Based on the premise that the addition of glass beads （GB） could hardly influence the linear viscoelasticity in low frequency （ω） region for homogeneous polymer systems, the dynamic rheological behaviors of unfil...Based on the premise that the addition of glass beads （GB） could hardly influence the linear viscoelasticity in low frequency （ω） region for homogeneous polymer systems, the dynamic rheological behaviors of unfilled and filled poly（methyl methyacrylate） （PMMA）/poly（styrene-co-acrylonitrile） （SAN） blends were studied in order to explore the effect of GB on the phase-separation of binary polymer matrix. Results show that GB has an induced effect on the phase-separation, which embodies that the phase-separation temperature （Ts） of PMMA/SAN blend filled with GB is lower than that of the unfilled system. The higher content of GB, the higher is the ＂secondary plateau＂ of ω in the terminal region of storage modulus （G＇） versus ω plot. The ＂secondary plateau＂ appearing in the terminal region is attributed to the phase-separation of PMMA/SAN blends and it becomes more fiat for filled polymer blends under the same conditions. However, it is suggested that this kind of ＂induced effect＂ is related to the GB content; the higher content of GB particles might enhance the interaction between the particles and polymer matrix. Moreover, it is found that the addition of GB also has an influence more or less on the morphology and domain size of polymer matrix. It is believed that the plot of dynamic viscosity （η＇） versus the loss viscosity （η＂） is sensitive to examine the effect induced by GB on the phase-separation of binary polymer matrix.展开更多
The compatibility and phase behavior of PS/SBR blends was studied with torsional braid analysis technique. The technique used in this study for preparation of braids was first developed by one of the authors, which gi...The compatibility and phase behavior of PS/SBR blends was studied with torsional braid analysis technique. The technique used in this study for preparation of braids was first developed by one of the authors, which gives more precise phase diagram as compared to other conventional methods. The results obtained are in good agreement with those obtained in our previous work.展开更多
The attainment of a better understanding and improvement of electrical properties of ternary blend is a task of particular scientific and economic importance. Ternary films of Poly (methylmethacrylate), Poly (ethlymat...The attainment of a better understanding and improvement of electrical properties of ternary blend is a task of particular scientific and economic importance. Ternary films of Poly (methylmethacrylate), Poly (ethlymathacrylate) and poly (vinlylidenefluoride) were prepared using solution cast technique. Thereafter, to study the hetro charges, homo-charges and interfacial charge formation in ternary system, the short circuit thermally stimulated discharge current (SC-TSDC) measurements were carried out on bilaterally metallized electrets. The ternary blend samples taken for the present investigations are hetrogeneous system involving three polymers differing in their conduction behaviour and dielectric property. Thus, unequal ohmic conduction currents arriving at the interface are expected to result in accumulation of charges at the interface or the Maxwell-Wagner effect. Clearly the Maxwell Wagner effect is expected to contribute discernibly to the observed TSDC’s of the ternary blends. The PMMA: PEMA: PVDF:: 100:100:50 blend exhibits highest tendency while 100:50:100 the least, towards the anomalous current flow. Moreover, the conductivity of 100: 100: 50 is found to be more and, therefore, a large amount of homocharge is injected leading to anomalous current.展开更多
The effect of substrate on the phase morphologies of PMMA/PS blend films was investigated by means of phase contrast microscope. PMMA/PS blend films were cast onto various substrates(such as glass substrate and PP sub...The effect of substrate on the phase morphologies of PMMA/PS blend films was investigated by means of phase contrast microscope. PMMA/PS blend films were cast onto various substrates(such as glass substrate and PP substrate) by spin-coating with thickness of about 10 μm. It was observed that there was a large difference of the phase inversion region between the blend films cast on glass and on PP substrates. On glass substrate, the phase inversion occurred at about \%Φ\%_m=0 4(PS mass fraction) while at \%Φ\%_m=0 5 on PP substrate. This implies that there is a shift of the phase inversion region with the change of substrate in cast polymer blend films. In other words, phase inversion region depends on the substrate. ATR-FTIR analysis was used to detect the composition of the surface and the bottom of the films(about 100 μm thick) obtained by evaporating solvent from the polymer blend solution. The ATR-FTIR spectra of the surface and the bottom of the PMMA/PS blend thin films cast on glass substrate and PP substrate showed that PMMA component preferentially segregated to glass substrate and PS component was enriched on the PP substrate. This selective segregation was due to the difference of the wetting abilities of PS and PMMA on the two kinds of substrates. The polymer-substrate interfacial tension γ were calculated and the results supported the ATR-FTIR results. It could be inferred that the shift of the phase inversion region with the change of the substrate in PMMA/PS blend film was due to the fact that the composition of the blend in the bulk changed, owing to the selective enrichment of one component of polymer blend to the substrate. In other words, the affinity between polymer and substrate can strongly influence the phase morphologies and the phase inversion region in polymer blend films.展开更多
Thin films of poly(methyl methacrylate)/polystyrene (PMMA/PS 80/20 W/W) blend prepared on glass substrate by spin-coating from a cosolvent, chloroform were studied. The formation of regular Voronoi patterns was found ...Thin films of poly(methyl methacrylate)/polystyrene (PMMA/PS 80/20 W/W) blend prepared on glass substrate by spin-coating from a cosolvent, chloroform were studied. The formation of regular Voronoi patterns was found under phase contrast microscopy (PCM). It was observed that there were clear concave boundaries in the PCM images by atomic force microscopy (AFM). Although the sample was annealed at 220℃ more than 7 h, no changes of the Voronoi pattern occurred, implying that the phase separation structure in the Voronoi pattern was almost complete during spin-coating process. It was believed that the formation of this pattern was due to the convection during spin-coating procedure.展开更多
Hybrid organic-inorganic perovskites have been the subject of recent intense interest due to advances in photovoltaic and other optoelectronic applications. However, their poor stability limits commercial market appli...Hybrid organic-inorganic perovskites have been the subject of recent intense interest due to advances in photovoltaic and other optoelectronic applications. However, their poor stability limits commercial market application We enhance water stability by post treatment preparation of hybrid metal halide perovskite nanocrystal-embedded polymethylmethacrylate （PM- MA） blend films. Through blending process without any cleaning of nanocrystals, crystalline hybrid organic-inorganic perovs-kite nanocrystals were incorporated into PMMA matrix with well-dispersion Passivation of PMMA on the surface of the per-ovskite nanocrystals results in decreased traps and a long photoluminescence （PL） lifetime despite the bromine vacancies in the crystal lattice. Moreover, such color purity and inherent high transmittance for fluorescence emission of perovskite nanocrystals will endow the films with promising potentials in diverse practice photonic applications.展开更多
基金This project was supported by the National Natural Science Foundation of China(No.20304014)the Special Funds for National Science Funds for Distinguished Young Scholars(No.50125312).
文摘Based on the premise that the addition of glass beads （GB） could hardly influence the linear viscoelasticity in low frequency （ω） region for homogeneous polymer systems, the dynamic rheological behaviors of unfilled and filled poly（methyl methyacrylate） （PMMA）/poly（styrene-co-acrylonitrile） （SAN） blends were studied in order to explore the effect of GB on the phase-separation of binary polymer matrix. Results show that GB has an induced effect on the phase-separation, which embodies that the phase-separation temperature （Ts） of PMMA/SAN blend filled with GB is lower than that of the unfilled system. The higher content of GB, the higher is the ＂secondary plateau＂ of ω in the terminal region of storage modulus （G＇） versus ω plot. The ＂secondary plateau＂ appearing in the terminal region is attributed to the phase-separation of PMMA/SAN blends and it becomes more fiat for filled polymer blends under the same conditions. However, it is suggested that this kind of ＂induced effect＂ is related to the GB content; the higher content of GB particles might enhance the interaction between the particles and polymer matrix. Moreover, it is found that the addition of GB also has an influence more or less on the morphology and domain size of polymer matrix. It is believed that the plot of dynamic viscosity （η＇） versus the loss viscosity （η＂） is sensitive to examine the effect induced by GB on the phase-separation of binary polymer matrix.
基金This work was supported by the Selected Research Program of Academia Sinica and National Natural Science Foundation of China.
文摘The compatibility and phase behavior of PS/SBR blends was studied with torsional braid analysis technique. The technique used in this study for preparation of braids was first developed by one of the authors, which gives more precise phase diagram as compared to other conventional methods. The results obtained are in good agreement with those obtained in our previous work.
文摘The attainment of a better understanding and improvement of electrical properties of ternary blend is a task of particular scientific and economic importance. Ternary films of Poly (methylmethacrylate), Poly (ethlymathacrylate) and poly (vinlylidenefluoride) were prepared using solution cast technique. Thereafter, to study the hetro charges, homo-charges and interfacial charge formation in ternary system, the short circuit thermally stimulated discharge current (SC-TSDC) measurements were carried out on bilaterally metallized electrets. The ternary blend samples taken for the present investigations are hetrogeneous system involving three polymers differing in their conduction behaviour and dielectric property. Thus, unequal ohmic conduction currents arriving at the interface are expected to result in accumulation of charges at the interface or the Maxwell-Wagner effect. Clearly the Maxwell Wagner effect is expected to contribute discernibly to the observed TSDC’s of the ternary blends. The PMMA: PEMA: PVDF:: 100:100:50 blend exhibits highest tendency while 100:50:100 the least, towards the anomalous current flow. Moreover, the conductivity of 100: 100: 50 is found to be more and, therefore, a large amount of homocharge is injected leading to anomalous current.
文摘The effect of substrate on the phase morphologies of PMMA/PS blend films was investigated by means of phase contrast microscope. PMMA/PS blend films were cast onto various substrates(such as glass substrate and PP substrate) by spin-coating with thickness of about 10 μm. It was observed that there was a large difference of the phase inversion region between the blend films cast on glass and on PP substrates. On glass substrate, the phase inversion occurred at about \%Φ\%_m=0 4(PS mass fraction) while at \%Φ\%_m=0 5 on PP substrate. This implies that there is a shift of the phase inversion region with the change of substrate in cast polymer blend films. In other words, phase inversion region depends on the substrate. ATR-FTIR analysis was used to detect the composition of the surface and the bottom of the films(about 100 μm thick) obtained by evaporating solvent from the polymer blend solution. The ATR-FTIR spectra of the surface and the bottom of the PMMA/PS blend thin films cast on glass substrate and PP substrate showed that PMMA component preferentially segregated to glass substrate and PS component was enriched on the PP substrate. This selective segregation was due to the difference of the wetting abilities of PS and PMMA on the two kinds of substrates. The polymer-substrate interfacial tension γ were calculated and the results supported the ATR-FTIR results. It could be inferred that the shift of the phase inversion region with the change of the substrate in PMMA/PS blend film was due to the fact that the composition of the blend in the bulk changed, owing to the selective enrichment of one component of polymer blend to the substrate. In other words, the affinity between polymer and substrate can strongly influence the phase morphologies and the phase inversion region in polymer blend films.
文摘Thin films of poly(methyl methacrylate)/polystyrene (PMMA/PS 80/20 W/W) blend prepared on glass substrate by spin-coating from a cosolvent, chloroform were studied. The formation of regular Voronoi patterns was found under phase contrast microscopy (PCM). It was observed that there were clear concave boundaries in the PCM images by atomic force microscopy (AFM). Although the sample was annealed at 220℃ more than 7 h, no changes of the Voronoi pattern occurred, implying that the phase separation structure in the Voronoi pattern was almost complete during spin-coating process. It was believed that the formation of this pattern was due to the convection during spin-coating procedure.
文摘Hybrid organic-inorganic perovskites have been the subject of recent intense interest due to advances in photovoltaic and other optoelectronic applications. However, their poor stability limits commercial market application We enhance water stability by post treatment preparation of hybrid metal halide perovskite nanocrystal-embedded polymethylmethacrylate （PM- MA） blend films. Through blending process without any cleaning of nanocrystals, crystalline hybrid organic-inorganic perovs-kite nanocrystals were incorporated into PMMA matrix with well-dispersion Passivation of PMMA on the surface of the per-ovskite nanocrystals results in decreased traps and a long photoluminescence （PL） lifetime despite the bromine vacancies in the crystal lattice. Moreover, such color purity and inherent high transmittance for fluorescence emission of perovskite nanocrystals will endow the films with promising potentials in diverse practice photonic applications.
