Surface Segregation of Branched Chain-ends in PDMS

It is well known that polymeric materials reorganize at their surfaces in order to minimize surface tension and free energy. This reorganization, driven by enthalpic and/or entropic forces, creates surface properties that can dramatically differ from the bulk. Enthalpically driven reorganization allows low energy groups to surface segregate and dominate the surface properties of the material. This is the case with polydimethylsiloxane (PDMS), where low surface energy pendant methyl groups accumulate at the surface. However, in some cases, higher energy groups can surface segregate when incorporated into branched or bulky polymer chain-ends. This process is entropically driven, in order to maximize polymer configurations in the bulk, despite increasing the enthalpy of the system. This research aims to study the surface segregation behavior of high energy, branched chain-ends within a PDMS network. Novel Silicone additives consisting of linear PDMS polymers, chain-end functionalized with branched polyester dendrimers containing quaternary ammonium cations (QACs) have been synthesized. The QACs provide the observable property of antimicrobial activity, which will be used to probe the surface segregation of the additive chain-ends.