of a specific polymer might differ by a factor of two from the value obtained by calibration with, e.g., polystyrene [30] (see Section 9.1). This problem can be resolved by the so-called universal calibration, which is based on the finding that the retention volume of a polymer is a single-valued function of the hydrodynamic volume of the polymer, irrespective of its chemical nature and... 

For many polymers K and a values can be found in the Polymer Handbook [23]. In a recent study by Vanhee et al. [30] the universal calibration has been applied using the polystyrene (PS) calibration curve to characterize rigid rod poly(p-phenylenes) (PPP). It turned out that due to its larger persistence length, PPP with a certain mass requires a much larger volume than PS for the same molecular weight. Ron et al. employed universal calibration for the characterization of erodible copolymers [58]. 

Figure 16 SEC molar mass distribution of poly(p-phenylene) P3 in THF after universal calibration based on Equations (31) (dashed) and (36) (dotted) and with polystyrene calibration (solid line). 

An example can best explain the procedure. A poly(bisphenolA carbonate) sample characterized by a broad-MMD was injected in an SEC apparatus, about 100 fractions were collected, and 24 of them were analyzed by MALDI [7]. Figure 15.2 reports the SEC trace of the PC sample. The trace covers a quite broad range of elution volumes and it is centered at about 30 ml. The polymer starts eluting at about 26 ml and ends at about 38 ml. The MALDI spectra yielded MP values (see above). Using this information, the SEC trace in Fig. 15.2 is calibrated and the average molar masses turn out to be Mw = 55,800, Mn = 23,600. 

The determination of the molecular weight of nanoparticles is performed by gel permeation chromatography (GPC). The experimental setup consists of a high performance liquid chromatography system with a size exclusion column and a refractive index detector. The nanoparticles are usually freeze-dried and dissolved in tetrahydrofuran for analysis on the system. Poly(styrene) or poly(methylmethacrylate) standards are used to calibrate the column, to enable the determination of number average molecular weight (Mn), as in... 

The use of our equations will be illustrated by applying them to a few systems from the literature showing simple kinetic behaviour. However, before starting the calculations we must ascertain how reliable the literature data are. There seems little reason to doubt the soundness of the rate data, but almost all the DP data, essential for the calculation of [Pn ], are suspect because in most researches the DP is obtained by GP chromatography (GPC) with a polystyrene (PSt) calibration. The extent of the uncertainty is revealed by two sets of measurements Cho and McGrath [19] found that for poly(nBVE)(PnBVE) the DP determined by vapour pressure osmometry (VPO), which one would favour as closest to the real DPn, is related to that found by GPC, DP(PSt), as... 

MALDI is the method of choice for the analysis of synthetic polymers because it usually provides solely intact and singly charged [62] quasimolecular ions over an essentially unlimited mass range. [22,23] While polar polymers such as poly(methylmethacrylate) (PMMA), [83,120] polyethylene glycol (PEG), [120,121] and others [79,122,123] readily form [M+H] or [M+alkali] ions, nonpolar polymers like polystyrene (PS) [99,100,105,106] or non-functionalized polymers like polyethylene (PE) [102,103] can only be cationized by transition metal ions in their l-t oxidation state. [99,100] The formation of evenly spaced oligomer ion series can also be employed to establish an internal mass calibration of a spectrum. [122]... 

Microspheres were monitored by scanning electron microscopy (SEM JEOL 35C), and their diameters were determined from the corresponding SEM microphotographs. Typically, ca. 500 particles in randomly sampled areas of microsphere specimens were analyzed. Molecular weight of poly(L-Lc) was determined by GPC. A system consisting of a LKB 2150 pump, Ultrastyragel 1,000, 500, 100, 100 columns, and Wyatt Optilab 903 interferometric refractometer was used for the measurements. GPC traces were analyzed by using calibration with narrow polydispersity < 1.15)... 

Table VI lists the results of this study of calculated molecular weight accuracy as a function of calibration method with the PVC poljnners. A PVC polymer sample was analyzed and molecular weight averages were calculated by means of each calibration method. All SEC peak processing parameters used for calculation of MWD values were held constant. As shown in Table VI, the universal calibration method provided a somewhat more accurate value than the Q-factor approximation method or the linear, poly-disperse standard method.

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