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In chemometric studies all predictor variables are usually collected in one data matrix X. This matrix is then analyzed by PLS regression or other methods. When data from several different sub-processes are collected in one matrix, there is a possibility that the effects of some sub-processes may vanish. If there is, for instance, mechanic data from one process and spectral data from another, the influence of the mechanic sub-process may not be detected. An application of multi-block (MB) methods, where the X-data are divided into several data blocks is presented in this study. By using MB methods the effect of a sub-process can be seen and an example with two blocks, near infra-red, NIR, and process data, is shown. The results show improvements in modelling task, when a MB-based approach is used. This way of working with data gives more information on the process than if all data are in one X-matrix. The procedure is demonstrated by an industrial continuous process, where knowledge about the sub-processes is available and X-matrix can be divided into blocks between process variables and NIR spectra. Copyright © 2008 John Wiley & Sons, Ltd.

When characterized with 13C-NMR, it was found that norbornene-ethylene copolymers had a more complicated microstructure when dimethylsilyl bis(indenyl) zirconium dichloride was used as the catalyst compared to ethylene bis(indenyl) zirconium dichloride. One could see more block sequences but less alternating sequences. For both catalysts the highest amounts of block sequences were obtained for high norbornene concentrations, medium to high Al/Zr ratios, and low polymerization temperatures. There were also more alternating sequences for high norbornene concentrations and high polymerization temperatures. The isolated norbornene units (separated by more than one ethylene unit) were all exoconfiguration. No unsaturation was seen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1071–1076, 1997

Two-site model analysis was carried out for 13 C n.m.r. of polypropylene polymerized by Ziegler-Natta catalyst with external alkoxysilane donors. Four effects of the external donors were found: selective poisoning of symmetric site; transformation of a symmetric to an asymmetric (but fluctuating) site; increase of whole isotacticity due to that of polymers obtained by the fluctuating site; and increase of isotacticity of the polymers obtained by the fluctuating site when the concentration of external donor is high enough.

Microstructural analysis was carried out on five isotactic polypropylenes produced with different heterogeneous Ziegler-Natta catalyst systems and different polymerization processes. The samples were fractionated according to stereostructure using a direct extraction method. Pentad tacticities of unfractionated samples and selected fractions were determined by 13 C n.m.r. spectroscopy. I.r. isotacticities were also measured. Statistical analysis of the polymerization mechanism was carried out on the basis of the two-site model from the pentad tacticities, and average lengths of meso and racemic sequences were determined. In addition to atactic and isotactic materials produced at different catalytic sites, the polypropylene samples contained syndiotactic material as stereoblocks in isotactic chains. On the basis of the analysis carried out on the fractions, slight differences in the microstructure were found to exist between the samples produced by different processes and catalyst types. These differences have a significant effect on average sequence lengths.

Correlations were sought between the structure of an external alkoxysilane donor and the microstructure of the polymer chain obtained by the polymerization of propene with a heterogeneous, high-activity Ziegler-Natta catalyst. Fourteen different alkoxysilanes of structure RnSi(OR′)4-n, where n = 1–3, R = n-alkyl or phenyl and R′ = C1–3-alkyl, were used as external donors. The polymers were fractionated by boiling heptane extraction. The microstructures of the polymers were studied by means of 13C NMR spectroscopy. The structure of the donor had a marked effect on the catalyst activity and isotacticity of the polymer. However, all of the alkoxysilanes tested produced qualitatively similar differences in the microstructure of poly(propylene): the size of the isotactic mmmm pentad peak varied with the donor efficiency, but the sizes of the non-isotactic pentad peaks were more or less constant relative to each other. In the boiling heptane soluble fraction, isotacticity and syndiotacticity increased and the viscosity-average molecular weight Mv decreased when a good external donor was used in the polymerization. Results indicate that all external alkoxysilane donors tested have the same qualitative effect on active centers, and only isotacticity, i.e., the number of mmmm sequences, can be controlled by an external alkoxysilane donor. The effectiveness and selectivity of deactivation strongly depend on the structure of the donor.