RAFT与点击化学结合合成SiO_2/PNIPAm杂化微球

Synthesis of SiO_2/PNIPAm Hybrid Microspheres by Combination of RAFT and Thiol-ene Click Chemistry

利用可逆加成-断裂链转移(RAFT)聚合与点击化学相结合的方法,将大分子链末端含巯基的聚(N-异丙基丙烯酰胺)(PNIPAm-SH)接枝到SiO2纳米粒子上制备了温度响应的SiO2为核、PNIPAm为壳的核-壳结构的SiO2/PNIPAm纳米杂化微球。采用FTIR、热重分析(TGA)、透射电镜(TEM)和动态光散射(DLS)对SiO2/PNIPAm杂化微球进行了表征。结果表明,SiO2/PNIPAm杂化微球粒径约为286 nm,尺寸均一。热重分析表明,PNIPAm接枝率为87%(质量分数),PNIPAm分子链在SiO2粒子上的接枝密度为0.4分子链/nm2。杂化微球表现出明显的温度响应性,温度从25℃升至35℃时,杂化微球粒径从286 nm减小至268 nm,PNIPAm壳层的厚度从16 nm减小至7 nm。

The temperature-responsive silica core-poly （ N-isopropylacrylamide ） shell （ SiO2/PNIPAm ） hybrid microspheres were prepared by grafting PNIPAm chains to SiO2 nanoparticles via the combination of reversible addition-fragmentation chain transfer （RAFT） and thiol-ene click chemistry. The SiO2/PNIPAm hybrid microspheres were characterized by means of FTIR, thermogravimetrie analysis （ TGA）, transmission electron microscopy （ TEM ） and dynamic laser scattering （ DLS ）. Nearly monodispersed SiO2/PNIPAm hybrid microspheres of 286 nm in average diameters were obtained. The grafting yield and grafting density of PNIPAm brushes on the SiO2 nanoparticles were about 87% and 0.4 chains/nm^2 respectively. The temperature-responsiveness of SiO2/PNIPAm hybrid microspheres was investigated by means of DLS. The hydrodynamic diameters （Dh ） of SiO2/PNIPAm hybrid microspheres decreased from about 286 nm to about 268 nm and the PNIPAm shell thicknesses decreased from about 16 nm to about 7 nm as the temperature of the aqueous medium increased from 25 ℃ to 35 ℃.