Self-Seeding of Oligo(p-phenylenevinylene)-b-poly(2-vinylpyridine) Micelles: Effect of Metal Ions
Self-Seeding of Oligo(p-phenylenevinylene)-b-poly(2-vinylpyridine) Micelles: Effect of Metal Ions
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寡(对亚苯基亚乙烯基)-b-聚(2-乙烯基吡啶)胶束的自种晶：金属离子的影响
DOI：
10.1021/acs.macromol.1c00965
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发表时间：
2021-07
期刊：
影响因子：
5.5
通讯作者：
Feng Chun
中科院分区：
文献类型：
--
作者：
Wang Zhiqin;Ma Chen;Huang Xiaoyu;Lu Guolin;Winnik Mitchell A.;Feng Chun
自接种是一种有用的协议，用于产生均匀长度的细长的纤维状嵌段共聚物胶束开始与胶束片段通过超声处理长的多分散胶束。在此过程中，胶束片段的悬浮液在选择性溶剂中加热至几乎所有片段溶解的温度。当溶液冷却时，存活的碎片作为胶束生长的种子核。虽然有证据表明电晕聚合物的性质和长度在确定胶束片段的特征溶解温度（Tc）和自接种过程的其他方面中起作用，但我们对这些影响的理解是有限的。在这里，我们研究了自播种的纤维状胶束片段在乙醇中的低聚（对苯撑乙烯基）-b-聚（2-乙烯基吡啶）（OPV 5-b-P2 VP 42，下标表示聚合度）嵌段共聚物，其中我们引入了不同量的二价金属离子（Cu 2+，Zn 2+，Mn 2+，和Cd 2+），以促进络合，而不影响包装的胶束核心。结果表明，随着金属离子含量从0增加到5%左右，OPV 5-b-P2 VP 42种子胶束的溶解阻力显著增加，当金属离子含量增加到20%时，其增加趋势更加平缓。这些现象可以解释为在P2 VP层内形成非共价交联。金属络合应导致冠链的尺寸的收缩，减少冠链排斥和施加在核心上的张力由拉伸的P2 VP链在无金属胶束。交联还需要额外的能量来破坏吡啶基和金属离子之间的链间配位键，以使单聚体从胶束中脱离和胶束的碎裂。金属离子络合也降低了P2 VP链的迁移率。这种效应似乎减缓了自接种过程中冷却/老化步骤中游离单聚体向存活种子胶束的添加速率。
Self-seeding is a useful protocol for generating elongated fiberlike block copolymer micelles of uniform length starting with micelle fragments obtained by sonication of long polydisperse micelles. In this process, the suspension of micelle fragments is heated in the selective solvent to temperatures where nearly all the fragments dissolve. The surviving fragments serve as seed nuclei for micelle growth when the solution is cooled. While there is evidence that the nature and length of the corona polymer plays a role in determining the characteristic dissolution temperature (Tc) of the micelle fragments and other aspects of the self-seeding process, our understanding of these effects are limited. Here, we examine self-seeding of fiberlike micelle fragments in ethanol of an oligo(p-phenylenevinylene)-b-poly(2-vinylpyridine) (OPV5-b-P2VP42, the subscripts denote degrees of polymerization) block copolymer in which we introduced different amounts of divalent metal ions (Cu2+, Zn2+Mn2+, and Cd2+) to promote complexation without affecting the packing of the micellar core. We found that the resistance of seed micelles of OPV5-b-P2VP42toward dissolution increased significantly as the percentage of metal ions to pyridyls was increased from 0 to about 5% and then showed a more gradual increase as the metal ion content was increased to 20%. These phenomena can be interpreted in terms of the formation of noncovalent cross-linking within the P2VP layer. Metal complexation should lead to contraction of the dimension of the corona chains, decreasing corona chain repulsion and the tension exerted on the core by the stretched P2VP chains in the metal-free micelles. Cross-linking would also require additional energy to break interchain coordinating bonds between pyridyls and metal ions for both the detachment of unimers from micelles and fragmentation of micelles. Metal ion complexation also reduces the mobility of P2VP chains. This effect appears to slow the addition rate of the free unimer to the surviving seed micelles in the cooling/aging step in the self-seeding process.
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