Highly-conjugated main chain polymers have been studied extensively in recent years as third order non-linear optical materials. However, in a non-centrosyinmetric system such as a polyene which has been substituted with an electron donor and acceptor group, the relaxation of certain selection rules results in an increase in the static third order hyperpolarisibility. Consequently, there has been recent interest in the third order non-linear optical properties of materials more typically studied for their quardratic non-linear response. One of the driving forces for this work has been the possibility of producing single device substrates possessing significant second and third order non-linearitics which could lead to highly integrated optical devices.