Tracking Single Polymer Growth down to Single-Monomer Resolution
Abstract
In a typical chain-growth polymerization reaction, each catalyst molecule adds monomers to a growing polymer chain. These growing chains can adopt diverse conformations, and the microscopic dynamics of polymer growth is expected to differ from one polymer to another, contributing to the differences in their microstructures, which are crucial for their bulk properties. How a single polymer grows dynamically was unknown, however. Supported by ARO, we, for the first time, have visualized polymer growth in real-time at the single-polymer level. We developed a magnetic tweezers (MT) based approach and focused on the ring-opening metathesis polymerization (ROMP) catalyzed by a GrubbsÕ catalyst, and discovered that individual polymers form conformationally entangled hairballs during real-time growth and these hairballs play key roles in determining the polymerization rates and the dispersion among individual polymers. Building on our achievements, the objective of our research here is to define the catalytic kinetics and dynamics of living polymerization reactions in real time at the single-polymer level down to single-monomer resolution. To achieve this objective, we propose to pursue two complementary directions, each using a distinct approach and both focusing on the model system of ROMP of linear polymers: 1) Tracking single polymer growth dynamics in real time using MT. 2) Imaging single polymer growth in real-time at single-monomer resolution using single-molecule fluorescence microscopy (SMFM). The proposed research is further strengthened by established collaborations with a synthetic polymer chemist and a theorist in simulations of polymer conformational dynamics. The expected contribution of the proposed research is two-fold: 1) On the technical side, it will provide two innovative single-molecule approaches that enable the measurements of living polymerization in real time, at the single-polymer level, and down to single-monomer resolution. 2) On the scientific side, it will provide insights into the real-time kinetics and non-equilibrium conformational dynamics of single polymers during living polymerization, the kinetic origin of chain length dispersion among individual polymers, and the microscopic sequence of copolymers. This contribution has broad significance and positive impact, and it is potentially transformative because: 1) It will provide new and drastically different ways for studying polymerization reactions, thus breaking new ground for polymer research. 2) It will help devise strategies to manipulate polymer growth kinetics for controlling chain length dispersions. 3) It will provide the microscopic sequence information of individual linear copolymers so that the microstructure of individual polymers can be correlated with their macroscopic properties. 4) It will positively impact AROÕs Polymer Chemistry Program. 5) The research traverses two different areas: single-molecule imaging/manipulation, and polymer chemistry and physics, bringing new scientific perspectives into both areas.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 15, 2018
- Source ID
- W911NF1810217
Entities
People
- Peng Chen
Organizations
- Army Contracting Command
- Cornell University
- United States Army