Browsing by Author "Lai, Bo-Han"

Now showing 1 - 5 of 5

Concentration-dependent self-assembly structures of an amphiphilic perylene diimide with tri(ethylene glycol) substituents at bay positions
(2017-01-01)
Wang, Xin
;
Zeng, Ting
;
Nourrein, Mohamed
;
Lai, Bo-Han
;
Shen, Kaiwen
In this work, an amphiphilic perylene diimide (1,7-TEG-PDI-C12) that bears two hydrophilic triethylene glycol (TEG) chains at its bay position, and two hydrophobic dodecyl chains at its imide position was synthesized to identify the roles of concentration and H-bonding on the self-assembly morphology of the amphiphilic PDI. Since 1,7-TEG-PDI-C12 was prepared from the reaction of two bifunctional reactants, TEG and N, N'-bis(n-dodecyl)- 1,7-dibromo-perylene-3,4: 9,10-tetracarboxylic diimide, careful choices of solvent, base, and the stoichiometry of crown ether and base were found to be critical in reaching high reaction yield under mild conditions. TEM and SEM results revealed the abundant concentration-dependent self-assembly morphologies of 1,7-TEG-PDI-C12. Characterization results including UV-vis, fluorescence, NMR, IR and XRD analysis show that the formation of the self-assembled structure is a synergetic result of the intermolecular pi-pi interaction and H-bonding of 1,7-TEG-PDI-C-12.
Estimating Percent Crystallinity of Polyethylene as a Function of Temperature by Raman Spectroscopy Multivariate Curve Resolution by Alternating Least Squares
(2017-03-07)
Samuel, Ashok Zachariah
;
Lai, Bo-Han
;
Lan, Shih-Ting
;
Ando, Masahiro
;
Wang, Chien-Lung
We have recently demonstrated a methodology to estimate the percent crystallinity (PC) of polymers directly with Raman spectroscopy and multivariate curve resolution (MCR) by alternating least-squares (ALS). In the MCR-ALS methodology, the Raman spectrum of a semicrystalline polymer is separated into two constituent components (crystalline and molten/amorphous) and their corresponding concentrations. The methodology necessitates that the Raman spectrum at any temperature be a linear combination of two MCR spectral components (one molten and one crystalline). This is true in the case of simple systems such as crystalline pendant alkyl domains in polymers (Samuel et al. Anal. Chem. 2016, 88, 4644). However, in the case of main chain polymer crystals (e.g., polyethylene), the situation can be complicated owing to several molecular changes in the lattice in addition to conformational reorganizations during melting. Under this circumstance, a simple two-state model may not be adequate and we describe the modifications required to treat such systems, keeping the basic principles of the proposed methodology unchanged. A comparative study with wide-angle X-ray scattering (WAXS) and Raman spectroscopy is also performed to substantiate our findings. In addition to estimating percent crystallinity (PC), our methodology is capable of revealing additional information, such as interchain interactions in crystal lattice, that in principle will help distinguishing polymorphic transformations, subtle changes in lamellar lattice dimensions, and other phase changes in polymers.
Influences of Structural Modification of S,N-Hexacenes on the Morphology and OFET Characteristics
(2019-06-19)
Huang, Yi-Fan
;
Wang, Chun-Kai
;
Lai, Bo-Han
;
Chung, Chin-Lung
;
Chen, Chin-Yi
Although chemical modifications on conjugated molecules are widely applied for the purpose of improving processability and device performances, the effect of the modification was far less investigated. Here, five S,N-hexacenes are studied to reveal the influences of (1) the lateral alkyl chain, (2) the terminal group (thiophene vs benzene), and (3) the end capping phenyl group of the hexacenes on the morphology and organic field-effect transistor (OFET) performances. Crystal arrays of the hexacenes were prepared via polydimethylsiloxane (PDMS)-assisted crystallization (PAC) prior to morphological and OFET characterizations. The lattice structures and crystal quality of the hexacenes were evaluated by microscopy and diffraction techniques including single-crystal diffractometer, electron diffraction, and grazing incidence wide-angle X-ray scattering. The systematic analyses led to the following conclusions: (1) the bulkier alkyl side chain assists to form more densely packed crystals with less structural defects; (2) the terminal thiophene rings bring about higher-lying E-HOMO, more ordered phase, and crystal orientation, whereas the terminal benzene rings deteriorate the structural order of the active layer and result in the liquid crystal phase; and (3) the phenyl end caps ameliorate the morphological order, intermolecular overlapping, thermal stability and elevate E-HOMO. Thus, EH-DTPTt-Ph delivers the highest mu(h), contributing to high-lying E-HOMO, well-oriented crystal array with a longer correlation length, and suitable lattice orientation. This systematic research provides the aspects about the effects of the functionalized S,N-hexacenes on the morphology and OFET characteristics, which is anticipated to be useful for the molecular design of heteroacenes.
Roles of 3-Ethylrhodanine in Attaining Highly Ordered Crystal Arrays of Ambipolar Diketopyrrolopyrrole Oligomers
(2017-05-03)
Wu, San-Lien
;
Huang, Yi-Fan
;
Hsieh, Chou-Ting
;
Lai, Bo-Han
;
Tseng, Po-Sen
Until now, only limited DPP oligomers delivered ambipolar semiconductor characteristics. To develop a facile strategy of preparing ambipolar mono-DPP oligomers, two dithienyl diketopyrrolopyrrole (DPPT) based-conjugated molecules, DPPT-RD and DPPT-DCV, which contain 3-ethylrhodanine (RD) and dicyano-2-vinyl (DCV) end substituents were synthesized. The influences of the -RD end substituents on the molecular properties, solid-state morphology, and OFET performances of the DPPT oligomer were investigated. The UV-vis absorption and CV results showed that the RD end substituents provide the DPPT oligomer suitable EHOMO and ELUMO for hole and electron injection from the Au source-drain electrodes. Moreover, the RD end substituents also improve the crystalline nature of the DPPT oligomer. That is, DPPT-RD can form crystal arrays with good lattice orientation, larger crystalline size, and without polymorphism. With those properties, DPPT-RD thus display ambipolar characteristic with mu(h) and mu(e) reaching 2.16 x 10(-2) and 7.27 x 10(-2) cm2 V-1 s(-1), respectively.
Synthesis and characterization of heterocyclic conjugated polymers containing planar benzo[c]cinnoline and tetraazapyrene structures for organic field-effect transistor application
(2019-03-01)
Lee, Shih-Wei
;
Chien, Shih-Hsuan
;
Chen, Jyh-Chien
;
Wang, Shih-Hao
;
Wang, Lee-Yih
Heterocyclic conjugated polymers BZCTVT and TAPTVT containing benzo[c]cinnoline (BZC) and tetraazapyrene (TAP), respectively, were prepared by using Stille coupling polymerization in microwave reactor. BZC and TAP act as acceptors and thiophene-vinylene-thiophene (TVT) acts as donors. Alkylated thiophene is the linker between acceptor and donor. This is the first time that tetraazapyrene was incorporated into conjugated polymers. The films of BZCTVT and TAPTVT showed maximum absorption wavelength at 522 and 534 nm, respectively. From cyclic voltammertry measurement, TAPTVT and BZCTVT exhibited low LUMO (-3.61 and -3.47 eV) and HOMO (-5.64 and -5.63 eV) energy levels. Even though BZC and TAP were planar structures, BZCTVT and TAPTVT showed large dihedral angles between alkylated thiophene and TVT (10.8-22.6 degrees), and between alkylated thiophene and BZC and TAP (22.2-30.3 degrees) based on their simulated energy-minimized geometry. The bottom-gate, top-contact OFETs based on TAPTVT and BZCTVT exhibited only p-channel behavior with hole mobility of 4.63 x 10(-4) and 1.04 x 10(-4) cm(2) V-1 s(-1) and current on/off ratios greater than 10(4) after thermal annealing. Grazing incidence X-ray diffraction (GIXRD) patterns suggested that thin films of TAPTVT and BZCTVT preferred edge-on orientation.