Percec Virgil, Rudick Jonathan G, Peterca Mihai, Wagner Martin, Obata Makoto, Mitchell Catherine M, Cho Wook-Dong, Balagurusamy Venkatachalapathy S K, Heiney Paul A
Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
J Am Chem Soc. 2005 Nov 2;127(43):15257-64. doi: 10.1021/ja055406w.
High cis content (81-99%) cis-transoidal polyphenylacetylene (PPA) jacketed with amphiphilic self-assembling dendrons, poly[(3,4-3,5)mG2-4EBn] with m = 8, 10, 12, 14, 16, and (S)-3,7-dimethyloctyl, were synthesized by Rh(C triple bond CPh)(nbd)(PPh(3))(2) (nbd = 2,5-norbornadiene)/N,N-(dimethylamino)pyridine (DMAP) catalyzed polymerization of macromonomers. The resulting cylindrical PPAs self-organize into hexagonal columnar lattices with intracolumnar order (Phi(h)(io)) and without (Phi(h)). The polymers with m = 12, 14, and 16 exhibit also a hexagonal columnar crystal phase (Phi(h,k)). The reversible Phi(h,k)-to-Phi(h)(io)-to- Phi(h) phase transition in these dendronized PPAs was analyzed by a combination of differential scanning calorimetry and small and wide-angle X-ray diffraction experiments performed on powder and oriented fibers. In the Phi(h,k) and Phi(h)(io) phases, the dendronized PPAs form helical porous columns. The helical pore disappears in the Phi(h) phase. This change is accompanied by a decrease of the external column diameter that is induced by stretching of the polymer backbone along the axis of the cylinder. The helix sense of the porous PPA is selected by homochiral alkyl dendritic tails. This transition is generated by an unprecedented conversion of the PPA backbone from the cis-cisoidal conformation in the Phi(h,k) and Phi(h)(io) phases to the cis-transoidal conformation in the Phi(h) phase. Under the same conditions, the pristine cis-PPA undergoes cis-trans isomerization and irreversible intramolecular 6pi electrocyclization of 1,3-cis,5-hexatriene sequences followed by chain cleavage. These processes are eliminated in the dendronized cis-PPA below its decomposition temperature.
通过Rh（C≡CPh）（nbd）（PPh₃）₂（nbd = 2,5 - 降冰片二烯）/N，N - 二甲基氨基吡啶（DMAP）催化的大分子单体聚合反应，合成了具有高顺式含量（81 - 99%）的顺 - 反式oidal聚苯乙炔（PPA），其被两亲性自组装树枝状分子[（3,4 - 3,5）mG₂ - 4EBn]包覆，其中m = 8、10、12、14、16以及（S） - 3,7 - 二甲基辛基。所得的圆柱形PPA自组装成具有柱内有序（Φₕ(io)）和无序（Φₕ）的六方柱状晶格。m = 12、14和16的聚合物还呈现出六方柱状晶相（Φₕ,k）。通过对粉末和取向纤维进行差示扫描量热法以及小角和广角X射线衍射实验相结合，分析了这些树枝状PPA中可逆的Φₕ,k - 到 - Φₕ(io) - 到 - Φₕ相转变。在Φₕ,k和Φₕ(io)相中，树枝状PPA形成螺旋多孔柱。在Φₕ相中螺旋孔消失。这种变化伴随着由聚合物主链沿圆柱体轴线拉伸引起的外柱直径减小。多孔PPA的螺旋方向由同手性烷基树枝状尾部选择。这种转变是由PPA主链前所未有的构象转变产生的，从Φₕ,k和Φₕ(io)相中的顺 - 顺式oidal构象转变为Φₕ相中的顺 - 反式oidal构象。在相同条件下，原始的顺式PPA会发生顺 - 反异构化以及1,3 - 顺式，5 - 己三烯序列的不可逆分子内6π电环化，随后发生链断裂。在树枝状顺式PPA低于其分解温度时，这些过程被消除。
