摘要:
The invention relates to a catalytical process for preparing poly(3-hydroxyalkanoates) by copolymerizing an oxirane compound with carbon monoxide in the presence of a) at least one single- or multicenter neutral transition metal complex (A) based on a metal of groups 5 to 11 of the Periodic Table of the Elements, in which the metal center(s) is/are present in the formal oxidation state 0, and/or b) at least one single- or multicenter anionic transition metal complex (B) based on a metal of groups 5 to 11 of the Periodic Table of the Elements, where multicenter transition metal complexes have metal centers which, without exception, are of the same transition metal, which comprises carrying out the copolymerization in the presence of at least one nucleophile other than hydroxy-substituted pyridine compounds.
摘要:
The present invention relates to compounds with a metal-carbon bond suitable for insertion of acrylonitrile, a process for the preparation of these compounds and the use of these compounds for further insertions of acrylonitrile and/or other monomers.
摘要:
The invention refers to a linear, isotactic polymer which has a structure of one or several C2 to C20 olefins, of which the isotacticity, due to a statistic distribution of stereoscopic errors in the polymer chain, is within the range of from 25 to 60% of [mmmm] pentad concentration with the proviso that an arbitrary or rather regular sequence of isotactic and atactic blocks is excluded, the polymer having a mean molecular weight Mw within the range of from 100,000 to 800,000 gms/mol and a TG of from −50 to +30.
摘要:
A nematic liquid crystal mixture having a positive dielectric anisotropy &Dgr;∈ of at least +4 and a birefringence &Dgr;n of at least 0.12, characterized in that the mixtures comprises one or more components having the core structure wherein L1, L2, Y and Z are each independently of one another H or F, one of Q1 and Q2 is 1,4-phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene and the other residue Q1 or Q2 is —CH2CH2—, —CH2CH2CH2CH2— or—if at least one of L1, L2, Y and Z denotes F—also a single bond, whereby this core structure can be optionally further fluorinated in the benzene rings.
摘要:
In functionalized linear alternating carbon monoxide copolymers of carbon monoxide and at least one 1-alkene (A), compound (A) is an aryl derivative substituted with at least one terminal allyl and/or homoallyl moiety and containing one or more polar groups, with the proviso that 4-allylanisole is excluded.
摘要:
A process for preparing a compound of the formula I where R1 and R2 are hydrogen or C1-C4-alkyl and R3 is C1-C10-alkyl, phenyl or C1-C4-alkyl-substituted phenyl, comprises reacting a compound II with a compound of the formula III where X is chlorine, bromine or iodine, in the presence of a Friedel-Crafts catalyst in one step to give a compound I.
摘要:
A catalyst system suitable for the polymerization of C.sub.2 -C.sub.10 -alk-1-enes comprising, as active ingredients, a complex compound of metals in Sub-groups IV and V of the Periodic Table and an oligomeric alumoxan compound is obtained by a procedure in which metals in Sub-groups IV and V of the Periodic Table are mixed with the oligomeric alumoxan compound and the resulting mixture is then applied to finely divided polymer. The catalyst system of the invention can be isolated after manufacture and is particularly suitable for the gas-phase polymerization of C.sub.2 -C.sub.10 -alk-1-enes.
摘要:
Novel phenylcyclohexanes of the formula I ##STR1## in which n is 0 to 7, Q.sup.1 and Q.sup.2 are H, or one of these radicals is alternatively CH.sub.3, r is 0, 1, 2, 3, 4 or 5, A is trans-1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene or a single bond, X is F, Cl, --CF.sub.3, --CN, --OCF.sub.3 or --OCHF.sub.2, and Y and Z are each, independently of one another, H or F, with the proviso that, in the case where A is a single bond, Q.sup.1 =Q.sup.2 =H and simultaneously X=CN, Y and/or Z are F.
摘要:
The invention relates to a liquid crystal display element which contains an electrically switchable, dielectrically positive twisted nematic liquid crystal layer between two substrates which together with a frame form a cell, and two layers with alignment layers thereon applied to the substrates. The liquid crystal mixture is based on SFM compounds. One of the electrodes forming an active matrix of non-linear switching elements is integrated within each picture element while the other electrode is the counter electrode. The alignment layer is an organic polymer layer which may be essential uniformly aligned by rubbing. The alignment layer results in an essential homogenous surface alignment of the liquid crystal layer with a surface tilt angle. The liquid crystal material comprises at least 30 wt. % of one or more compounds according to formula I ##STR1## wherein R, Z.sup.1, Z.sup.2, A.sup.1, A.sup.2, X, Y and n are herein defined, and the alignment layer is based on at least partially fluorinated polyimides.
摘要:
The invention relates to a nematic liquid-crystal composition especially for active matrix displays with high voltage holding ratio, good low temperature stability and without reversed domains.