pH、温度和光三重敏感的PDMAEMA-AZO的研究

Studies on PDMAEMA-AZO with pH, temperature and light triple-sensitivity

摘要:

在含偶氮苯的三硫酯链转移剂（CTA-AZO）存在下，将甲基丙烯酸二甲氨基乙酯（DMAEMA）通过可逆加成断裂链转移（RAFT）聚合，制备了pH、温度和光三重敏感的含偶氮苯端基的聚甲基丙烯酸二甲氨基乙酯聚合物（PDMAEMA-AZO）。采用紫外光谱（UV）、红外光谱（FTIR）、核磁共振氢谱（1HNMR）和凝胶渗透色谱（GPC）对PDMAEMA-AZO的结构进行了表征，并考察了聚合物的光敏性、温敏性和pH敏感性。GPC结果表明，PDMAEMA-AZO的相对分子质量可控，且相对分子质量分布（PDI）小于1.78。PDMAEMA-AZO在不同溶剂中（氯仿、乙醇和水）的光敏性实验结果显示，该聚合物在氯仿、乙醇和水中均能够快速进行可逆光致顺反异构反应，在紫外与可见光的交替照射下，快速达到光稳态。PDMAEMA-AZO的温敏性实验表明，与聚甲基丙烯酸二甲氨基乙酯（PDMAEMA）相比，PDMAEMA-AZO的低临界溶解温度（LCST）更低。随着聚合物浓度的增加，其LCST降低，且相变窗口变窄。当pH超过9.44时，该聚合物的LCST保持不变，pH由9.44下降到7.34时，LCST升高，pH＜7.34时不再具有温敏性，说明该类聚合物是一种pH控制的具备LCST的温敏性聚合物。在紫外与可见光交替照射下，PDMAEMA-AZO 的LCST 表现为可逆的升高和降低，表明聚合物PDMAEMA-AZO具备光控温敏性。

Abstract:

Azobenzene-terminated poly(dimethylaminoethylmethacrylate) (PDMAEMA-AZO) with pH, temperature and light triple-sensitivity was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization of dimethylaminoethylmethacrylate (DMAEMA) at present of azobenzene-containing trithiocarbonate chain transfer agent (CTA-AZO). The structure of the prepared PDMAEMA-AZO polymer was characterized by ultraviolet spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectroscopy (1HNMR) and gel permeation chromatography (GPC), and the properties of photo, temperature and pH-sensitivity of the polymer were investigated. The results of GPC indicate that the relative molecular weight of the as-synthesized polymers is controllable and the molecular weight distribution (PDI) is below 1.78. The photosensitivity of PDMAEMA-AZO polymer in water, ethanol and chloroform shows that PDMAEMA-AZO polymer can undergo rapid and reversible cis-trans photo-isomerization subjected to UV and visible light alternately, and quickly reach photo stable state. The thermosensitivity of PDMAEMA-AZO shows that the lower critical solution temperature (LCST) of PDMAEMA-AZO is lower than that of PDMAEMA. The LCST of polymer decreases with the increase of its concentration, and the window of the phase transition is narrowed. When the pH exceeds 9.44, the LCST of the PDMAEMA-AZO polymer remains unchanged. When the pH drops from 9.44 to 7.34, the LCST increases, and when the pH is less than 7.34, it is no longer temperature sensitive. The above thermosesitivity results indicate that the polymer was a LCST-type temperature-sensitive polymer under the control of pH. Finally, the LCST of the polymer reversibly increases and decreases subjected to multiple alternating irradiation of UV and visible light, which shows that the PDMAEMA-AZO polymer has light-controlled thermosensitivity.