A new degradable aliphatic poly(butylene-co-e-caprolactone carbonate) (PBCL) was synthesized through the terpolymerization of carbon dioxide, 1,2-butylene oxide (BO) and e-caprolactone (CL), a polymer supported bimeta...A new degradable aliphatic poly(butylene-co-e-caprolactone carbonate) (PBCL) was synthesized through the terpolymerization of carbon dioxide, 1,2-butylene oxide (BO) and e-caprolactone (CL), a polymer supported bimetallic complex (PBM) was used as a catalyst. The terpolymers prepared were characterized by FT-IR,1H NMR, 13C NMR, WXRD and DSC. The hydrolysis tests were carried out to appraise the degradability of the copolymers.展开更多
In this paper, a new bulge-forming technology is described to manufacture a polycarbonate semisphere shell. Some experiments have been done, and the experimental results show that this technique is feasible to form po...In this paper, a new bulge-forming technology is described to manufacture a polycarbonate semisphere shell. Some experiments have been done, and the experimental results show that this technique is feasible to form polycarbonate part. But the wall thickness distribution of the bulged specimen by this method is not so even.展开更多
Acetone diffusion in polycarbonate was investigated by spin-echo <sup>1</sup>H NMR imaging method at room temperature. The result shows that the diffusion process satisfies Case Ⅱdiffusion. The velocity o...Acetone diffusion in polycarbonate was investigated by spin-echo <sup>1</sup>H NMR imaging method at room temperature. The result shows that the diffusion process satisfies Case Ⅱdiffusion. The velocity of diffusion front is 13.8nm sec<sup>-1</sup>（0.05mm/h）.展开更多
In this paper the miscibility of poly (ε-caprolactone) (PCL) and aliphatic polycarbonate (APC) is studied by using DSC. The results show that PCL and APC are miscible in all ranges of composition. The interaction par...In this paper the miscibility of poly (ε-caprolactone) (PCL) and aliphatic polycarbonate (APC) is studied by using DSC. The results show that PCL and APC are miscible in all ranges of composition. The interaction parameter between the polymers is calculated from the melting point depression data. Using optical microscope, the shapes of the PCL spherulites in the blends are observed.展开更多
By implanting B+ and O+ ions respectively into polycarbonate (PC) plates, the sur-face mechanical properties of PC have been improved. Measurement by Nano IndenterⅡ showed that the hardness of samples increased 7-25 ...By implanting B+ and O+ ions respectively into polycarbonate (PC) plates, the sur-face mechanical properties of PC have been improved. Measurement by Nano IndenterⅡ showed that the hardness of samples increased 7-25 times than that before implan-tation; and the modulus of elasticity raised 2-5 times. The wear-resistance was testedby ball crusher; the width and depth of the wear-streak decreased by 1/3-1/2 or evenmore. The structure, deformation and appearance were analyzed by using Micro-FTIR Spectra, ESCA method and the steps instrument. These analyses showed thatthe structure of PC had been modified: a series of new cross-linking yielded, it de-pends on the Linear Energy Transition (LET) of implanted ions in the high polymercompounds.展开更多
Thermo-responsive multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene glycol)(PEG) and poly(propylene glycol)(PPG) blocks,using triphosgene as coupling agent and pyridine as catalys...Thermo-responsive multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene glycol)(PEG) and poly(propylene glycol)(PPG) blocks,using triphosgene as coupling agent and pyridine as catalyst.The aqueous solutions of thermo-responsive polycarbonates were investigated by rheological measurements.Steady-state shear measurements reveal that the polycarbonate solutions exhibit shear-thinning behavior and the hydrophilic content has a pronounced effect on the flow behavior of the polycarbonates aqueous solutions.The shear viscosity decreases with increasing poly(ethylene oxide)(PEO) composition.The increase of viscosity with increasing concentration is probably attributed to the formation of stronger network owing to interchain entanglement of PEO block at higher concentration.When the flow curves are fitted to the power law model,flow index is obtained to be less than 1,as exhibiting typical pesudoplastic fluid.The viscoelastic properties of the system also show close dependence on the composition of polycarbonates.Temperature sweep confirms that the multiblock polycarbonates exhibit thermo-responsive properties.For 7% aqueous solution of polycarbonate with composition ratio of EO to PO of 1/1,the sol-gel transition occurs at 37 ℃,which makes the system suitable as an injectable drug delivery system.展开更多
The flame-retarded polycarbonate(PC) has been made with octaphenyl polyhedral silsesquioxane(OPS) and/or caged bicyclic phosphate(Trimer).Thermal gravimetric analysis(TGA),Fourier-transform infrared(FTIR),TGA-FTIR,lim...The flame-retarded polycarbonate(PC) has been made with octaphenyl polyhedral silsesquioxane(OPS) and/or caged bicyclic phosphate(Trimer).Thermal gravimetric analysis(TGA),Fourier-transform infrared(FTIR),TGA-FTIR,limiting oxygen index(LOI),and mechanical tests have been employed to characterize the modified PC.The additives of OPS and Trimer in PC have been proved to be effective flame-retardants because of the synergistic interaction between the elements of P and Si.The role of OPS and Trimer in PC degradation are different:OPS participates in the charring of PC,while Trimer makes PC degrade in advance.In addition,OPS and Trimer induced obvious differences in the mechanical properties of PC.展开更多
To provide convenience for the translation among specimens,orthogonal experimental method was used to research the relationship between geometrical dimensions(length,width and thickness) and total elongation of polyca...To provide convenience for the translation among specimens,orthogonal experimental method was used to research the relationship between geometrical dimensions(length,width and thickness) and total elongation of polycarbonate sheet,and simulations of tensile specimens with different geometrical dimensions had been conducted by the finite element method,then regression analysis method was used to create the relationship formula between geometrical dimensions and total elongation.It was found that:the shorter the length of specimen is,the better the plasticity is,and they had the power exponent relationship;the larger the width and thickness are,the better the plasticity is,and they had the direct proportion relationship with the total elongation.展开更多
Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide ran...Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant (ε') The loss tangent (tanδ), dielectric loss factor (ε''), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4) MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ- dose. The induced changes in the electrical conductivity due to γ-rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage;the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.展开更多
In this research, recycled-polyethylene terephthalate (PET) and polycarbonate (RPET/PC) blends fabricated by vented barrel injection molding were presented to better understand the effect of devolatilization during mo...In this research, recycled-polyethylene terephthalate (PET) and polycarbonate (RPET/PC) blends fabricated by vented barrel injection molding were presented to better understand the effect of devolatilization during molding process. The effect of dried pellets, non-dried pellets, using an opened-vented hole, and using a closed-vented hole on the miscibility, morphology, thermal properties and mechanical properties of RPET/PC blends was investigated. The results indicated that no drying decreases dispersion, thermal properties, and mechanical properties of RPET/PC blends due to hydrolysis degradation of recycled-PET during the injection molding process. Using the venting system with non-dried RPET/PC blends partially improves dispersion, thermal properties and molecular weight of RPET/PC blends processed without drying, giving results that are similar to those processed with drying. Regarding the flexural properties, using the venting system without drying prevents the flexural properties from decreasing in RPET/PC blends, if the amount of RPET is less than 75 wt%. When the content of RPET is over 75 wt%, using the venting system does not eliminate the decrease in flexural properties of RPET/PC blends. When the venting system is applied to non-dried RPET, despite hydrolysis degradation of RPET not being completely eliminated, the damaging effects are nonetheless reduced compared with those samples processed without the venting system. As a result, vented barrel injection molding hardly prevents non-dried RPET/PC blends from having reduced flexural properties when the content of RPET is greater than 75 wt%.展开更多
Crystal nucleation is important to control the product properties in industrial crystallization processes. To investigate crystallization phenomena, methods which rely on microscopic volumes have gained relevance over...Crystal nucleation is important to control the product properties in industrial crystallization processes. To investigate crystallization phenomena, methods which rely on microscopic volumes have gained relevance over the last decade. Microfluidic devices are suitable for carrying out crystallization experiments based on a large set of individual droplets in the nanoliter range. In this work, we propose a simple method to manufacture such devices from polycarbonate as an alternative to conventional chips made of poly (dimethylsiloxane). The microfluidic device consists of two main functional parts: A T-junction for droplet generation and a section for storage and observation of up to 400 individual droplets. Using these manufactured devices, it is easy to produce and store highly monodisperse droplets of substances that require either a hydrophilic or hydrophobic surface of the microchannel. Since crystal nucleation is a stochastic process which depends on the sample volume, a reproducible droplet volume is of great importance for crystallization experiments. The versatile applicability of the manufactured devices is demonstrated for substances which are used in different crystallization applications, for example, solution crystallization (aqueous potassium nitrate solution) and melt crystallization (ethylene glycol distearate). Finally, we demonstrate that the manufactured microfluidic devices in our experimental setup can be used to conduct crystal nucleation measurements. Based on these measurements we discuss our results with respect to state-of-the-art nucleation models.展开更多
Dielectric barrier discharge is used as a cheap technique for surface treatment of polycarbonate. The discharge system is working in open air at atmospheric pressure. The treatments are carried out at low discharge po...Dielectric barrier discharge is used as a cheap technique for surface treatment of polycarbonate. The discharge system is working in open air at atmospheric pressure. The treatments are carried out at low discharge powers (1.5 and 2 W) for treatment time (2.5 - 15 min). The treated samples show decrease in the contact angle and increase in the crystallinity, thermal stability and surface roughness. The effect of ozone on the increase in the oxygen containing functional groups is discussed. The treatment process shows effective limitation of the migration of bisphenol A from the surface of polycarbonate due to the cross linking. Zero migration of bisphenole A is recorded as the sample is treated for 7.5 min. The treatment process is found to be very efficient with very low cost.展开更多
The nature of the MnCl2 salt as a filler to polycarbonate , including their composition, particles dimensions and homogeneity of distribution have been studied using different spectroscopic techniques (XRD, DSC and TG...The nature of the MnCl2 salt as a filler to polycarbonate , including their composition, particles dimensions and homogeneity of distribution have been studied using different spectroscopic techniques (XRD, DSC and TGA). A slight increases in the chain-chain separation due to the interaction of the MnCl2 salt with the polycarbonate chains was observed , while a decrease in the optical energy gap (Eopt ) of the polycarbonate polymer with increasing the salt concentration was detected .However employing impedance spectroscopy in the frequency range 10Hz up to 106 Hz. reveals an increase in the dielectric permittivity and conductivity with increasing salt展开更多
Lexan polycarbonate films were irradiated by 8MeV electron beam at different fluences and characterized using X-ray Diffractogram (XRD), UV-Visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Differe...Lexan polycarbonate films were irradiated by 8MeV electron beam at different fluences and characterized using X-ray Diffractogram (XRD), UV-Visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The structural parameters such as degree of crystallinity and crystallite size were found to decrease after irradiation due to chain-scission. he UV-Visible spectroscopic study show the formation of chromophore groups upon irradiation and was reduced at larger wavelength. FTIR Study shows the carbonate linkage was found to be the radiation-sensitive linkage and benzene ring does not undergo any changes after irradiation. The DSC studies showed a decrease in glass transition temperature and heat of fusion after irradiation due to chain-scission which indicates polymer was moving towards more disordered state. Thermal decomposition temperature of Lexan polycarbonate increases upon irradiation.展开更多
This work was aimed to investigate the changes brought about in the polymer polycarbonate irradiated to different doses of γ-radiation. Yellowing of the samples with the increase of γ-absorbed dose was observed. The...This work was aimed to investigate the changes brought about in the polymer polycarbonate irradiated to different doses of γ-radiation. Yellowing of the samples with the increase of γ-absorbed dose was observed. The changes in the optical properties were studied by recording UV-Visible absorbance spectra of the pristine and irradiated polycarbonate films. A simultaneous coexistence of direct and indirect band gaps was observed. The indirect band gap values were found lower in comparison to the corresponding values of direct band gap in the pristine and γ-irradiated poly-carbonate. Both types of the optical band gap energies had decreasing tendency with the increasing γ-radiation dose. Urbach energy was also determined from the tail of absorption edge which was found to have increasing tendency with progressive γ-radiation dose. Increase in carbon cluster size with the increasing γ absorbed dose was also shown. This increase in the number of carbon atoms (N) in a cluster can be correlated to the optical energy band gap (Eg). Moreover, the FTIR spectra of pristine and irradiated PC samples suggest chain scissoring with apparently the elimination of carbon di/monoxide.展开更多
Metallic nanowires have attracted enormous attention since they open up exciting applications in the fields of electronics, plasmonics, sensors, green energy, and many more. Due to the large surface-area-to-volume rat...Metallic nanowires have attracted enormous attention since they open up exciting applications in the fields of electronics, plasmonics, sensors, green energy, and many more. Due to the large surface-area-to-volume ratio, however, they show enhanced chemical activity compared to their bulk counterparts and therefore are more easily susceptible to oxidization.展开更多
The innovation in polymer design to rival conventional polyethylene glycol(PEG)is an important approach to achieving a more sustainable society.Here,cyclic PEG-like polycarbonates having high molecular weight(4.4–49....The innovation in polymer design to rival conventional polyethylene glycol(PEG)is an important approach to achieving a more sustainable society.Here,cyclic PEG-like polycarbonates having high molecular weight(4.4–49.5 kg/mol)were enabled through zwitterionic ring-opening polymerization(ZROP)of macrocyclic carbonates(MCs)mediated by N-heterocyclic carbene(NHC).The thermodynamic behavior of polymerization depends on the ring size of monomers.During this process,the ZROP of 11-membered MC was driven by the change of enthalpy(ΔH_(p))which differed from the ZROP of 14-membered MC driven by the entropic change(ΔS_(p)).Cyclic polycarbonates depicted improved thermostability(T_(d5%)≥204℃)and higher glass transition temperatures(T_(g)>–40℃)in comparison to their linear analogues(T_(d5%)≤185℃,T_(g)~–50℃).In addition,the mechanism of ZROP of MC was addressed through computational study.A distinct mechanism of polymerization distinguishable from the well-known NHC-mediated ZROP of cyclic esters was revealed,where the zwitterion from nucleophilic addition to MC,i.e.tetrahedral intermediate,cannot be ring-opened probably due to the delocalization of negative charge on the carbonate group,but serves as an active center for the polymerization.In comparison to PEG,the attained polymer demonstrated comparable hydrophilic and biocompatible properties,as revealed by the results of contact angle and in vitro cytotoxicity studies,suggesting that cyclic polycarbonate hold the promise as the alternative of PEG.展开更多
Thermoplastic polycarbonate polyurethanes(PCUs) are multiblock copolymers that have been applied for medical devices for long time. Aliphatic diols are common chain extenders(CE) involved in the composition of the har...Thermoplastic polycarbonate polyurethanes(PCUs) are multiblock copolymers that have been applied for medical devices for long time. Aliphatic diols are common chain extenders(CE) involved in the composition of the hard segments of PCU. However, limited knowledge was discovered about how the chemical structure of CE affects the hydrogen bonding organization within PCUs and their mechanical properties.To investigate this problem, a group of PCUs were synthesized respectively by extending the polymer chain with 1,4-butanediol(BDO),aminoethanol(MEA), ethanediol(EO) as three kinds of chain extenders. Tiny differences in the CE chemical structure results in remarkable variations in phase separation, condensed morphologies, thermal and mechanical properties, which are characterized by Fourier transform infrared spectrometer, atomic force microscopy, small-angle X-ray scattering, differential scanning calorimetry, and tensile tests. The microstructural evolution during unilateral deformation and the different mechanism induced by the different CEs was probed and unveil by in situ wide-and small-angle X-ray diffraction. Symmetry of CE can improve the organization of the hydrogen bonding. The coherence strength of the urethane/urea group also plays a key role by comparing the two PCUs with ethanediol and aminoethanol.展开更多
Two bio-based seven-membered cyclic carbonate monomers M1 and M2 were synthesized in three steps from myrcene,which could produce polycarbonates via ring-opening polymerization using metal or organic catalysts.The fun...Two bio-based seven-membered cyclic carbonate monomers M1 and M2 were synthesized in three steps from myrcene,which could produce polycarbonates via ring-opening polymerization using metal or organic catalysts.The functionalizable olefin moieties in resulting polycarbonates have driven post-polymerization modifications via radical cross-linking and hydrogenation,enabling the resulting polymers with tunable thermal properties.More importantly,the chemical recycling of P(M)s was achieved through"monomer→polymer⇄dimer",which presented a platform for the synthesis of chemically recyclable biobased polycarbonates.展开更多
文摘A new degradable aliphatic poly(butylene-co-e-caprolactone carbonate) (PBCL) was synthesized through the terpolymerization of carbon dioxide, 1,2-butylene oxide (BO) and e-caprolactone (CL), a polymer supported bimetallic complex (PBM) was used as a catalyst. The terpolymers prepared were characterized by FT-IR,1H NMR, 13C NMR, WXRD and DSC. The hydrolysis tests were carried out to appraise the degradability of the copolymers.
文摘In this paper, a new bulge-forming technology is described to manufacture a polycarbonate semisphere shell. Some experiments have been done, and the experimental results show that this technique is feasible to form polycarbonate part. But the wall thickness distribution of the bulged specimen by this method is not so even.
文摘Acetone diffusion in polycarbonate was investigated by spin-echo <sup>1</sup>H NMR imaging method at room temperature. The result shows that the diffusion process satisfies Case Ⅱdiffusion. The velocity of diffusion front is 13.8nm sec<sup>-1</sup>（0.05mm/h）.
基金The subject supported by National Natural Science Foundation of China
文摘In this paper the miscibility of poly (ε-caprolactone) (PCL) and aliphatic polycarbonate (APC) is studied by using DSC. The results show that PCL and APC are miscible in all ranges of composition. The interaction parameter between the polymers is calculated from the melting point depression data. Using optical microscope, the shapes of the PCL spherulites in the blends are observed.
基金This work was supported by MOE Key Laboratory for Heavy Ion Physics, Peking University.
文摘By implanting B+ and O+ ions respectively into polycarbonate (PC) plates, the sur-face mechanical properties of PC have been improved. Measurement by Nano IndenterⅡ showed that the hardness of samples increased 7-25 times than that before implan-tation; and the modulus of elasticity raised 2-5 times. The wear-resistance was testedby ball crusher; the width and depth of the wear-streak decreased by 1/3-1/2 or evenmore. The structure, deformation and appearance were analyzed by using Micro-FTIR Spectra, ESCA method and the steps instrument. These analyses showed thatthe structure of PC had been modified: a series of new cross-linking yielded, it de-pends on the Linear Energy Transition (LET) of implanted ions in the high polymercompounds.
基金Projects(2006GG2203007) supported by the Scientific Research Project of Shandong Province,China
文摘Thermo-responsive multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene glycol)(PEG) and poly(propylene glycol)(PPG) blocks,using triphosgene as coupling agent and pyridine as catalyst.The aqueous solutions of thermo-responsive polycarbonates were investigated by rheological measurements.Steady-state shear measurements reveal that the polycarbonate solutions exhibit shear-thinning behavior and the hydrophilic content has a pronounced effect on the flow behavior of the polycarbonates aqueous solutions.The shear viscosity decreases with increasing poly(ethylene oxide)(PEO) composition.The increase of viscosity with increasing concentration is probably attributed to the formation of stronger network owing to interchain entanglement of PEO block at higher concentration.When the flow curves are fitted to the power law model,flow index is obtained to be less than 1,as exhibiting typical pesudoplastic fluid.The viscoelastic properties of the system also show close dependence on the composition of polycarbonates.Temperature sweep confirms that the multiblock polycarbonates exhibit thermo-responsive properties.For 7% aqueous solution of polycarbonate with composition ratio of EO to PO of 1/1,the sol-gel transition occurs at 37 ℃,which makes the system suitable as an injectable drug delivery system.
基金Sponsored by the National High Technology Research and Development Program of China("863"Program)(2007AA03Z538)
文摘The flame-retarded polycarbonate(PC) has been made with octaphenyl polyhedral silsesquioxane(OPS) and/or caged bicyclic phosphate(Trimer).Thermal gravimetric analysis(TGA),Fourier-transform infrared(FTIR),TGA-FTIR,limiting oxygen index(LOI),and mechanical tests have been employed to characterize the modified PC.The additives of OPS and Trimer in PC have been proved to be effective flame-retardants because of the synergistic interaction between the elements of P and Si.The role of OPS and Trimer in PC degradation are different:OPS participates in the charring of PC,while Trimer makes PC degrade in advance.In addition,OPS and Trimer induced obvious differences in the mechanical properties of PC.
基金Sponsored by the National Natural Science Foundation of China (Grant No. 50675044)the Heilongjiang Provincial Natural Science Foundation Key Program (Grant No. ZD200811)
文摘To provide convenience for the translation among specimens,orthogonal experimental method was used to research the relationship between geometrical dimensions(length,width and thickness) and total elongation of polycarbonate sheet,and simulations of tensile specimens with different geometrical dimensions had been conducted by the finite element method,then regression analysis method was used to create the relationship formula between geometrical dimensions and total elongation.It was found that:the shorter the length of specimen is,the better the plasticity is,and they had the power exponent relationship;the larger the width and thickness are,the better the plasticity is,and they had the direct proportion relationship with the total elongation.
文摘Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant (ε') The loss tangent (tanδ), dielectric loss factor (ε''), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4) MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ- dose. The induced changes in the electrical conductivity due to γ-rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage;the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.
文摘In this research, recycled-polyethylene terephthalate (PET) and polycarbonate (RPET/PC) blends fabricated by vented barrel injection molding were presented to better understand the effect of devolatilization during molding process. The effect of dried pellets, non-dried pellets, using an opened-vented hole, and using a closed-vented hole on the miscibility, morphology, thermal properties and mechanical properties of RPET/PC blends was investigated. The results indicated that no drying decreases dispersion, thermal properties, and mechanical properties of RPET/PC blends due to hydrolysis degradation of recycled-PET during the injection molding process. Using the venting system with non-dried RPET/PC blends partially improves dispersion, thermal properties and molecular weight of RPET/PC blends processed without drying, giving results that are similar to those processed with drying. Regarding the flexural properties, using the venting system without drying prevents the flexural properties from decreasing in RPET/PC blends, if the amount of RPET is less than 75 wt%. When the content of RPET is over 75 wt%, using the venting system does not eliminate the decrease in flexural properties of RPET/PC blends. When the venting system is applied to non-dried RPET, despite hydrolysis degradation of RPET not being completely eliminated, the damaging effects are nonetheless reduced compared with those samples processed without the venting system. As a result, vented barrel injection molding hardly prevents non-dried RPET/PC blends from having reduced flexural properties when the content of RPET is greater than 75 wt%.
文摘Crystal nucleation is important to control the product properties in industrial crystallization processes. To investigate crystallization phenomena, methods which rely on microscopic volumes have gained relevance over the last decade. Microfluidic devices are suitable for carrying out crystallization experiments based on a large set of individual droplets in the nanoliter range. In this work, we propose a simple method to manufacture such devices from polycarbonate as an alternative to conventional chips made of poly (dimethylsiloxane). The microfluidic device consists of two main functional parts: A T-junction for droplet generation and a section for storage and observation of up to 400 individual droplets. Using these manufactured devices, it is easy to produce and store highly monodisperse droplets of substances that require either a hydrophilic or hydrophobic surface of the microchannel. Since crystal nucleation is a stochastic process which depends on the sample volume, a reproducible droplet volume is of great importance for crystallization experiments. The versatile applicability of the manufactured devices is demonstrated for substances which are used in different crystallization applications, for example, solution crystallization (aqueous potassium nitrate solution) and melt crystallization (ethylene glycol distearate). Finally, we demonstrate that the manufactured microfluidic devices in our experimental setup can be used to conduct crystal nucleation measurements. Based on these measurements we discuss our results with respect to state-of-the-art nucleation models.
文摘Dielectric barrier discharge is used as a cheap technique for surface treatment of polycarbonate. The discharge system is working in open air at atmospheric pressure. The treatments are carried out at low discharge powers (1.5 and 2 W) for treatment time (2.5 - 15 min). The treated samples show decrease in the contact angle and increase in the crystallinity, thermal stability and surface roughness. The effect of ozone on the increase in the oxygen containing functional groups is discussed. The treatment process shows effective limitation of the migration of bisphenol A from the surface of polycarbonate due to the cross linking. Zero migration of bisphenole A is recorded as the sample is treated for 7.5 min. The treatment process is found to be very efficient with very low cost.
文摘The nature of the MnCl2 salt as a filler to polycarbonate , including their composition, particles dimensions and homogeneity of distribution have been studied using different spectroscopic techniques (XRD, DSC and TGA). A slight increases in the chain-chain separation due to the interaction of the MnCl2 salt with the polycarbonate chains was observed , while a decrease in the optical energy gap (Eopt ) of the polycarbonate polymer with increasing the salt concentration was detected .However employing impedance spectroscopy in the frequency range 10Hz up to 106 Hz. reveals an increase in the dielectric permittivity and conductivity with increasing salt
文摘Lexan polycarbonate films were irradiated by 8MeV electron beam at different fluences and characterized using X-ray Diffractogram (XRD), UV-Visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The structural parameters such as degree of crystallinity and crystallite size were found to decrease after irradiation due to chain-scission. he UV-Visible spectroscopic study show the formation of chromophore groups upon irradiation and was reduced at larger wavelength. FTIR Study shows the carbonate linkage was found to be the radiation-sensitive linkage and benzene ring does not undergo any changes after irradiation. The DSC studies showed a decrease in glass transition temperature and heat of fusion after irradiation due to chain-scission which indicates polymer was moving towards more disordered state. Thermal decomposition temperature of Lexan polycarbonate increases upon irradiation.
文摘This work was aimed to investigate the changes brought about in the polymer polycarbonate irradiated to different doses of γ-radiation. Yellowing of the samples with the increase of γ-absorbed dose was observed. The changes in the optical properties were studied by recording UV-Visible absorbance spectra of the pristine and irradiated polycarbonate films. A simultaneous coexistence of direct and indirect band gaps was observed. The indirect band gap values were found lower in comparison to the corresponding values of direct band gap in the pristine and γ-irradiated poly-carbonate. Both types of the optical band gap energies had decreasing tendency with the increasing γ-radiation dose. Urbach energy was also determined from the tail of absorption edge which was found to have increasing tendency with progressive γ-radiation dose. Increase in carbon cluster size with the increasing γ absorbed dose was also shown. This increase in the number of carbon atoms (N) in a cluster can be correlated to the optical energy band gap (Eg). Moreover, the FTIR spectra of pristine and irradiated PC samples suggest chain scissoring with apparently the elimination of carbon di/monoxide.
文摘Metallic nanowires have attracted enormous attention since they open up exciting applications in the fields of electronics, plasmonics, sensors, green energy, and many more. Due to the large surface-area-to-volume ratio, however, they show enhanced chemical activity compared to their bulk counterparts and therefore are more easily susceptible to oxidization.
基金the China Postdoc Council(OCPC)for the financial support of Postdoctoral International Exchange Program(No.YJ20210095)the financial support from the National Natural Science Foundation of China(No.22078150)+3 种基金National Key R&D Program of China(No.2021YFC2101904)the Jiangsu National Synergetic Innovation Center for Advanced Materials(SICAM)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture(No.XTB2201)the Top-Notch Academic Programs Project of Jiangsu Higher Education Institutions(TAPP)。
文摘The innovation in polymer design to rival conventional polyethylene glycol(PEG)is an important approach to achieving a more sustainable society.Here,cyclic PEG-like polycarbonates having high molecular weight(4.4–49.5 kg/mol)were enabled through zwitterionic ring-opening polymerization(ZROP)of macrocyclic carbonates(MCs)mediated by N-heterocyclic carbene(NHC).The thermodynamic behavior of polymerization depends on the ring size of monomers.During this process,the ZROP of 11-membered MC was driven by the change of enthalpy(ΔH_(p))which differed from the ZROP of 14-membered MC driven by the entropic change(ΔS_(p)).Cyclic polycarbonates depicted improved thermostability(T_(d5%)≥204℃)and higher glass transition temperatures(T_(g)>–40℃)in comparison to their linear analogues(T_(d5%)≤185℃,T_(g)~–50℃).In addition,the mechanism of ZROP of MC was addressed through computational study.A distinct mechanism of polymerization distinguishable from the well-known NHC-mediated ZROP of cyclic esters was revealed,where the zwitterion from nucleophilic addition to MC,i.e.tetrahedral intermediate,cannot be ring-opened probably due to the delocalization of negative charge on the carbonate group,but serves as an active center for the polymerization.In comparison to PEG,the attained polymer demonstrated comparable hydrophilic and biocompatible properties,as revealed by the results of contact angle and in vitro cytotoxicity studies,suggesting that cyclic polycarbonate hold the promise as the alternative of PEG.
基金financially supported by the National Natural Science Foundation of China (No.21774135)。
文摘Thermoplastic polycarbonate polyurethanes(PCUs) are multiblock copolymers that have been applied for medical devices for long time. Aliphatic diols are common chain extenders(CE) involved in the composition of the hard segments of PCU. However, limited knowledge was discovered about how the chemical structure of CE affects the hydrogen bonding organization within PCUs and their mechanical properties.To investigate this problem, a group of PCUs were synthesized respectively by extending the polymer chain with 1,4-butanediol(BDO),aminoethanol(MEA), ethanediol(EO) as three kinds of chain extenders. Tiny differences in the CE chemical structure results in remarkable variations in phase separation, condensed morphologies, thermal and mechanical properties, which are characterized by Fourier transform infrared spectrometer, atomic force microscopy, small-angle X-ray scattering, differential scanning calorimetry, and tensile tests. The microstructural evolution during unilateral deformation and the different mechanism induced by the different CEs was probed and unveil by in situ wide-and small-angle X-ray diffraction. Symmetry of CE can improve the organization of the hydrogen bonding. The coherence strength of the urethane/urea group also plays a key role by comparing the two PCUs with ethanediol and aminoethanol.
基金This work was supported by the National Natural Science Foundation of China(No.22071163)the Fundamental Research Funds for the Central Universities of China(Nos.YJ201924,YJ202209).
文摘Two bio-based seven-membered cyclic carbonate monomers M1 and M2 were synthesized in three steps from myrcene,which could produce polycarbonates via ring-opening polymerization using metal or organic catalysts.The functionalizable olefin moieties in resulting polycarbonates have driven post-polymerization modifications via radical cross-linking and hydrogenation,enabling the resulting polymers with tunable thermal properties.More importantly,the chemical recycling of P(M)s was achieved through"monomer→polymer⇄dimer",which presented a platform for the synthesis of chemically recyclable biobased polycarbonates.
