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在混合反应溶剂体系DMF/H2O中,利用表面引发的单电子活性自由基聚合法(SET-LRP)制备了接枝有荧光和温敏性聚(N-异丙基丙烯酰胺)(PNIPAAM)刷的纤维素纳米晶.红外光谱和固体核磁共振13C谱中PNIPAAM特征峰的出现证明了接枝的成功.接枝前后的重量变化和核磁共振1H谱分析表明,随着混合溶剂中水的比例增加,单体转化率和接枝聚合物刷的分子量逐渐增加.热重和示差扫描量热分析显示,随着纤维素纳米晶表面接枝聚合物刷长度的增加,其分解温度和玻璃化转变温度均由低温向高温方向移动,并逐渐接近纯PNIPAAM的相应温度.由于PNIPAAM的温敏性,表面接枝的纤维素纳米晶表现出与染料溶液相反的温致荧光增强性能.
In the mixed reaction solvent system DMF / H2O, grafted fluorescent and temperature sensitive poly (N-isopropylacrylamide) (PNIPAAM) brushes were prepared by surface initiated single electron living radical polymerization (SET-LRP) Of the cellulose nanocrystals.FIR spectroscopy and solid-state NMR 13C spectrum in PNIPAAM characteristic peaks appear to prove the success of grafting before and after gravimetric changes and 1H nuclear magnetic resonance spectroscopy analysis showed that as the proportion of water in the mixed solvent increased , The monomer conversion rate and the molecular weight of the graft polymer brush increased gradually.The thermogravimetric analysis and differential scanning calorimetry analysis showed that with the increase of brush length of graft polymer on the surface of cellulose nanocrystal, the decomposition temperature and glass transition temperature All moved from low temperature to high temperature and gradually approached the corresponding temperature of pure PNIPAAM.The surface-grafted cellulose nanocrystals exhibited temperature-induced fluorescence enhancement contrary to the dye solution due to the thermal sensitivity of PNIPAAM.