Synthesis and characterization of tethered poly(n-isopropylacrylamide) for quantitative cell adhesion studies

Environmentally responsive (or “smart”) polymers represent a new approach for controlling biofouling release. Poly(N-isopropylacrylamide) (PNIPAAm) is a thermo responsive polymer that can potentially be used to control biofouling, as it exhibits a change in its relative hydrophobicity above and below its lower critical solution temperature (LCST ~ 32C). This thesis reports on grafted PNIPAAm brushes, synthesized using a relatively simple and rapid method which allows atom transfer radical polymerization (ATRP) in presence of air. In this study the structure, purity and thermally responsive behavior of grafted brushes have been characterized using X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy, Fourier transform infra-red spectroscopy, ellipsometry and contact angle measurements. Together all these studies proved that uniform, controlled and high molecular weight PNIPAAm brushes can be produced using ARGET ATRP. A quantitative study of detachment of marine bacteria from these surfaces, both above and below the LCST using a spinning disc apparatus is also reported. This device applies a linear range of reproducible shear forces to cells attached at the interface of a single sample. In this work, a model marine bacterium, Cobetia marina, which adheres more readily to hydrophobic surfaces, was attached to PNIPAAm grafted surfaces at 37C and subjected to varied detachment forces in artificial sea water. We found that the number of adherent cells decreased non-linearly with applied force and the cell detachment at the interface required lesser shear force at lower temperatures evaluated. The ability to directly correlate a measurable force to bacterial attachment and release represents a step forward in understanding of interactions between PNIPAAm and bacterial cells. Our work demonstrates the potential of stimuli responsive polymers as possible fouling-release agents, and suggests that grafted PNIPAAm (or similar polymers) may be useful as regenerable fouling-release surfaces.Chemical EngineeringMastersUniversity of New Mexico. Dept. of Chemical and Nuclear EngineeringLopez, Gabriel P.Canavan, HeatherWhitten, Davi