Semicrystalline polymers constitute the large majority of polymeric materials in use today. While the basic symmetries of polymer crystals are not different from their small molecular counterparts, the long-chain nature of polymers does significantly affect their crystallization behavior. Understanding the structure and morphology of semicrystalline polymers is crucial to improving their properties and broadening their applications. This project concerns the structural control of polymer crystals. The overarching goal of this research is to achieve unique spherical polymer crystals by controlling the crystallization conditions and/or the polymer molecular structure and to elucidate the morphology and the fundamental molecular-level processes involved in such curved-crystal growth. It is anticipated that these well-controlled spherical crystals may find applications in the fields of drug delivery and immunotherapy. The educational component of the proposal includes: 1) Mentoring graduate and undergraduate students. 2) Addressing the need for the education of modern polymer science by developing two class modules that will be used in graduate courses at Drexel University. 3) Involving high school students and teachers, particularly under-represented populations, in the proposed research activities.
The long-chain nature of polymers brings the most interesting feature to their crystallization behavior: the intricate amorphous domains in a crystalline material. The hierarchical morphology of the intertwining crystalline and amorphous phases accounts for some unique properties of semicrystalline polymers. Based on the correlation between crystal morphology and translational symmetry, polymer crystals are divided into shape-symmetry commensurate crystals and shape-symmetry incommensurate crystals (SSICs). In the latter, crystal morphology dictates broken translational symmetry along at least one unit-cell axis. This project aims to systematically investigate a class of polymer spherical crystals in the context of SSICs. Two approaches, namely a top-down templating technique and a bottom-up molecular engineering method, will be employed to break the translational symmetry in polymer crystals. The recently discovered spherical crystalsomes will be used as the model system. Accordingly, the specific aims of the proposed work are: 1) Understanding curvature-dependent crystallization and melting in polymer crystalsomes. 2) Developing complex crystalsomes via morphological control. 3) Fabricating crystalsomes using spontaneous translational symmetry breaking. This project will advance the field of polymer crystallization and lead to a library of crystalsomes as tailor-designed polymeric nanoparticles. Potential applications for these include drug delivery and immunotherapy. .
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
