A method of decreasing the UV light degradation of a UV-light degradable polymer comprising adding to said polymer an effective amount of a compound of formula (IX): ##STR00001## wherein, R.sup.19, R.sup.20 and R.sup.21 are the same or different and are selected from the group consisting of C.sub.1-C.sub.30 alkyl, C.sub.3-C.sub.8 cycloalkyl, substituted alkyl, substituted cycloalkyl, ester, aryl, heteroaryl, heterocycloalkyl, substituted aryl, substituted heteroaryl, substituted heterocycloalkyl, and amino; R.sup.17 and R.sup.23 are the same or different and are selected from the group consisting of C.sub.1-C.sub.30 alkyl, C.sub.3-C.sub.8 cycloalkyl, substituted alkyl, substituted cycloalkyl, ester, aryl, heteroaryl, heterocycloalkyl, substituted aryl, substituted heteroaryl, substituted heterocycloalkyl, cyano, and amino; R.sup.18 and R.sup.22 are the same or different and are selected from the group consisting of substituted diphenylmethylene, unsubstituted diphenylmethylene, substituted 9H-fluorene, and unsubstituted 9H-fluorene; t and u are each in the range of 1 to 100; s is in the range of 0 to 100; and a, b, c, and d are each in the range of 0 to 4.