No abstract

The grafting reaction of methyl methacrylate onto polybutadiene (PB) was investigated with different chromatographic techniques, including high‐performance liquid chromatography (HPLC) and online coupled two‐dimensional liquid chromatography. As a result of the grafting reaction, a complex mixture of nongrafted PB, the graft copolymer PB‐g‐PMMA [where PMMA is poly(methyl methacrylate)], and the PMMA homopolymer was formed. The complete separation of all the products of the grafting reaction was achieved with gradient HPLC. By the combination of gradient HPLC and size exclusion chromatography in a fully automated two‐dimensional chromatography setup, the complex distributions of the chemical composition and molar mass were fingerprinted simultaneously. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3143–3148, 2003

Separation of blends of styrene-butadiene rubber and butyl rubber was accomplished by gradient HPLC. Using a polar stationary phase and chloroformcyclohexane as eluent, the blends were separated with regard to chemical composition, irrespective of the molar masses of the components. The exact chemical structure of the blend components was analysed by coupling the chromatographic separation to FTIR detection. FTIR spectra of the components reveal information on styrene and butadiene contents and the conformation of the butadiene units (1,2-, 1,4-cis and 1,4-trans units). Complete separation of the blends with respect to chemical composition and molar mass was achieved by two-dimensional liquid chromatography. Combining gradient HPLC and size exclusion chromatography in a fully automated 2D chromatography set-up, the complex distributions of chemical composition and molar mass were fingerprinted simultaneously.

Crosslinked styrene‐butadiene and butadiene rubbers can efficiently be analyzed by liquid chromatography and FT‐IR spectroscopy. In a first step the vulcanizate is pyrolyzed under mild conditions. The resulting high molar mass fragments are extracted from the bulk material and analyzed by size exclusion chromatography. The molar masses of the extractables are in the range of 3 000 to 25 000 g/mol. The chemical composition as a function of molar mass is visualized by coupled SEC‐FT‐IR spectroscopy. By quantitative analysis of the FT‐IR spectra the concentrations of the different structural units, including styrene, 1,4‐trans‐butadiene, 1,2‐vinylbutadiene, and 1,4‐cis‐butadiene, are determined. It is shown that the chemical composition of the original non‐crosslinked rubbers and the chemical composition of the extractables are rather identical. Therefore, this technique can be used to obtain structural information on rubber formulations even in the case when the material is already vulcanized.SEC chromatograms of SBR 1712 and the extractables after pyrolysis, stationary phase: SDV linear, mobile phase: THF, detector: ELSD.magnified imageSEC chromatograms of SBR 1712 and the extractables after pyrolysis, stationary phase: SDV linear, mobile phase: THF, detector: ELSD.

As reported by Lara A. Estroff and co‐workers , the porous networks formed by hydrogel matrices (freeze‐dried silica gel in the background) provide a versatile medium for crystal growth of a wide range of calcium carbonate structures. Shown from top to bottom are single‐crystal equilibrium morphologies, non‐equilibrium “hopper crystals”, polycrystalline aggregates, and spherulites. In addition, the crystalline products can incorporate the hydrogel matrix forming crystalline composites.