CAREER: Shape Responses of Ultrathin Hydrogel Microcapsules

University Of Alabama At Birmingham, Birmingham AL

Investigators

Abstract

TECHNICAL SUMMARY: The goal of this CAREER proposal is to develop a novel class of shape-adaptable materials using pH-sensitive hollow hydrogel microparticles (capsules) of specific shapes, and to gain a fundamental understanding of pH-induced capsule shape transformations. To date, environmental control over materials shape remains a major challenge due to experimental difficulties that hinder integration of stimuli-responsiveness into shaped structures. The key task in this work is to understand how shape responses can be controlled by varying capsule geometry, dimensions, chemical structure, and thickness of hydrogel wall. The objectives of this project are: (i) to develop synthesis of hydrogel capsules of various shapes using a layer-by-layer approach; (ii) to explore pH-triggered dimensional and shape transformations in the shaped capsules; and (iii) to investigate pH-triggered changes in capsule mechanical properties and permeability. In this project a series of pH-sensitive anionic and cationic copolymers bearing cross-linkable amino groups will be synthesized and assembled into ultrathin hydrogel films and shape-specific hydrogel capsules. The effects of hydrogel composition, thickness, and stiffness as well as capsule geometry and dimensions on pH-triggered volume transitions and on the related capsule physical properties, including wall swelling/shrinkage, capsule size/shape transformations, mechanical properties, and permeability will be studied. Fundamental correlation between complex shapes and physical and chemical properties will be explored using a combination of in situ techniques such as ATR-FTIR, scattering techniques, ellipsometry, optical and electron microscopy, and nanoindentation. The knowledge obtained in the proposal can be used in controlling size- and shape-transition phenomena in microgels and multilayer capsules. NON-TECHNICAL SUMMARY: This project on creation of shape-transformable hollow particles (capsules) offers prospects for developing materials with novel actuation characteristics having applications for controlled drug delivery, tissue engineering, and pH-regulating transport in microfluidic devices. These structures may have unique properties as compared to simple spheres including shape-guided interactions, a greater stability in flow, and shape-directed flow behavior and cellular uptake. The educational aspect of this project is to develop a polymer sciences program at U. Alabama Birmingham (UAB) promoting learning and research opportunities from the high school through the graduate level. The program will combine elements of traditional polymer chemistry with developing awareness of the needs of the UAB biomedical research community for specialized polymers. The program will have a strong influence on education in the field in the Southeast, with potentially significant social and economic impact. High school, undergraduate, and graduate students including underrepresented minorities will be trained in modern aspects of polymer science including state-of-the-art synthetic and analytical methods and intensive multidisciplinary collaborations throughout and beyond UAB. Educational and outreach activities involve developing new B.S. and Ph.D. programs in polymer science at UAB and creating "PolymerBridge" to enhance the impact on and to increase the opportunities for underrepresented minorities in polymer science. "PolymerBridge I" will be designed for 11-12th graders with instructor-developed demonstrations and include hands-on lab work, while "PolymerBridge II" will target high school science and chemistry teachers.