The polymer dispersity index (PDI) is a vital metric for characterizing molecular weight distribution, significantly influencing polymer material performance. However, achieving precise control over PDI in polymer synthesis remains a substantial challenge. In this study, we introduce an approach for modifying the PDI of poly(methyl acrylate) (PMA) in switchable reversible addition-fragmentation chain transfer radical polymerizations (RAFT). The devised strategy involves the utilization of photoresponsive hexaarylbiimidazole (HABI) as a mediator, coupled with temporal programming, to cyclically deactivate and reactivate propagating radicals at distinct stages throughout the polymerization process. The precise timing of the light stimulus is facilitated through computer-controlled single-chip microcomputer technology, ensuring automatic modulation of the optical state and mitigating operational inaccuracies. By manipulating external light conditions, the PDI of PMAs can be systematically adjusted within the range of 1.80 to 2.59. Validation through successful chain-extension experiments and analysis via MALDI-TOF MS confirm the preservation of good chain-end fidelity across PMAs with varying PDIs fabricated through this methodology.

中文翻译：

---

使用时间程序控制系统通过光响应 RAFT 聚合控制分子量分布


聚合物分散指数 （PDI） 是表征分子量分布的重要指标，对聚合物材料的性能有显著影响。然而，在聚合物合成中实现对 PDI 的精确控制仍然是一项重大挑战。在这项研究中，我们介绍了一种在可切换的可逆加成-碎裂链转移自由基聚合 （RAFT） 中修饰聚丙烯酸甲酯 （PMA） 的 PDI 的方法。设计的策略涉及利用光响应性六芳基咪唑 （HABI） 作为介质，结合时间编程，在整个聚合过程的不同阶段循环灭活和重新激活传播的自由基。通过计算机控制的单芯片微计算机技术，可以实现光刺激的精确定时，确保光学状态的自动调制并减轻操作不准确。通过操纵外部光照条件，可以在 1.80 到 2.59 的范围内系统地调整 PMA 的 PDI。通过成功的链延伸实验和通过 MALDI-TOF MS 进行的分析进行验证，证实了通过该方法制备的不同 PDI 的 PMA 之间保持了良好的链端保真度。