Synthesis and characteristics of poly(3,4-azopyridylene)(PAP),conductivity and oxygen-binding affinity of its complex with meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrinatocobalt(II)(COP)were studied.PAP was p...Synthesis and characteristics of poly(3,4-azopyridylene)(PAP),conductivity and oxygen-binding affinity of its complex with meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrinatocobalt(II)(COP)were studied.PAP was prepared by oxidative polymerization of 3,4-diaminopyridine(DAP)in DMF solution using CuCl/pyridine as the catalyst.IR and NMR results showed that the peak of amido group in DAP was converted to the azo group in PAP and a π conjugated polymer was synthesized.The average molecular weight of PAP was determined to be 5.0×10~3.The PAP-CoP complex was prepared by complexing the pyridyl group of PAP with the fifth coordination site of CoP in DMF solution.In comparison with the CoP complex with a non-π conjugated polymer,the PAP-CoP complex shows good electroconductivity of 5.8×10^(-6) S cm^(-1).The PAP-CoP complex displays a reversible change in the UV-Visible absorption spectrum from the deoxy form to the oxy or oxygen-binding one with an isosbestic point,in response to the partial oxygen pressure of the atmosphere.The oxygen- response behavior was monitored at the absorbance ascribed to the oxy form at 548 nm to give the oxygen-binding affinity. The oxygen-binding equilibrium curves of PAP-CoP complex obey a Langmuir isotherm.DMF has great effects on the oxygen-binding properties of the PAP-CoP complex.The oxygen-binding affinity of PAP-CoP complex in the solid state is higher than that in DMF solution.With decreasing temperature,the oxygen-binding affinity of the PAP-CoP complex increases.展开更多
The extent to which counterions bind to polyelectrolytes influences a variety of polymer-based applications, including polyelectrolyte enhanced ultrafiltration and forward osmosis using polyelectrolytes as draw agents...The extent to which counterions bind to polyelectrolytes influences a variety of polymer-based applications, including polyelectrolyte enhanced ultrafiltration and forward osmosis using polyelectrolytes as draw agents. Potentiometric titrations of poly (2-vinylpyridine) (P2VP), poly (3-vinylpyridine) (P3VP), and poly (4-vinylpydine) (P4VP) were performed using HBr, HCl, HNO<sub>3</sub>, and HClO<sub>4</sub> in both the presence and absence of added NaCl. Because of the systematic differences among the three polyelectrolytes, titration results provide insight into the role of polymer structure in the relative extents to which various counterions bind. Titration data reveal that ionization properties vary as functions of polymer investigated, titrant used, degree of protonation, and added salt concentration. Acid dissociation constants of the pyridinium moieties were found to generally increase with increasing degree of protonation, though appreciable differences were exhibited among the three polymers investigated. For all three polymers, Cl<sup>-</sup> demonstrated the lowest affinity for the charged pyridinium residues, while the affinities associated with Br<sup>-</sup> and NO<sup>-</sup>3</sub> were nearly identical to each other. The relative extent of binding for CIO<sup>-</sup>4</sub> varied across the polymers investigated, and was greatest for P4VP.展开更多
Biodegradable Nanoparticles (NPs) are under intense investigation due to their potential application in targeted drug delivery. Upon their entry to the biological system, they encounter the immune system, which limits...Biodegradable Nanoparticles (NPs) are under intense investigation due to their potential application in targeted drug delivery. Upon their entry to the biological system, they encounter the immune system, which limits their availability at the intended site. Most importantly, the innate immune system is the one that acts as the first line of defense against foreign materials. It can be activated by collectin proteins which recognize the structural pattern of polysaccharide on the surface of microorganisms. NPs may interact with these proteins in a similar way, and the interaction may lead to beneficial outcomes in vaccine delivery. On the other hand, in targeted drug delivery, it is desirable for the NPs not to be recognized as foreign material as this may lead to their fast elimination from the system through mechanism such as opsonization. We investigated the interaction of PEGylated and un-PEGylated PLGA NPs with Recombinant Human Mannose-Binding Protein (HMBP) in an effort to understand the effect of surface modification on their binding to the protein. Results show that both PLGA-COOH and PLGA-PEG-NH2 bind to HMBP as studied using dynamic light scattering (DLS), fluoresce and UV-vis spectroscopy. However, their binding is shown to have different effect on the structure of the protein. Study done using fluorescence spectroscopy displayed a decrease in fluorescence emission of the protein upon binding to PLGA-COOH. On the other hand the fluorescence emission of the protein increased upon binding to the PLGA-PEG-NH2 indicating conformational changes in the protein structure.展开更多
The effect of temperature on the electrical conductivity(σ)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt%of those CNFs is analyzed.At ...The effect of temperature on the electrical conductivity(σ)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt%of those CNFs is analyzed.At 40°C,the CNFs show stable n-type character(S=-4.8μV·K^(-1))with anσof ca.165 S·m^(-1),while the PVDF/CNF composite film shows anσof ca.9 S·m^(-1)and near-zero S(S=-0.5μV·K^(-1)).This experimental reduction in S is studied by the density functional tight binding(DFTB)method revealing a contact electron transfer from the CNFs to the PVDF in the interface.Moreover,in the temperature range from 40°C to 100°C,theσ(T)of the CNFs and PVDF/CNF film,successfully described by the 3D variable range hopping(VRH)model,is explained as consequence of a thermally activated backscattering mechanism.On the contrary,the S(T)from 40°C to 100°C of the PVDF/CNF film,which satisfactorily matches the model proposed for some multi-walled carbon nanotube(MWCNT)doped mats;however,it does not follow the increase in S(T)found for CNFs.All these findings are presented with the aim of discerning the role of these n-type vapor grown carbon nanofibers on theσand S of their melt-mixed polymer composites.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.50373035)Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘Synthesis and characteristics of poly(3,4-azopyridylene)(PAP),conductivity and oxygen-binding affinity of its complex with meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrinatocobalt(II)(COP)were studied.PAP was prepared by oxidative polymerization of 3,4-diaminopyridine(DAP)in DMF solution using CuCl/pyridine as the catalyst.IR and NMR results showed that the peak of amido group in DAP was converted to the azo group in PAP and a π conjugated polymer was synthesized.The average molecular weight of PAP was determined to be 5.0×10~3.The PAP-CoP complex was prepared by complexing the pyridyl group of PAP with the fifth coordination site of CoP in DMF solution.In comparison with the CoP complex with a non-π conjugated polymer,the PAP-CoP complex shows good electroconductivity of 5.8×10^(-6) S cm^(-1).The PAP-CoP complex displays a reversible change in the UV-Visible absorption spectrum from the deoxy form to the oxy or oxygen-binding one with an isosbestic point,in response to the partial oxygen pressure of the atmosphere.The oxygen- response behavior was monitored at the absorbance ascribed to the oxy form at 548 nm to give the oxygen-binding affinity. The oxygen-binding equilibrium curves of PAP-CoP complex obey a Langmuir isotherm.DMF has great effects on the oxygen-binding properties of the PAP-CoP complex.The oxygen-binding affinity of PAP-CoP complex in the solid state is higher than that in DMF solution.With decreasing temperature,the oxygen-binding affinity of the PAP-CoP complex increases.
文摘The extent to which counterions bind to polyelectrolytes influences a variety of polymer-based applications, including polyelectrolyte enhanced ultrafiltration and forward osmosis using polyelectrolytes as draw agents. Potentiometric titrations of poly (2-vinylpyridine) (P2VP), poly (3-vinylpyridine) (P3VP), and poly (4-vinylpydine) (P4VP) were performed using HBr, HCl, HNO<sub>3</sub>, and HClO<sub>4</sub> in both the presence and absence of added NaCl. Because of the systematic differences among the three polyelectrolytes, titration results provide insight into the role of polymer structure in the relative extents to which various counterions bind. Titration data reveal that ionization properties vary as functions of polymer investigated, titrant used, degree of protonation, and added salt concentration. Acid dissociation constants of the pyridinium moieties were found to generally increase with increasing degree of protonation, though appreciable differences were exhibited among the three polymers investigated. For all three polymers, Cl<sup>-</sup> demonstrated the lowest affinity for the charged pyridinium residues, while the affinities associated with Br<sup>-</sup> and NO<sup>-</sup>3</sub> were nearly identical to each other. The relative extent of binding for CIO<sup>-</sup>4</sub> varied across the polymers investigated, and was greatest for P4VP.
文摘Biodegradable Nanoparticles (NPs) are under intense investigation due to their potential application in targeted drug delivery. Upon their entry to the biological system, they encounter the immune system, which limits their availability at the intended site. Most importantly, the innate immune system is the one that acts as the first line of defense against foreign materials. It can be activated by collectin proteins which recognize the structural pattern of polysaccharide on the surface of microorganisms. NPs may interact with these proteins in a similar way, and the interaction may lead to beneficial outcomes in vaccine delivery. On the other hand, in targeted drug delivery, it is desirable for the NPs not to be recognized as foreign material as this may lead to their fast elimination from the system through mechanism such as opsonization. We investigated the interaction of PEGylated and un-PEGylated PLGA NPs with Recombinant Human Mannose-Binding Protein (HMBP) in an effort to understand the effect of surface modification on their binding to the protein. Results show that both PLGA-COOH and PLGA-PEG-NH2 bind to HMBP as studied using dynamic light scattering (DLS), fluoresce and UV-vis spectroscopy. However, their binding is shown to have different effect on the structure of the protein. Study done using fluorescence spectroscopy displayed a decrease in fluorescence emission of the protein upon binding to PLGA-COOH. On the other hand the fluorescence emission of the protein increased upon binding to the PLGA-PEG-NH2 indicating conformational changes in the protein structure.
基金financially supported by the European Regional Development Fund through the Operational Competitiveness Program and the National Foundation for Science and Technology of Portugal(FCT)(No.UID/CTM/00264/2020 of Centre for Textile Science and Technology(2C2T)on its components Base and programmatic)support from project GreenAuto-Green Innovation for the Automotive Industry-PPS 3-Technical Textiles for the vehicle(Refa C6448637037-00000013)financed by EU funds,through the Plano de Recuperacao e Resiliência(PRR),managed by IAPMEI,I.P.-Agência para a Competitividade e Inovacao+2 种基金support within the scope of the project CICECO-Aveiro Institute of Materials,UIDB/50011/2020,UIDP/50011/2020&LA/P/0006/2020,financed by national funds through the FCT/MCTES(PIDDAC)support from the Spanish Ministry of Universities with European Union funds-Next Generation EU through a Margarita Salas fellowshipsupport received from National Science Foundation under PREM award DMR 2122178。
文摘The effect of temperature on the electrical conductivity(σ)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt%of those CNFs is analyzed.At 40°C,the CNFs show stable n-type character(S=-4.8μV·K^(-1))with anσof ca.165 S·m^(-1),while the PVDF/CNF composite film shows anσof ca.9 S·m^(-1)and near-zero S(S=-0.5μV·K^(-1)).This experimental reduction in S is studied by the density functional tight binding(DFTB)method revealing a contact electron transfer from the CNFs to the PVDF in the interface.Moreover,in the temperature range from 40°C to 100°C,theσ(T)of the CNFs and PVDF/CNF film,successfully described by the 3D variable range hopping(VRH)model,is explained as consequence of a thermally activated backscattering mechanism.On the contrary,the S(T)from 40°C to 100°C of the PVDF/CNF film,which satisfactorily matches the model proposed for some multi-walled carbon nanotube(MWCNT)doped mats;however,it does not follow the increase in S(T)found for CNFs.All these findings are presented with the aim of discerning the role of these n-type vapor grown carbon nanofibers on theσand S of their melt-mixed polymer composites.
