Tuning the Crystallization Behavior of Block Copolymers with Phospholipid Hybridization

Block copolymer (BCP) self-assembly and crystallization processes can modify their mechanical, optical, and transport properties. Some physical and chemical ways to control BCP self-assembly have been developed over the years. However, studies on modulating the crystallization behavior, particularly crystallite size and orientation, are lacking and remain challenging. In this work, we investigate the use of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) phospholipids additives that expand the utility of conventional confinement effects in directing methoxy-poly(ethylene glycol)-b-poly(e-caprolactone) (mPEG-b-PCL) assembly and crystallization on solid supports. mPEG-b-PCL/DPPC hybrid films assemble into multilamellar structures where BCP and lipid layers align in registry throughout the film thickness. DPPC tails and crystalline PCL chains interact at the molecular level: i) DPPC tails un-tilt forming a liquid ordered phase and ii) PCL crystallites re-orient. We suggest that the PCL chains on the fold plane (of orthorhombic lattice) maximize molecular binding with vertically aligned acyl tails of the DPPC by rotating the PCL crystallite by 20 degrees. Our results provide a new approach for switchable crystallization routes of polymeric systems.