Synthesis and characterisation of organogels from ABA triblock copolymers

Polystyrene-block-poly(2-ethylhexanyl acrylate)-block-polystyrene triblock copolymers with different molar masses were synthesised by atom transfer radical polymerisation which led to the formation of elastic gels in paraffin oil. Copolymers with control over molecular weight and low polydispersity were first obtained with different midblock lengths (10 000, 20 000, 60 000 g center dot mol(-1)). In paraffin oil, some triblock copolymers led to a gelation process due to appropriate chain length and concentration. We assumed that polystyrene endblocks aggregated into micelles whereas poly(2-ethylhexanyl acrylate) midblocks formed loops or bridges between different micelles leading to the formation of a physical network of interconnected polymer chains. Rheological measurements proved that time and slow controlled cooling improved the elastic properties with the creation of new interactions in the network.