A capped poly(arylene ether) copolymer having the formula: or wherein Q 1a is a C 1 -C 12 primary or secondary alkyl; Q 1b is halogen, C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each occurrence of Q 2 is independently hydrogen, halogen, unsubstituted or substituted C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each occurrence of R 1, R 2, R 3, and R 4 is independently hydrogen, halogen, C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each occurrence of R 5 is independently Q 1a or a (C 1 -C 6 -hydrocarbyl)(C 1 -C 6 -hydrocarbyl)aminomethylene group; z is 0 or 1; x and y represent the relative mole ratios of the arylene ether units wherein x and y are independently 0 to 50, or e is the number of moles of the arylene ether unit; Y is a divalent linking group of the formula wherein each occurrence of R a, R b, R c, R d, and R e is independently hydrogen, C 1 -C 12 hydrocarbyl, or C 1 -C 6 hydrocarbylene, optionally wherein R a and R b or R c and R d together are a C 4 -C 8 alkylene group; and each occurrence of D is independently a group of the formula wherein each occurrence of G is independently C 1 -C 12 hydrocarbylene; each occurrence of Q is independently C 1 -C 6 alkylene or C 6 -C 12 arylene, wherein a is 0 or 1; each occurrence of A is independently a single bond or -O-; each occurrence of J is independently a single bond, C 1 -C 6 alkylene, or -(CH 2) n NH(CH 2) n (C=O)O- wherein n is 1 to 6; and each occurrence of Z is independently of the formula wherein W a is O or S; each of R and R' is independently hydrogen, C 1 -C 12 hydrocarbyl, or C 1 -C 6 hydrocarbylene, optionally wherein both R and R' together are a C 2 -C 8 alkylene group; and m is 0 or 1. Q 1a is a C 1 -C 12 primary or secondary alkyl; Q 1b is halogen, C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each occurrence of Q 2 is independently hydrogen, halogen, unsubstituted or substituted C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each occurrence of R 1, R 2, R 3, and R 4 is independently hydrogen, halogen, C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each occurrence of R 5 is independently Q 1a or a (C 1 -C 6 -hydrocarbyl)(C 1 -C 6 -hydrocarbyl)aminomethylene group; z is 0 or 1; x and y represent the relative mole ratios of the arylene ether units wherein x and y are independently 0 to 50, or e is the number of moles of the arylene ether unit; Y is a divalent linking group of the formula each occurrence of G is independently C 1 -C 12 hydrocarbylene; each occurrence of Q is independently C 1 -C 6 alkylene or C 6 -C 12 arylene, wherein a is 0 or 1; each occurrence of A is independently a single bond or -O-; each occurrence of J is independently a single bond, C 1 -C 6 alkylene, or -(CH 2) n NH(CH 2) n (C=O)O- wherein n is 1 to 6; and each occurrence of Z is independently of the formula W a is O or S; each of R and R' is independently hydrogen, C 1 -C 12 hydrocarbyl, or C 1 -C 6 hydrocarbylene, optionally wherein both R and R' together are a C 2 -C 8 alkylene group; and m is 0 or 1.