Abstract: The present invention concerns chiral doping agents allowing a modification to be induced in the spiral pitch of a cholesteric liquid crystal, said doping agents including a biactivated chiral unit at least one of whose functions allows a chemical link to be established with an isomerisable group, for example by radiation, said group possibly having a polymerisable or co-polymerisable end chain. These new chiral doping agents find application in particular in a color display.

Abstract: The present invention concerns chiral doping agents allowing a modification to be induced in the spiral pitch of a cholesteric liquid crystal, said doping agents including a biactivated chiral unit at least one of whose functions allows a chemical link to be established with an isomerisable group, for example by radiation, said group possibly having a polymerisable or co-polymerisable end chain.

Abstract: A liquid crystal composition comprising a low molecular weight liquid crystal in the interior of which a cross-linking network is formed by polymerization of a prepolymer of formula I: ##STR1## X being a non-mesogenic bivalent radical, the free bonds of which form an angle smaller than 180.degree.;B.sub.1 and B.sub.2 being rigid cyclic groups which would confer liquid crystal properties to the prepolymer if X was such that=180.degree..R.sub.1 and R.sub.2 being the same or different, each representing an optionally substituted alkyl, alkoxy, arylalkyl or aralalkoxy chain;A.sub.1 and A.sub.2 being the same or different, each representing a reactive polymerizable function. Display cells comprising the liquid crystal composition having a low commutation voltage.

Abstract: The invention relates to rare earth cryptates consisting of at least one rare earth salt complexed by a macropolycyclic compound corresponding to one of formulae I or II below, in which:the ring ##STR1## is the N.sub.2 O.sub.4 macrocycle, the N.sub.2 O.sub.3 macrocycle or the bis--bipyridine macrocycle;Y is a spacer arm or group which consists of a divalent organic radical selected from linear or branched C.sub.1 to C.sub.20 alkylene groups optionally containing one or more double bonds and/or optionally being interrupted by one or more heteroatoms such as oxygen, nitrogen, sulfur or phosphorus, or from C.sub.5 to C.sub.8 cycloalkylene groups or C.sub.6 to C.sub.14 arylene groups, the said alkylene or arylene groups optionally being substituted by alkyl, aryl or sulfonate groups;Z is a functional group capable of bonding covalently with a biological substance;R is a methyl group or represents the group --Y--Z; andR' is hydrogen or a group --COOR", in which R" is a C.sub.1 to C.sub.

Abstract: The invention relates to rare earth cryptates consisting of at least one rare earth salt complexed by a macropolycyclic compound corresponding to one of formulae I or II below, in which:the ring ##STR1## is the N.sub.2 O.sub.4 macrocycle, the N.sub.2 O.sub.3 macrocycle or the bis-bipyridine macrocycle;Y is a spacer arm or group which consists of a divalent organic radical selected from linear or branched C.sub.1 to C.sub.20 alkylene groups optionally containing one or more double bonds and/or optionally being interrupted by one or more heteroatoms such as oxygen, nitrogen, sulfur or phosphorus, or from C.sub.5 to C.sub.8 cycloalkylene groups or C.sub.6 to C.sub.14 arylene groups, the said alkylene or arylene groups optionally being substituted by alkyl, aryl or sulfonate groups;Z is a functional group capable of bonding covalently with a biological substance;R is a methyl group or represents the group --Y--Z; andR' is hydrogen or a group --COOR", in which R" is a C.sub.1 to C.sub.

Abstract: The invention relates to rare earth cryptates consisting of at least one rare earth salt complexed by a macropolycyclic compound corresponding to one of formulae I or II below, in which:the ring ##STR1## is the N.sub.2 O.sub.4 macrocycle, the N.sub.2 O.sub.3 macrocycle or the bis-bipyridine macrocycle;Y is a spacer arm or group which consists of a divalent organic radical selected from linear or branched C.sub.1 to C.sub.20 alkylene groups optionally containing one or more double bonds and/or optionally being interrupted by one or more heteroatoms such as oxygen, nitrogen, sulfur or phosphorus, or from C.sub.5 to C.sub.8 cycloalkylene groups or C.sub.6 to C.sub.14 arylene groups, the said alkylene or arylene groups optionally being substituted by alkyl, aryl or sulfonate groups;Z is a functional group capable of bonding covalently with a biological substance;R is a methyl group or represents the group --Y--Z; andR' is hydrogen or a group --COOR", in which R" is a C.sub.1 to C.sub.

Abstract: The invention relates to rare earth cryptates consisting of at least one rare earth salt complexed by a macropolycyclic compound corresponding to one of formulae I or II below, in which:the ring ##STR1## is the N.sub.2 O.sub.4 macrocycle, the N.sub.2 O.sub.3 macrocycle or a bis-bipyridine macrocycle;Y is a spacer arm or group which consists of a divalent organic radical selected from linear or branched C.sub.1 to C.sub.20 alkylene groups optionally containing one or more double bonds and/or optionally being interrupted by one or more heteroatoms such as oxygen, nitrogen, sulfur or phosphorus, or from C.sub.5 to C.sub.8 cycloalkylene groups or C.sub.6 to C.sub.