通过活性自由基聚合和酯交换反应的串联催化的两亲性PEG-官能化梯度共聚物,Macromolecules

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通过活性自由基聚合和酯交换反应的串联催化的两亲性PEG-官能化梯度共聚物
Macromolecules ( IF 5.1 ) Pub Date : 2017-01-20 00:00:00 , DOI: 10.1021/acs.macromol.6b02358
Yusuke Ogura ₁ , Takaya Terashima ₁ , Mitsuo Sawamoto ₁

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通过串联催化钌催化的活性自由基聚合（LRP）和烷氧基钛介导的酯基转移反应，合成了具有聚乙二醇侧基的两亲梯度共聚物。可以通过调节两个反应的动力学平衡来催化控制梯度序列。串联催化是产生两亲梯度和顺序控制共聚物的最有效和通用的系统之一。通常，在Ti（O i -Pr）₄存在下，将甲基丙烯酸甲酯（MMA）与钌催化剂和氯化物引发剂聚合为起始单体分子筛（MS 4A）在80°C下作为溶剂的聚（乙二醇）甲醚（PEG-OH）。在LRP期间，疏水性MMA同时酯交换为亲水性PEG甲基丙烯酸酯（PEGMA），得到MMA / PEGMA梯度共聚物。梯度顺序直接由瞬时单体组成（从单独的MMA变为溶液中富含PEGMA的混合物）确定。LRP和酯交换反应的同步催化因此提供了梯度共聚物，其组成从起始端到正在增长的对应物线性变化。此外，两亲性MMA / PEGMA梯度共聚物表现出对梯度序列具有特异性的自组装，热响应性和热性质，与两亲性随机或嵌段对应物不同。

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Amphiphilic PEG-Functionalized Gradient Copolymers via Tandem Catalysis of Living Radical Polymerization and Transesterification

Amphiphilic gradient copolymers with poly(ethylene glycol) pendants were synthesized via tandem catalysis of ruthenium-catalyzed living radical polymerization (LRP) and titanium alkoxide-mediated transesterification. The gradient sequence can be catalytically controlled by tuning the kinetic balance of the two reactions. The tandem catalysis is one of the most efficient and versatile systems to produce amphiphilic gradient and sequence-controlled copolymers. Typically, methyl methacrylate (MMA) was polymerized as a starting monomer with a ruthenium catalyst and a chloride initiator in the presence of Ti(Oi-Pr)₄ and molecular sieves (MS 4A) in poly(ethylene glycol) methyl ether (PEG-OH) as a solvent at 80 °C. Hydrophobic MMA was concurrently transesterified into hydrophilic PEG methacrylate (PEGMA) during LRP to give MMA/PEGMA gradient copolymers. The gradient sequence is directly determined by the instantaneous monomer composition changing from MMA alone to PEGMA-rich mixture in solution. Synchronized catalysis of LRP and transesterification thus affords gradient copolymers whose composition linearly changes from an initiating terminal to a growing counterpart. Additionally, amphiphilic MMA/PEGMA gradient copolymers showed self-assembly, thermoresponsive, and thermal properties specific to the gradient sequence, distinct from amphiphilic random or block counterparts.

更新日期：2017-01-20

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