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2019 Volume 37 Issue 11
2019, 37(11): 1045-1052
doi: 10.1007/s10118-019-2313-1
Abstract:
Here, through the synergism between kinetic dynamic imine-exchange control and thermodynamic control, rarely observed compressible, porous, crystalline covalent organic framework (COF) aerogels were synthesized, the mechanism behind which is a framework crystallization induced self-assembly (FCISA) process. The prepared COF aerogel possessed extremely high BET surface over 2000 m2·g−1 and high maximum equilibrium adsorption capacity toward bisphenol-A of 699 mg·g−1 in aqueous solution.
Here, through the synergism between kinetic dynamic imine-exchange control and thermodynamic control, rarely observed compressible, porous, crystalline covalent organic framework (COF) aerogels were synthesized, the mechanism behind which is a framework crystallization induced self-assembly (FCISA) process. The prepared COF aerogel possessed extremely high BET surface over 2000 m2·g−1 and high maximum equilibrium adsorption capacity toward bisphenol-A of 699 mg·g−1 in aqueous solution.
2019, 37(11): 1053-1059
doi: 10.1007/s10118-019-2325-x
Abstract:
Integrating multiple functions into one gel that can be widely applied to electronic devices as well as chemical and biomedical engineering remains a big challenge. Here, a multifunctional ionic liquid/dynamic covalent bonds (ionic/DCB) type gel was designed and synthesized via one-pot polymerization. With the assistance of electrostatic interaction provided by the imidazolium cations of IL and the reversible DCB of boronic ester, as-prepared ionic/DCB gel showed good stretchable properties and high ionic conductivity at ambient conditions. In addition, the electrostatic interaction between imidazolium cations and sulfonate anions and the reversible DCB led to enhanced chain mobility and thereby excellent self-healing properties. Particularly, sulfonate anions in ionic/DCB gel could alleviate the migration of electronegative polysulfide and promote the transportation of electropositive lithium ion in lithium-sulfur battery system. Therefore, this work provides a new insight to promote the current research on self-healing gels, hopefully expanding their applications in electronic devices.
Integrating multiple functions into one gel that can be widely applied to electronic devices as well as chemical and biomedical engineering remains a big challenge. Here, a multifunctional ionic liquid/dynamic covalent bonds (ionic/DCB) type gel was designed and synthesized via one-pot polymerization. With the assistance of electrostatic interaction provided by the imidazolium cations of IL and the reversible DCB of boronic ester, as-prepared ionic/DCB gel showed good stretchable properties and high ionic conductivity at ambient conditions. In addition, the electrostatic interaction between imidazolium cations and sulfonate anions and the reversible DCB led to enhanced chain mobility and thereby excellent self-healing properties. Particularly, sulfonate anions in ionic/DCB gel could alleviate the migration of electronegative polysulfide and promote the transportation of electropositive lithium ion in lithium-sulfur battery system. Therefore, this work provides a new insight to promote the current research on self-healing gels, hopefully expanding their applications in electronic devices.
2019, 37(11): 1065-1082
doi: 10.1007/s10118-019-2304-2
Abstract:
This paper reviews some of our recent works on phase behaviors of particulate systems with a soft-core interaction potential. The potential is purely repulsive and bounded, i.e., it is finite even when two particles completely overlap. The one-sided linear spring (harmonic) potential is one of the representatives. This model system has been successively employed to study the jamming transition, i.e., the formation of rigid and disordered packings of hard particles, and establish the jamming physics. This is actually based on the " hard” aspect of the potential, because at low densities and when particle overlap is tiny the potential resembles the hard sphere limit. At high densities, the potential exhibits its " soft” aspect: with the increase of density, there are successive reentrant crystallizations with many types of solid phases. Taking advantage of the dual nature of the potential, we investigate the criticality of the jamming transition from different perspectives, extend the jamming scenario to high densities, reveal the novel density evolution of two-dimensional melting, and find unexpected formation of quasicrystals. It is surprising that such a simple potential can exhibit so rich and unexpected phenomena in phase transitions. The phase behaviors discussed in this paper are also highly regarded in polymer science, which may thus shed light on our understanding of polymeric systems or inspire new ideas in studies of polymers.
This paper reviews some of our recent works on phase behaviors of particulate systems with a soft-core interaction potential. The potential is purely repulsive and bounded, i.e., it is finite even when two particles completely overlap. The one-sided linear spring (harmonic) potential is one of the representatives. This model system has been successively employed to study the jamming transition, i.e., the formation of rigid and disordered packings of hard particles, and establish the jamming physics. This is actually based on the " hard” aspect of the potential, because at low densities and when particle overlap is tiny the potential resembles the hard sphere limit. At high densities, the potential exhibits its " soft” aspect: with the increase of density, there are successive reentrant crystallizations with many types of solid phases. Taking advantage of the dual nature of the potential, we investigate the criticality of the jamming transition from different perspectives, extend the jamming scenario to high densities, reveal the novel density evolution of two-dimensional melting, and find unexpected formation of quasicrystals. It is surprising that such a simple potential can exhibit so rich and unexpected phenomena in phase transitions. The phase behaviors discussed in this paper are also highly regarded in polymer science, which may thus shed light on our understanding of polymeric systems or inspire new ideas in studies of polymers.
2019, 37(11): 1083-1091
doi: 10.1007/s10118-019-2312-2
Abstract:
Protein internal dynamics is essential for its function. Exploring the internal dynamics of protein molecules as well as its connection to protein structure and function is a central topic in biophysics. However, the atomic motions in protein molecules exhibit a great degree of complexities. These complexities arise from the complex chemical composition and superposition of different types of atomic motions on the similar time scales, and render it challenging to explicitly understand the microscopic mechanism governing protein motions, functions, and their connections. Here, we demonstrate that, by using neutron scattering, molecular dynamics simulation, and deuteration technique, one can address this challenge to a large extent.
Protein internal dynamics is essential for its function. Exploring the internal dynamics of protein molecules as well as its connection to protein structure and function is a central topic in biophysics. However, the atomic motions in protein molecules exhibit a great degree of complexities. These complexities arise from the complex chemical composition and superposition of different types of atomic motions on the similar time scales, and render it challenging to explicitly understand the microscopic mechanism governing protein motions, functions, and their connections. Here, we demonstrate that, by using neutron scattering, molecular dynamics simulation, and deuteration technique, one can address this challenge to a large extent.
2019, 37(11): 1092-1098
doi: 10.1007/s10118-019-2248-6
Abstract:
Sonogashira coupling of two different diketopyrrolopyrrole (DPP)-containing dihaloarenes with the same aromatic bisalkyne resulted in two new conjugated polymers with the same backbone but different pendant groups on the DPP moiety. The polymers were found to have designed chemical structures via structural characterizations in comparison with three monomers. The molecular weight measurement further demonstrated the formation of polymers with polydispersity index around 2, consistent with the polycondensation nature of the polymerization based on Sonogashira coupling. Both polymers could dissolve in many organic solvents, and the one with long alkyl side group on DPP moiety had better solubility. Photophysical investigation showed that both polymers had typical absorption/emission of conjugated polymers, and varying the solvent did not have large influence. Compared with other polar solvents, toluene reduced the quantum yield of fluorescence of the polymers, especially for the one with long alkyl pedant group, accompanying with slight red-shift in absorption/emission. The difference in the absorption/emission wavelengths between the polymers was similar to that between the corresponding monomers. Adding water into the THF solution of polymers reduced the emission intensity but no red-shift was observed. Discussion about the structure-property relationships was carried out in detail.
Sonogashira coupling of two different diketopyrrolopyrrole (DPP)-containing dihaloarenes with the same aromatic bisalkyne resulted in two new conjugated polymers with the same backbone but different pendant groups on the DPP moiety. The polymers were found to have designed chemical structures via structural characterizations in comparison with three monomers. The molecular weight measurement further demonstrated the formation of polymers with polydispersity index around 2, consistent with the polycondensation nature of the polymerization based on Sonogashira coupling. Both polymers could dissolve in many organic solvents, and the one with long alkyl side group on DPP moiety had better solubility. Photophysical investigation showed that both polymers had typical absorption/emission of conjugated polymers, and varying the solvent did not have large influence. Compared with other polar solvents, toluene reduced the quantum yield of fluorescence of the polymers, especially for the one with long alkyl pedant group, accompanying with slight red-shift in absorption/emission. The difference in the absorption/emission wavelengths between the polymers was similar to that between the corresponding monomers. Adding water into the THF solution of polymers reduced the emission intensity but no red-shift was observed. Discussion about the structure-property relationships was carried out in detail.
2019, 37(11): 1099-1104
doi: 10.1007/s10118-019-2277-1
Abstract:
A highly efficient and eco-friendly protocol for the synthesis of an alternating copolymer poly(7,7′-diazaisoindigo-alt-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene) (PAIID-4FTVT) via direct arylation polycondensation (DArP) is presented. Through detailed study, we found that the inhibitory effect of 7,7′-diazaisoindigo on DArP stemmed from the coordination of N atom with catalyst can be overcome by using dimethylacetamide (DMAc) as the co-solvent. Thus, PAIID-4FTVT with number-average molecular weight (Mn) > 100 kDa was synthesized via DArP by optimizing the content of DMAc. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy revealed that PAIID-4FTVT was defect-free. Top gate and bottom contact (TG/BC) organic thin-film transistors (OTFTs) were fabricated to characterize the semiconducting properties of the polymers. PAIID-4FTVT displayed unipolar n-type characteristics with the electron mobility (μe) strongly dependent on Mn. The highest μe up to 0.25 cm2·V–1·s–1 was achieved with the high molecular weight sample.
A highly efficient and eco-friendly protocol for the synthesis of an alternating copolymer poly(7,7′-diazaisoindigo-alt-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene) (PAIID-4FTVT) via direct arylation polycondensation (DArP) is presented. Through detailed study, we found that the inhibitory effect of 7,7′-diazaisoindigo on DArP stemmed from the coordination of N atom with catalyst can be overcome by using dimethylacetamide (DMAc) as the co-solvent. Thus, PAIID-4FTVT with number-average molecular weight (Mn) > 100 kDa was synthesized via DArP by optimizing the content of DMAc. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy revealed that PAIID-4FTVT was defect-free. Top gate and bottom contact (TG/BC) organic thin-film transistors (OTFTs) were fabricated to characterize the semiconducting properties of the polymers. PAIID-4FTVT displayed unipolar n-type characteristics with the electron mobility (μe) strongly dependent on Mn. The highest μe up to 0.25 cm2·V–1·s–1 was achieved with the high molecular weight sample.
2019, 37(11): 1105-1112
doi: 10.1007/s10118-019-2278-0
Abstract:
Gram-negative bacteria can cause serious infections and are well known problems in biomedical practices. Biofilms of gram-negative bacteria are notorious for their frequently encountered resistance toward antibiotics. We demonstrate that α/β chimeric polypeptide molecular brush (α/β CPMB) exerts potent activities against antibiotic-resistant gram-negative bacteria. MTT viability assay, bacterial colony counting, and live/dead staining all indicate that α/β CPMB not only inhibits biofilm formation of gram-negative Pseudomonas aeruginosa and Acinetobacter baumannii, but also effectively disrupts mature biofilms that are highly resistant to one of the most active antibiotics—colistin. The superior antibacterial performance of the α/β CPMB implies its potential topical applications in treating biofilms.
Gram-negative bacteria can cause serious infections and are well known problems in biomedical practices. Biofilms of gram-negative bacteria are notorious for their frequently encountered resistance toward antibiotics. We demonstrate that α/β chimeric polypeptide molecular brush (α/β CPMB) exerts potent activities against antibiotic-resistant gram-negative bacteria. MTT viability assay, bacterial colony counting, and live/dead staining all indicate that α/β CPMB not only inhibits biofilm formation of gram-negative Pseudomonas aeruginosa and Acinetobacter baumannii, but also effectively disrupts mature biofilms that are highly resistant to one of the most active antibiotics—colistin. The superior antibacterial performance of the α/β CPMB implies its potential topical applications in treating biofilms.
2019, 37(11): 1113-1118
doi: 10.1007/s10118-019-2287-z
Abstract:
A novel switchable luminescent thermometer based on thermo-responsive triblock copolymer poly(ethylene glycol)-b-poly(acrylamide-co-acrylonitrile-co-dimethylaminoethylmethacrylate) (PEO113-b-P(AAm264-co-AN112-co-DMA8)) and Eu-containing polyoxometalate (Eu-POM) was successfully constructed. The copolymer synthesized by RAFT exhibited a linear response to temperature variations in aqueous media, which was quite different from the uncharged copolymer P(AAm-co-AN) having a specific upper critical solution temperature (UCST). Eu-POM was surrounded around thermo-responsive blocks through electrostatic interactions, and its luminescence could be finely tuned due to the sensitivity of copolymer to the temperature variation. In cold water, POMs were trapped in highly hydrophobic cores, exhibiting an intense emission. With the upraising of temperature, the emission intensity presented a gradual decrease and showed a linear correlation with temperature. When the complex solution cooled down, the luminescence could also be perfectly restored. This temperature-luminescence correlation could be held for numerous trials, showing a potential application in thermometer.
A novel switchable luminescent thermometer based on thermo-responsive triblock copolymer poly(ethylene glycol)-b-poly(acrylamide-co-acrylonitrile-co-dimethylaminoethylmethacrylate) (PEO113-b-P(AAm264-co-AN112-co-DMA8)) and Eu-containing polyoxometalate (Eu-POM) was successfully constructed. The copolymer synthesized by RAFT exhibited a linear response to temperature variations in aqueous media, which was quite different from the uncharged copolymer P(AAm-co-AN) having a specific upper critical solution temperature (UCST). Eu-POM was surrounded around thermo-responsive blocks through electrostatic interactions, and its luminescence could be finely tuned due to the sensitivity of copolymer to the temperature variation. In cold water, POMs were trapped in highly hydrophobic cores, exhibiting an intense emission. With the upraising of temperature, the emission intensity presented a gradual decrease and showed a linear correlation with temperature. When the complex solution cooled down, the luminescence could also be perfectly restored. This temperature-luminescence correlation could be held for numerous trials, showing a potential application in thermometer.
2019, 37(11): 1119-1129
doi: 10.1007/s10118-019-2268-2
Abstract:
A reversible disulfide bond-based self-healing polyurethane with triple shape memory properties was prepared by chain extending of random copolymer poly(lactide-co-caprolactone) (PCLA), hexamethylene diisocyanate (HDI), polytetrahydrofuran (PTMEG), and 4,4′-aminophenyl disulfide. The chemical structures were characterized using 1H nuclear magnetic resonance (1H-NMR) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). The thermal properties, self-healing properties, triple-shape memory effect, and quantitative shape memory response were evaluated by differential scanning calorimetry (DSC), tensile tests, two-step programming process thermal mechanical experiments, and subsequent progressive thermal recovery. The self-healing mechanism and procedures were investigated using polarizing optical microscopy (POM) and an optical profiler. It was concluded that self-healing properties (up to 60%) and triple-shape memory properties around 35 and 50 °C (with shape fixation ratios of 94.3% and 98.3%, shape recovery ratios of 76.6% and 85.1%, respectively) were integrated to the shape memory polyurethane. As-prepared polyurethane is expected to have potential applications in multi-shape coatings, films, and step-by-step deploying structures.
A reversible disulfide bond-based self-healing polyurethane with triple shape memory properties was prepared by chain extending of random copolymer poly(lactide-co-caprolactone) (PCLA), hexamethylene diisocyanate (HDI), polytetrahydrofuran (PTMEG), and 4,4′-aminophenyl disulfide. The chemical structures were characterized using 1H nuclear magnetic resonance (1H-NMR) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). The thermal properties, self-healing properties, triple-shape memory effect, and quantitative shape memory response were evaluated by differential scanning calorimetry (DSC), tensile tests, two-step programming process thermal mechanical experiments, and subsequent progressive thermal recovery. The self-healing mechanism and procedures were investigated using polarizing optical microscopy (POM) and an optical profiler. It was concluded that self-healing properties (up to 60%) and triple-shape memory properties around 35 and 50 °C (with shape fixation ratios of 94.3% and 98.3%, shape recovery ratios of 76.6% and 85.1%, respectively) were integrated to the shape memory polyurethane. As-prepared polyurethane is expected to have potential applications in multi-shape coatings, films, and step-by-step deploying structures.
2019, 37(11): 1130-1141
doi: 10.1007/s10118-019-2263-7
Abstract:
The efficient Cu(0) wire-catalyzed single-electron transfer-living radical polymerization (SET-LRP) in organic solvents and mixtures of the organic solvents with water has been thoroughly investigated. Oligo(ethylene oxide) methyl ether acrylate was used as an exemplar oligomer monomer to determine the optimum polymerization conditions for rapid, controlled, and quantitative production of well-defined polymers. The effects of Cu(0)-wire length (12.5 or 4.5 cm), ligand type (tris(dimethylaminoethyl)amine, Me6-TREN, or tris(2-aminoethyl)amine, TREN), and solvent type (dipolar aprotic solvents, cyclic ethers, alcohol, or acetone) on the polymerization have been evaluated. Kinetic experiments were performed for all polymerizations to assess the " living” behavior of each system employed. Importantly, TREN could be used as a replacement for Me6-TREN in Cu(0) wire-catalyzed SET-LRP of oligomer monomer, which probably provides the most economical and efficient methodology since TREN is 80 times less expensive than Me6-TREN. The high chain-end fidelity of resulting polymer was experimentally verified by thiol-Michael addition reaction at the α-Br chain end and subsequent chain extension with methyl acrylate.
The efficient Cu(0) wire-catalyzed single-electron transfer-living radical polymerization (SET-LRP) in organic solvents and mixtures of the organic solvents with water has been thoroughly investigated. Oligo(ethylene oxide) methyl ether acrylate was used as an exemplar oligomer monomer to determine the optimum polymerization conditions for rapid, controlled, and quantitative production of well-defined polymers. The effects of Cu(0)-wire length (12.5 or 4.5 cm), ligand type (tris(dimethylaminoethyl)amine, Me6-TREN, or tris(2-aminoethyl)amine, TREN), and solvent type (dipolar aprotic solvents, cyclic ethers, alcohol, or acetone) on the polymerization have been evaluated. Kinetic experiments were performed for all polymerizations to assess the " living” behavior of each system employed. Importantly, TREN could be used as a replacement for Me6-TREN in Cu(0) wire-catalyzed SET-LRP of oligomer monomer, which probably provides the most economical and efficient methodology since TREN is 80 times less expensive than Me6-TREN. The high chain-end fidelity of resulting polymer was experimentally verified by thiol-Michael addition reaction at the α-Br chain end and subsequent chain extension with methyl acrylate.
2019, 37(11): 1142-1151
doi: 10.1007/s10118-019-2267-3
Abstract:
Although synthetic rubbers show continuously improved mechanical properties, natural rubber (NR) remains irreplaceable in the rubber family due to its superior mechanical properties. A mainstream viewpoint regarding the superiority of NR is that NR possesses a natural network formed by linking the poly(cis-1,4-isoprene) chain terminals to protein and phospholipid aggregates; after vulcanization, the natural network additionally contributes to rubber mechanics by both increasing the network density and promoting the strain-induced crystallization (SIC) behavior. However, the reason why the natural network promotes SIC is still unclear; in particular, only using the increased network density cannot explain our finding that the NR shows smaller onset strain of SIC than Gel (the gel component of NR with higher network density) and even vulcanized NR. Herein, we point out that the inhomogeneous chain deformation is the alternative reason why SIC of NR takes place at smaller strain than that of Gel. More specifically, although the natural network is homogenous on the subchain length scale based on the proton double-quantum NMR results, it is essentially inhomogeneous on mesoscale (100 nm), as revealed by the small angle X-ray scattering analysis. This inhomogeneous network also leads to the mesoscale deformation inhomogeneity, as detected by the orientation of stearic acid (SA) probe, thus resulting in the smaller onset strain of SIC of NR. Based on the experimental results, a mesoscale model is proposed to qualitatively describe the crucial roles of inhomogeneous structure and deformation of natural network in NR’s mechanical properties, providing a clue from nature to guide the development of high-performance rubbers with controlled structures at mesoscale.
Although synthetic rubbers show continuously improved mechanical properties, natural rubber (NR) remains irreplaceable in the rubber family due to its superior mechanical properties. A mainstream viewpoint regarding the superiority of NR is that NR possesses a natural network formed by linking the poly(cis-1,4-isoprene) chain terminals to protein and phospholipid aggregates; after vulcanization, the natural network additionally contributes to rubber mechanics by both increasing the network density and promoting the strain-induced crystallization (SIC) behavior. However, the reason why the natural network promotes SIC is still unclear; in particular, only using the increased network density cannot explain our finding that the NR shows smaller onset strain of SIC than Gel (the gel component of NR with higher network density) and even vulcanized NR. Herein, we point out that the inhomogeneous chain deformation is the alternative reason why SIC of NR takes place at smaller strain than that of Gel. More specifically, although the natural network is homogenous on the subchain length scale based on the proton double-quantum NMR results, it is essentially inhomogeneous on mesoscale (100 nm), as revealed by the small angle X-ray scattering analysis. This inhomogeneous network also leads to the mesoscale deformation inhomogeneity, as detected by the orientation of stearic acid (SA) probe, thus resulting in the smaller onset strain of SIC of NR. Based on the experimental results, a mesoscale model is proposed to qualitatively describe the crucial roles of inhomogeneous structure and deformation of natural network in NR’s mechanical properties, providing a clue from nature to guide the development of high-performance rubbers with controlled structures at mesoscale.
2019, 37(11): 1152-1161
doi: 10.1007/s10118-019-2283-3
Abstract:
Thermoplastic poly(ether-ester-urethane)s were synthesized from poly(L-lactide) diols (PLLA diols), polytetrahydrofuran diol (PTMG diols), 4,4′-dicyclohexylmethane diisocyanate (HMDI), and 1,4-butanediol (BDO) by a two-step reaction, and the morphology and property of the resultant TPU could be adjusted by varying the PLLA contents. The soft segment was composed of PLLA and PTMG diols. By controlling the percentage of PLLA in the soft segment, the glass transition temperature and mechanical properties of the polyurethanes could be regulated. Based on the FTIR spectrum, we found that two kinds of hydrogen bonding existed individually in soft matrix and hard domain. The hydrogen bonding in soft matrix was unstable, which could be destroyed during elongation. With in situ stretching WAXS and SAXS experiments, we found that the PLLA crystal was destroyed and the PLLA domain oriented along the stretch direction. Finally, we proposed a schematic model to illustrate the microstructures of these elastomers before and after stretch.
Thermoplastic poly(ether-ester-urethane)s were synthesized from poly(L-lactide) diols (PLLA diols), polytetrahydrofuran diol (PTMG diols), 4,4′-dicyclohexylmethane diisocyanate (HMDI), and 1,4-butanediol (BDO) by a two-step reaction, and the morphology and property of the resultant TPU could be adjusted by varying the PLLA contents. The soft segment was composed of PLLA and PTMG diols. By controlling the percentage of PLLA in the soft segment, the glass transition temperature and mechanical properties of the polyurethanes could be regulated. Based on the FTIR spectrum, we found that two kinds of hydrogen bonding existed individually in soft matrix and hard domain. The hydrogen bonding in soft matrix was unstable, which could be destroyed during elongation. With in situ stretching WAXS and SAXS experiments, we found that the PLLA crystal was destroyed and the PLLA domain oriented along the stretch direction. Finally, we proposed a schematic model to illustrate the microstructures of these elastomers before and after stretch.
2019, 37(11): 1162-1168
doi: 10.1007/s10118-019-2258-4
Abstract:
Amphiphilic diblock copolymers self-assemble into a variety of micellar structures with diverse shapes in selective solvents. Here, we study the concentration and temperature dependence of the packing structure of spherical micelles of a polyisoprene-b-poly(2-vinylpyridine) (PI-b-P2VP) diblock copolymer in toluene using synchrotron radiation small angle X-ray scattering (SR-SAXS) and atomic force microscopy (AFM) techniques. Randomly packed spherical micelles are detected in dilute solutions, while in concentrated solutions, face-centered cubic (FCC), body-centered cubic (BCC) mixed crystal structures, and pure BCC crystal structures are observed with an increase in concentration. In situ SAXS experiments on the FCC/BCC mixed crystal structures reveal a novel FCC/BCC → BCC → Disorder → BCC phase behavior during the thermal annealing process. These results demonstrated that the BCC phase is apparently more stable than the FCC phase in the current sphere-packing system and FCC/BCC is a metastable state. The incompatibility of the PI and P2VP blocks decreases at a higher temperature and renders the variation of domain spacing.
Amphiphilic diblock copolymers self-assemble into a variety of micellar structures with diverse shapes in selective solvents. Here, we study the concentration and temperature dependence of the packing structure of spherical micelles of a polyisoprene-b-poly(2-vinylpyridine) (PI-b-P2VP) diblock copolymer in toluene using synchrotron radiation small angle X-ray scattering (SR-SAXS) and atomic force microscopy (AFM) techniques. Randomly packed spherical micelles are detected in dilute solutions, while in concentrated solutions, face-centered cubic (FCC), body-centered cubic (BCC) mixed crystal structures, and pure BCC crystal structures are observed with an increase in concentration. In situ SAXS experiments on the FCC/BCC mixed crystal structures reveal a novel FCC/BCC → BCC → Disorder → BCC phase behavior during the thermal annealing process. These results demonstrated that the BCC phase is apparently more stable than the FCC phase in the current sphere-packing system and FCC/BCC is a metastable state. The incompatibility of the PI and P2VP blocks decreases at a higher temperature and renders the variation of domain spacing.
2019, 37(11): 1169-1175
doi: 10.1007/S10118-019-2269-1
Abstract:
The blends of novel branched poly(ethylene succinate) (b-PES) and poly(vinyl phenol) (PVPh) were prepared via a solution and casting method. The miscibility, melting behavior, spherulitic morphology and growth, and crystal structure of b-PES/PVPh blends were investigated in detail. PVPh was miscible with b-PES over the whole compositions as evidenced by the single composition dependent glass transition temperature. Double melting behavior occurred in neat b-PES and b-PES/PVPh 85/15 blend after isothermal melt crystallization, which may be explained by the melting, recrystallization, and remelting mechanism. In addition, the depression of equilibrium melting point of an 85/15 blend was also found, confirming again the miscibility between the two components. The addition of PVPh caused the decrease of nucleation density and crystal growth rates of b-PES spherulites in the blend. The crystal structure of b-PES was unchanged before and after blending; moreover, the crystallinity of b-PES decreased slightly in the blend.
The blends of novel branched poly(ethylene succinate) (b-PES) and poly(vinyl phenol) (PVPh) were prepared via a solution and casting method. The miscibility, melting behavior, spherulitic morphology and growth, and crystal structure of b-PES/PVPh blends were investigated in detail. PVPh was miscible with b-PES over the whole compositions as evidenced by the single composition dependent glass transition temperature. Double melting behavior occurred in neat b-PES and b-PES/PVPh 85/15 blend after isothermal melt crystallization, which may be explained by the melting, recrystallization, and remelting mechanism. In addition, the depression of equilibrium melting point of an 85/15 blend was also found, confirming again the miscibility between the two components. The addition of PVPh caused the decrease of nucleation density and crystal growth rates of b-PES spherulites in the blend. The crystal structure of b-PES was unchanged before and after blending; moreover, the crystallinity of b-PES decreased slightly in the blend.
2019, 37(11): 1176-1182
doi: 10.1007/s10118-019-2274-4
Abstract:
In this work, a unique model is proposed for predicting the tensile strength of binary polymer blends considering the effects of polymer/polymer interface and the morphological variation of the system. The modeling was performed based on the combination of analytical and artificial neural network (ANN) modeling methods. For the analytical part, Kolarik’s model was developed in accordance with the system requirements and ANN was simultaneously involved in order to interpret some effective model parameters using the tensile test result of an actual sample (e.g. the yield strength and thickness of the interface, etc.). Furthermore, the model accuracy was evaluated by comparing the tensile test results of differently prepared iPP/PA and PS/PMMA blend samples and also some other data from literature with the model predictions. It was revealed that the designed ANN perfectly elevates the capability of the analytical section in order to predict the tensile strength of binary polymer blends with different compositions (prediction error < 10%).
In this work, a unique model is proposed for predicting the tensile strength of binary polymer blends considering the effects of polymer/polymer interface and the morphological variation of the system. The modeling was performed based on the combination of analytical and artificial neural network (ANN) modeling methods. For the analytical part, Kolarik’s model was developed in accordance with the system requirements and ANN was simultaneously involved in order to interpret some effective model parameters using the tensile test result of an actual sample (e.g. the yield strength and thickness of the interface, etc.). Furthermore, the model accuracy was evaluated by comparing the tensile test results of differently prepared iPP/PA and PS/PMMA blend samples and also some other data from literature with the model predictions. It was revealed that the designed ANN perfectly elevates the capability of the analytical section in order to predict the tensile strength of binary polymer blends with different compositions (prediction error < 10%).
