Abstract
The modification of the PPV molecular structure induced by side chain substitution on the phenylene ring has a marked effect on the optical absorption and photoemission of PPV derivatives. The influence of the molecular mass on the photophysical properties of a PPV derivative involving an alkoxy side chain: poly(2-methoxy,5-octoxy-1,4-phenylenevinylene) (PMOX) is shown by the difference of the emission responses of low molecular weight PMOX (
M
̄
w
=4
900
) or high molecular weight PMOX (
M
̄
w
=55
,885) in a chloroform solution, appearing at 540 and 605
nm, respectively. Such a difference no more holds for PMOX thin layers deposited on glass substrates (emissions at 605 and 615
nm, respectively, for the two molecular weights). These effects are attributed to the confinement of the exciton causing a blue shift of the emission for low molecular weight PMOX in dilute solution, whereas a larger extent of the exciton is allowed by interchain interactions in the condensed phase. The photoluminescence peak of high molecular weight PMOX can be decomposed into two components at 602 and 630
nm. The red shifted component is attributed in this case to the formation of interchain dimer excitations.