Rod-Coil Type Miktoarm Star Copolymers Consisting of Polyfluorene and Polylactide: Precise Synthesis and Structure-Morphology Relationship
Rod-Coil Type Miktoarm Star Copolymers Consisting of Polyfluorene and Polylactide: Precise Synthesis and Structure-Morphology Relationship
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聚芴和聚丙交酯棒-线圈型米克托臂星形共聚物：精确合成及结构-形貌关系
DOI：
10.1039/c5py01031d
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发表时间：
2015
影响因子：
4.6
通讯作者：
Wen-Chang Chen and Toshifumi Satoh
中科院分区：
文献类型：
--
作者：
Kengo Saito;Takuya Isono;Han-Sheng Sun;Toyoji Kakuchi;Wen-Chang Chen and Toshifumi Satoh
采用Suzuki-Miyaura偶联聚合和活性开环聚合相结合的方法，合成了一系列以聚[2，7-（9，9-二己基芴）]（PF）和聚乳酸（PLA）为棒状和螺旋状臂的棒状-螺旋状杂臂星星共聚物。首先，以4-（四氢吡喃-2 ′-氧甲基）-碘苯/Pd2（dba）3/t-Bu3P为引发体系，通过2-（7-溴-9，9-二己基-9H-芴-2-基）-4，4，5，5-四甲基-1，2，3-二氧杂硼杂环戊烷的聚合反应，制备了α-链端含羟基的PF（PF-BnOH）。在几个链端修饰后，获得了在α-链端具有一个、两个和三个羟基的PF（分别为PF-OH、PF-（OH）2和PF-（OH）3），其分散度（λ）值小于1.29。以所得的PF-OH、PF-（OH）2和PF-（OH）3为引发剂，采用有机碱催化外消旋丙交酯的ROP反应，合成了AB型线性二嵌段共聚物（PF-b-PLA）和AB 2、AB 3型杂臂星星共聚物（PF-b-PLA）2和PF-b-PLA 3）。通过同步辐射小角X射线散射（SAXS）和透射电子显微镜（TEM）对热退火PF-b-（PLA）xs（x = 1，2和3）中的自组装纳米结构进行了本体评价。结果表明，PF质量分数为0.52-0.56的PF-b-PLA、PF-b-（PLA）2和PF-b-（PLA）3在PF基体中形成的PLA柱状结构有序性较差，这是由于PF链段间存在较强的杆-杆相互作用。另一方面，这些BCP与PF的重量分数为0.22 - 0.23表现出六方密堆积圆柱（Hex）的形态，其中圆柱形的PF相嵌入在PLA基体中。更有趣的是，尽管每种BCP具有相当的分子量和PF重量分数，但Hex形态的结构域间距（d）值随着PLA臂数的增加而降低：PF-b-PLA的d = 26.4 nm，PF-b-（PLA）2的d = 21.7 nm，PF-b-（PLA）3的d = 18.6 nm。
A series of rod–coil miktoarm star copolymers consisting of poly[2,7-(9,9-dihexylfluorene)] (PF) and polylactide (PLA) arms as the rod and coil segments, respectively, were synthesized by combining the chain-growth Suzuki–Miyaura coupling polymerization and living ring-opening polymerization (ROP). First, PFs having a hydroxyl group at the α-chain end (PF–BnOH) were prepared by the polymerization of 2-(7-bromo-9,9-dihexyl-9H-fluorene-2-yl)4,4,5,5-tetramethyl-1,2,3-dioxaborolane using the initiating system of 4-(tetrahydropyran-2′-yloxymethyl)-iodobenzene/Pd2(dba)3/t-Bu3P. After a couple of chain end modifications, PFs having one, two, and three hydroxyl groups at the α-chain end (PF–OH, PF–(OH)2, and PF–(OH)3, respectively) were obtained with dispersity (Đ) values of less than 1.29. The obtained PF–OH, PF–(OH)2, and PF–(OH)3 were used as the initiators for the organic base-catalyzed ROP of rac-lactide to produce the AB type linear diblock (PF-b-PLA) and AB2 and AB3 type miktoarm star copolymers (PF-b-(PLA)2 and PF-b-(PLA)3, respectively). The self-assembled nanostructures in the thermally-annealed PF-b-(PLA)xs (x = 1, 2, and 3) were evaluated in the bulk by synchrotron small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The PF-b-PLA, PF-b-(PLA)2, and PF-b-(PLA)3 with the PF weight fractions of 0.52–0.56 were found to form poorly ordered PLA cylindrical structures in the PF matrix due to a strong rod–rod interaction of the PF segment. On the other hand, these BCPs with the PF weight fractions of 0.22–0.23 exhibited the hexagonally close-packed cylinder (Hex) morphologies, in which the cylindrical PF phase was embedded in the PLA matrix. More interestingly, the domain-spacing (d) values for the Hex morphologies decreased with the increasing PLA arm number despite each BCP having a comparable molecular weight and PF weight fraction: d = 26.4 nm for PF-b-PLA, d = 21.7 nm for PF-b-(PLA)2, and d = 18.6 nm for PF-b-(PLA)3.