Controlling Heterogeneous Structure in Polymer Networks

heterogeneous network.jpg

Modern polymer network design typically targets a profile of various physical, chemical and mechanical properties (amongst many others). Since it’s unlikely that a single monomer can be employed to build a network that conforms to all the bulk properties desired, heterogeneous systems that combine different monomeric units must be employed. Of importance in this type of material design, is being able to manipulate the distribution of the different components within a system (between being broadly distributed, or having discrete distinct phases). One approach to developing heterogeneous materials is through the physical blending of two polymers, however this approach cannot be employed for applications where in situ polymerization is needed. 

I study phase-separation based approaches to designing heterogeneous networks, typically with photo-initiated polymerizations to expand the scope of application for such materials. Since the formation of heterogeneous structures occurs by thermodynamically driven de-mixing, these polymerizations can be employed for in situ applications (application of coatings, biomaterials, etc.). I find approaches to efficiently manipulate the balance between the thermodynamic driving force for phase separation and the physical limitations imposed by the formation of a three-dimensional network. Furthermore, I am interested in identifying applications where heterogeneous networks can provide enhanced utility to currently employed network systems. An example of this is when I demonstrated how phase separation could be used to design networks with reduced interfacial polymerization stress while maintaining mechanical integrity – a type of design that is needed for dental and coatings applications. 

Designing Biomimetic Interfaces via Polymerization Techniques

Dynamic behavior of marble treated with A photopolymerized coating.

Dynamic behavior of a non-treated marble dropped into water.

The coating renders the surface non-wetting, so that air pockets form along the surface upon entry to avoid contact with water.

The smooth surface and intrinsic hydrophilicity of the marble allows for a smooth entry into the water.

The control of surface chemistry and morphology is very important as it influences how a material interacts with an external environment. For applications such as adhesives, membranes, and coatings the resulting interaction of a polymeric interface with liquids is a critical design parameter. Natural surfaces such as the lotus leaf and rose petals have unique wetting behaviors (superhydrophobicity and parahydrophobicity, respectively) which, with the aid of microscopy, have been attributed to the presence of regular micro- and nanoscale topographical features on these interfaces. Taking inspiration from nature, my research looks to design surfaces with regular features synthetically to mimic unique wetting regimes on a larger scale. I explore two different approaches to design interfaces: the electrodeposition of conducting monomers as well as exploiting photo-initiated polymerizations to rapidly design and pattern interfaces. My work seeks to find efficient methods to pattern surfaces with unique morphologies and how to make those surfaces long-lasting and strong for large-scale applications.