Analysis of block copolymer

Bravo, 1984). Hybrids of these systems, where chromatography and electrophoresis are used in each spatial dimension, were reported nearly 40 years ago (Efron, 1959). Belenkii and coworkers reported on the analysis of block copolymers by TLC (Gankina et al., 1991 Litvinova et al., 1991). Two-block copolymers of styrene and f-butyl methacrylate were separated first with regard to chemical composition by TLC at critical conditions, followed by a SEC-type separation to determine the molar masses of the components. 

As a result of the dependence of universal calibration on column elution behavior (i.e., anomalous behavior due to adsorption or exclusion), the contribution of the polymer core and shell components (33,34) to hydrodynamic behavior must be fully understood if competent analysis of block copolymers and branched heteropolymers is to be made. It is hoped that with the advent of appropriate MW, composition, and branched polymer standards, the limits of fit of universal calibration to biopolymers such as lignin can be judged. 

It should be noted that the critical condition approach can also be used for the analysis of block copolymers. At present, there exists a theory based on the latticelike model74) describing different modes of chromatography of block copolymers which makes possible to find conditions for separation according to composition. The analysis of experimental work pertaining to this question is, however, beyond the scope of this review. 

The GPC analysis of block copolymers is handicapped by the difficulty in obtaining a calibration curve. A method has recently been suggested to circumvent this difficulty by using the calibration curves of homopolymers. This method has been extended so that the calibration curves of block copolymers of various compositions can be constructed from the calibration curve of one-component homopolymers and Mark-Houwink parameters. The intrinsic viscosity data on styrene-butadiene and styrene-methyl methacrylate block polymers were used for verification. The average molecular weight determined by this method is in excellent agreement with osmometry data while the molecular weight distribution is considerably narrower than what is implied by the polydispersity index calculated from the GPC curve in the customary manner. 

The equivalence ratio can be calculated from the Mark-Houwink coefficient, K, of component homopolymers. The composition distribution in the chromatogram of a block copolymer is negligible. The peak point of a block copolymer chromatogram corresponds to the average structure of the polymer. Thus, analysis of block copolymers is reduced to analysis of the peak point. Analyses of anionic block copolymer structures have been successfully accomplished by this peak analysis technique with the aid of equivalence ratio. 

After separations of homopolymers and blockcopolymers, e.g. by selective extraction, the first characterization step for the block copolymers is an analysis of their molar masses. Since all the usual methods can be used, these will not be described in detail here, but it should be noted that GPC has proved particularly useful for the analysis of block copolymers 55 64). In addition to simply giving a mean molar mass... 

Under such chromatographic conditions it is possible to determine the heterogeneities of the polymer chain selectively and without any influence of the polymer chain length. LC-CC has been successfully used for the determination of the functionality type distribution of telechelics and macromonomers [104-109], for the analysis of block copolymers [111-114], macrocyclic polymers [115], and polymer blends [116-118]. 

Lee B, Park I et al (2005) Structural analysis of block copolymer thin films with grazing incidence small-angle X-ray scattering. Macromolecules 38 4311 —4323... 

The first proof of the validity of this approach was given by Gankina et al. [19] for the analysis of block copolymers by thin layer chromatography. Column liquid chromatography was used by Zimina et al. [20] for the analysis of poly(styrene-b/ock-methyl methacrylate) and poly(styrene-Wock-terr-butyl methacrylate). However, the critical conditions were established only for the polar part of the block copolymers, i.e. PMMA and PtBMA, respectively. Thus, only the polystyrene block was analyzed. 

LCCC is a powerful tool for the analysis of block copolymers. Lee et al. analyzed a copolymer containing blocks of poly(ethylene oxide) and blocks of poly(lactide) by LCCC, and tiiey were able to determine the conditions in which chains with lactic blocks of different size are eluted at almost the same time. The LCCC chromatogram shows a series of narrow peaks, and the MALDI-TOF spectra of the LCCC fractions confirm that each structure contains exclusively one type of oligomer. 

An exhaustive, critical review of the status concerning current statistical thermodynamic analysis of block copolymer domain formation will not be presented here. A precis only of the major theories is given and the predictions from each noted, fuller details are available in the original publications. Furthermore, whilst the earlier theories of Meierand Williams " were important in stimulating interest and defining the questions to be addressed, they are not considered here since the more recent ideas encompass all the features of the earlier theories. 

Applications summarized in Table 1,2 and 3, document that CEEC maybe found for many individual polymers as well as structural segment of a polymer sample. The unique sensitivity of LCCC to different characteristics of macromolecules, has been, to date primarily utilized for analysis of block copolymers (AB or ABA) as well as analysis of functionality of homopolymers (Fig. 12). Blends of polymers and structurally different macromolecules, i.e., cyclic versus linear versus branched and even with different tacticity, have been separated. Graft copolymers has been studied [43,117] as well as random copolymers [111,153,154] (Fig. 13). 

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