Self-Assembly and Stimuli Responsive Disassembly of Dendritic and Oligomeric Amphiphiles

Stimuli response is a fundamental process prevalent in all living systems, where a specific function (response) is generated in the presence of a given environmental cue (stimulus). Engineering materials for this process is often accomplished through another basic process, “self-assembly”. By understanding the key aspects of these processes scientists have developed a broad range of materials for a wide array of applications. This dissertation will primarily focus on developing stimuli responsive nanocarriers based on supramolecular assemblies of amphiphilic dendrimers and oligomers for safe transport and selective release of molecular cargo. Our concurrent goal is to also investigate several parameters which affect the molecular encapsulation and/or release through systematic structure property relationships. Dendrimeric and Oligomeric amphiphiles are chosen as components of stimuli responsive assemblies, as they offer desirable assembly properties as polymers (low CAC and better stability) combined with desired molecular characteristics as small molecules (uniformly disperse and reproducible). With amphiphilic dendron based assemblies: we have not only demonstrated their utility in stimuli responsive delivery using a biological (enzyme) and non-biological (temperature) stimulus, but also established the key assembly properties which dictate the nature of stimuli response. Specifically, we have deciphered the effect of unimer-aggregate equilibrium, kinetics of host and guest exchange, amphiphile molecular weight, and assembly size on stimuli responsive characteristics. Oligomeric amphiphiles lack systematically branched architecture as dendrons, nonetheless they offer a good platform to study structure property correlations. We explore this aspect with temperature as well as photo responsive oligomeric amphiphiles. More importantly we have also shown that through rational molecular design variations (length and backbone) oligomeric amphiphile assemblies exhibit features similar to dendrimer amphiphiles. In addition to this, the ease of oligomer synthesis and the simplicity of molecular designs make them good candidates for a wide range of applications