Liquid-crystalline medium, characterised in that it comprises one or more compounds of the formula I in which R denotes a) in each case, independently of one another, a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, where, in addition, one or more CH 2 groups in these radicals may each be replaced, independently of one another, by -C≡C-, -CH=CH-, - O-, -O -, - - or -O- in such a way that O atoms are not linked directly to one another, b) a group -Sp-P, or c) F, Cl, H, Br, CN, SCN, NCS or SF 5, A denotes a) cyclohexane or cyclohexene, b) benzene, in which one or two CH groups may be replaced by N, or c) a radical from the group bicyclo[1.1.1]pentane, bicyclo[2.2.2]octane, spiro[3.3]heptane, selenophene, thiophene, furan, anthracene, phenanthrene, chroman, adamantane, in which one or more double bonds may be replaced by single bonds, one or more CH groups may be replaced by N, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, and Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, m denotes 0, 1, 2 or 3, for polycyclic rings A also more, n denotes 3, 4 or more, P denotes a polymerisable group, Sp denotes a spacer group, or a polymer comprising one or more polymerised compounds of the formula I. R denotes a) in each case, independently of one another, a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, where, in addition, one or more CH 2 groups in these radicals may each be replaced, independently of one another, by -C≡C-, -CH=CH-, - O-, -O -, - - or -O- in such a way that O atoms are not linked directly to one another, b) a group -Sp-P, or c) F, Cl, H, Br, CN, SCN, NCS or SF 5, a) in each case, independently of one another, a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, where, in addition, one or more CH 2 groups in these radicals may each be replaced, independently of one another, by -C≡C-, -CH=CH-, - O-, -O -, - - or -O- in such a way that O atoms are not linked directly to one another, b) a group -Sp-P, or c) F, Cl, H, Br, CN, SCN, NCS or SF 5, A denotes a) cyclohexane or cyclohexene, b) benzene, in which one or two CH groups may be replaced by N, or c) a radical from the group bicyclo[1.1.1]pentane, bicyclo[2.2.2]octane, spiro[3.3]heptane, selenophene, thiophene, furan, anthracene, phenanthrene, chroman, adamantane, in which one or more double bonds may be replaced by single bonds, one or more CH groups may be replaced by N, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, and Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, a) cyclohexane or cyclohexene, b) benzene, in which one or two CH groups may be replaced by N, or c) a radical from the group bicyclo[1.1.1]pentane, bicyclo[2.2.2]octane, spiro[3.3]heptane, selenophene, thiophene, furan, anthracene, phenanthrene, chroman, adamantane, in which one or more double bonds may be replaced by single bonds, one or more CH groups may be replaced by N, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, and Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, m denotes 0, 1, 2 or 3, for polycyclic rings A also more, n denotes 3, 4 or more, P denotes a polymerisable group, Sp denotes a spacer group,