| 摘要 |
Nematic cpds. with negative dielectric anisotropy of formula (I) are new: m = 1 or 2; r = 0 or 1; m+r = 1 or 2; R1 and R2 = 1-12C alkyl or alkoxy with straight or branched and opt. chiral chains; Z = CH2CH2, OCH2, OCO, COO or a direct bond; one of X and Y = F, Cl, Br or CN and the other = H, F, Cl, Br or CN; provided that m = r = 1 when X = Y = CN
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