The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene） （E39B18） with anionic surfactant sodium dodecyl sulphate （SDS） and cationic surfactant hexadecyltrimethylammonium bromide...The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene） （E39B18） with anionic surfactant sodium dodecyl sulphate （SDS） and cationic surfactant hexadecyltrimethylammonium bromide （CTAB） were studied by using various techniques such as surface tension, conductivity, steady-state fluorescence and dynamic light scattering. Surface tension measurements were used to determine the critical micelle concentration （CMC） and thereby the free energy of micellization （AGmic）, free energy of adsorption （AG^ds）, surface excess concentration （F） and minimum area per molecule （A）. Conductivity measurements were used to determine the critical micelle concentration （CMC）, critical aggregation concentration （CAC）, polymer saturation point （PSP）, degree of ionization （tr） and counter ion binding （l]）. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles taken place due to the interactions of diblock copolymers with ionic surfactants. The ratio of the first and third vibronic peaks （11/Is） indicated the polarity of the pyrene micro environment and was used for the detection of micelle as well as polymer-surfactant interactions. Aggregation number （N）, number of binding sites （n） and free energy of binding （AGb） for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by the fluorescence quenching method.展开更多
The chemical grafting of thiol terminated poly（sodium styrenesulfonate） （HS-PSSS） chains from sodium nitrate （NaNO3） salt solution to a gold surface was investigated with a quartz crystal microbalance with dissi...The chemical grafting of thiol terminated poly（sodium styrenesulfonate） （HS-PSSS） chains from sodium nitrate （NaNO3） salt solution to a gold surface was investigated with a quartz crystal microbalance with dissipation monitoring （QCM-D） in different salt concentrations, It was found that at low salt concentration grafting density of HS-PSSS was low and the grafted chains adopted a mushroom conformation. With the increase of salt concentration polyelectrolyte chains underwent a transition toward coiled state due to reduction of electrostatic repulsion and as a result more chains were grafted on the surface, When the grafting density reached a certain limit after which further grafting caused repulsion between already grafted HS-PSSS chains and as a result grafted chains adopted a brush conformation.展开更多
The associative properties of methoxy (CH3O-) ended E58B11 and hydroxyl (-OH) ended E56B19 oxyethylene-oxybuty- lene diblock copolymers in aqueous solution at different temperature are reported in this paper. For both...The associative properties of methoxy (CH3O-) ended E58B11 and hydroxyl (-OH) ended E56B19 oxyethylene-oxybuty- lene diblock copolymers in aqueous solution at different temperature are reported in this paper. For both copolymers, E represents an oxyethylene (-[CH2CH2O]-) unit and B an oxybutylene (-[CH(C2H5)CH2O]-) unit while the subscripts denote the number average block length. Surface tension measurements were used to find out surface excess concentrations (Γm), area per molecule (αs1 ) at air/water interface and Gibbs free energy for adsorption (△G0ads ) for the pre-micellar region at four temperatures. Likewise thermodynamic parameters of micellization such as, critical micelle concentrations (CMC), enthalpy of micellization (△H0mic ), standard free energy of micellization (△G0mic) and entropy of micellization (△S0mic ), were also obtained using surface tension measurements. Solution densities were used to deter-mine the partial specific volume of micelle ( Vmic) and micellar density (ρmic). Dilute solution viscosities have been used to estimate the intrinsic viscosities [η], solute-solvent interaction parameter (KH) and hydration value of micelle (Wh) at various temperatures. The effect of temperature on the micelle properties is also discussed.展开更多
N-Isopropylacrylamide and vinyl imidazole copolymer,P(NIPAM-co-VI),was synthesized by free radical emulsion polymerization.Then,the copolymer and silver nanoparticle composite,P(NIPAM-co-VI)-Ag,was pre-pared by in sit...N-Isopropylacrylamide and vinyl imidazole copolymer,P(NIPAM-co-VI),was synthesized by free radical emulsion polymerization.Then,the copolymer and silver nanoparticle composite,P(NIPAM-co-VI)-Ag,was pre-pared by in situ reduction of AgNO3 with NaBH4.Due to the coexistence of thermal-responsive PNIPAM and pH-responsive PVI,P(NIPAM-co-VI)and P(NIPAM-co-VI)-Ag exhibited both thermal and pH responsibility,their size would change while altering the temperature or pH of the circumvent.Their thermal and pH dual responsive properties were studied by dynamic light scattering(DLS).P(NIPAM-co-VI)-Ag could be stably dispersed in water at a pH range from 3.0 to 9.3,which is favorable to use P(NIPAM-co-VI)-Ag as a catalyst in the reduction reaction of p-nitrophenol.The reaction rate constant(kapp)increased with the decrease of pH or the increase of VI content in the copolymer.展开更多
基金financially supported by Pakistan Science foundation(PSF)and Higher Education Commission(HEC) Pakistan
文摘The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene） （E39B18） with anionic surfactant sodium dodecyl sulphate （SDS） and cationic surfactant hexadecyltrimethylammonium bromide （CTAB） were studied by using various techniques such as surface tension, conductivity, steady-state fluorescence and dynamic light scattering. Surface tension measurements were used to determine the critical micelle concentration （CMC） and thereby the free energy of micellization （AGmic）, free energy of adsorption （AG^ds）, surface excess concentration （F） and minimum area per molecule （A）. Conductivity measurements were used to determine the critical micelle concentration （CMC）, critical aggregation concentration （CAC）, polymer saturation point （PSP）, degree of ionization （tr） and counter ion binding （l]）. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles taken place due to the interactions of diblock copolymers with ionic surfactants. The ratio of the first and third vibronic peaks （11/Is） indicated the polarity of the pyrene micro environment and was used for the detection of micelle as well as polymer-surfactant interactions. Aggregation number （N）, number of binding sites （n） and free energy of binding （AGb） for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by the fluorescence quenching method.
基金financially supported by the Higher Education Commission(HEC) of Pakistan under the indigenous PhD scholarship program
文摘The chemical grafting of thiol terminated poly（sodium styrenesulfonate） （HS-PSSS） chains from sodium nitrate （NaNO3） salt solution to a gold surface was investigated with a quartz crystal microbalance with dissipation monitoring （QCM-D） in different salt concentrations, It was found that at low salt concentration grafting density of HS-PSSS was low and the grafted chains adopted a mushroom conformation. With the increase of salt concentration polyelectrolyte chains underwent a transition toward coiled state due to reduction of electrostatic repulsion and as a result more chains were grafted on the surface, When the grafting density reached a certain limit after which further grafting caused repulsion between already grafted HS-PSSS chains and as a result grafted chains adopted a brush conformation.
文摘The associative properties of methoxy (CH3O-) ended E58B11 and hydroxyl (-OH) ended E56B19 oxyethylene-oxybuty- lene diblock copolymers in aqueous solution at different temperature are reported in this paper. For both copolymers, E represents an oxyethylene (-[CH2CH2O]-) unit and B an oxybutylene (-[CH(C2H5)CH2O]-) unit while the subscripts denote the number average block length. Surface tension measurements were used to find out surface excess concentrations (Γm), area per molecule (αs1 ) at air/water interface and Gibbs free energy for adsorption (△G0ads ) for the pre-micellar region at four temperatures. Likewise thermodynamic parameters of micellization such as, critical micelle concentrations (CMC), enthalpy of micellization (△H0mic ), standard free energy of micellization (△G0mic) and entropy of micellization (△S0mic ), were also obtained using surface tension measurements. Solution densities were used to deter-mine the partial specific volume of micelle ( Vmic) and micellar density (ρmic). Dilute solution viscosities have been used to estimate the intrinsic viscosities [η], solute-solvent interaction parameter (KH) and hydration value of micelle (Wh) at various temperatures. The effect of temperature on the micelle properties is also discussed.
基金support from the Na-tional Natural Science Foundation of China(Nos.51073042,51103026,51373035,and 51373040)the Shanghai Scientific and Technological Innovation Pro-ject(Nos.11JC1400600,10431903000 and 124119a2400)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20110071120006).
文摘N-Isopropylacrylamide and vinyl imidazole copolymer,P(NIPAM-co-VI),was synthesized by free radical emulsion polymerization.Then,the copolymer and silver nanoparticle composite,P(NIPAM-co-VI)-Ag,was pre-pared by in situ reduction of AgNO3 with NaBH4.Due to the coexistence of thermal-responsive PNIPAM and pH-responsive PVI,P(NIPAM-co-VI)and P(NIPAM-co-VI)-Ag exhibited both thermal and pH responsibility,their size would change while altering the temperature or pH of the circumvent.Their thermal and pH dual responsive properties were studied by dynamic light scattering(DLS).P(NIPAM-co-VI)-Ag could be stably dispersed in water at a pH range from 3.0 to 9.3,which is favorable to use P(NIPAM-co-VI)-Ag as a catalyst in the reduction reaction of p-nitrophenol.The reaction rate constant(kapp)increased with the decrease of pH or the increase of VI content in the copolymer.
