Co-assembled DNA-protein polymer bottlebrushes : main-chain stiffening & liquid crystallinity

Bottlebrushes are macromolecules consisting of a backbone polymer onto which side chains are either physically or chemically grafted. Early theories suggested that attaching side chains to a (flexible) backbone molecule would induce the so-called main-chain stiffening effect. This newly formed bottlebrush molecule should therefore behave as a semi-flexible polymer rather than a flexible polymer. Due to this semi-flexible behaviour bottlebrushes should also be able to show liquid crystalline behaviour. However, there are very few examples of bottlebrush systems that are able to make liquid crystalline phases. In this thesis, we present a co-assembled bottlebrush system that consist of DNA as the backbone molecule and genetically engineered protein polymers as side chains. This co-assembled system is one of the few bottlebrush systems that actually does show liquid crystalline behaviour. This ability makes this bottlebrush system a perfect system to explain why it is so very difficult to make liquid crystalline phases with bottlebrushes. We have shown that attaching side chains will, at first, result in an effectively more flexible bottlebrush system. Only for systems with very densely packed and long side chains is the stiffness of the bottlebrush molecule increasing. Moreover, with osmotic stress experiments we have shown that the presence of free polymers also has a negative influence on the stiffness of bottlebrush molecules and hence this reduces the tendency for the system to form liquid crystals.