There is provided a photostable and synergistically enhanced topical sunscreen composition that provides increased substantivity, waterproofness, sweat resistance and rub off resistance. There is further provided methods of enhancing the photostability of a sunscreen active in a topical sunscreen composition, synergistically enhancing the UV absorbance of a topical sunscreen composition having a sunscreen active, and enhancing the substantivity, waterproofness, sweat resistance and rub off resistance in a topical sunscreen composition. The preferred compositions and methods have a sunscreen active, a cosmetically acceptable vehicle, and novel 2-substituted-3,3-diaryl-2-propenoic acid derivatives with [A] a C.sub.16 to C.sub.50 straight or branched chain, substituted or un-substituted, conjugated or non-conjugated hydrocarbon, or [B] a siloxane, polysiloxane, organo-modified polysiloxane residue, a group represented by the formula R.sup.10[Si(R.sup.10).sub.2].sub.n-- and R.sup.11 which is a silicone residue derived from a silicone represented by the formula R.sup.11OH having a molecular weight up to about 30,000, wherein each R.sup.10 is independently selected from the group consisting of alkyl, alkoxy, aryl and aryloxy and n is from 1 to about 500.