An amphiphilic alternating light-harvesting copolymer of narrow polydispersity containing an average of 38 acenaphthylene and maleic acid units with a terminal 9,10-diphenylanthryl energy acceptor has been synthesized by reversible addition-fragmentation chain transfer polymerization. Fluorescence and fluorescence anisotropy measurements of the polymer in methanol and aqueous solutions have been used to characterize energy transfer processes and conformational dynamics. The increased energy transfer efficiencies approaching 100% observed in low-pH aqueous solutions compared to those in more basic aqueous and methanol solutions can be attributed to the formation of a contracted polymer coil and reduced acenaphthenyl excimer formation.