Structural study of symmetric diblock copolymer thin films

Thin diblock copolymer lm have been investigated by x-ray and neutron reflectivity as well as small angle x-ray and neutron scattering. Two model systems have been investigated. PS-PDMS (25 kg/mol-25 kg/mol), which has a glass transition temperature of ca. 100°Cfor the PS-block. This means that the structure can be frozen below that temperature, thus the development of the lamella structure may be follow by reflectivity.

It was, however, not possible to reach the expected equilibrium structure. Hence the second model system, deuterateted PEP-PDMS (4.4 kg/mol-4.4 kg/mol) was chosen for its low glass transition temperature -56°C. This means that the system spontaneously should form lammela ordered structures at room temperature.

This ordering was studied by neutron reflectivity and small angle neutron scattering in the temperature range from -140°C(below PDMS' glass transition temperature, -127°C) and up to 250°C(above the order-disorder temperature, 165°C). Results were found to be in perfect agreement with theory. Surface morphology as function of temperature was also measured, and holes in the surface resembled the periodicity measured by reflectivity.