Polyamidoamine (PAMAM) dendrimers of G1.0 and 2.0 were synthesized by the repeated Michael addition and ester aminolysis of ethylenediamine and methyl acrylate. Through the reductive amination reaction of primary amines in PAMAM and carbonyl groups in 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl (4-oxo-TEMPO), the water-soluble PAMAM immobilized TEMPO (PAMAM-TEMPO) was successfully prepared. The obtained PAMAM-TEMPO was characterized by Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectrophotometer (UV-Vis). PAMAM-TEMPO was used as catalyst instead of free TEMPO for selective catalytic oxidation of primary hydroxyl groups in cellulose with water as reaction medium. The results showed that the catalytic performance of G1.0 PAMAM-TEMPO with 28.8% TEMPO loading was equivalent to free TEMPO. After salting out the supernatant of oxidation mixture, PAMAM-TEMPO was recovered by extraction with N,N-dimethylformamide and reused for further oxidation cycles. No significant reduction in catalytic performance was found after 4 oxidation cycles. The recovery of PAMAM-TEMPO after each cycle was about 90%. By sonication of oxidized cellulose obtained with G1.0 PAMAM-TEMPO as catalyst, the individualized cellulose nanofibers with approximately 10 nm in diameter were successfully prepared. This is the first report on the use of immobilized TEMPO catalysts comparable to the performance of free TEMPO to oxidize cellulose in water.

通过重复的迈克尔加成反应和乙二胺和丙烯酸甲酯的酯氨解反应，合成G1.0和2.0的聚酰胺型胺（PAMAM）树状聚合物。通过PAMAM中的伯胺和4-oxo-2,2,6,6-四甲基哌啶-1-氧基（4-oxo-TEMPO）中的羰基的还原胺化反应，水溶性PAMAM固定了TEMPO（PAMAM-TEMPO ）已成功准备。通过傅立叶变换红外光谱（FT-IR）和紫外可见分光光度计（UV-Vis）对所得的PAMAM-TEMPO进行表征。使用PAMAM-TEMPO代替游离TEMPO作为催化剂，以水为反应介质选择性催化氧化纤维素中的伯羟基。结果表明，负载量为28.8％的G1.0 PAMAM-TEMPO的催化性能与游离TEMPO相当。盐析氧化混合物的上清液后，通过用N，N-二甲基甲酰胺萃取来回收PAMAM-TEMPO，并用于进一步的氧化循环。在4个氧化循环后未发现催化性能的显着降低。每个循环后，PAMAM-TEMPO的回收率约为90％。通过超声处理以G1.0 PAMAM-TEMPO为催化剂获得的氧化纤维素，成功制备了直径约10 nm的单条纤维素纳米纤维。这是关于使用固定化TEMPO催化剂的性能与游离TEMPO相比可用于氧化水中纤维素性能的第一份报告。每个循环后，PAMAM-TEMPO的回收率约为90％。通过超声处理以G1.0 PAMAM-TEMPO为催化剂获得的氧化纤维素，成功制备了直径约10 nm的单条纤维素纳米纤维。这是关于使用固定化TEMPO催化剂的性能与游离TEMPO相比可用于氧化水中纤维素性能的第一份报告。每个循环后，PAMAM-TEMPO的回收率约为90％。通过超声处理以G1.0 PAMAM-TEMPO为催化剂获得的氧化纤维素，成功制备了直径约10 nm的单条纤维素纳米纤维。这是关于使用固定化TEMPO催化剂的性能与游离TEMPO相比可用于氧化水中纤维素性能的第一份报告。