Our research interests center on the structure and morphology of ordered polymeric systems and hybrid materials for energy, biomedical, and nanocomposites applications.
1. Polymer Crystal Engineering
Crystalline polymers have been extensively studied over the past six decades and are commonly used as commodity materials, significantly impacting our daily lives. By utilizing controlled polymer crystallization, we design and grow functional polymer single crystals for various applications, including drug delivery, actuators, surface modification, nanoparticle synthesis, surface-enhanced Raman spectroscopy, catalysis, and artificial nanomotors.
Polymer Crystalsomes: Crystallization is governed by translational symmetry, but at a nanoscale curved interface, crystalline packing can be disrupted due to the curved geometry’s incompatibility with conventional three-dimensional translational symmetry. By utilizing a nanoemulsion crystallization method or molecularly engineering the crystallization systems, we have created a library of nanosized polymer single crystal-like capsules, called crystalsomes. These crystalsomes exhibit broken translational symmetry and show great promise for encapsulation and drug delivery applications.
Functional polymer single crystals: To further investigate the interplay between polymer single crystals and low-dimensional solids, Li has utilized polymer single crystals as nanoscale functional materials. We demonstrated that by controlling chain folding, a polymer single crystal can function as a nanoscale “tape” to harvest various nanoparticles, forming a 2D free-standing sandwich structure. This nanoscale sandwich structure enables a wide range of applications for polymer single crystals, including use as molecular shuttles, in surface-enhanced Raman spectroscopy, and for Janus nanoparticle synthesis.
Related publications: Adv. Mater.2005, 17: 1198. Nano Letters, 2006, 6,1007. JACS 2006, 128, 1692. Macromolecules, 2008, 41, 9516. Nature Nanotech., 2009, 4, 358. Polymer2009, 50: 953. J. Polym. Sci. Pt. B-Polym. Phys.2009,47: 2436. Carbon, 2012, 50, 1769. Polymer2011, 52: 3633. ACS Nano, 2012, 6, 1204. Sci. Chi. Chem.2012, 55, 802. Macro. Rap. Commun,2013, 34, 251. Macromolecules, 2013, 46, 2877−2891.
Related publications: JACS, 2007 129, 12. Macromolecules, 2008, 41, 149. JACS2008 129, 11594. Macromolecules, 2009, 42, 9394. Macro. Rap. Commun.2010, 31, 169. Macromolecules, 2010, 43, 9918. J. Mater. Chem., 2011, 21, 13155. J. Phys. Chem. Lett. 2012, 3, 1346. J. Mater. Chem.2012, 22, 15526. Macromolecules, 2012, 45, 8780. Nanoscale, 2012, 4, 7641. ACS Nano, 2013, 7, 5192-5198.
2. Solid Polymer Electrolytes (SPEs) for Energy Storage.
While considerable efforts have been devoted to studying SPEs and synthesizing numerous polymer electrolytes, most research has concentrated on enhancing their ionic conductivity and mechanical properties. However, the overall performance of SPE-based all-solid-state lithium batteries still requires substantial improvement. Our group has systematically investigated the structure and properties of various network polymer electrolyte systems to further enhance SPE performance in complete lithium battery devices.
Our group recently used the polymer single-crystal system to address a longstanding question about how semicrystalline morphology impacts ion transport. We quantitatively demonstrated that polymer crystallization affects ion transport in two ways: structurally (through tortuosity) and dynamically (via tethered chain confinement).
Related publications: Nano Lett.2012, 2, 310. Macromolecules 2014, 47, 3978-3986. Macromolecules 2015,48, 4503–4510. Adv. Mater. 2015, 27, 5995–6001. Adv Energy Mater. 2018, 8, 1801885. Nano Lett. 2020, 20, 6914–6921.
3. Biomimicry and Biomaterials.
The orientation and spatial distribution of nanocrystals in the organic matrix are two distinctive structural characteristics associated with natural bone. Synthetic soft materials have been used to successfully control the orientation of mineral crystals. The spatial distribution of minerals in a synthetic scaffold, however, has yet to be reproduced in a biomimetic manner. We use block copolymer-decorated polymer nanofibers to achieve biomineralized fibrils with precise control of both mineral crystal orientation and spatial distribution. Exquisite nanoscale structural control in biomimetic hybrid materials has been demonstrated.
Related publications: Macromolecules 2008, 41: 9516. Macromolecules 2010, 43: 9918. ACS Nano, 2013, 7, 8251-8257.
4. Sustainable Polymer Nanocomposites.
Polylactic acid, polyurathane, and cellulose nanocrystals, silica nanoparticles, and POSS have been incorporated into polymer nanocomposites using ins-situ polymerization and blending methods.
Related publications: Polymer2006, 47: 1678. Polymer2010, 51: 2191. Polym. Degr. Stab.2012, 97, 192. Macromolecules2012, 45, 993.
5. Liquid CrystallineBlock Copolymers.
hierachical nanostructures are constructed using liquid crystalline block copolymers. Subtle competition between liquid crysatlline order and block copolymer order have been studied by combining small angle X-ray and transmission electron microscopy.
Related publications: Macromolecules2004, 37: 2854. J. Am. Chem. Soc.2005, 127: 15481. Macromolecules2006, 39: 517. Macromolecules2007, 40: 840. Macromolecules2007, 40: 5095. Soft Matter2008, 4: 458. Macromolecules2009, 42: 3510. Polymer2010,51: 3693.