The RAFT aqueous emulsion polymerization of methyl methacrylate (MMA) is conducted at 70 °C using poly(glycerol monomethacrylate) (PGMA) as a steric stabilizer block. This non-ionic precursor has previously proved to be highly effective for the RAFT aqueous emulsion polymerization of various vinyl monomers such as benzyl methacrylate (BzMA), 2,2,2-trifluoroethyl methacrylate (TFEMA), isopropylideneglycerol monomethacrylate (IPGMA) or glycidyl methacrylate. However, an unexpected constraint was encountered in the case of MMA. Targeting a degree of polymerization (DP) of 20 to 100 for the PMMA block led to colloidal dispersions of kinetically-trapped spherical nanoparticles ranging in size from 17 nm to 31 nm. On the other hand, targeting DPs above 100 invariably led to the formation of highly flocculated spherical nanoparticles. This rather limited DP range is in striking contrast to the much higher DPs that can be targeted without loss of colloidal stability when using more hydrophobic monomers such as BzMA, TFEMA or IPGMA. The same flocculation problem was also evident when employing a PGMA precursor containing an anionic carboxylate end-group, but a series of colloidally stable dispersions could be obtained when using an anionic poly(methacrylic acid) stabilizer. Finally, the efficient removal of RAFT end-groups from PGMA₅₀-PMMA₈₀ nanoparticles was achieved by visible light irradiation using a blue LED source (λ = 405 nm). UV GPC studies confirmed that up to 87% dithiobenzoate end-groups can be removed from such nanoparticles within 12 h at 80 °C. On the other hand, using excess H₂O₂ under the same conditions only led to 24% end-group removal. This is because this water-soluble reagent has restricted access to the hydrophobic PMMA cores.

中文翻译：

---

甲基丙烯酸甲酯的 RAFT 水乳液聚合：观察使用非离子空间稳定剂嵌段时的意外限制

甲基丙烯酸甲酯 (MMA) 的 RAFT 水乳液聚合在 70 °C 下使用聚（甘油单甲基丙烯酸酯）（PGMA）作为空间稳定剂嵌段进行。这种非离子前体先前已被证明对各种乙烯基单体的 RAFT 水乳液聚合非常有效，例如甲基丙烯酸苄酯 (BzMA)、甲基丙烯酸 2,2,2-三氟乙酯 (TFEMA)、异亚丙基甘油单甲基丙烯酸酯 (IPGMA) 或甲基丙烯酸缩水甘油酯. 但是，在 MMA 的情况下遇到了意外的限制。将 PMMA 嵌段的聚合度 (DP) 设为 20 至 100，可产生大小为 17 nm 至 31 nm 的动力学捕获的球形纳米粒子的胶体分散体。另一方面，目标 DP 高于 100 总是会导致高度絮凝的球形纳米粒子的形成。这种相当有限的 DP 范围与使用更多疏水性单体（如 BzMA、TFEMA 或 IPGMA）时可以在不损失胶体稳定性的情况下靶向更高的 DP 形成鲜明对比。当使用含有阴离子羧酸盐端基的 PGMA 前体时，同样的絮凝问题也很明显，但当使用阴离子聚（甲基丙烯酸）稳定剂时，可以获得一系列胶体稳定的分散体。最后，从 PGMA 中有效去除 RAFT 端基 但是当使用阴离子聚（甲基丙烯酸）稳定剂时，可以获得一系列胶体稳定的分散体。最后，从 PGMA 中有效去除 RAFT 端基 但是当使用阴离子聚（甲基丙烯酸）稳定剂时，可以获得一系列胶体稳定的分散体。最后，从 PGMA 中有效去除 RAFT 端基₅₀ -PMMA ₈₀纳米颗粒是通过使用蓝色 LED 光源 ( λ = 405 nm)的可见光照射获得的。UV GPC 研究证实，在 80 °C 下，12 小时内可以从此类纳米颗粒中去除高达 87% 的二硫代苯甲酸酯端基。另一方面，在相同条件下使用过量的 H ₂ O ₂仅导致 24% 的端基去除。这是因为这种水溶性试剂限制了对疏水性 PMMA 核心的访问。