Formation and material properties of giant liquid crystal polymersomes

Polymersomes are vesicles made of amphiphilic diblock copolymers. Giant polymersomes of several tens of microns in diameter can be prepared from low Tg (glass transition temperature) flexible (coil-coil) copolymers by processes such as rehydration swelling or electroformation. These techniques are, however, inefficient in producing giant polymersomes composed of high Tg and/or rigid-flexible (rod-coil) copolymers. We have used an alternative method based on the formation of an inverted emulsion to produce giant unilamellar rod-coil polymersomes. We have selected copolymers whose hydrophobic moieties are glassy liquid crystalline polymers. The viscoelasticity of individual polymersomes has been measured by micropipette aspiration. Whereas the elastic modulus was found to be of the same order of magnitude as the one of prototypical vesicles made of coil-coil copolymers, the membrane viscosity of this new class of polymersomes was about three orders of magnitude more viscous than their coil-coil counterparts. The versatile method used here to form giant polymersomes could be useful for designing and studying novel functional polymer capsules. The results highlight the possibility of widely tuning the mechanical properties of polymersomes by selecting or synthesizing the proper copolymer.