Silicon-containing polymers, structure

For a review and books of optically active dialkylpolysilanes and diarylpolysilanes, (a) Fujiki, M. Macromol. Rapid Commun. 2001, 22, 539. (b) Fujiki, M. Koe, J. R. In Silicon-Containing Polymers The Science and Technology of Their Synthesis and Applications. Kluwer, Dordrecht, 2000, Chapter 24. (c) Koe, J. R. Fujiki, M. Nakashima, H. Moton-aga, M. In Synthetic Macromolecules with Higher Structural Order. Khan, I. (Ed.). ACS Symposium Series 812. American Chemical Society, Washington, DC, 2002. 

SiC is an excellent nonoxide ceramic with high-temperature stability and suitable mechanical properties. Since silicon-containing polymers are generally used for preparing nonoxide ceramics, various polymeric precursors with different structures have been designed. Preceramic polycarbosilane (PCS), used for preparing commercial Nicalon fiber,... 

The ADMET step condensation polymerization of carbosila- and carbosiloxa-dienes has generated a new class of unsaturated silicon-containing polymers when monomer structure/reactivity relationships, as described earher for the polar functionalities, are obeyed (equation 22). 

Figure 20 Structures of silicon-containing polymers discussed in Section 12.04.1.4.2.(iii).

MALDI-TOF-MS) has the potential to identify the fractions separated by SEC, LACCC or LAC. This method was developed by Karas et al. and by Tanaka et al. in 1988. The method was first applied for investigations of silicon-containing polymers in 1995, for example by Lorenz and by Tang. MALDI-TOF-MS represents a powerful tool not only for the determination of chemical structure but also for SEC calibration. SEC calibration for specific polymers is still problematic, since there are no commercially available standards. Therefore a calibration by the coupling of different modes of liquid chromatography with MALDI-TOF-MS is preferred. 

Michl, J. and R. West. 2000. Electronic structure and spectroscopy of polysUanes. In Silicon-containing polymers The science and technology of their synthesis and applications, eds. J. Chojnowski, R.G. Jones, and W. Ando, Dordrecht, The Netherlands Kluwer Academic, 499. 

Kawakami, Y., Control of the Stereochemical structure of Silicon-Containing Polymers. Macromol. Symp. 2001,174,145-153. 

Michl J, West R (2000). Electronic structure and spectroscopy of polysilanes. In Jones RG, Ando W, Chojnowski J (eds) Silicon containing polymers. Kluwer Academic, Dordrecht, pp 499-529... 

Fig. 20. Examples of silicon-containing polymers for use in bilayer resist formulations. The top structure is used in a 248-rnn bilayer CA resist. The scanning electron micrograph shows the high aspect ratio images that can be obtained using 248-mn projection lithc a-phy with a bilayer resist based on this polymer. The bottom structure shows an example of a silicon-containing polymer designed for use in 193-nm lithography.

Molecular design and precision synthesis of silicon-containing polymers are described. Polymerizations of substituted silacyclobutanes by phenyllithium and platinum complexes gave poly(carbosilane)s of head to tail regular structure. However, extensive chain transfer seems to have occurred in the polymerization by platinum complexes. 

Silicon-containing polymers, such as poly(siloxane) (3), poly(carbosilane) (4,5), and poly(silylene) (6) have found practical importance in many areas of applications, but they have been insufficiently studied in relation to their primary structure, stereoregularity, molecular weight, and higher order structure. 

Conclusion. Approaches to molecular design of primary structure of silicon-containing polymers were illustrated for poly(carbosilane)s with controlled molecular weight and for stereoregular poly(carbosilane) and poly(carbosiloxane). 

Size exclusion chromatography-mass spectroscopy has been applied to structural and molecular weight studies on silicon containing polymers including hyperbranched alkoxysiloxane [30], polydimethyl siloxane [31], methyl acryloxypropyl trimethoxy silone [32] and phosphazines. 

Bernhard Rieger obtained his PhD in chemistry at the Ludwig-Maximilians-Universitat, Munich in 1988. After a postdoctoral research at the University of Massachusetts in Amherst, Department of Polymer Science and Engineering from 1988 till 1989, he joined the BASF Company for research about metallocene polymerizations, from 1989 till 1991. After his habilitation from 1991 till 1995 at the Eberhard-Karls-University in Tubingen, he was a Professor at the University of Ulm from 1995 on, as well as Head of the Department of Materials and Catal) until 2006. Since thea he has been head ofthe WACKER Chair of Macromolecular Science at the Technische Universitat Miinchen. His main research interests are homogeneous polymerization catalysis, where numerous publications concern the alkene/CO copolymerizatioa as well as silicon-containing polymers and self-assembled functional surface structures. 

A series of chelate polymers has been prepared from tetraalkoxy metals and A, jV,A, A -tetrakis(2-hydroxyethyl)diamines (33). Dimethylacetamide is used as the solvent. The reactants that are used to introduce silicon and tin are their tetraethoxy derivatives, whereas tetraisopropoxytitanium was used to incorporate titanium. Polymers of different backbone and metal structure were prepared. From the scant data that are reported about the products, correlations of properties versus structure cannot be made. One point of interest is the much higher melting point that was found for the silicon-containing polymer (R = in [58])as compared to the tin and titanium polymers. 

---