Chain Dynamics and Layering within Polyelectrolyte Multilayer Films Svelana A. Sukhishvili, Stevens Institute of Technology, DMR Understanding and controlling structure of layer-by-layer (LbL) polymer films is critically important for applications of such films as antireflective coatings or sequential delivery of drug from surfaces. We explore major factors that affect dynamics and structure of LbL films. With well-defined polycations 1 and poly(methacrylic acid) (PMAA) of varied molecular weights, we study dynamics of polymer chains within LbL films using fluorescence recovery after photobleaching (FRAP) and neutron reflectometry (NR). T his year we have focused on (a) exploring the molecular weight dependence of polymer diffusion for two different film assembly regimes, i.e. “linear” and “exponential” film growth, as well as (b) assessing the degree of chain motion within PEMs as a function of polyanion molecular weight and concentration of small ions. We have discovered that in exponentially grown films, D showed a stronger molecular weight dependence than in lineally deposited films, i.e. D~M -1.4 (Fig. 1), suggesting strong effects of film layering on chain dynamics. Another important finding concerns the effect of salt concentration on chain mobility. We found exponential dependence of PMAA chain diffusion coefficients on NaCl concentration, with preserved anisotropy of chain motions at early stages of film intermixing (Fig. 2, left). We have also explored the effect of molecular weight on diffusion anisotropy, and found strongly enhanced chain intermixing (Fig. 2, right) and a decrease in diffusion anisotropy with short polymer chains. Our findings motivate further development of theoretical and experimental insights on the dynamic behavior of layered PEM films. Fig. 1. Schematic representation of multilayers used in measurements of diffusion coefficients of PMAA chains within PEM films in FRAP experiments (top), and two scaling laws for molecular-weight dependence of PMAA diffusion found in different regimes of film deposition (bottom). Fig. 2. Scaling of diffusion coefficients of PMAA chains in directions parallel and perpendicular to the substrate with salt concentration (left), as well as the dependence of D  on PMAA molecular weight (right). 0.4 M NaCl NR: Vertical diffusion D // = 5.1× e 7.6 [NaCl] cm 2 s -1 D ﬩ = 6.8× e 7.5[NaCl] cm 2 s -1 D = Ke n[NaCl] D // D﬩D﬩ ≈ 10 4

Results of the project are now being incorporated into one course 1 and included in seven presentations 2, as well as at the Research and Entrepreneurship Day at Stevens in April 2014, which gathers a broad audience of NY/NJ entrepreneurs, National Lab representatives, and high school teachers. Graduate students involved in the project are significantly enriching their knowledge through systematic interactions with researchers at ORNL. Specifically, a graduate student Victor Selin (Fig.1, blue, left) has travelled twice to ORNL to perform neutron reflectivity experiments (Fig. 2). Experience obtained at ORNL is disseminated to undergraduate and high school students. In summer of 2014, one undergraduate student, Victoria Albright (Fig. 1, in white), and one high-school ACS SEED student (Fig.1, in red) have been working on the NSF project. We continue shaping the Polymers in Our Lives module for implementation in high school classrooms. To that end, graduate students meet with Debra Brockway (Fig. 3), a science educator from Stevens’ Center for Innovation in Engineering and Science Education (CIESE) to discuss implementation of the module with our group. CIESE is a nationally recognized center whose goal is to improve K-12 science and mathematics education through internet- based curriculum materials and bringing cutting-edge research into K-12 classrooms. Chain Dynamics and Layering within Polyelectrolyte Multilayer Films Svelana A. Sukhishvili, Stevens Institute of Technology, DMR Fig. 1. Graduate, undergraduate and high-school students during summer of 2014: graduate students Victor Selin (in blue, left), Yuhao Wang (in blue, right), an undergraduate students Victoria Albright (in white), and a high-school ACS SEED student Bianelly Tellez (in red) participate in the project. Fig. 3. A science educator Debra Brockway collaborating with graduate students Victor Selin (Fig.1, in blue, left) and Yuhao Wang (Fig. 1, in blue, right) to promote the development and implementation of Polymers in Our Lives module into the high school setting. Fig. 2. Spallation Neutron Source (Oak Ridge National Laboratory) used by a Ph.D. student Victor Selin to perform neutron reflectivity experiments. 2014