Surfactant-free, radical precipitation copolymerization of N-isopropylmethacrylamide and the cationic co-monomer N-(3-aminopropyl) methacrylamide hydrochloride (APMH) was carried out to prepare microgels functionalized with primary amines. The morphology and hydrodynamic diameter of the microgels were characterized by atomic force microscopy and photon correlation spectroscopy, with the effect of NaCl concentration and initiator type on the microgel size and yield being investigated. When a 2,2′-azobis (2-amidinopropane) dihydrochloride (V50)-initiated reaction was carried out in pure water, relatively small microgels (∼160 nm in diameter) were obtained in low yield (∼20%). However, both the yield and size increased if the reaction was carried out in saline or by using ammonium persulfate as initiator instead of V50. Stable amine-laden microgels in the range from 160 to 950 nm in diameter with narrow size distributions were thus produced using reaction media with controlled salinity. Microgel swelling and electrophoretic mobility values as a function of pH, ionic strength, and temperature were also studied, illustrating the presence of cationic sidechains and their influence on microgel properties. Finally, the availability of the primary amine groups for post-polymerization modification was confirmed via modification with fluorescein-N-hydroxysuccinamide.

中文翻译：

---

聚（N-异丙基甲基丙烯酰胺）阳离子微凝胶的合成及理化性质

N-异丙基甲基丙烯酰胺和阳离子共聚单体 N-(3-氨基丙基) 甲基丙烯酰胺盐酸盐 (APMH) 的无表面活性剂自由基沉淀共聚反应制备了伯胺功能化的微凝胶。通过原子力显微镜和光子相关光谱表征微凝胶的形态和流体动力学直径，研究了 NaCl 浓度和引发剂类型对微凝胶尺寸和产率的影响。当在纯水中进行 2,2'-偶氮双（2-脒基丙烷）二盐酸盐（V50）引发的反应时，以低产率（约 20%）获得相对较小的微凝胶（直径约 160 nm）。然而，如果反应在盐水中进行或使用过硫酸铵作为引发剂而不是 V50，则产率和尺寸都会增加。因此，使用具有受控盐度的反应介质生产了直径在 160 到 950 nm 范围内且具有窄尺寸分布的稳定的负载胺的微凝胶。还研究了作为 pH、离子强度和温度函数的微凝胶溶胀和电泳迁移率值，说明了阳离子侧链的存在及其对微凝胶特性的影响。最后，通过用荧光素-N-羟基琥珀酰胺改性证实了伯胺基团可用于聚合后改性。说明阳离子侧链的存在及其对微凝胶性质的影响。最后，通过用荧光素-N-羟基琥珀酰胺进行改性，证实了伯胺基团可用于聚合后改性。说明阳离子侧链的存在及其对微凝胶性质的影响。最后，通过用荧光素-N-羟基琥珀酰胺进行改性，证实了伯胺基团可用于聚合后改性。