Polymeric tandem dyes with linker groups

A polymer compound comprising:

• a Förster resonance energy transfer (FRET) acceptor chromophore having an acceptor transition dipole moment and being covalently linked to a polymer backbone;
• and
• a FRET donor chromophore having a donor transition dipole moment and being covalently linked to the polymer backbone,
• wherein:
• the FRET acceptor chromophore and the FRET donor chromophore have a J-value greater than about 1×1010 and the polymer compound adopts a confirmation in solution at physiological conditions wherein the effective distance between the FRET acceptor chromophore and the FRET donor chromophore is less than about 50.0 nm and the acceptor transition dipole and the donor transition dipole are substantially parallel or substantially antiparallel, and
• the polymer backbone comprises the following structure in the repeating units:
• wherein:
• R4 is, at each occurrence, independently OH, SH, O−, S−, ORd or SRd;
• R5 is, at each occurrence, independently oxo, thioxo or absent;
• L3 is, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;
• L4 is, at each occurrence, independently an alkylene or heteroalkylene linker;
• and
• m is, at each occurrence, independently an integer of one or greater.