Laboratory of Sustainable Polymers, Department of Analytical Chemistry and Organic Chemistry , University Rovira i Virgili , Tarragona 43007 , Spain.
Roy & Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104-6323 , United States.
Biomacromolecules. 2019 Aug 12;20(8):3200-3210. doi: 10.1021/acs.biomac.9b00892. Epub 2019 Jul 25.
The use of stimuli-cleavable difunctional initiators containing a discrete single-type cleavable junction represents a general strategy to prepare mid-chain-degradable vinylic polymers. Here, we present a series of α-haloester-type programmed initiators encoding multiple single-type and dual-type cleavable junctions. Multiple single-cleavage groups increase the cleavage rate, whereas double-dual sites provide access to multiple mechanisms for cleavage. Single-electron transfer living radical polymerization was employed to generate well-defined mid-chain-cleavable poly(methyl acrylate)s designed with low-pH, low-pH/reduction, or low-pH/UV light cleavable linkages. Kinetic studies demonstrated that the polymerizations are living when using various catalytic Cu(0) sources (wire and powder), ligands (Me-TREN and TREN), and solvent sources (homogeneous and "programmed" biphasic). Moreover, structural analyses by NMR and matrix-assisted laser desorption/ionization-time-of-flight confirmed the near-perfect chain-end functionality of these stimuli-cleavable polymers derived from programmed initiators. A rigorous gel permeation chromatography study demonstrated that the combination of multiple acetal, disulfide, or 2-nitroresorcinol-derived acetal junctions offer attractive possibilities in terms of selective cleavage and orthogonal degradation.
使用含有离散单类型可裂解接头的刺激响应双官能引发剂代表了一种制备中链可降解乙烯基聚合物的通用策略。在这里，我们提出了一系列含有多个单类型和双类型可裂解接头的α-卤代酯型程序引发剂。多个单裂解基团增加了裂解速率，而双双重位点则为裂解提供了多种机制。采用单电子转移活性自由基聚合来生成设计具有低 pH、低 pH/还原或低 pH/UV 光可裂解键的中链可裂解聚（甲基丙烯酸甲酯）。动力学研究表明，使用各种催化 Cu(0)源（线和粉末）、配体（Me-TREN 和 TREN）和溶剂源（均相和“编程”两相）时，聚合是活性的。此外，通过 NMR 和基质辅助激光解吸/电离-飞行时间分析证实了这些由程序引发剂衍生的刺激响应可裂解聚合物的近乎完美的链端官能团。严格的凝胶渗透色谱研究表明，多种缩醛、二硫键或 2-硝基间苯二酚衍生的缩醛接头的组合在选择性裂解和正交降解方面提供了有吸引力的可能性。
