• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.505-512
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• 2014

A new donor-accepter-donor-accepter-donor (D-A-D-A-D) type 2,1,3-benzothiadiazole-thiophene-based acceptor unit 2,5-di(4-(5-bromo-4-octylthiophen-2-yl)-2,1,3-benzothiadiazol-7-yl)thiophene ($DTBTTBr_2$) was synthesized. Copolymerized with fluorene and indeno[1,2-b]fluorene electron-rich moieties, two alternating narrow band gap (NBG) copolymers PF-DTBTT and PIF-DTBTT were prepared. And two copolymers exhibit broad and strong absorption in the range of 300-700 nm with optical band gap of about 1.75 eV. The highest occupied molecular orbital (HOMO) energy levels vary between -5.43 and -5.52 eV and the lowest unoccupied molecular orbital (LUMO) energy levels range from -3.64 to -3.77 eV. Potential applications of the copolymers as electron donor material and $PC_{71}BM$ ([6,6]-phenyl-$C_{71}$ butyric acid methyl ester) as electron acceptors were investigated for photovoltaic solar cells (PSCs). Photovoltaic performances based on the blend of PF-DTBTT/$PC_{71}BM$ (w:w; 1:2) and PIF-DTBTT/$PC_{71}BM$ (w:w; 1:2) with devices configuration as ITO/PEDOT: PSS/blend/Ca/Al, show an incident photon-to-current conversion efficiency (IPCE) of 2.34% and 2.56% with the open circuit voltage ($V_{oc}$) of 0.87 V and 0.90 V, short circuit current density ($J_{sc}$) of $6.02mA/cm^2$ and $6.12mA/cm^2$ under an AM1.5 simulator ($100mA/cm^2$). The photocurrent responses exhibit the onset wavelength extending up to 720 nm. These results indicate that the resulted narrow band gap copolymers are viable electron donor materials for polymer solar cells.

• Macromolecular Research
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• v.12 no.1
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• pp.127-133
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• 2004

We have studied the surface micelle formation of polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) at the air-water interface. A series of four PS-b-P2VPs were synthesized by anionic polymerization, keeping the PS block length constant (28 kg/㏖) and varying the P2VP block length (1, 11, 28, or 59 kg/㏖). The surface pressure-area ($\pi$-A) isotherms were measured and the surface morphology was studied by atomic force microscopy (AFM) after Langmuir-Blodgett film deposition onto silicon wafers. At low surface pressure, the hydrophobic PS blocks aggregate to form pancake-like micelle cores and the hydrophilic P2VP block chains spread on the water surface to form a corona-like monolayer. The surface area occupied by a block copolymer is proportional to the molecular weight of the P2VP block and identical to the surface area occupied by a homo-P2VP. It indicates that the entire surface is covered by the P2VP monolayer and the PS micelle cores lie on the P2VP monolayer. As the surface pressure is increased, the $\pi$-A isotherm shows a transition region where the surface pressure does not change much with the film compression. In this transition region, which displays high compressibility, the P2VP blocks restructure from the monolayer and spread at the air-water interface. After the transition, the Langmuir film becomes much less compressible. In this high-surface-pressure regime, the PS cores cover practically the entire surface area, as observed by AFM and the limiting area of the film. All the diblock copolymers formed circular micelles, except for the block copolymer having a very short P2VP block (1 kg/㏖), which formed large, non-uniform PS aggregates. By mixing with the block copolymer having a longer P2VP block (11 kg/㏖), we observed rod-shaped micelles, which indicates that the morphology of the surfaces micelles can be controlled by adjusting the average composition of block copolymers.

• Journal of Chest Surgery
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• v.31 no.10
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• pp.919-923
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• 1998

Background: Calcific degeneration is unavoidable in either homo- or heterografts implanted in the human body. We have developed a calcification-resistant cardiovascular tissue patch using a novel technique of anticalcification. Materials and methods: Fresh bovine pericardium was harvested at the slaughter house and transfered to the laboratory in Hank's solution. After trimming and fixing the pericardium, it was embedded in 4$^{\circ}C$ 0.65% glutaraldehyde for a week and then washed by phosphate-buffered saline(PBS) of pH 7.4. This prepared pericardium was then stored in 2.5% sulphonated polyethyleneoxide(PEO-SO3) solution for 2 days at room temperature and reversed by 4$^{\circ}C$ NaBH4 solution for 16 hours. To evaluate the calcification-resistance of surface modified bovine pericardium with PEO-SO3, either glutaraldehyde- treated(GA group, n=4) or PEO-SO3-treated pericardial patch(PEO-SO3 group, n=4) was implanted into adult mongrel dog to reconstruct the main pulmonary artery and the descending aorta using a partial clamp technique. After 1 month follow-up, the implanted patches were retrieved to evaluate the pathologic findings and the content of calcium and phosphorous. Results: The PEO-SO3 group showed substantially less retraction and significantly less calcium deposition than the GA group in both aortic(7.10$\pm$1.05 vs. 13.81$\pm$2.33 mg/g of dried tissue) and pulmonary positions(1.55$\pm$0.29 vs. 6.72$\pm$0.70 mg/g)(p<0.01). Phosphorous contents were also less in the PEO-SO3 group than the GA group significantly, 8.11$\pm$1.07 mg/g vs. 19.33$\pm$4.31 mg/g in the aortic and 2.58$\pm$0.40 vs. 12.60$\pm$3.40 mg/g in thepulmonary position(p<0.01). Conclusions: These findings suggest that PEO-SO3 modified bovine pericardium is highly calcification-resistant but further study is needed to evaluate the long-term biological safety and compatibility of the prosthesis.