CAREER: Multiscale Modeling of Polymersomes

Cuny College Of Staten Island, Staten Island NY

Investigators

Abstract

NON-TECHNICAL SUMMARY This CAREER award supports theoretical and computational research and education on how chain-like molecular units, or polymers, can assemble themselves to form vesicles that confine a solution. The vesicles, called polymersomes, have diverse applications in the soft materials community as drug delivery devices or even as tiny, nanoscale, flasks for chemical reactions. The shape of the polymersome can be tailored in response to external stimuli such as temperature or type of solvent. The PI will focus on polymersomes made of a particular kind of polymer that contains a hydrophilic molecular building block, one that can dissolve or mix with water, that is connected to a hydrophobic molecular building block which does not mix well with water. At low concentrations in water, depending on the polymer length and exact ratio of hydrophobic to hydrophilic groups, these polymers can assemble into spherical shapes, worm-like shapes, or vesicle-like shapes. The PI will use computation and focus investigation on the self-assembly of these polymers into polymersomes. This award will use molecular dynamics simulation methods to investigate both the self-assembly of these polymersomes as well as their elastic properties. In molecular dynamics, the rule by which atoms and molecules interact with each other is mathematically described by a force field. This award will create new force fields to simulate polymersomes at large length-scales on the order of microns and long time-scales on the order of hundreds of microseconds. The PI will aim to develop these force fields so that they accurately describe the elastic properties of the polymersomes. In addition, these force fields will be used to investigate how adding change to the polymers changes the properties of the polymersome membrane. Furthermore, the PI will utilize specialized techniques in molecular dynamics simulation to investigate the formation of pores in the membrane, as well as change the membrane shape. Complementing the above research activities, proposed educational and outreach activities include strengthening the local educational and research environment of College of Staten Island and City University of New York (CUNY), and more closely integrating the institutions with local NY teachers. Working with a local high school teacher who is an alumna of College of Staten Island, the PI has developed several course modules that introduce students to concepts in chemistry. The PI will test and assess the impact of these modules. Moreover, the PI will establish a two- day workshop to introduce local high school teachers to computational chemistry and high-performance computing, in collaboration with the High-Performance Computing Center at CUNY, entitled Workshop for Teaching Science with Computational Chemistry. The PI will assess the impact of this workshop through surveys of the teachers after and during the next school year to see how this impacts and enhances the classroom environment, with the guidance of the Director for Academic Assessment at CSI. The proposed research and the educational activities are all enhanced by the PI's experience and current activity in mentoring minorities and females interested in the STEM fields all the way from the high school to postdoctoral level. TECHNICAL SUMMARY This CAREER award supports theoretical and computational research and education to develop and utilize multi-scale computational methods with the aim of deducing design principles to control the properties of polymersomes. Nearly all soft materials, particularly materials based on polymeric self-assembly, are far from their equilibrium state. Not only is this a challenge, but it is also an opportunity to harness the structure, morphology, and transformation kinetics of self-assemblies to optimize materials properties. Indeed, the ability to tune molecular assembly shape in response to external stimuli has numerous applications in tailoring the thermodynamic, mechanical, and photonic properties of materials. This research activity aims to develop multi-scale computational approaches that will provide fundamental insight into the design principles guiding the elastic properties of charged polymeric membranes, including polymersomes. Polymersomes, in particular, stimuli-responsive polymersomes have diverse applications as nanocarriers, nanoreactors, and even as biomimectic systems. Within the scope of this project the PI will develop a computational toolbox that can be used to engineer polymersomes with key physical properties. Specifically, the PI will design coarse grain force fields for common diblock copolymers that self-assemble into polymersomes, and use an array of approaches in molecular dynamics to characterize and predict their elastic properties. Next, the PI will utilize various computational methodologies to predict the stability of these polymersomes, specifically the energy required to porate the membrane, as well as characterize their stimuli-responsive change in shape. A focus of this research project is the development of computational methods and force fields to characterize intermediate morphologies and shape transformations underlying molecular self-assembly of amphiphilic molecules. These new computational techniques would be both verified and experimentally validated, and would allow for the rational design of new diblock copolymer mixtures that can self-assemble into the polymersome morphology, that can be tested by experimental collaborators. New computational methods that inform the design of diverse morphological self-assemblies from the molecular level up, that also incorporate their potential for dynamic shape transformation, can impact multiple soft materials fields. Outcomes of the proposed research will allow for molecular design strategies that can be used to tailor amphiphiles to optimize their dynamic response to external stimuli such as solvent or salt concentration. For example, the diblock copolymers discussed within this proposal can be tailored for applications such as drug delivery or as catalytically active nanomotors. Complementing the above research activities, proposed educational and outreach activities include strengthening the local educational and research environment of College of Staten Island and City University of New York (CUNY), and more closely integrating the institutions with local NY teachers. Working with a local high school teacher who is an alumna of College of Staten Island, the PI has developed several course modules that introduce students to concepts in chemistry such as surfactant micellization. The PI will test and assess the impact of these modules. Moreover, the PI will establish a two-day workshop to introduce local high school teachers to computational chemistry and high-performance computing, in collaboration with the High-Performance Computing Center at CUNY, entitled Workshop for Teaching Science with Computational Chemistry. The PI will assess the impact of this workshop through surveys of the teachers after and during the next school year to see how this impacts and enhances the classroom environment, with the guidance of the Director for Academic Assessment at CSI. The proposed research and the educational activities are all enhanced by the PI's past experience and current activity in mentoring minorities and females interested in the STEM fields all the way from the high school to postdoctoral level. 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.