Ifuku Shinsuke, Kadla John F
Advanced Biomaterials Chemistry Laboratory, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
Biomacromolecules. 2008 Nov;9(11):3308-13. doi: 10.1021/bm800911w. Epub 2008 Oct 21.
Regioselective copolymerization of N-isopropylacrylamide (NIPAM) onto cellulose was achieved by atom transfer radical polymerization (ATRP) using a regioselectively modified 6- O-bromoisobutyryl-2,3-di- O-methyl cellulose macroinitiator. Varying the ratio of NIPAM to macroinitiator to ligand to transition metal in a Cu(I)Br/ N, N, N', N'', N'''-pentamethyldiethylenetriamine (PMDETA) catalyst system affected graft yield and degree of polymerization. ATRP proceeded to completion without any trace of the macroinitiator, and a degree of polymerization (DP) of polyNIPAM up to 46.3 was obtained. Increasing the DP of the NIPAM component increased both the thermal decomposition temperature and the glass transition temperature of the copolymer. The grafting of NIPAM also affected the solubility properties of the methylcellulose. The 6- O-polyNIPAM-2,3-di- O-methyl cellulose formed a stable suspension in water at room temperature and underwent a hydrophillic-to-hydrophobic transition and copolymer precipitation when the temperature was raised above 30 degrees C.
通过原子转移自由基聚合（ATRP），使用区域选择性修饰的6-O-溴异丁酰基-2,3-二-O-甲基纤维素大分子引发剂，实现了N-异丙基丙烯酰胺（NIPAM）在纤维素上的区域选择性共聚。在Cu（I）Br/N，N，N'，N''，N'''-五甲基二亚乙基三胺（PMDETA）催化剂体系中，改变NIPAM与大分子引发剂、配体与过渡金属的比例，会影响接枝产率和聚合度。ATRP反应完全进行，没有任何大分子引发剂的痕迹，得到的聚NIPAM的聚合度（DP）高达46.3。增加NIPAM组分的DP会提高共聚物的热分解温度和玻璃化转变温度。NIPAM的接枝也影响了甲基纤维素的溶解性。6-O-聚NIPAM-2,3-二-O-甲基纤维素在室温下在水中形成稳定的悬浮液，当温度升高到30℃以上时，会发生亲水到疏水的转变和共聚物沉淀。
