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118. Polymer nanocomposite containing CdS–ZnS core–shell particles: Optical properties and morphology.

Author

Lu, Shih-Yuan, Wu, Mei-Ling, and Chen, Hsin-Lung

Subjects
COMPOSITE materials, SULFIDES, CADMIUM, ZINC
Abstract

Composites of nanosized CdS–ZnS core–shell particles well dispersed in polycetyl- p-vinylbenzyldimethylammonium chloride (PCVDAC) were fabricated and their optical properties and morphology were studied. The core-shell particles of less than 10 nm in size were prepared with the reverse micellar solutions formed by a polymerizable anionic surfactant, CVDAC, and a direct thermal radical polymerization of the micellar solution led to the nanocomposite containing well-dispersed core–shell particles. The shell was inferred from small angle x-ray scattering to be around a monolayer thick. This monolayer coating, however, was enough to produce an appreciable enhancement in photoluminescence for the ZnS-coated CdS system (wider band gap material on narrower band gap material), and a degradation in photoluminescence for the CdS-coated ZnS system. However, a complete coverage of the CdS core with ZnS was required to realize the photoluminescence enhancement for the ZnS-coated CdS system. The polymer domains in the composite were found to be composed of lamellar stacks due to the comb-like structure of PCVDAC. The interlamellar distance was 3.9 nm with smectic liquid crystalline texture observed under polarized optical microscope. The core–shell particles were believed to locate at the grain boundary of the liquid crystalline domains. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2003
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134. Accessing the Frank–Kasper Phase of Block Copolymer via Selective Incorporation of Metal Salt

Author

Hsiao, Yu-Jung, Huang, Zi-En, Sahare, Aditya, Chen, Meng-Zhe, Lin, Yu-Hsuan, and Chen, Hsin-Lung

Abstract

The formation of Frank–Kasper (FK) phase in block copolymers (BCPs) has been achieved through delicate design of the chemical structure and architecture of the BCP, as well as by blending with homopolymer or another BCP component. Here, we report a new approach of generating FK phase via selective incorporation of a metal salt into a BCP. Specifically, the selective incorporation of lithium perchlorate (LiClO4) into the poly(ethylene oxide) (PEO) domain of a cylinder-forming poly(ethylene oxide)-block-poly(1,2-butadiene) (PEO-b-PB) was found to create a window for the spherical phase at the higher temperature, in which the micelles packed preferentially into FK σ phase or dodecagonal quasicrystal (DDQC). The addition of a bivalent salt, magnesium perchlorate (Mg(ClO4)2), expanded the spherical phase window further, where the micelles still preferred packing in the σ and DDQC phases. Nevertheless, with sufficiently high Mg(ClO4)2concentration, the micelles were found to organize into the Laves C14 phase instead of recovering the DDQC and σ phases during cooling from the disordered micelle phase. We proposed that the preferential solubilization of salt in the PEO core increased the effective interaction parameter of the BCP, leading to greater stretching of the constituent blocks due to the formation of a larger core. The increased tendency to reduce the conformational free energy penalty of the coronal blocks facilitated the access of spherical phase at higher core volume fractions, thereby promoting the micelle organization into FK phases. The present study highlights the effectiveness of metal salts in promoting the complex packing of BCP micelles, providing a simple alternative for modulating the structure of spherical phase.

Published
2024
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135. Highly Stretchable Free-Standing Poly(acrylic acid)-block-poly(vinyl alcohol) Films Obtained from Cobalt-Mediated Radical Polymerization

Author

Wang, Fu-Sheng, Wang, Tzu-Fang, Lu, Hung-Hsun, Ao-Ieong, Wai-Sam, Wang, Jane, Chen, Hsin-Lung, and Peng, Chi-How

Abstract

The block copolymers of poly(acrylic acid)-b-poly(vinyl alcohol) (PAA-b-PVA) were obtained from the hydrolysis of poly(methyl acrylate)-b-poly(vinyl acetate) (PMA-b-PVAc), which was synthesized by cobalt-mediated radical polymerization (CMRP) using the cobalt(II) porphyrin complex (CoII(TMP)) as the mediator. The mechanical properties of the PAA-b-PVA free-standing films could be tuned by the pH of the aqueous solution used to cast the films. The block copolymer films showed a much higher tensile strain and fractural tensile strength than the films prepared from the blends of PAA and PVA homopolymers. FTIR and morphological characterizations suggested that the tensile properties of the films were governed by both the hydrogen bonding between PVA and PAA that led to interpolymer complexation and the phase-separated morphology. For a given type of material, the greater extent of interpolymer complexation attained at lower solution pH led to the film with better tensile properties. The difference in the length scale of phase separation was responsible for the large difference in the tensile properties between block copolymer and blend films, where the characteristic nanostructure formed in the block copolymer prescribed a considerably larger amount of interface which enhanced the tensile properties significantly.

Published
2024
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136. List of Contributors

Author

Arif P., Mohammed, Bao, Suping, Bhoje Gowd, E., Bin, Yuezhen, Chen, Hsin-Lung, Cyras, V.P., D'Amico, D.A., Das, Sonalee, Kalarikkal, Nandakumar, Krishnan, Deepthi, Langhe, Deepak, Larrañaga, Aitor, Liang, Guodong, Liu, Chien-Liang, Lizundia, Erlantz, Manfredi, L.B., Mohanty, Smita, Mugica, Agurtzane, Müller, Alejandro J., Murthy, N. Sanjeeva, Nagarajan, Selvaraj, Nandan, Bhanu, Nayak, Sanjay K., Palacios, Jordana K., Pan, Pengju, Prud'homme, Robert E., Qiu, Zhaobin, Samal, Sushanta K., Samanta, Pratick, Schultz, Jerold M., Shalu, Singh, Rajendra Kumar, Sivaprasad, Vijayan Pillai, Song, Ping, Thomas, Sabu, Tien, Nguyen-Dung, Wang, Hai, Wei, Zhiyong, Xie, Qing, Yu, Chengtao, Zhu, Fangming, and Zubitur, Manuela

Published
2018
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