Polymer gel-permeation chromatography

As for conventional linear polymers, gel permeation chromatography (GPC) can be used to find information on the composition of dendrimers, including their polydispersities. Obtaining standards of known relative molar mass and polydispersity is a problem with dendrimers, so the approach that has been taken most often is to use polystyrene standards, as described in Chapter 6. 

The major factor influencing the thermal and mechanical properties is the composition differences between the polymers. Gel permeation chromatography measurements have shown that the molecular weight averages and molecular weight distributions are not significantly different for the samples which have been studied and are therefore not seen as important as far as Tg and mechanical measurements are concerned. 

For determining the molar mass of branched polymers gel permeation chromatography can be used. An important quantity in this connection is the hydrodynamic volume of the polymer coil, which, as shown before in Eq. (9.27), is proportional to the product [rj M. According to Benoit and co-workers (1966) the hydrodynamic volume is the key size parameter in the establishment of a universal calibration curve for gel permeation chromatography columns (see Chap. 2) if log (h/]M) is plotted versus the elution volume for a variety of polymers, the data fit a single curve. 

Molecular weight determination in polymers - gel permeation chromatography (GPC) see Chapter 8... 

Gel permeation chromatography, exclusion chromatography. gel filtration chromatography. A technique for separating the components of a mixture according to molecular volume differences. A porous solid phase (a polymer, molecular sieve) is used which can physically entrap small molecules in the pores whilst large molecules pass down the column more rapidly. A solvent pressure up to 1000 psi may be used. 

Two classes of micron-sized stationary phases have been encountered in this section silica particles and cross-linked polymer resin beads. Both materials are porous, with pore sizes ranging from approximately 50 to 4000 A for silica particles and from 50 to 1,000,000 A for divinylbenzene cross-linked polystyrene resins. In size-exclusion chromatography, also called molecular-exclusion or gel-permeation chromatography, separation is based on the solute s ability to enter into the pores of the column packing. Smaller solutes spend proportionally more time within the pores and, consequently, take longer to elute from the column. 

At first glance, the contents of Chap. 9 read like a catchall for unrelated topics. In it we examine the intrinsic viscosity of polymer solutions, the diffusion coefficient, the sedimentation coefficient, sedimentation equilibrium, and gel permeation chromatography. While all of these techniques can be related in one way or another to the molecular weight of the polymer, the more fundamental unifying principle which connects these topics is their common dependence on the spatial extension of the molecules. The radius of gyration is the parameter of interest in this context, and the intrinsic viscosity in particular can be interpreted to give a value for this important quantity. The experimental techniques discussed in Chap. 9 have been used extensively in the study of biopolymers. 

This chapter contains one of the more diverse assortments of topics of any chapter in the volume. In it we discuss the viscosity of polymer solutions, especially the intrinsic viscosity the diffusion and sedimentation behavior of polymers, including the equilibrium between the two and the analysis of polymers by gel permeation chromatography (GPC). At first glance these seem to be rather unrelated topics, but features they all share are a dependence on the spatial extension of the molecules in solution and applicability to molecular weight determination. 

Gel permeation chromatography (GPC) is the term found most widely in the polymer literature. In this context it is used most widely as an analytical... 

Among the techniques employed to estimate the average molecular weight distribution of polymers are end-group analysis, dilute solution viscosity, reduction in vapor pressure, ebuUiometry, cryoscopy, vapor pressure osmometry, fractionation, hplc, phase distribution chromatography, field flow fractionation, and gel-permeation chromatography (gpc). For routine analysis of SBR polymers, gpc is widely accepted. Table 1 lists a number of physical properties of SBR (random) compared to natural mbber, solution polybutadiene, and SB block copolymer. 

Specialized training is an absolute requirement for technical service personnel. A typical example is a person involved in supporting a polymer for which the use is the manufacture of rotationaHy molded consumer products. The technical service person is expected to be reasonably familiar with topics such as polymer rheology evaluations, gel-permeation chromatography, rotational mol ding, color science, regulatory requirements for use, mechanical and photochemical behavior of the pigmented polymer, optics, and so forth. Expertise of this variety caimot be expected to be obtained without careful... 

Molecular weights of PVDC can be determined directly by dilute solution measurements in good solvents (62). Viscosity studies indicate that polymers having degrees of polymerization from 100 to more than 10,000 are easily obtained. Dimers and polymers having DP < 100 can be prepared by special procedures (40). Copolymers can be more easily studied because of thek solubiUty in common solvents. Gel-permeation chromatography studies indicate that molecular weight distributions are typical of vinyl copolymers. 

Gel-permeation chromatography studies of epoxy resins prepared by the taffy process shown n values = 0, 1, 2, 3, etc, whereas only even-numbered repeat units are observed for resins prepared by the advancement process. This is a consequence of adding a difunctional phenol to a diglycidyl ether derivative of a difunctional phenol in the polymer-forming step. 

The crowning development in MW determination was the invention of gel permeation chromatography, the antecedents of which began in 1952 and which was finally perfected by Moore (1964). A column is filled with pieces of cross-linked macroporous resin and a polymer solution (gel) is made to flow through the column. The polymer solute permeates the column more slowly when the molecules are small, and the distribution of molecules after a time is linked not only to the average MW but also, for the first time with these techniques, to the vital parameter of MW distribution. 

The properties of flexible polymer chains moving in porous structures, that is, in structures with geometric constraints such as tubes or slits, apart from their Tclevance for various applications such as filtration, gel permeation chromatography, oil recovery, etc., pose an exciting problem of statistical... 

Size exclusion was first noted in the late fifties when separations of proteins on columns packed with swollen maize starch were observed (Lindqvist and Storgards, 1955 Lathe and Ruthven, 1956). The run time was typically 48 hr. With the advent of a commercial material for size separation of molecules, a gel of cross-linked dextran, researchers were given a purposely made material for size exclusion, or gel filtration, of solutes as described in the classical work by Porath and Flodin (1959). The material, named Sephadex, was made available commercially by Pharmacia in 1959. This promoted a rapid development of the technique and it was soon applied to the separation of proteins and aqueous polymers. The work by Porath and Flodin promoted Moore (1964) to apply the technique to size separation, gel permeation chromatography of organic molecules on gels of lightly cross-linked polystyrene (i.e., Styragel). 

II. AMERICAN POLYMER GEL-PERMEATION/SIZE EXCLUSION CHROMATOGRAPHY (GPC/SEC) COLUMN REPACKING... 

The selection of the right gel-permeation chromatography (GPC) column or column combination for a special task is a multistage procedure. First, a decision about the type of column has to be made according to the polymer samples in question ... 

The oligomerization of cardanol with boron trifluoride etharate as the initiator was studied in detail by Antony et al. [171]. The reaction conditions were optimized by using gel permeation chromatography as 140°C with an initiator concentration of 1%. GPC data indicate conversion of all monoene, diene, and triene components into polymer except the saturated component, indicating participation of all the unsaturated components in polymerization. It is possible that the initiation of po-... 

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