(621b) Tuning Polymer Dynamics Via Sequence Control

A number of studies over the past decade have pointed towards a complex and potentially profoundly useful dependence of copolymer dynamics on chain sequence. For example, both experiments and simulations have indicated that alternating and statistical copolymers can exhibit significantly differing (by 10’s of kelvin) glass transition temperatures Tg at equal composition. Given the evolution of synthetic capability towards increasing sequence control, this dependence may open the door to greatly enhanced control of polymer thermal behavior at relatively fixed composition. Indeed, these observations suggest that sequence control might enable access to dynamical properties relevant to applications in next-generation polymer membranes, coatings, and batteries with modulated permeabilities, ion mobilities, etc.

Our previous simulations on coarse-grained polymer sequences pointed toward a potentially unexploited regime of extreme sequence sensitivity of Tg upon approach to alternating copolymers. Within this regime, simulations suggested that sequence can exquisitely tune local packing preferences, and thus strongly alter dynamics and glass formation. At the same time, given the central role of segmental packing in glass formation, local structural effects in chemically realistic copolymers may play an important role in modulating these effects. Such an interplay is challenging to explore in coarse bead-based polymer models due to their relatively simple local structure. Here we describe the results of new molecular dynamics simulations of all-atom copolymer models. We explore the interplay between chain sequence and composition, segmental packing, and segmental dynamics. These simulations provide new insights into the design and control of sequence copolymers with targeted dynamics and glass formation behavior.

This work was supported by grant FA9550-22-1-0427 funded bythe the Department of Defense, Air Force Research Laboratory.