Dye, filler made therefrom, compositions including the filler, and method of determining degree of cure of such compositions

A treated filler comprising:

• an inorganic filler having on at least a portion of its surface a compound of formula
• wherein
• R is hydrogen or alkyl;
• X is alkylene, arylalkylene, or alkylarylene, wherein alkylene, arylalkylene, and alkylarylene are optionally interrupted by at least one of an ether, thioether, amine, amide, ester, thioester, carbonate, thiocarbonate, carbamate, thiocarbamate, urea, or thiourea, and wherein alkylene is optionally interrupted by arylene;
• W is hydroxyl, a sulfonic acid group, a phosphonic acid group, a carboxylic acid group, —NHR1, epoxy, or —Si(Y)x(Z1)3-x;
• R1 is hydrogen, alkyl, aryl, arylalkylenyl, or alkylarylenyl;
• Y is alkyl, aryl, arylalkylenyl, or alkylarylenyl;
• each Z1 is independently halide, hydroxyl, alkoxy, aryloxy, acyloxy, polyalkyleneoxy, —O— covalently bonded to the surface of the filler, or —O— bonded to another silicon atom to form a siloxane, wherein alkoxy and acyloxy are optionally substituted by halogen, and wherein aryloxy is optionally substituted by halogen, alkyl, or haloalkyl;
• and
• x is 0 or 1,
• and wherein the compound is at least one of covalently bonded or ionically bonded to the inorganic filler.