Imprintability of polymers for thermal nanoimprint

This investigation follows the idea to characterise polymers for thermal imprint, in contrast to the classical rheological characterisation route, directly by means of an imprint process. For this purpose the polymers under investigation, a PS and a PMMA of comparable molecular weight (350 kg/mol) are imprinted at different temperatures under conditions of partial cavity filling. The development of characteristic effects, namely physical self-assembly, limited imprint depth and recovery is investigated. Imprintability test results are correlated with parameters obtained from rheology, in particular with the viscosity, the minimum flow time constant and the elastic compliance. In addition, the temperature behaviour is discussed in terms of the WLF-parameters. It turns out, that PMMA requires lower molecular weights than PS for efficient thermal imprint. Differences in the recovery behaviour of both materials can be understood from the elastic compliance and time constants measured. An optimum viscosity for thermal imprint at around 106 Pas is estimated.