Design and development of stimuli-responsive materials: pH sensitive polymersomes and poly(olefin sulfone)s

Stimuli-responsive materials are materials exhibit a response when exposed to specific external triggers. These materials are powerful tools for material development in areas such as encapsulation, photoresists, sensors, self-healing materials, drug delivery, and transient electronic devices. A variety of chemical triggers can be employed to stimulate materials, for this work the focus has been on pH-responsive materials. Materials which can be triggered with pH have a variety of applications in biological and industrial fields. This thesis is split into two main parts: 1) the development of acid-triggerable covalently-crosslinked polymersomes and 2) the design and synthesis of base-, heat-, and fluoride-sensitive poly(olefin sulfone)s. Polymersomes are a useful approach for encapsulation but are susceptible to environmental stressors and leakage. By tuning the nanoscale architecture of the polymersomes with reversible chemical modifications, their stability can be improved while still allowing triggered release capabilities that permanently cross-linked polymersomes lack. Using dynamic covalent imine chemistry, terminally functionalized polymers were reversibly connected within polymersome membranes in the presence of reactive linkers. The connection of these polymer was investigated using two polymersome systems, poly(styrene-b-acrylic acid) in Chapter 2 and poly(styrene-b-ethylene oxide) in Chapter 3. Poly(olefin sulfone)s are a class of polymers known to degrade in the presence of base, as well as through thermolysis and radiolysis. In order to develop novel materials for applications in encapsulation and transient electronic devices, molecular design criteria needed to achieve rapid, base degradation of poly(olefin sulfone)s at room temperature were investigated,. Poly(vinyl ester sulfone)s and poly(vinyl butyl carbonate sulfone)s were synthesized and shown to degrade more rapidly than aliphatic poly(olefin sulfone)s (Chapter 4 and 5). Additional work has focus on the design of fluoride sensitive poly(olefin sulfone)s and the modulation of the thermal degradation of poly(tert-butyl carbonate sulfone) and poly(phthalaldehyde) (Chapter 5)