Metal‐containing polymer films are of interest for sensor, magnetic, nonlinear optical, and catalytic applications. This communication describes the preparation of poly(p‐xylylene) coatings incorporating Ge crystals from Ge‐containing paracyclophane monomer. Vapor pyrolysis of the monomer gives copolymer films with Ge fragments, which are thermally decomposed to Ge crystals. This leads to an increase in film conductivity and there is the potential for an application as a humidity sensor.

New thermotropic mesomorphic compounds containing a [2.2]paracyclophane (PC) unit were synthesized and investigated (Scheme). Carboxylic acids were selected as the starting PC building blocks. The influence of structural features on the stability of the mesomorphic phases was studied (Figs. 1 and 2): for this purpose, the structures of the PC-carboxylate unit and the organic fragment of the aryl-ester moiety were varied systematically. Esters derived from PC-monocarboxylic acid did not exhibit liquid-crystalline (LC) properties, while diaryl PC-dicarboxylates favored mesomorphism. Dicarboxylate substituents arranged in the paraposition provided LC phases in a broad temperature range and considerably increased the mesomorphic interval in comparison with that of the structurally related pseudo-para PC derivatives.Introduction. ± Unique physical properties, providing wide application in electrooptic devices and particularly the recent discovery of new mesophases, such as antiferroelectric, ferrielectric, and twist-grain boundary phases, have put chiral liquidcrystalline (LC) materials in the centre of liquid-crystal research [1] [2]. Historically, up to now, most chiral LC compounds contain molecules incorporating a centre of chirality. More recently, compounds with planar and axial chirality are beginning to attract the growing interest of researchers dealing with LC materials. The unique geometry of this type of compounds provides a rigid interaction between the origin of the symmetry-breaking chirality and the mesogenic unit, thus resulting in a definite fixation of the source of chirality in a LC matrix.In principle, planar chirality could drastically change the physical properties of the resultant LC material: 1) In terms of molecular structure, a rigid steric coupling between the transverse dipole, chiral centre, and the mesogen rod should maximize the local ferroelectric polarization [3], allowing consideration of the above compounds as possible chiral dopants for ferroelectric compositions, which are able to confer a high value of spontaneous polarization (P s ) to the achiral host [4]. 2) Electro-optical effects exhibited by LC materials such as electroclinic effects or nonlinear optical (NLO) properties are expected to be larger for compounds with rigid interaction between the chiral and optical portions of the molecule [5].However, the bulkiness of the structural units necessary to realize an axis or a plane of chirality significantly disturbs the desired rigid rod-like shape of the molecule, thus creating a serious obstacle to achieving stable mesomorphic properties. So far, only a

SUMMARY Block copolymers of unsubstituted polyb-xylylene)(PPX) and Ge-or Sn-organic bridged PPX (GePPX and SnPPX) were prepared by pyrolysis of specially synthesized organometallic p-cyclophane precursors followed by deposition and polymerization of the thus produced p-xylylene monomers. The copolymer structure and thermal behavior were investigated depending on deposition temperature (10 and -196 "C). The copolymer PPX-GePPX obtained from solid monomers deposited at -196°C (2a) consists of long quasiindependent PPX and GePPX blocks and has paracrystalline structure. Thermal treatment of 2a near 160°C yields crystalline regions of PPX along with paracrystalline aggregates of GePPX. Pyrolysis of this system near 300°C in an inert atmosphere results in the formation of Ge crystals in PPX matrix. In contrast, the copolymer PPX-GePPX produced by simultaneous deposition and polymerization at 10 "C (2a') contains shorter blocks of PPX and GePPX than the copolymer deposited at -196°C. Copolymer 2a' turns to the amorphous state during thermal treatment, and its pyrolysis does not lead to Ge-crystal formation; hence the supramolecular structure of the polymer plays an important role in inorganic phase formation. The copolymer PPX-SnPPX (2b) is formed only at a deposition temperature of -196°C; deposition at 10°C yields oligomeric resins. The structure of 2b is nearly the same as that of 2a; pyrolysis of 2b in air results in Sn02-crystal formation in a PPX matrix.

Chiral liquid-crystalline (LC) compounds constitute a central topic of present-day research on liquid crystals. For example, not only are the well-established applications of thermochromic materials as well as twisted nematic (TN) and supertwisted nematic (STN) displays based on chirality, but so are ferro-, ferri-, and antiferroelectric, second-harmonic ZUSCHRIFTEN

Symmetrically 4,16‐disubstituted (3a–c) and bridged (6a, b) organometallic paracyclophane derivatives have been synthesized for use as monomeric precursors of organometallic poly‐p‐xylylenes. Both types of compounds were obtained by lithiation of the appropriately substituted paracyclophane bromides (1 or 4) and subsequent quenching of the resulting lithioparacyclophane derivatives with organometallic electrophiles. For the synthesis of 4,16‐bis(trimethylsilyl)[2.2]paracyclophane (3a) we also examined the Grignard reaction, and as a result the first successful use of a 4,16‐bis Grignard reagent is described. According to the spectral data, the bridged compounds 6a, c are formed as diastereomeric mixtures of a meso‐ and a d,l form. The diastereomers were separated by fractional recrystallization and characterized.