We have performed time-resolved photoluminescence (PL) measurements to study the transfer of excitons from noninteracting polymer chains to chain aggregates for thin films of polyindenofluorene with different attached side chains. The transfer time is shown to be fast (approximate to 35 ps) and side-chain independent indicating that the substitution of different side chains does not affect the local concentration of aggregate sites within aggregate-containing domains, but rather the extent to which such domains are formed. We find the aggregate emission efficiency to be relatively high (greater than or equal to 20%) while still lower than the efficiency of emission from non-interacting chains.