Browsing by Author "Lu, Chu-Hua"

Now showing 1 - 17 of 17

Hydrogen Bond-Mediated Self-Assembly of Polyhedral Oligomeric Silsesquioxane-Based Supramolecules
(2010-08-05)
Shih, Ruey-Sheng
;
Lu, Chu-Hua
;
Kuo, Shiao-Wei
;
Chang, Feng-Chih
;
應用化學系
In this study, a functionalized pentaerythritol star polyester compound [tetrakis(nicotinoxymethyl)methane, TNMM] and an octakis[dimethyl(4-hydroxyphenethyl)siloxy]silsesquioxane (OP-POSS) were synthesized and used as tetrahedral and cubic building blocks, respectively, for three-dimensional, hydrogen-bond-mediated, polyhedral oligomeric silsesquioxane- (POSS-) based supramolecular network structures. With noncovalent chain extension of hydrogen bonds between its pyridine and phenol groups, the PUSS-based supramolecular networks exhibited thermally reversible properties. Compared with the glass transition temperature of OP-POSS (ca. 20 degrees C) and the melting temperature of TNMM (ca. 70 degrees C), the hydrogen-bond-mediated miscible blend of 40 wt % TNMM in OP-POSS exhibited a single and higher glass transition temperature (37 degrees C). Because of its strong intermolecular hydrogen bonding, the dewetting pattern of the blend of 40 wt % TNMM in OP-POSS formed ringlike structures rather than the droplets formed by pure OP-POSS. A transparent, brittle, and glassy solid at room temperature, the blend of 40 wt % TNMM in OP-POSS is an explicit and successful example of a PUSS-based hydrogen-bonded supramolecular network.
Polyhedral Oligomeric Silsesquioxane-Encapsulating Amorphous Palladium Nanoclusters as Catalysts for Heck Reactions
(2011-05-01)
Lu, Chu-Hua
;
Chang, Feng-Chih
;
應用化學系
;
Department of Applied Chemistry
Palladium nanoparticles (Pd NPs) capped with a certain protective group possessing stable reactivity of Pd-catalyzed reactions has been quickly and easily synthesized. The thiol-Pd(2+) complexes of C(12)-Pd(2+) and POSS-Pd(2+) are prepared by the ligand exchange of acetate groups on Pd(OAc)(2) with 1-dodecanthiol and SH-POSS (polyhedral oligomeric silsesquioxane), respectively. After thermal treatment at 120 degrees C for 30 min, the C(12)-Pd(2+) and POSS-Pd(2+) turn into C(12)-Pd(0) and POSS-Pd(0) NPs through the reduction of palladium cations with thiol groups. Unlike the well-known metallic Pd NPS with constituent Pd atoms arranged in an orderly repeating pattern, the cores of these thial-Pd(0) NPs are composed of a disordered (amorphous) aggregation of Pd atoms due to the steric hindrance caused by the affinity between in situ Pd atoms and thial groups. The relatively larger gaps between two adjacent POSS moieties, formed by solvent permeation when one isobutyl group approaches another, can be employed as transportation channels for reactants such as iodobenzene (IB). Thus, methyl trans-cinnamate is produced as soon as the reactants of IB and methyl acrylate are added in the POSS-Pd(0) NP-catalyzed Heck coupling. In contrast, an activation time of similar to 1 h is needed for C(12)-Pd(0) NPs to replace these long-alkyl protective groups with iodobenzene.
Self-Assembled Fernlike Microstructures of Polyhedral Oligomeric Silsesquioxane/Gold Nanoparticle Hybrids
(2009-03-05)
Lu, Chu-Hua
;
Kuo, Shiao-Wei
;
Huang, Chih-Feng
;
Chang, Feng-Chih
;
應用化學系
We have used a thiol-functionalized polyhedral oligomeric silsesquioxane (SH-POSS) as a protective group for the preparation of POSS-protected gold nanoparticles (POSS-Au NPs). The organic/inorganic hybrid SH-POSS NPs exhibited an interesting platelike morphology arising from steric hindrance between the isobutyl groups of SH-POSS. An XRD study of the SH-POSS crystal revealed the relatively large interstice (1.64 nm lattice constant a > 1.3 nm diameter SH-POSS) on the basal plane of the unit cell, which resulted in a platelike morphology having lateral dimensions on the order of a few micrometers and thicknesses of a few hundred nanometers. In addition to behaving as a stabilizer for the preparation of Au NPs, an excess of SH-POSS colloids led to the formation of a crystalline template that incorporated the POSS-Au hybrid NPs on its surface, providing a unique fernlike microstructure. After removal of the POSS template (through sublimation and decomposition to a silica char) at 350 degrees C in air for I h, nanosized Au islands having diameters of 50-100 nm and thicknesses of 2-20 nm were sintered onto the substrate. As a result, SH-POSS is an excellent protective group for the preparation of Au NPs of high stability in the powder state. In addition, we suspect that SH-POSS crystals could be used to disperse Au NPs onto substrates for a wide range of applications (e.g., Au catalysts).
Self-assembly behavior and photoluminescence property of bispyrenyl-POSS nanoparticle hybrid
(2011-06-01)
Lu, Chu-Hua
;
Tsai, Chia-Hua
;
Chang, Feng-Chih
;
Jeong, Kwang-Un
;
Kuo, Shiao-Wei
Two flexible ether bonds were designed to connect two pyrene rings on a polyhedral oligomeric silsesquioxane (BPy-POSS) to enrich the fraction of "intrinsic intramolecular pyrene-dimer" on the surface of crystal isobutyl-POSS (iBu-POSS) thin-films. Compared to the monomer emission of 1-pyrenemethanol (Py-OH), the emission spectra of BPy-POSS in dichloromethane show the large proportion of intramolecular and intermolecular excimers due to the formation of pyrenyl dimers or aggregates via the easy rotation of two adjacent ether bonds and the pi-pi interaction of pyrene rings, respectively. By blending inert iBu-POSS, the fluorescent dimers or aggregates of 5 wt.% and 20 wt.% BPy-POSS are distributed on the surface of iBu-POSS crystal fractal pattern as shown by confocal photoluminescence microscopy. Upon exposure to the vapors of nitrobenzene, the 5 wt.% BPy-POSS blend shows the similar quenching efficiency as 100 wt.% BPy-POSS blends, indicating the better excimer dispersion for vapor permeability of blend thin-films. (c) 2011 Elsevier Inc. All rights reserved.
Self-Assembly Structures through Competitive Interactions of Crystalline-Amorphous Diblock Copolymer/Homopolymer Blends: Poly(epsilon-caprolactone-b-4-vinyl pyridine)/Poly(vinyl phenol)
(2009-05-26)
Chen, Wan-Chun
;
Kuo, Shiao-Wei
;
Lu, Chu-Hua
;
Jeng, U-Ser
;
Chang, Feng-Chih
A series of immiscible crystalline-amorphous diblock copolymers, poly(epsilon-caprolactone)-b-(4-vinyl pyridine) (PCL-b-P4VP), were synthesized through combination of sequential ring-opening and controlled living free radical (nitroxide-mediated) polymerizations and then blended with poly(vinyl phenol) (PVPh) homopolymer. Miscibility and self-assembly morphologies mediated by hydrogen-bonding interactions of this new A-B/C type polymer blend are discussed in detail. Self-assembly morphologies of these immiscible PCL-b-P4VP diblock copolymers change through competitive hydrogen-bonding interactions with the increase of PVPh contents The SAXS profiles also reveal a sharp primary peak and highly long-range order reflections such as cylinder or sphere structure at relatively lower PVPh content, which is consistent with TEM images. DSC, WAXD, and FT-IR analyses provide positive evidence that the pyridine group of P4VP is a significantly stronger hydrogen-bond acceptor than the carbonyl group of PCL with the hydroxyl group of PVPh and results in the excluded and confined PCL phase.
Star Block Copolymers Through Nitroxide-Mediated Radical Polymerization From Polyhedral Oligomeric Silsesquioxane (POSS) Core
(2010-06-15)
Lu, Chu-Hua
;
Wang, Jui-Hsu
;
Chang, Feng-Chih
;
Kuo, Shiao-Wei
;
應用化學系
A series of star block copolymers were prepared through nitroxide-mediated radical polymerization (NMRP) from polyhedral oligomeric silsesquioxanes (POSS) nanoparticle by core-first polymerization. Eight N-alkoxyamine groups were incorporated onto the eight corners of a POSS cube through quantitative hydrosilylation through addition of octakis(dimethylsiloxy)silsesquioxane (O(8)M(8)(H) POSS) with 1-(2-(allyloxy)-1-phenylethoxy)-2,2,6,6-tetramethyl-piperidine (allyl-TEMPO) and Karstedt's agent (a platinum divinylsiloxane complex) was used as a catalyst. Octa-N-alkoxyamines POSS (OT-POSS) were used as platform to synthesize star polystyrene-POSS ((PS)(8)-POSS) homopolymer and diblock copolymers of poly(styrene-block-4-vinyl-pyridine)-POSS ((PS-b-P4VP)(8)-POSS) and poly(styrene-block-acetoxystyrene) ((PS-b-PAS)(8)-POSS) through NMRP. In addition, subsequent selective hydrolysis of the acetyl protective group of (PS-b-PAS)(8)-POSS, the poly(styrene-block-vinyl phenol) ((PS-b-PVPh)(8)-POSS) with strong hydrogen bonding group was obtained. The detailed chemical structure and self-assembled structures of these star block copolymers based on POSS were characterized by (1)H NMR, FTIR, SEC, TEM, and SAXS analyses.
Supramolecular ionic strength-modulating microstructures and properties of nacre-like biomimetic nanocomposites containing high loading clay
(2012)
Zhu, Weijun
;
Lu, Chu-Hua
;
Chang, Feng-Chih
;
Kuo, Shiao-Wei
;
應用化學系
"In this study, we prepare thick nacre-like polymer clay nanocomposite films by a simple solution casting method. Nanoclay sheets with soft polymer coatings are used as ideal building blocks with intrinsic hard/soft character. The water-soluble poly(vinyl alcohol) (PVA) was chosen as an organic binder to connect each smectic clay sheet in the form of a nacre-like microstructure. The polymer-clay composite is in the form of a membrane in which the clay sheets are like stacked bricks. In addition, when applying normal stress larger than the yield stress-about 40 MPa-white shear bands develop at strains larger than 10%, much like the conditions where crazing of organic PVA is suppressed by inorganic fillers of clay sheets. Their corresponding microstructure and mechanical properties are studied using wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques and a tensile testing machine and are discussed in detail."
Surface Modification of Gold Nanoparticles with Polyhedral Oligomeric Silsesquioxane and Incorporation within Polymer Matrices
(2009-04-15)
Kuo, Shiao-Wei
;
Wu, Yung-Chien
;
Lu, Chu-Hua
;
Chang, Feng-Chih
;
應用化學系
A new approach to achieve polymer-mediated gold ferromagnetic nanocomposites in a polyhedral oligomeric silsesquioxane (POSS)-containing random copolymer matrix has been developed. Stable and narrow distributed gold nanoparticles modified by 3-mercaptopropylisobutyl POSS to form Au-POSS nanoparticles are prepared by two-phase liquid-liquid method. These Au-POSS nanoparticles form partial particle aggregation by blending with poly(n-butyl methacrylate) (PnBMA) homopolymer because of poor miscibility between Au-POSS and PnBMA polymer matrix. The incorporation the POSS moiety into the PnBMA main chain as a random copolymer matrix displays well-dispersed gold nanoparticles because the POSS-POSS interaction enhances miscibility between gold nanoparticles and the PnBMA-POSS copolymer matrix. This gold-containing nanocomposite exhibits ferromagnetic phenomenon at room temperature. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 811-819, 2009
Surface modification of poly(2-methoxy-5-(2 '-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) by confined photo-catalytic oxidation
(2012-02-15)
Yen, Ying-Chieh
;
Cheng, Chih-Chia
;
Wang, Yeh-Sheng
;
Chu, Yu-Lin
;
Lu, Chu-Hua
In this study, the surface of pi-conjugated polymer, poly(2-methoxy-5(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV), was successfully modified with the sulfate anion (SO4-) groups by the confined photo-catalytic oxidation (CPO). After the surface modification, the water contact angle of MEH-PPV is changed from 95.5 degrees to 82.1 degrees without influence on its optical properties (based on the UV and PL spectra), and the water droplet can be absorbed on the modified MEH-PPV surface without sliding even at substrate tilt angles of 90 degrees and 180 degrees. The CPO on the MEH-PPV surface is able to further expand the use of MEH-PPV for applications. In addition, the water transport test indicates that the modified MEH-PPV can be a candidate for transporting water droplet. (C) 2011 Elsevier Inc. All rights reserved.
Syntheses and characterizations of the multiple morphologies formed by the self-assembly of the sernicrystalline P4VP-b-PCL diblock copolymers
(2007-08-10)
Chan, Shih-Chi
;
Kuo, Shiao-Wei
;
Lu, Chu-Hua
;
Lee, Hsin-Fang
;
Chang, Feng-Chih
A series of semicrystalline diblock copolymers of poly(4-vinylpyridine-b-epsilon-caprolactone) (P4VP-b-PCL) have been synthesized by the living ROP of CL followed by the TEMPO polymerization of 4-VP. Depending on the relative block length and different solvent compositions, these copolymers self-assemble into different supramolecular structures in toluene/dichloromethane (DCM) solution, including spherical micelles, bowl-shaped vesicles, multilayer vesicles, porous spheres, and large compound micelles. In methanol/DCM solution system, the crystalline PCL core disturbs the balance of free energy, thus results in a series of morphological changes including spherical micelles, worm-like rods, vesicles, coexisted vesicles and lamella, and finally platelet lamella. (c) 2007 Elsevier Ltd. All rights reserved.
Syntheses and specific interactions of poly(epsilon-caprolactone)-block-poly(vinyl phenol) copolymers obtained via a combination of ring-opening and atom-transfer radical polymerizations
(2006-11-01)
Kuo, Shiao-Wei
;
Huang, Chih-Feng
;
Lu, Chu-Hua
;
Lin, Ho-May
;
Jeong, Kwang-Un
A series of PCL-b-PVPh diblock copolymers were prepared through combinations of ring-opening and atom-transfer radical polymerizations of c-caprolactone and 4-acetoxystyrene, and subsequent selective hydrolysis of the acetyl protective group. This PCL-b-PVPh diblock copolymer shows a single glass transition temperature over the entire composition range, indicating that this copolymer is able to form a miscible amorphous phase due to the formation of intermolecular hydrogen bonding between the hydroxyl of PVPh and the carbonyl of PCL. In addition, DSC analyses also indicated that the PCL-b-PVPh diblock copolymers have higher glass transition temperatures than their corresponding PCL/PVPh blends. FT-IR was used to study the hydrogen-bonding interaction between the PVPh hydroxyl group and the PCL carbonyl group at various compositions.
Synthesis and characterization of amorphous octakis-functionalized polyhedral oligomeric silsesquioxanes for polymer nanocomposites
(2008-08-26)
Sheen, Yuung-Ching
;
Lu, Chu-Hua
;
Huang, Chih-Feng
;
Kuo, Shiao-Wei
;
Chang, Feng-Chih
We have synthesized the polyhedral oligomeric silsesquioxane (POSS) derivatives OS-POSS and OA-POSS through the hydrosilylation of styrene and 4-acetoxystyrene, respectively, with octakis(dimethylsiloxy)-silsesquioxane (Q(8)M(8)(H)). We then prepared OP-POSS through acetoxyl hydrazinolysis of OA-POSS with hydrazine monohydrate. The chemical structures of these POSS derivatives were characterized using FTIR and H-1 NMR spectroscopy and MALDI-TOF mass spectrometry. Unlike Q(8)M(8)(H), which is crystalline, these three hydrosilylated POSS derivatives are liquids at 25 degrees C. Through DSC and XRD analyses, we found that they exhibit polymer-like glass transitions and amorphous halos. These octakis-functionalized POSS derivatives can be regarded as amorphous glasses possessing low glass transition temperatures, the values of which depend on the intermolecular interactions of their outer organic groups. To investigate the dispersion of these POSS derivatives in polymer nanocomposites, we blended OS-POSS, OA-POSS, and OP-POSS with polystyrene, poly(4-acetoxystyrene), and poly(4-vinylpyridine), respectively, and investigated the effects of the resulting intermolecular aromatic hydrophobic, dipole-dipole, and hydrogen-bonding interactions, respectively. Dipole-dipole interactions provided the best dispersion of OA-POSS in poly(4-acetoxystyrene), in which the POSS-polymer intermolecular interactions were of similar strength to the POSS-POSS interactions. (C) 2008 Elsevier Ltd. All rights reserved.
Synthesis and Characterization of Poly (epsilon-caprol actone-b-4-vinylpyridine): Initiation, Polymerization, Solution Morphology, and Gold Metalation
(2009-02-24)
Lu, Chu-Hua
;
Huang, Chih-Feng
;
Kuo, Shiao-Wei
;
Chang, Feng-Chih
;
應用化學系
We have synthesized a difunctional initiator-the hydroxyl-4-oxo-N-alkoxyamine (HOA)-by first mixing benzoyl peroxide (BPO) and 4-hydroxyl-2,2,6,6-tetramethylpiperdinooxy (4-OH-TEMPO) in styrene at temperatures below 25 degrees C to give the 4-oxo-N-alkoxyamine (OA) and then hydrolyzing the benzoate ester on OA with NaOH. This low-temperature preparation of OA reveals that benzyloxyl radicals can be generated from the BPO through redox reaction with 4-OH-TEMPO its well as through thermal decomposition. The N-oxoammonium cation (i.e., the oxidative state of 4-OH-TEMPO), which formed as a side product, mediated the alcohol oxidation to give OA. We prepared three PCL-b-P4VP diblock copolymers (BCI-3) from HOA through two-step polymerizations: (i) diethylaluminum alkoxide-induced ring-opening polymerization of epsilon-caprolactone at 25 degrees C followed by (ii) nitroxide-mediated radical polymerization of 4-vinylpyridine Lit 125 degrees C. With the combination of biodegradable hydrophobic PCL blocks and polymeric blocks of P4VP ligands, we used the immiscible PCL-b-P4VP copolymers to transport AuCl(4) anions from aqueous phases to organic phases and to stabilize Au nanoparticles in the PCL-b-P4VP micelles Au-BC1-3 after reduction with NaBH(4).
The effect of sulfonic acid groups within a polyhedral oligomeric silsesquioxane containing cross-linked proton exchange membrane
(2010-01-06)
Yen, Ying-Chieh
;
Ye, Yun-Sheng
;
Cheng, Chih-Chia
;
Lu, Chu-Hua
;
Tsai, Li-Duan
In this study, polyhedral oligomeric silsesquioxane (POSS) moieties were incorporated into sulfonated poly(ether ether ketone) (SPEEK) to form a new cross-linked proton exchange membrane (PEM). The distribution of the POSS containing cross-linkers with or without sulfonic acid groups dictates the water behavior and connectivity of hydrophilic domains of the PEM. A PEM formed by incorporating 17.5 wt% of the cross-linker (containing POSS macromer and sulfonic acid groups) into SPEEK exhibits high proton conductivity (0.0153 S/cm), low methanol permeability (1.34 x 10(-7) cm(2)/s), and high selectivity (1.14 x 10(5) Ss/cm(3)). (C) 2009 Elsevier Ltd. All rights reserved.
The Self-Assembled Structure of the Diblock Copolymer PCL-b-P4VP Transforms Upon Competitive Interactions with Octaphenol Polyhedral Oligomeric Silsesquioxane
(2009-12-16)
Lu, Chu-Hua
;
Kuo, Shiao-Wei
;
Chang, Wen-Teng
;
Chang, Feng-Chih
;
應用化學系
This paper describes the miscibility and self-assembly, mediated by hydrogen-bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(epsilon-caprolactone)-block-(4-vinyl pyridine)] (PCL-b-P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen-bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP-POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long-range order, such as cylindrical and spherical structures, at relatively low OP-POSS contents, and short-range order or disordered structures at higher OP-POSS contents. Analyses performed using differential scanning calorimetry, wide-angle X-ray diffraction, and FT-IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen-bond acceptors toward the OH group of OP-POSS than are the C=O groups of the PCL block, thereby resulting in excluded and confined PCL phases.
Thermal conductivity and structure of non-covalent functionalized graphene/epoxy composites
(2011-12-01)
Teng, Chih-Chun
;
Ma, Chen-Chi M.
;
Lu, Chu-Hua
;
Yang, Shin-Yi
;
Lee, Shie-Heng
Non-covalent functionalization was used to functionalize graphene nanosheets (GNSs) through pi-pi stacking of pyrene molecules with a functional segmented polymer chain, which results in a remarkable improvement in the thermal conductivity of GNS-filled polymer composites. The functional segmented poly(glycidyl methacrylate) containing localized pyrene groups (Py-PGMA) was prepared by atom transfer radical polymerization, and Py-PGMA was characterized by nuclear magnetic resonance spectroscopy. Raman spectra, X-ray photoelectron spectroscopy and thermogravimetric analysis reveal the characteristics of Py-PGMA-GNS. Differential scanning calorimetry indicated that the functional groups on Py-PGMA-GNSs can generate covalent bonds with the epoxy matrix, and further form a cross-linked structure in Py-PGMA-GNS/epoxy composites. The Py-PGMA on the GNS surface not only plays an important role to facilitate a homogeneous dispersion in the polymer matrix but also improves the GNS-polymer interaction, which results in a high contact area. Consequently, the thermal conductivity of integrated Py-PGMA-GNS/epoxy composites exhibited a remarkable improvement and is much higher than epoxy reinforced by multi-walled carbon nanotubes or GNSs. The thermal conductivity of 4 phr Py-PGMA-GNS/epoxy has about 20% (higher than that of pristine GNS/epoxy) and 267% (higher than pristine MWCNT/epoxy). (C) 2011 Elsevier Ltd. All rights reserved.
Thermal properties and surface energy characteristics of interpenetrating polyacrylate and polybenzoxazine networks
(2008-10-17)
Lu, Chu-Hua
;
Su, Yi-Che
;
Wang, Chih-Feng
;
Huang, Chih-Feng
;
Sheen, Yuung-Ching
We have prepared semi-interpenetrating polyacrylate networks (PA/BA-m s-IPNs) through rapid photo-polymerization of a triacrylate monomer (TMPTA) in the presence of a photomitiator (1184), a tetramercaptane transfer agent (4SH), and N-methyl-bisbenzoxazine (BA-m). Next, we prepared novel fully interpenetrating polyacrylate (PA) and polybenzoxazine (PBZ) networks (PA/PBZ f-IPNs) through thermal polymerization of the BA-m monomer at 180 degrees C for 4 h. For the PA/BA-m s-IPNs, the BA-m monomers can be frozen and dispersed in the UV-cured PA network within 5 min to inhibit macrophase separation. After thermal polymerization, the phenol units of the ring-opened PBZ segments can form a hydrogen-bonding interface with the carbonyl groups to improve the compatibility between the PBZ microdomains and the PA networks. From an analysis using Kissinger's method, the non-isothermal kinetics of the thermal polymerization for the PA/BA-m s-IPNs indicate that an increase in the PA content increased the steric hindrance of PBZ polymerization. We used DSC, TGA, and contact angle analyses to determine the glass transition temperature, thermal stability, and surface free energy, respectively, of the PA/PBZ f-IPNs. The thermal stability and surface free energy of these PA/PBZ f-IPNs display linear relationships with respect to the PBZ content. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.