The present invention relates to compounds represented by the following Formula Ia, in which each R1-R6 can in each case be independently selected from hydrogen or hydrocarbyl (e.g., methyl); R7 is a multivalent linking group, such as L1 is a divalent linking group, such as a bond or divalent optionally substituted hydrocarbyl; each L2 independently represents a flexible segment, such as divalent linear or branched C1-C25 alkyl; each L3 independently represents a rigid segment including, for example, optionally substituted phenylen-1,4-diyl groups; t is from 1 to 4; m and p are each independently from 0 to 4 for each t, provided that the sum of m and p is at least 1 for each t; and E can be hydrogen or optionally substituted hydrocarbyl. The present invention also relates to compositions, such as liquid crystal compositions, and articles, such as optical elements, that include the compound represented by Formula Ia.