(604b) Manipulation of Surface Chemistry Via Polymer Chain-End Segregation in Topologically Constrained Materials

The manipulation of surface chemistry, and more precisely the hydrophilic/hydrophobic nature of an interfacial material, is essential for applications in coatings, biomaterials, and microfluidic devices. To engineer surface hydrophobicity, past research has relied heavily on the proclivity of low surface energy compounds such as fluorinated alcohols or polymers to self-segregate towards an exposed interface, thus maximizing the hydrophobicity of the resultant surface. This has been particularly relevant for the design of hydrophobic cross-linked coating materials that have associated high modulus, rigidity, and thermal resistance. While this is an effective approach to create interfaces with relatively low surface energy and strong hydrophobic character, many applications require hydrophilic surface chemistries or at a minimum patterning of hydrophobicity and hydrophilicity. As one example, natural interfaces that are efficient at water capture, guidance and collection typically have patterned and spatially resolved domains of hydrophobicity and hydrophilicity. Since the segregation of fluorinated compounds is driven by the minimization of surface energy, the development of hydrophilic surface chemistry must be engineered using separate strategies. Currently, many researchers utilize secondary post-functionalization of polymeric interfaces, which typically requires additional precursors and reagents. Here we explore how the design of polymer chain ends can be exploited to promote the segregation of higher surface energy (i.e., hydrophilic) groups towards an air/polymer interface, thus increasing the surface hydrophilicity of polymeric materials in a single polymerization procedure. This design relies on the enhanced mobility of chain ends and the entropic gain by residing at an exposed interface. We explore how the ultimate concentration and nature (polar / nonpolar) of polymer chain ends influence surface wettability in topologically constrained materials (e.g., rigid, cross-linked networks formed via photopolymerization). In particular, we highlight how linear polymers with engineered polar chain-ends can be integrated into UV-curable formulations to increase the hydrophilic character of resultant coating materials. Furthermore, we will highlight how these polymer additives can also be utilized in heterogeneous formulations that undergo phase separation during polymerization, resulting in spatial segregation of polymer chain ends across the coating interface. This work provides a framework from which hydrophilic surface chemistry can be easily engineered and patterned in rigid coating materials, yet without the use of secondary functionalization procedures.