Tailored Interfaces with Amphiphilic Polymers

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ABSTRACT CTS-9616797 This proposal aims to explore the structure and Properties of adsorbed layers of block copolymers in which one block is a nonadsorbing polyelectrolyte and the other block is an adsorbing hydrophobic block. the objective is to learn how to create layers of polymers on substrates in aqueous environments that confer useful properties on the solid interfaces. Properties of interest might include adhesion, friction, particle and cellular deposition, surface charge, swelling, hydration and hardness. The technological areas that this work will influence range from aqueous dispersions of particles, as in printing and coating, to biointerfaces, arising in biomaterials, drug delivery and biotechnology. The proposed work will be based on the synthesis of several series of hydrophobically modified polyelectrolytes corresponding to the above description. The synthesis will be controlled to produce systematic variations of well-defined molecular weights in each of the blocks, and with a variety of chemical species enabling controlled changes in segment hydrophilicity, linear charge density, populations of quenched vs. annealed charge sites, molecular architecture and chain flexibility to be explored. Careful investigation of the solution preparation methods and properties is an essential feature of this work, since we anticipate that the properties of the surface layers can be strongly affected by the nature and history of the solutions from which they are prepared. Adsorption of these molecules will be conducted under varying solution conditions and will be followed in real time by in situ ellipsometry, supported by exploratory studies of the layers by neutron reflection and related methods. Properties of these layers, and additional structural information will be obtained by direct measurement of forces of interaction between the layers using the surface forces apparatus. Frictional forces between the layers will be studied via a lateral force measurement attachment t o the surface forces instrument. At the conclusion of this proposed work, we will have developed a body of data enabling the predictive design of aqueous interfaces decorated with polymeric amphiphiles. We will determine how the adsorption of these polymers depends on molecular structure and solution properties, and, how an adsorbed layer of a certain molecular weight and chain density behaves with respect to normal and frictional force interactions. The understanding of these properties will require an improved knowledge of polyelectrolyte physics, to which this work will contribute, as well as providing a body of data useful to engineers involved in the development and processing of soft materials and complex fluids.