We then consider the variation of the luminescence bandwidth, estimated by fitting the main emission component (at 650 nm and 550 nm for 1,3-PDA and 1,4-PDA respectively and at 420 nm for 1,4-XDA) with a Gaussian and taking its FWHM (Figure ). The broad luminescence of 1,4-XDA is not considered in this analysis as its superimposition to the narrow component makes it hard to isolate correctly, especially at higher temperatures.