Long MD simulations are carried out using a detailed all-atom force field to investigate the effect of pH or, equivalently, degree of ionization α^– (= 0, 50, 100%) and degree of polymerization N (= 20, 23, 46, 70, and 110) on the structure and dynamics of poly(acrylic acid) (PAA) at infinite dilution. To ensure the validity and add to the reliability of our research conclusions, a systematic validation of several molecular mechanics force fields is performed. It is observed that the generalized AMBER force field in combination with the RESP charge fitting method best describes both the structural and dynamical behavior of PAA in comparison to experimentally obtained data. It is found that ⟨R_g²⟩^0.5changes with N as ⟨R_g²⟩^0.5 ∼ N^ν, with ν = 0.27 at α^– = 0% degree of ionization (acidic conditions), ν = 0.94 at α^– = 50% degree of ionization (neutral conditions), and ν = 0.87 at α^– = 100% degree of ionization (basic conditions), which is in perfect agreement with theory. The global shape of the PAA chain in the solution is quantified in terms of the three eigenvalues of the average radius-of-gyration tensor, the relative shape anisotropy κ², and the asphericity parameter b. It is revealed that at α^– = 0%, the chain adopts a spherelike conformation, while at α^– = 50 and 100%, its conformation is flattened and flexible. In addition, it is revealed that as the degree of ionization increases, the persistence length L_p increases, which suggests that PAA chains become stiffer with increasing pH. The global and local conformational changes of the PAA chain with the degree of ionization are found to be highly related to the solvation of the polymer. Finally, it is revealed that the diffusion coefficient D of the center of mass of PAA also exhibits a power law scaling with N, D ∼ N^ν, with ν = 0.25 at α^– = 0% degree of ionization, ν = 0.46 at α^– = 50% degree of ionization (neutral conditions), and ν = 0.44 at α^– = 100% degree of ionization (basic conditions), in excellent agreement with recent experimental data and theoretical predictions.

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Rapid innovation in chemicals and materials calls for innovative integrated approaches that can assess their impacts across different areas. The Safe and Sustainable-by-Design (SSbD) framework, developed by the European Commission's Joint Research Centre (JRC), offers a comprehensive approach with which to evaluate the safety and sustainability of chemicals and materials across their lifecycle. While SSbD uses various modeling approaches to assess impacts on human health, the environment, and socioeconomic factors, these are often applied independently, hindering a holistic understanding of the complex interactions between these factors and thus the simultaneous optimization of function, cost, safety and sustainability. This review describes existing predictive models and available strategies for their integration to facilitate more comprehensive and holistic chemical and material impact assessments. Specifically, we examine three model integration strategies: consensus integration that combines model predictions for the same impact categories, weighted aggregation that combines different scores in a unified one, and pipeline integration that links models sequentially to create a more unified assessment. Furthermore, we address key concepts related to the uncertainty of model predictions and the applicability domain of models, highlighting how these evolve in integrated frameworks. Insights into the applications of these integration strategies and challenges will allow a more accurate, coherent, and sustainable approach to chemical and material safety and sustainability assessments.