Mapping Composition Evolution through Synthesis, Purification, and Depolymerization of Random Heteropolymers.

Random heteropolymers (RHPs) consisting of three or more comonomers have been routinely used to synthesize functional materials. While increasing the monomer variety diversifies the side-chain chemistry, this substantially expands the sequence space and leads to ensemble-level sequence heterogeneity. Most studies have relied on monomer composition and simulated sequences to design RHPs, but the questions remain unanswered regarding heterogeneities within each RHP ensemble and how closely these simulated sequences reflect the experimental outcomes. Here, we quantitatively mapped out the evolution of monomer compositions in four-monomer-based RHPs throughout a design-synthesis-purification-depolymerization process. By adopting a Jaacks method, we first determined 12 reactivity ratios directly from quaternary methacrylate RAFT copolymerization experiments to account for the influences of competitive monomer addition and the reversible activation/deactivation equilibria. The reliability of in silico analysis was affirmed by a quantitative agreement (<4% difference) between the simulated RHP compositions and the experimental results. Furthermore, we mapped out the conformation distribution within each ensemble in different solvents as a function of monomer chemistry, composition, and segmental characteristics via high-throughput computation based on self-consistent field theory (SCFT). These comprehensive studies confirmed monomer composition as a viable design parameter to engineer RHP-based functional materials as long as the reactivity ratios are accurately determined and the livingness of RHP synthesis is ensured.

Global accurate diabatic potential surfaces for the reaction H + Li2.

The adiabatic potential energies for the lowest three states of a Li2H system are calculated with a high level ab initio method (MCSCF/MRCI) with a large basis set (aV5Z). The accurate three dimensional B-spline fitting method is used to map the global adiabatic potential energy surfaces, using the existing adiabatic potential energies, for the lowest two adiabatic states of the title reaction system. The different vibrational states and corresponding energies are studied for the diatomic molecule of reactant and products. In order to clearly understand the nonadiabatic process, the avoided crossing area and conical intersection are carefully studied. For further study of the nonadiabatic dynamic reaction, the diabatic potential energy surfaces are deduced in the present work.

Accurate Potential Energy Surfaces for the Three Lowest Electronic States of N(2D) + H2(X1∑g +) Scattering Reaction.

The three lowest full three-dimensional adiabatic and three diabatic global potential energy surfaces are reported for the title system. The accurate ab initio method (MCSCF/MRCI) with larger basis sets (aug-cc-pVQZ) is used to reduce the adiabatic potential energies, and the global adiabatic potential energy surfaces are deduced by a three-dimensional B-spline fitting method. The conical intersections and the mixing angles between the lowest three adiabatic potential energy surfaces are precisely studied. The most possible nonadiabatic reaction pathways are predicted, i.e., N(2D) + H2(X1∑g +) → NH2(22A') → CI (12A'-22A') → NH2(12A') → CI (12A″-12A') → NH2(12A″) → NH(X3∑-) + H(2S). The products of the first excited state (NH(a1Δ) + H(2S)) and the second excited state (NH(b1∑g +) + H(2S)) can be generated in these nonadiabatic reaction pathways too.