Degradable Poly(N-isopropylacrylamide) with Tunable Thermosensitivity by Simultaneous Chain- and Step-Growth Radical Polymerization
Degradable Poly(N-isopropylacrylamide) with Tunable Thermosensitivity by Simultaneous Chain- and Step-Growth Radical Polymerization
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DOI：
10.1021/ma2000465
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发表时间：
2011-04-12
期刊：
影响因子：
5.5
通讯作者：
Kamigaito, Masami
中科院分区：
文献类型：
--
作者：
Mizuntani, Masato;Satoh, Kotaro;Kamigaito, Masami
聚（N-异丙基丙烯酰胺）[聚（NIPAM）]是最具吸引力的聚合物材料之一，因为它在水溶液中具有热刺激响应特性。 1 众所周知，聚 (NIPAM) 的水溶液表现出可逆的液固相变，临界溶液温度 (LCST) 较低，介于 31 至 35°C 之间。这种热响应特性使该材料可用于跨学科应用，例如生物工程和纳米技术领域的生物传感器和膜。最近在开发良好控制的 NIPAM 自由基聚合方面所做的努力，使我们深入了解了聚 (NIPAM) 的一级结构（例如分子量及其分布、2 端基、3 立构规整度 4 和嵌段共聚物 5）对热响应性能的影响。其中，CuCl/三[2-(二甲氨基)乙基]胺(Me6TREN)系统有效地诱导丙烯酰胺(包括NIPAM)在特定溶剂(例如DMF、2-丙醇、水和DMF/水混合物)中快速且良好控制地聚合，以产生即使在环境温度下也具有窄分子量分布(MWD)的聚合物。 6, 7 该系统被称为金属催化原子转移或单电子转移（SET）活性自由基聚合。同时，我们最近发现与受控自由基聚合相同的金属催化可以演变成分子中具有非共轭碳-碳双键（CdC）和活性碳-氯（C-Cl）键的设计单体的逐步增长自由基加聚。 8 在该聚合反应中，单体中的活性 CX 键被金属催化剂激活，形成自由基物种，该自由基物种与另一个单体分子的 CdC 双键加成，生成 C-C 键作为主链，以及非活性 CX 键作为侧链。此外，我们通过明智地选择催化剂，成功地将逐步增长自由基加聚与金属催化聚合结合起来，其中通过单一金属催化剂通过自由基中间体同时进行逐步和链增长聚合。 9 例如，使用 CuCl/1, 1, 4, 7, 10, 10-六甲基三乙烯四胺 (HMTETA) 同时实现丙烯酸甲酯 (MA) 的活性自由基聚合和酯连接的 3-丁烯基 2-氯丙酸酯 (1) 的自由基加聚，得到受控聚合物，其中具有受控链长的均聚物链段通过酯键连接。
Poly (N-isopropylacrylamide)[poly (NIPAM)] is one of the most attractive polymeric materials because it has a thermal stimuli-responsive character in aqueous solutions. 1 The aqueous solution of poly (NIPAM) is well-known to exhibit a reversible liquidÀsolid phase transition with a lower critical solution temperature (LCST) between 31 and 35 C. This thermoresponsive property has allowed this material to be used in interdisciplinary applications, such as biosensors and membranes, in the fields of bioengineering and nanotechnology. Recent efforts in developing the well-controlled radical polymerization of NIPAM have provided an insight into the influence of the primary structure of poly (NIPAM), such as the molecular weight and its distribution, 2 end groups, 3 tacticity, 4 and block copolymers, 5 on the thermoresponsive properties. Among them, the CuCl/tris [2-(dimethylamino) ethyl] amine (Me6TREN) system effectively induced fast and well-controlled polymerizations of acrylamides, including NIPAM, in specific solvents, such as DMF, 2-propanol, water, and DMF/water mixture, to produce polymers having a narrow molecular weight distribution (MWD) even at ambient temperature. 6, 7 The system is referred to as the metal-catalyzed atom transfer or single-electron transfer (SET) living radical polymerization.Meanwhile, we recently found that the same metal catalysis as in the controlled radical polymerization can be evolved into the step-growth radical polyaddition of designed monomers possessing unconjugated carbonÀcarbon double (CdC) and an active carbonÀchlorine (CÀCl) bonds in a molecule. 8 In this polymerization, the active C—X bond in the monomer is activated by the metal catalysts to form a radical species, which adds to the CdC double bond of another monomer molecule to generate a CÀC bond as the main chain, along with an inactive C—X bond as the pendant. Furthermore, we have successfully combined the step-growth radical polyaddition with the metalcatalyzed polymerization by the judicious choice of the catalyst, in which the simultaneous step-and chain-growth polymerization proceeds via the radical intermediates by the single metal catalyst. 9 For example, the simultaneous living radical polymerization of methyl acrylate (MA) and radical polyaddition of an ester-linked 3-butenyl 2-chloropropionate (1) was achieved with CuCl/1, 1, 4, 7, 10, 10-hexamethyltriethylenetetramine (HMTETA) to afford the controlled polymers, in which the homopolymer segments with the controlled chain length were connected by the ester linkage.