Browsing by Author "Cheng, Stephen Z. D."

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A Supramolecular "Double-Cable" Structure with a 129(44) Helix in a Columnar Porphyrin-C-60 Dyad and its Application in Polymer Solar Cells
(2012-11-01)
Wang, Chien-Lung
;
Zhang, Wen-Bin
;
Sun, Hao-Jan
;
Van Horn, Ryan M.
;
Kulkarni, Rahul R.
A novel porphyrin-C-60 dyad (PCD1) is designed and synthesized to investigate and manipulate the supramolecular structure where geometrically isotropic [such as [60]fullerene (C-60)] and anisotropic [such as porphyrin (Por)] units coexist. It is observed that PCD1 possesses an enantiomeric phase behavior. The melting temperature of the stable PCD1 thermotropic phase is 160 degrees C with a latent heat (Delta H) of 18.5 kJ mol(-1). The phase formation is majorly driven by the cooperative intermolecular PorPor and C60C60 interactions. Structural analysis reveals that this stable phase possesses a supramolecular double-cable structure with one p-type Por core columnar channel and three helical n-type C-60 peripheral channels. These double-cable columns further pack into a hexagonal lattice with a = b = 4.65 nm, c = 41.3 nm, alpha = beta = 90 degrees and gamma = 120 degrees. The column repeat unit is determined to possess a 129(44) helix. With both donor (D; Pro) and acceptor (A; C-60) units having their own connecting channels as well as the large D/A interface within the supramoleculassr double-cable structure, PCD1 has photogenerated carriers with longer lifetimes compared to the conventional electron acceptor [6,6]-phenyl-C-61-butyric acid methyl ester. A phase-separated columnar morphology is observed in a bulk-heterojunction (BHJ) material made by the physical blend of a low band-gap conjugated polymer, [poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothia-diazole)] (PCPDTBT), and PCD1. With a specific phase structure in the solid state and in the blend, PCD1 is shown to be a promising candidate as a new electron acceptor in high performance BHJ polymer solar cells.
Crystal structure and molecular packing of an asymmetric giant amphiphile constructed by one C-60 and two POSSs
(2014-08-18)
Lin, Ming-Champ
;
Hsu, Chih-Hao
;
Sun, Hao-Jan
;
Wang, Chien-Lung
;
Zhang, Wen-Bin
Based on our recent understanding and development of functionalized molecular nanoparticles (MNPs) as building blocks for constructing various giant molecules, we report our efforts on design and synthesis of an asymmetric giant amphiphile, diBPOSS-C-60, composed of one [60]fullerene (C-60) covalently linked with two isobutyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS) MNPs. Its crystal structure and molecular packing were investigated. The compositional asymmetry between C-60 and BPOSS led to a "sandwich-layered" molecular packing scheme, where a single layer of C-60 is sandwiched between double BPOSS layers: a so-called "one-and-half-layered" structure. Within these layers, the molecules further organized into crystalline arrays. Interestingly, this compound can be viewed as size amplification of a class of atomically thin, two-dimensional layered transition metal dichalcogenides with the "one-and-half-layered" structure. 2014 Elsevier Ltd. All rights reserved.
Crystal structure and molecular packing of an asymmetric giant amphiphile constructed by one C-60 and two POSSs
(2014-08-18)
Lin, Ming-Champ
;
Hsu, Chih-Hao
;
Sun, Hao-Jan
;
Wang, Chien-Lung
;
Zhang, Wen-Bin
Based on our recent understanding and development of functionalized molecular nanoparticles (MNPs) as building blocks for constructing various giant molecules, we report our efforts on design and synthesis of an asymmetric giant amphiphile, diBPOSS-C-60, composed of one [60]fullerene (C-60) covalently linked with two isobutyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS) MNPs. Its crystal structure and molecular packing were investigated. The compositional asymmetry between C-60 and BPOSS led to a "sandwich-layered" molecular packing scheme, where a single layer of C-60 is sandwiched between double BPOSS layers: a so-called "one-and-half-layered" structure. Within these layers, the molecules further organized into crystalline arrays. Interestingly, this compound can be viewed as size amplification of a class of atomically thin, two-dimensional layered transition metal dichalcogenides with the "one-and-half-layered" structure. 2014 Elsevier Ltd. All rights reserved.
Facile Synthesis and Photophysical Properties of SphereSquare Shape Amphiphiles Based on Porphyrin[60]Fullerene Conjugates
(2013-05-01)
Wang, Chien-Lung
;
Zhang, Wen-Bin
;
Yu, Xinfei
;
Yue, Kan
;
Sun, Hao-Jun
Molecules constructed from a combination of zero-dimensional ([60]fullerene (C60)) and two-dimensional (porphyrin (Por)) nanobuilding blocks represent an intriguing category of spheresquare shape amphiphiles. These spheresquare shape amphiphiles possess interesting optoelectronic properties. To efficiently synthesize a large variety of C60Por shape amphiphiles, a facile route based on Steglich esterification was developed. The synthetic strategy enables the preparation of hydroxy-functionalized Por precursors () with high purity in a one-pot procedure. All of the C60Por shape amphiphiles () can be readily synthesized in good yields through subsequent Steglich esterification with a highly soluble carboxylic acid derivative of methanofullerene (). Photophysical studies indicated weak electronic coupling between the C60 and Por moieties and suggest an edge-to-face alignment for the moieties. The fluorescence of electronically excited Por portions of each amphiphile was efficiently quenched, which was indicative of electron transfer from 1Por to the C60 group(s). Increasing the number of C60 groups on the shape amphiphiles led to more pronounced quenching of the Por fluorescence, which indicated the potential for more effective generation of charge-separated species, C60.Por+., from the photoexcited C60Por shape amphiphiles.
Formation of honeycomb structures and superhydrophobic surfaces by casting a block copolymer from selective solvent mixtures
(2007-02-02)
Tung, Pao-Hsiang
;
Kuo, Shiao-Wei
;
Jeong, Kwang-Un
;
Cheng, Stephen Z. D.
;
Huang, Chih-Feng
Poly(vinyl phE!nol)-block-polystyrene (PVPh-b-PS) diblock copolymers are synthesized by sequential anionic polymerization with sec-butyl lithium as the initiator. The Pvph-b-PS diblock copolymer is cast (on a substrate) from several solvent mixtures that contain tetrahydrofuran/toluene ratios of 1:0.1, 1:1, and 1:2. After solvent evaporation the resulting films are characterized by SEM, TEM, and contact angle measurements. A honeycomb structure is fabricated from the vesicle structure at relatively low toluene contents. On the contrary, at relatively higIier toluene contents, a micelle structure with porous microspheres is formed, which possesses higher surface roughness and results in film surface superhydrophobicity. The simple method described here that uses common/selective mixed solvents may be easily extended to prepare honeycomb structures and superhydrophobic surfaces simultaneously from a wide variety of block copolymers by carefully controlling the weight composition of the block copolymer and the selective solvent con-tent.
Investigation of hydrogen-bonding mediated molecular packing of diketopyrrolopyrrole based donor-acceptor oligomers in the solid state
(2019-01-03)
Yang, Kun
;
Li, Xiang
;
Huang, Yi-Fan
;
Bhatta, Ram S.
;
Liu, Jiawei
Two diketopyrrolopyrrole (DPP)-based donor-acceptor oligomers with thermal labile 2-methylhexyl-2-oxylcarbonyl (mHoc) groups, mHocPBT and mHocTBT, were synthesized and characterized to study the hydrogenbonding mediated molecular packing in solid state. The soluble oligomers can be converted to strong intermolecular hydrogen-bonded and pigment-like materials HPBT and HTBT by annealing the casted solid film at a temperature between 180 and 200 degrees C. The formation of intermolecular hydrogen bonding significantly altered the conformation of the molecules, molecular packing structure and related optical properties of the oligomers, with HPBT molecule exhibiting bathochromic shift and HTBT molecule exhibiting hypsochromic shift on UV/Vis spectra. Spin-casted mHocTBT and HTBT films also exhibited interesting morphology and charge transport properties. Even though the single mHocTBT oligomer molecule has a better coplanar molecular conformation as compared with that of HTBT, an enhanced pi-pi stacking structure and larger crystal grain size rendered HTBT film better charge transport performance.
Phase behaviour and Janus hierarchical supramolecular structures based on asymmetric tapered bisamide
(2012)
Sun, Hao-Jan
;
Wang, Chien-Lung
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Hsieh, I-Fan
;
Hsu, Chih-Hao
;
Van Horn, Ryan M.
A precisely defined molecular Janus compound based on asymmetric tapered 1,4-bis[3,4,5-tris(alkan-1-yloxy) benzamido] benzene bisamide (abbreviated as C(22)PhBAEO(3)) was designed and synthesized, and its phase behavior was fully investigated. The C(22)PhBAEO(3) compound possesses a rigid core with three aromatic rings connected with amide bonds which possess the ability to form hydrogen (H) bonds. Three hydrophobic alkyl flexible tails and three hydrophilic flexible methyl terminated triethylene glycol tails are located at the other end. Major phase transitions and their origins in C(22)PhBAEO(3) were studied via DSC and 1D WAXD techniques. Its hierarchical supramolecular crystal structure was further identified through combined techniques of 2D WAXD and SAXS as well as SAED. Results based on computer simulations confirmed the structure determination. It was found that the C(22)PhBAEO(3) possesses three phases through various thermal treatments including a micro-phase separated columnar liquid crystal (col.) phase, a metastable crystal I phase and a stable crystal II phase. Among them, the crystal II phase showed that the columnar structure possesses 3D inter-column order and highly crystalline alkyl tails with a long-range overall orientational order. Four C(22)PhBAEO(3) molecules self-assembled into a phase-separated disc with an ellipsoidal shape having a C-2 symmetry along the disc normal. These discs then stacked on top of each other to generate a 1D asymmetric column through H-bonding, and further packed into a 3D long-range ordered monoclinic lattice. The unit cell parameters of this lattice were determined to be a = 5.08 nm, b = 2.41 nm, c = 0.98 nm, alpha = 90 degrees, beta = 90 degrees, and gamma = 70.5 degrees. The alkyl chain tails crystallize within the hydrophobic layers and possess a relatively fixed orientation with respect to the column packing due to the selective interactions based on the hydrophobic/hydrophilic microphase separation. Both phase behaviour and unit cell structure showed significant difference compared with the symmetrically tapered counterparts. The results provided a new approach of fine-tuning not only in the Janus supramolecular structures but also in the formation pathway of the self-assembling process in order to meet the specific requirements for optical and biological applications.