作者:Daniel Klinger、Katharina Landfester
DOI:10.1039/c0sm00638f
日期:——
Two classes (type A and type B) of novel photolabile divinyl functionalized crosslinkers based on o-nitrobenzyl derivatives were synthesized and investigated with regard to their photolytic performance upon UV irradiation. The systematic variation of the molecular structure resulted in different degradation rates depending on the irradiation conditions. Thus, the successive and independent cleavage is enabled by either adjusting the applied wavelengths or irradiation times. The respective molecules were used to build up photodegradable PMMA microgels by free radical copolymerization with MMA in a miniemulsion polymerization process. UV light-induced degradation of the swollen microgels was monitored by time dependent turbidity measurements and the resulting kinetics were found to correlate with the photolysis rates of the respective crosslinkers in solution. The irradiation wavelength-controlled selective partial cleavage of type B crosslinking points was achieved by UV irradiation with λ > 315 nm and resulted in particles with extensively increased volumes consisting of highly swollen networks. In addition, the irradiation time-controlled selective complete degradation of particles containing type B crosslinkers was accomplished. By using broadband UV light containing wavelengths of λ < 315 nm, the successive complete particle disintegration of type B and type A microgels was observed. Hence, the specific performance of the synthesized microgels can be precisely triggered by means of the used UV light wavelengths, doses and intensities, thus representing a great potential as new light-responsive nanoscaled materials.
我们合成了两类(A 型和 B 型)基于邻硝基苄基衍生物的新型光敏二乙烯基官能化交联剂,并研究了它们在紫外线照射下的光解性能。分子结构的系统性变化导致了不同的降解速率,这取决于辐照条件。因此,通过调整应用波长或辐照时间,可以实现连续和独立的裂解。通过在微型乳液聚合过程中与 MMA 进行自由基共聚,相应的分子被用于构建可光降解的 PMMA 微凝胶。紫外线诱导的膨胀微凝胶降解是通过随时间变化的浊度测量来监测的,结果发现其动力学与溶液中各交联剂的光解率相关。通过 λ > 315 纳米的紫外线辐照,实现了受辐照波长控制的 B 型交联点的选择性部分裂解,并产生了由高度膨胀的网络组成的体积广泛增大的颗粒。此外,还实现了对含有 B 型交联剂的颗粒进行辐照时间控制的选择性完全降解。通过使用波长为 λ < 315 nm 的宽带紫外线,可以观察到 B 型和 A 型微凝胶颗粒相继完全分解。因此,合成的微凝胶的特殊性能可以通过所使用的紫外光波长、剂量和强度来精确触发,因而具有作为新型光响应纳米材料的巨大潜力。