Orthogonal Self-Assembly in Folding Block Copolymers
Orthogonal Self-Assembly in Folding Block Copolymers
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DOI：
10.1021/ja310422w
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发表时间：
2013-01-09
影响因子：
15
通讯作者：
Meijer, E. W.
中科院分区：
文献类型：
--
作者：
Hosono, Nobuhiko;Gillissen, Martijn A. J.;Meijer, E. W.
本文报道了阿坝三嵌段共聚物的合成和表征，该共聚物含有两个互补的缔合基序，并通过正交自组装折叠成单链聚合物纳米颗粒（SCPNs）。该共聚物使用原子转移自由基聚合（ATRP）制备，并且在A和B嵌段中具有不同的侧基官能团（A嵌段中的醇和B嵌段中的乙炔）。后官能化后，A嵌段含有邻硝基苄基保护的2-脲基嘧啶酮（UPy）部分和B嵌段苯-1，3，5-三甲酰胺（BTA）部分。虽然受保护的UPy基团在邻硝基苄基的光诱导脱保护后二聚化，但当温度降低时，BTA部分自组装成螺旋聚集体。在稀释条件下的两步热/光照射处理中，阿坝嵌段共聚物在分子内形成基于BTA的螺旋聚集体和UPy二聚体。两个自组装基序的顺序关联导致聚合物的单链折叠，从而提供具有分隔化内部的纳米尺寸的颗粒。变温NMR研究表明，BTA和UPy自组装步骤正交发生（即，没有相互干扰）。此外，通过圆二色谱法监测BTA部分分子内自组装成螺旋聚集体表明，聚集体的稳定性几乎不依赖于UPy二聚化。尺寸排阻色谱法（SEC）和小角X-射线散射分析提供的证据，显着减少的流体动力学体积和回转半径，分别在光诱导脱保护的UPy基团后，一个30-60%的聚合物链的大小减少使用SEC在CHCl 3中观察到。通过原子力显微镜（AFM）的分子成像证实了由于BTA和UPy基团的分子内缔合导致的单个聚合物链的显著收缩。由正交自组装诱导的超分子相互作用产生的逐步折叠过程产生由不同的微结构域组成的分隔化的SCPNs，所述微结构域模仿蛋白质中的两个二级结构元件。
We herein report the synthesis and characterization of ABA triblock copolymers that contain two complementary association motifs and fold into single-chain polymeric nanoparticles (SCPNs) via orthogonal self-assembly. The copolymers were prepared using atom-transfer radical polymerization (ATRP) and possess different pendant functional groups in the A and B blocks (alcohols in the A block and acetylenes in the B block). After postfunctionalization, the A block contains o-nitrobenzyl-protected 2-ureidopyrimidinone (UPy) moieties and the B block benzene-1,3,5-tricarboxamide (BTA) moieties. While the protected UPy groups dimerize after photoinduced deprotection of the o-nitrobenzyl group, the BTA moieties self-assemble into helical aggregates when temperature is reduced. In a two-step thermal/photoirradiation treatment under dilute conditions, the ABA block copolymer forms both BTA-based helical aggregates and UPy dimers intramolecularly. The sequential association of the two self-assembling motifs results in single-chain folding of the polymer, affording nanometer-sized particles with a compartmentalized interior. Variable-temperature NMR studies showed that the BTA and UPy self-assembly steps take place orthogonally (i.e., without mutual interference) in dilute solution. In addition, monitoring of the intramolecular self-assembly of BTA moieties into helical aggregates by circular dichroism spectroscopy showed that the stability of the aggregates is almost independent of UPy dimerization. Size-exclusion chromatography (SEC) and small-angle X-ray scattering analysis provided evidence of significant reductions in the hydrodynamic volume and radius of gyration, respectively, after photoinduced deprotection of the UPy groups; a 30-60% reduction in the size of the polymer chains was observed using SEC in CHCl3. Molecular imaging by atomic force microscopy (AFM) corroborated significant contraction of individual polymer chains due to intramolecular association of the BTA and UPy groups. The stepwise folding process resulting from orthogonal self-assembly-induced supramolecular interactions yields compartmentalized SCPNs comprised of distinct microdomains that mimick two secondary-structuring elements in proteins.