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2018 Volume 36 Issue 9
2018, 36(9):
Abstract:
2018, 36(9): 999-1010
doi: 10.1007/s10118-018-2124-9
Abstract:
Dendrimers are macromolecules characterized by high controlled size, shape and architecture, presence of inner cavities able to accommodate small molecules and many peripheral functional groups to bind target entities. They are of eminent interest for biomedical applications, including gene transfection, tissue engineering, imaging, and drug delivery. The well-known pharmacological activities of ursolic and oleanolic acids are limited by their small water solubility, non-specific cell distribution, low bioavailability, poor pharmacokinetics, and their direct administration could result in the release of thrombi. To overcome such problems, in this paper we described their physical incorporation inside amino acids-modified polyester-based dendrimers which made them highly water-soluble. IR, NMR, zeta potential, mean size of particles, buffer capacity and drug release profiles of prepared materials were reported. The achieved water-soluble complexes harmonize a polycationic character and a buffer capacity which presuppose efficient cell penetration and increased residence time with a biodegradable cell respectful scaffold, thus appearing as a promising team of not toxic prodrugs for safe administration of ursolic and oleanolic acids.
Dendrimers are macromolecules characterized by high controlled size, shape and architecture, presence of inner cavities able to accommodate small molecules and many peripheral functional groups to bind target entities. They are of eminent interest for biomedical applications, including gene transfection, tissue engineering, imaging, and drug delivery. The well-known pharmacological activities of ursolic and oleanolic acids are limited by their small water solubility, non-specific cell distribution, low bioavailability, poor pharmacokinetics, and their direct administration could result in the release of thrombi. To overcome such problems, in this paper we described their physical incorporation inside amino acids-modified polyester-based dendrimers which made them highly water-soluble. IR, NMR, zeta potential, mean size of particles, buffer capacity and drug release profiles of prepared materials were reported. The achieved water-soluble complexes harmonize a polycationic character and a buffer capacity which presuppose efficient cell penetration and increased residence time with a biodegradable cell respectful scaffold, thus appearing as a promising team of not toxic prodrugs for safe administration of ursolic and oleanolic acids.
2018, 36(9): 1011-1018
doi: 10.1007/s10118-018-2107-x
Abstract:
Thermo-responsive butyl acrylate/furfuryl methacrylate copolymer-based (PBF backbone) graft (co)polymers with dynamic covalent linkages between their backbones and side chains via the Diels-Alder reaction of furan/maleimide were synthesized. Atom transfer radical polymerization (ATRP) was used to synthesize graft copolymers with thermo-responsive transformation from graft copolymers to linear polymers with bimodal or wide MWD. The NMR measurements indicated that the Diels-Alder reaction and retro-Diels-Alder reaction occurred, depending on the change of the temperature, meaning that the side chains could be cleaved and reformed according to the variation of the temperature. GPC measurements demonstrated that the molecular weights of the polymers were thermo-responsive. Furthermore, three graft copolymers with various branching chains (PBF-g-PBA, PBF-g-P(BMA-co-MA) and PBF-g-PBMA) were compared to study the influence of compatibility between the backbone and the branching chain on the efficiency of Diels-Alder reaction after the cleavage of the DA linkage. The results showed that the ability of the side chains to come back to the main chain was strongly affected by the compatibility between the backbone and the side chains and the flexibility of the polymer chains.
Thermo-responsive butyl acrylate/furfuryl methacrylate copolymer-based (PBF backbone) graft (co)polymers with dynamic covalent linkages between their backbones and side chains via the Diels-Alder reaction of furan/maleimide were synthesized. Atom transfer radical polymerization (ATRP) was used to synthesize graft copolymers with thermo-responsive transformation from graft copolymers to linear polymers with bimodal or wide MWD. The NMR measurements indicated that the Diels-Alder reaction and retro-Diels-Alder reaction occurred, depending on the change of the temperature, meaning that the side chains could be cleaved and reformed according to the variation of the temperature. GPC measurements demonstrated that the molecular weights of the polymers were thermo-responsive. Furthermore, three graft copolymers with various branching chains (PBF-g-PBA, PBF-g-P(BMA-co-MA) and PBF-g-PBMA) were compared to study the influence of compatibility between the backbone and the branching chain on the efficiency of Diels-Alder reaction after the cleavage of the DA linkage. The results showed that the ability of the side chains to come back to the main chain was strongly affected by the compatibility between the backbone and the side chains and the flexibility of the polymer chains.
2018, 36(9): 1019-1026
doi: 10.1007/s10118-018-2116-9
Abstract:
Highly regioregular, head-to-tail coupled poly(3-octylesterthiophene) was synthesized by the Pd-catalysed oxidative C―H/C―H coupling polycondensation. The regioregularity of polymer products was confirmed by the 1H-NMR technique. Furthermore, the effects of various reaction factors including polymerization temperature, solvents and catalysts etc. on the yield, molecular weight and structural regioregularity of the resultant polymers were systematically studied. The optical, electrochemical and crystallization properties of the resultant P3OET with different HT regioregularities in solution and film state were studied by UV-Vis and fluorescent spectroscopy, cyclic voltammetry and X-ray diffraction (XRD), resepectively.
Highly regioregular, head-to-tail coupled poly(3-octylesterthiophene) was synthesized by the Pd-catalysed oxidative C―H/C―H coupling polycondensation. The regioregularity of polymer products was confirmed by the 1H-NMR technique. Furthermore, the effects of various reaction factors including polymerization temperature, solvents and catalysts etc. on the yield, molecular weight and structural regioregularity of the resultant polymers were systematically studied. The optical, electrochemical and crystallization properties of the resultant P3OET with different HT regioregularities in solution and film state were studied by UV-Vis and fluorescent spectroscopy, cyclic voltammetry and X-ray diffraction (XRD), resepectively.
2018, 36(9): 1027-1035
doi: 10.1007/s10118-018-2137-4
Abstract:
Ca/SBA-15 solid bases with different Ca/Si atomic ratios were prepared by a one-pot route and employed as catalysts for the production of poly(isosorbide carbonate) (PIC) from diphenyl carbonate and isosorbide via a transesterification polymerization process. The relationship between physicochemical properties and catalytic performance for Ca/SBA-15 in this melt process was investigated by means of various characterization techniques. It was found that basic site amount and strength were responsible for this transesterification process; the weak and medium basic sites inclined to promote polycondensation reaction. It was worth noting that strong basic sites could favor the decomposition of the resultant PIC, resulting in the decrease of weight-average molecular weight (Mw) and yield, and the sample with Ca/Si atomic ratio of 0.4 exhibited the best catalytic performance, giving PIC with Mw of 4.88 × 104 g/mol and Tg of 169 °C at the optimal conditions. This excellent activity can be ascribed to the presence of rich basic sites and specific basic strength on the surface of 0.4Ca/SBA-15.
Ca/SBA-15 solid bases with different Ca/Si atomic ratios were prepared by a one-pot route and employed as catalysts for the production of poly(isosorbide carbonate) (PIC) from diphenyl carbonate and isosorbide via a transesterification polymerization process. The relationship between physicochemical properties and catalytic performance for Ca/SBA-15 in this melt process was investigated by means of various characterization techniques. It was found that basic site amount and strength were responsible for this transesterification process; the weak and medium basic sites inclined to promote polycondensation reaction. It was worth noting that strong basic sites could favor the decomposition of the resultant PIC, resulting in the decrease of weight-average molecular weight (Mw) and yield, and the sample with Ca/Si atomic ratio of 0.4 exhibited the best catalytic performance, giving PIC with Mw of 4.88 × 104 g/mol and Tg of 169 °C at the optimal conditions. This excellent activity can be ascribed to the presence of rich basic sites and specific basic strength on the surface of 0.4Ca/SBA-15.
2018, 36(9): 1036-1042
doi: 10.1007/s10118-018-2109-8
Abstract:
Hydrogen-bonded polymer complex films with the thickness ranging from 50 nm to 2400 nm were prepared by layer-by-layer (LbL) assembly of poly(2-ethyl-2-oxazoline) (PEOX) and poly(acrylic acid) (PAA). The dewetting behavior of PEOX/PAA films under hydrothermal condition was investigated. It was found that the dewetting occurred at solid-liquid interface, and the typical morphologies such as holes, irregular cellular structure, and droplets were observed. Atomic force microscopy (AFM) revealed the initial rupture of the film. Microscopic Raman and infrared (IR) imaging demonstrated that the PEOX and PAA chains remained association during the dewetting process.
Hydrogen-bonded polymer complex films with the thickness ranging from 50 nm to 2400 nm were prepared by layer-by-layer (LbL) assembly of poly(2-ethyl-2-oxazoline) (PEOX) and poly(acrylic acid) (PAA). The dewetting behavior of PEOX/PAA films under hydrothermal condition was investigated. It was found that the dewetting occurred at solid-liquid interface, and the typical morphologies such as holes, irregular cellular structure, and droplets were observed. Atomic force microscopy (AFM) revealed the initial rupture of the film. Microscopic Raman and infrared (IR) imaging demonstrated that the PEOX and PAA chains remained association during the dewetting process.
2018, 36(9): 1043-1046
doi: 10.1007/s10118-018-2117-8
Abstract:
Silk reinforced silk-fibroin-based composites were prepared by embedding of silk textile into regenerated silk fibroin (RSF) matrix. The breaking stress and breaking strain of the composites were found 37.7 MPa and 71.1% respectively at (95 ± 5)% RH. Morphological analysis was carried out to observe fracture behavior of the samples. The in vitro biodegradation test showed that the composite degraded slowly and lost 70% weight at the end of 168 h. Moreover, compared with RSF pure film, the composite kept strength and toughness much longer time. In conclusion, this composite has the potential for more accurate cytology research and biomedical tests in the future.
Silk reinforced silk-fibroin-based composites were prepared by embedding of silk textile into regenerated silk fibroin (RSF) matrix. The breaking stress and breaking strain of the composites were found 37.7 MPa and 71.1% respectively at (95 ± 5)% RH. Morphological analysis was carried out to observe fracture behavior of the samples. The in vitro biodegradation test showed that the composite degraded slowly and lost 70% weight at the end of 168 h. Moreover, compared with RSF pure film, the composite kept strength and toughness much longer time. In conclusion, this composite has the potential for more accurate cytology research and biomedical tests in the future.
2018, 36(9): 1047-1054
doi: 10.1007/s10118-018-2100-4
Abstract:
The influence of the surface interaction on the mesoscopic structure of grafted polymers in good solvents has been examined. At high surface coverage, tethered polymers are in the brush state and the parabolic segment density profile is confirmed by self-consistent field theory (SCFT) calculations. It is found that this is a universal behavior for a whole range of surface interactions from complete repulsion to strong attraction. More interestingly, finite surface repulsion may lead to the maximum in the proximal layer of its segment density profile, which is significantly different from both the depletion layer of pure repulsion and the adsorbing layer of attraction. In addition to the brush state on both repulsive and attractive surfaces, three additional surface states were identified by analyzing the scaling behavior of the layer thickness of polymer brushes: the mushroom state on repulsive substrates, the dilute and the semidilute surface states on attractive substrates.
The influence of the surface interaction on the mesoscopic structure of grafted polymers in good solvents has been examined. At high surface coverage, tethered polymers are in the brush state and the parabolic segment density profile is confirmed by self-consistent field theory (SCFT) calculations. It is found that this is a universal behavior for a whole range of surface interactions from complete repulsion to strong attraction. More interestingly, finite surface repulsion may lead to the maximum in the proximal layer of its segment density profile, which is significantly different from both the depletion layer of pure repulsion and the adsorbing layer of attraction. In addition to the brush state on both repulsive and attractive surfaces, three additional surface states were identified by analyzing the scaling behavior of the layer thickness of polymer brushes: the mushroom state on repulsive substrates, the dilute and the semidilute surface states on attractive substrates.
2018, 36(9): 1055-1062
doi: 10.1007/s10118-018-2131-x
Abstract:
Although bioinspired sacrificial bonds have been demonstrated to be efficient in improving the mechanical properties of polymer materials, the effect of binding energy of a specific dynamic bond on the ultimate mechanical performance of a polymer network with dual-crosslink remains unclear. In this contribution, diamine and sulfur curing package are introduced simultaneously into a sulfonated cis-1,4-polyisoprene to create dually-crosslinked cis-1,4-polyisoprene network with sulfonate-aminium ionic bonds as the sacrificial bonds. Three diamines (primary, secondary and tertiary) with the same spacer between the two nitrogen atoms are used to create the ionic bonds with different binding energies. Although the binding energy of ionic bond does not affect the glass transition temperature of cis-1,4-polyisoprene (IR), it exerts definite influences on strain-induced crystallization and mechanical performance. The capabilities of diamine in dissipating energy, promoting strain-induced crystallization and enhancing the mechanical performance are in the same order of secondary diamine > primary diamine > tertiary diamine. The variations in mechanical performances are correlated to the binding energy of the ionic bond, which is determined by p Ka values.
Although bioinspired sacrificial bonds have been demonstrated to be efficient in improving the mechanical properties of polymer materials, the effect of binding energy of a specific dynamic bond on the ultimate mechanical performance of a polymer network with dual-crosslink remains unclear. In this contribution, diamine and sulfur curing package are introduced simultaneously into a sulfonated cis-1,4-polyisoprene to create dually-crosslinked cis-1,4-polyisoprene network with sulfonate-aminium ionic bonds as the sacrificial bonds. Three diamines (primary, secondary and tertiary) with the same spacer between the two nitrogen atoms are used to create the ionic bonds with different binding energies. Although the binding energy of ionic bond does not affect the glass transition temperature of cis-1,4-polyisoprene (IR), it exerts definite influences on strain-induced crystallization and mechanical performance. The capabilities of diamine in dissipating energy, promoting strain-induced crystallization and enhancing the mechanical performance are in the same order of secondary diamine > primary diamine > tertiary diamine. The variations in mechanical performances are correlated to the binding energy of the ionic bond, which is determined by p Ka values.
2018, 36(9): 1063-1069
doi: 10.1007/s10118-018-2112-0
Abstract:
Gelatin, a natural proteinous polymer, was used to co-electrospin with poly(butylene succinate) (PBS) in order to improve the mechanical properties of PBS membrane and facilitate its applications in biomedical field. The PBS/gelatin blend membranes have narrower distribution of fiber diameter and smoother surface than neat PBS membrane. The contact angles, water absorption rates and water uptakes of the PBS/gelatin blend membranes were measured, showing increased hydrophilicity. The interaction between PBS and gelatin was investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). The mechanical properties of PBS/gelatin blend membranes in both dry and wet states were evaluated by uniaxial tensile tests. In the dry state, the PBS/gelatin blend membrane containing 10% gelatin has a 3-times increase in tensile strength without any adverse effect on ductility because of the existence of interaction between the two blend components, little change in crystallinity of PBS, and possible interaction between any adjacent fibers; the tensile strength and elongation at break are even better in the wet state attributed to some gelatin on fiber surfaces, which act as a binder in the presence of water. The potential applications of PBS/gelatin blend membranes were demonstrated by successful immobilization of thrombin, a clinically-used hemostatic drug. The thrombin-loaded membrane could be used for rapid hemostasis.
Gelatin, a natural proteinous polymer, was used to co-electrospin with poly(butylene succinate) (PBS) in order to improve the mechanical properties of PBS membrane and facilitate its applications in biomedical field. The PBS/gelatin blend membranes have narrower distribution of fiber diameter and smoother surface than neat PBS membrane. The contact angles, water absorption rates and water uptakes of the PBS/gelatin blend membranes were measured, showing increased hydrophilicity. The interaction between PBS and gelatin was investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). The mechanical properties of PBS/gelatin blend membranes in both dry and wet states were evaluated by uniaxial tensile tests. In the dry state, the PBS/gelatin blend membrane containing 10% gelatin has a 3-times increase in tensile strength without any adverse effect on ductility because of the existence of interaction between the two blend components, little change in crystallinity of PBS, and possible interaction between any adjacent fibers; the tensile strength and elongation at break are even better in the wet state attributed to some gelatin on fiber surfaces, which act as a binder in the presence of water. The potential applications of PBS/gelatin blend membranes were demonstrated by successful immobilization of thrombin, a clinically-used hemostatic drug. The thrombin-loaded membrane could be used for rapid hemostasis.
2018, 36(9): 1070-1076
doi: 10.1007/s10118-018-2147-2
Abstract:
Isocyanate-treated graphite oxides (iGOs) were well-dispersed into the polystyrene (PS) thin films and formed a novel network structure. With control in fabrication, an iGOs-web layer was horizontally embedded near the surface of the films and thus formed a composite slightly doped by iGOs. This work demonstrated that the iGOs network can remarkably depress the dewetting process in the polymer matrix of the composite, while dewetting often leads to rupture of polymer films and is considered as a major practical limit in using polymeric materials above their glass transition temperatures (Tg). Via annealing the 50–120 nm thick composite and associated neat PS films at temperatures ranging from 35 °C to 70 °C aboveTg, surface morphology evolution of the films was monitored by atomic force microscopy (AFM). The iGOs-doped PS exhibited excellent thermal stability, i.e., the number of dewetting holes was greatly reduced and the long-term hole growth was fairly restricted. In contrast, the neat PS film showed serious surface fluctuation and a final rupture induced by ordinary dewetting. The method developed in this work may pave a road to reinforce thin polymer films and enhance their thermal stability, in order to meet requirements by technological advances.
Isocyanate-treated graphite oxides (iGOs) were well-dispersed into the polystyrene (PS) thin films and formed a novel network structure. With control in fabrication, an iGOs-web layer was horizontally embedded near the surface of the films and thus formed a composite slightly doped by iGOs. This work demonstrated that the iGOs network can remarkably depress the dewetting process in the polymer matrix of the composite, while dewetting often leads to rupture of polymer films and is considered as a major practical limit in using polymeric materials above their glass transition temperatures (Tg). Via annealing the 50–120 nm thick composite and associated neat PS films at temperatures ranging from 35 °C to 70 °C aboveTg, surface morphology evolution of the films was monitored by atomic force microscopy (AFM). The iGOs-doped PS exhibited excellent thermal stability, i.e., the number of dewetting holes was greatly reduced and the long-term hole growth was fairly restricted. In contrast, the neat PS film showed serious surface fluctuation and a final rupture induced by ordinary dewetting. The method developed in this work may pave a road to reinforce thin polymer films and enhance their thermal stability, in order to meet requirements by technological advances.
2018, 36(9): 1077-1083
doi: 10.1007/s10118-018-2125-8
Abstract:
In this study, a constitutive model based on microscopic physical mechanism of silicone rubber foams was established. A theoretical statistical model of rubber elasticity considering the effect of dangling chains was modified to build this model. When a strain amplification factor (X) was introduced, the theoretical model could fit the tensile stress-strain data of mono- and bi-modal foam matrix well (Adj. R-Square = 0.9989, 0.9983). Parameters related to the polymer network, namely, average molecular weight (Mc) and volume fraction (ϕ) of chain segments between adjacent cross-linking points (network strands), were calculated by probabilistic method from the number-average molecular weight (Mn), vinyl content (wVi) of the primary polysiloxanes and percent conversion (q) of vinyl groups. The primary and infinite strain amplification factors (X0, X∞) and decay exponent (z), introduced by X and related to the nanoparticles, were obtained by fitting. Inspired by the fact that the actual strain of matrix was lower than that of the foams’, we introduced another item, strain hysteresis item (H, related with the foam porosity and cell structure), into the statistical model as well. With the same above values of Mc, ϕ, X0 and X∞, the model could also fit the compressive stress-strain data of mono- and bi-modal foams well (Adj. R-Square = 0.9948, 0.9985). Interestingly, the strain hysteresis items of the mono- and bi-modal foams almost completely coincided under all experimental strains, which may be attributed to the almost equal porosity and similar cell structure of the two foams. This constitutive model may connect the macroscopic stress-strain behaviour to the parameters of microscopic molecular structures, promisingly providing a basis for the performance improvement and optimization of silicone rubber foams.
In this study, a constitutive model based on microscopic physical mechanism of silicone rubber foams was established. A theoretical statistical model of rubber elasticity considering the effect of dangling chains was modified to build this model. When a strain amplification factor (X) was introduced, the theoretical model could fit the tensile stress-strain data of mono- and bi-modal foam matrix well (Adj. R-Square = 0.9989, 0.9983). Parameters related to the polymer network, namely, average molecular weight (Mc) and volume fraction (ϕ) of chain segments between adjacent cross-linking points (network strands), were calculated by probabilistic method from the number-average molecular weight (Mn), vinyl content (wVi) of the primary polysiloxanes and percent conversion (q) of vinyl groups. The primary and infinite strain amplification factors (X0, X∞) and decay exponent (z), introduced by X and related to the nanoparticles, were obtained by fitting. Inspired by the fact that the actual strain of matrix was lower than that of the foams’, we introduced another item, strain hysteresis item (H, related with the foam porosity and cell structure), into the statistical model as well. With the same above values of Mc, ϕ, X0 and X∞, the model could also fit the compressive stress-strain data of mono- and bi-modal foams well (Adj. R-Square = 0.9948, 0.9985). Interestingly, the strain hysteresis items of the mono- and bi-modal foams almost completely coincided under all experimental strains, which may be attributed to the almost equal porosity and similar cell structure of the two foams. This constitutive model may connect the macroscopic stress-strain behaviour to the parameters of microscopic molecular structures, promisingly providing a basis for the performance improvement and optimization of silicone rubber foams.
2018, 36(9): 1084-1092
doi: 10.1007/s10118-018-2121-z
Abstract:
The effects of film thickness and composition ratio on the morphology evolution of polystyrene (PS)/poly(vinyl methyl ether) (PVME) blend thin films were investigated. Diverse morphology evolutions including droplet-matrix structure, hole emergence, bicontinuous structure formation, percolation-to-droplet transition could be observed under annealing in two-phase region, depending on film thickness and composition ratio. The mechanism for these morphology variations was related to the complex effects of phase separation, dewetting and preferential wetting. The comparison between the thickness of bottom PVME layer and the twice of gyration radius 2Rg(PVME) played a dominant role in morphology control. Only when the PS/PVME film had specific film thickness and compositional symmetry, phase separation and dewetting could happen in sequence.
The effects of film thickness and composition ratio on the morphology evolution of polystyrene (PS)/poly(vinyl methyl ether) (PVME) blend thin films were investigated. Diverse morphology evolutions including droplet-matrix structure, hole emergence, bicontinuous structure formation, percolation-to-droplet transition could be observed under annealing in two-phase region, depending on film thickness and composition ratio. The mechanism for these morphology variations was related to the complex effects of phase separation, dewetting and preferential wetting. The comparison between the thickness of bottom PVME layer and the twice of gyration radius 2Rg(PVME) played a dominant role in morphology control. Only when the PS/PVME film had specific film thickness and compositional symmetry, phase separation and dewetting could happen in sequence.
