We use Brownian dynamics (BD) simulations resolved at the level of a Kuhn step to calculate the rate at which a telechelic polymer with surface-adhering endcaps transitions from a bridge between two flat surfaces to a loop on a single surface. We then use self-consistent field theory to obtain the equilibrium ratio of bridges to loops and apply the principle of detailed balance to obtain the slower loop-to-bridge times from the faster bridge-to-loop times. The bridge-to-loop transition time has two scaling regimes: one where it is approximately equal to the time for a lone hydrophobic particle to desorb from a surface, and the other where it is dominated by the retraction time of the polymer; approximate formulas for both times are given. The results are important for interpreting the dynamics and rheolo latex coating fluids, in which colloidal particles are dynamically bridged by telechelic rheology-modifying polymers.

The signac data management framework (https://signac.io) helps researchers execute reproducible computational studies, scales workflows from laptops to supercomputers, and emphasizes portability and fast prototyping. With signac, users can track, search, and archive data and metadata for filebased workflows and automate workflow submission on high performance computing (HPC) clusters. We will discuss recent improvements to the software’s feature set, scalability, scientific applications, usability, and community. Newly implemented synced data structures, features for generalized workflow execution, and performance optimizations will be covered, as well as recent research using the framework and changes to the project’s outreach and governance as a response to its growth.

We investigate the transition between the overdamped and underdamped regimes in Langevin dynamics simulations with significant conservative forces by comparing direct simulations with theories of Kramers, Mel'nikov and Meshkov (MM), and Larson and Lightfoot (LL). The need for clarification is made evident by noting that the most commonly cited theories of Kramers and MM do not apply in the overdamped limit to escape times from a Lennard-Jones (LJ) potential, because Kramers and MM do not account for the flatness of the LJ potential at the escape position, which allows for a region of nearly free Brownian diffusion near the escape position. While the little-known LL approach does consider an LJ potential, it does not properly consider the underdamped regime, and so a complete description is only achieved by combining the LL and MM results into a single general equation, which we validate for the first time by an explicit comparison with Langevin simulations.

This “Innovation in Engineering Teaching Practices” paper will describe the student led co-curricular REACT (Research Education and Activities for Classroom Teachers) program at the University X. REACT was formed in 2017 to bring K-12 math and science teachers from the midwest together for a one-day, interactive learning experience to help incorporate research into their classrooms. Teachers listen to graduate student talks, go on research lab tours and are provided novel lesson plans and materials for two hands-on activities that can be used in their K-12 classrooms. Graduate students from eleven engineering and science departments collaborate to develop these materials and ensure they meet the Next Generation Science Standards (NGSS). Teachers earn continuing education credits for attending. REACT is an opportunity not only for teachers to learn about the cutting-edge research happening at University X, but also serves as a professional development tool for graduate students, giving them the opportunity to work on science communication skills as well as participate in curricula development. The program has also developed a unique funding model, where university professors and departments sponsor individual teachers, so attendance and all materials are free for educators. Since 2017, REACT has hosted ninety K-12 teachers from seventy different school districts. Similar workshops are being developed at other universities based on REACT’s model. At times, the distance between graduate school and K-12 education can seem very large, but as one REACT participant stated: “REACT has been an effective way to bridge the gap between the research community at University X and the education sphere.”

We combine the self-consistent field theory and the Derjaguin approximation to predict the polymer-induced colloidal interactions and the nonuniform distributions of the loops and bridges of telechelic polymers adsorbed onto particle surfaces when the polymers are compressed or stretched as a function of interparticle distance. We validate our approach by comparing its predictions to those of Brownian dynamics simulations. We also determine the dependence of intercolloidal interactions on particle size and surface coverage as well as the molecular structures of telechelic polymers, including chain length and missing associating ends, which are important parameters in the design of commercial latex coatings. By mapping the predicted interparticle interaction strengths to Baxter temperatures, we can quantitatively predict the phase behaviors of the mixtures of colloids and telechelic polymers.