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2011 Volume 29 Issue 2
2011, 29(2): 133-140
doi: 10.1007/s10118-011-1032-z
Abstract:
Functional polyacetylenes containing pyridinium side groups (PPyA-MX, X = Br and I) were successfully synthesized. Spectroscopic techniques such as 1H-NMR, 13C-NMR, and FTIR spectroscopy were used to characterize the structure of the obtained polymers. The characterization data were well consistent with the expected macromolecular structures. PPyA-MI had good solubility in polar organic solvents and low solubility in water, while PPyA-MBr had good solubility in both polar organic solvents and water.
Functional polyacetylenes containing pyridinium side groups (PPyA-MX, X = Br and I) were successfully synthesized. Spectroscopic techniques such as 1H-NMR, 13C-NMR, and FTIR spectroscopy were used to characterize the structure of the obtained polymers. The characterization data were well consistent with the expected macromolecular structures. PPyA-MI had good solubility in polar organic solvents and low solubility in water, while PPyA-MBr had good solubility in both polar organic solvents and water.
2011, 29(2): 141-148
doi: 10.1007/s10118-010-1003-9
Abstract:
Nanocomposites from nanoscale silica particles (NS), diglycidylether of bisphenol-A based epoxy (DGEBA), and 3,5-diamino-N-(4-(quinolin-8-yloxy) phenyl) benzamide (DQPB) as curing agent were obtained from direct blending of these materials. The effect of nanosilica (NS) particles as catalyst on the cure reaction of DGEBA/DQPB system was studied by using non-isothermal DSC technique. The activation energy (Ea) was obtained by using Kissinger and Ozawa equations. The Ea value of curing of DGEBA/DQPB/10% NS system showed a decrease of about 10 kJ/mol indicating the catalytic effect of NS particles on the cure reaction. The Ea values of thermal degradation of the cured samples of both systems were 148 kJ/mol and 160 kJ/mol, respectively. The addition of 10% of NS to the curing mixture did not have much effect on the initial decomposition temperature (Ti) but increased the char residues from 20% to 28% at 650C.
Nanocomposites from nanoscale silica particles (NS), diglycidylether of bisphenol-A based epoxy (DGEBA), and 3,5-diamino-N-(4-(quinolin-8-yloxy) phenyl) benzamide (DQPB) as curing agent were obtained from direct blending of these materials. The effect of nanosilica (NS) particles as catalyst on the cure reaction of DGEBA/DQPB system was studied by using non-isothermal DSC technique. The activation energy (Ea) was obtained by using Kissinger and Ozawa equations. The Ea value of curing of DGEBA/DQPB/10% NS system showed a decrease of about 10 kJ/mol indicating the catalytic effect of NS particles on the cure reaction. The Ea values of thermal degradation of the cured samples of both systems were 148 kJ/mol and 160 kJ/mol, respectively. The addition of 10% of NS to the curing mixture did not have much effect on the initial decomposition temperature (Ti) but increased the char residues from 20% to 28% at 650C.
2011, 29(2): 149-155
doi: 10.1007/s10118-010-1004-8
Abstract:
A series of new Schiff base polyamides (PAs) were synthesized by polycondensation of benzilbisthiosemicarbazone diamine (LH6) with different commercially available aliphatic and aromatic diacid chlorides. The monomer and all the PAs were characterized by FTIR, 1H-NMR, and elemental analysis. The prepared polyamides showed inherent viscosities in the range of 0.30-0.36 dL/g in DMF at 25C, indicating their moderate molecular weight. The PAs were completely soluble in aprotic polar solvents such as dimethylformamide (DMF), N-methylpyrolidone (NMP), tetrachloroethane (TCE), dimthylsulfoxide (DMSO) and also in H2SO4 and partially soluble in THF, acetone and chloroform at room temperature. Thermal analysis showed that these PAs were practically amorphous and exhibited 10% weight loss above 220C.
A series of new Schiff base polyamides (PAs) were synthesized by polycondensation of benzilbisthiosemicarbazone diamine (LH6) with different commercially available aliphatic and aromatic diacid chlorides. The monomer and all the PAs were characterized by FTIR, 1H-NMR, and elemental analysis. The prepared polyamides showed inherent viscosities in the range of 0.30-0.36 dL/g in DMF at 25C, indicating their moderate molecular weight. The PAs were completely soluble in aprotic polar solvents such as dimethylformamide (DMF), N-methylpyrolidone (NMP), tetrachloroethane (TCE), dimthylsulfoxide (DMSO) and also in H2SO4 and partially soluble in THF, acetone and chloroform at room temperature. Thermal analysis showed that these PAs were practically amorphous and exhibited 10% weight loss above 220C.
2011, 29(2): 157-163
doi: 10.1007/s10118-010-1008-4
Abstract:
Eucommia ulmoides gum (EU gum), known as gutta percha in Southeast Asia, is a natural polymer with double characteristics of rubber and plastic. In present paper, tand-T curve and hysteresis loss (HL) were chosen to characterize its damping property. The results indicated that its tand value would increase with rising of temperature when T 0C and form another damping peak at 40-80C besides Tg peak. This phenomenon resulted from meltage of crystals of EU gum could increase its damping property at ambient-high temperature. Its tand value even exceeded those of conventional damping rubbers, such as nitrile-butadiene rubber (NBR) and chlorinated isobutene-isoprene rubber (CIIR).
Eucommia ulmoides gum (EU gum), known as gutta percha in Southeast Asia, is a natural polymer with double characteristics of rubber and plastic. In present paper, tand-T curve and hysteresis loss (HL) were chosen to characterize its damping property. The results indicated that its tand value would increase with rising of temperature when T 0C and form another damping peak at 40-80C besides Tg peak. This phenomenon resulted from meltage of crystals of EU gum could increase its damping property at ambient-high temperature. Its tand value even exceeded those of conventional damping rubbers, such as nitrile-butadiene rubber (NBR) and chlorinated isobutene-isoprene rubber (CIIR).
2011, 29(2): 165-172
doi: 10.1007/s10118-010-1027-1
Abstract:
Cross-linked poly(diallyldimethylammonium chloride) and its derivative copolymers were synthesized and used as phase transfer catalyst in the nucleophilic substitution reaction especially halogen exchange reactions. In addition, the effect of hydrophilic-hydrophobic character of the polymers in the nucleophilic reactions was investigated.
Cross-linked poly(diallyldimethylammonium chloride) and its derivative copolymers were synthesized and used as phase transfer catalyst in the nucleophilic substitution reaction especially halogen exchange reactions. In addition, the effect of hydrophilic-hydrophobic character of the polymers in the nucleophilic reactions was investigated.
2011, 29(2): 173-179
doi: 10.1007/s10118-011-1024-z
Abstract:
Ultra-fine fibrous mats with magnolol entrapped have been prepared by electrospinning biodegradable copolymer poly(ethylene glycol) blocked poly(L-lactide). Drug entrapment was perfect which was confirmed by scanning electron microscopy and differential scanning calorimetry. According to in vitro drug release investigation by high performance liquid chromatography, it was found that fibers with 10%, 20% and 30% drug entrapped respect to polymer (mass ratio) presented dramatically different drug release behavior and degradation behavior under the effect of proteinase K. The reason may be that fibers with 10% drug entrapped was more easily affected by enzyme while, to some degree, magnolol in fibers with 20% and 30% entrapped prevented polymer from being degraded by enzyme.
Ultra-fine fibrous mats with magnolol entrapped have been prepared by electrospinning biodegradable copolymer poly(ethylene glycol) blocked poly(L-lactide). Drug entrapment was perfect which was confirmed by scanning electron microscopy and differential scanning calorimetry. According to in vitro drug release investigation by high performance liquid chromatography, it was found that fibers with 10%, 20% and 30% drug entrapped respect to polymer (mass ratio) presented dramatically different drug release behavior and degradation behavior under the effect of proteinase K. The reason may be that fibers with 10% drug entrapped was more easily affected by enzyme while, to some degree, magnolol in fibers with 20% and 30% entrapped prevented polymer from being degraded by enzyme.
2011, 29(2): 181-190
doi: 10.1007/s10118-010-1016-4
Abstract:
Inverse microemulsion system of cetyltrimethylammonium bromide (CTAB) molecules is utilized for virtually monodispersed and controlled growth of HClpolyaniline (PANI) nanoparticles at room temperature (ca. 300 K). The templated electroconductive polymer reveals lamellar crystalline structure under X-ray diffraction signifying marked sub-chain alignment of the polymerized nanoparticles. The nanostructured polymer has spherically symmetric morphology in a size range of 2.0 nm to 6.0 nm under electron microscope examination. Gel permeation chromatography gives polydispersity index of 1.02 for nanostructured polymer in agreement with the size monodispersity transpired by electron microscopy. The d.c. electrical conductivity sdc of PANI at room temperature is 10.11 S/cm whereas the variation of conductivity with temperature in the range 227303 K reveals that the conducting mechanism can be considered as three-dimensional variable-range-hopping (3D-VRH). UV-Vis spectrum indicates two broad absorption bands due to polaron formation that contributes to enhanced electrical conductivity of the polymer. The fundamental absorption edge in the polymer is formed by direct allowed transitions to the extent that the optical band gap value was found to be 2.35 eV. The crystalline nanostructure and homogeneous doping attained in the cationic template of amphiphile are argued as contributing factors to the enhanced conductivity of the polymer.
Inverse microemulsion system of cetyltrimethylammonium bromide (CTAB) molecules is utilized for virtually monodispersed and controlled growth of HClpolyaniline (PANI) nanoparticles at room temperature (ca. 300 K). The templated electroconductive polymer reveals lamellar crystalline structure under X-ray diffraction signifying marked sub-chain alignment of the polymerized nanoparticles. The nanostructured polymer has spherically symmetric morphology in a size range of 2.0 nm to 6.0 nm under electron microscope examination. Gel permeation chromatography gives polydispersity index of 1.02 for nanostructured polymer in agreement with the size monodispersity transpired by electron microscopy. The d.c. electrical conductivity sdc of PANI at room temperature is 10.11 S/cm whereas the variation of conductivity with temperature in the range 227303 K reveals that the conducting mechanism can be considered as three-dimensional variable-range-hopping (3D-VRH). UV-Vis spectrum indicates two broad absorption bands due to polaron formation that contributes to enhanced electrical conductivity of the polymer. The fundamental absorption edge in the polymer is formed by direct allowed transitions to the extent that the optical band gap value was found to be 2.35 eV. The crystalline nanostructure and homogeneous doping attained in the cationic template of amphiphile are argued as contributing factors to the enhanced conductivity of the polymer.
2011, 29(2): 191-196
doi: 10.1007/s10118-010-1017-3
Abstract:
SBR compounds including the N-isopropyl-N'-phenyl-p-phenylenediamine-modified clay (organoclay) were prepared. Effects of modified clay and antioxidant (IPPD) contents on mechanical and rheological properties of SBR composites were studied. FTIR results confirmed that the clay was chemically modified by IPPD and changed into an organoclay. X-ray diffraction (XRD) results confirmed the increase in interlayer distance of the clay due to the insertion of IPPD. Rheological and cure characteristics of SBR compounds were determined using RPA (Rubber Process Analyzer) and rheometer. Scorch time and cure time of SBR compounds decreased with introduction of the organoclay. Mechanical properties and heat aging resistance of the SBR composites were improved significantly by incorporation of the organoclay.
SBR compounds including the N-isopropyl-N'-phenyl-p-phenylenediamine-modified clay (organoclay) were prepared. Effects of modified clay and antioxidant (IPPD) contents on mechanical and rheological properties of SBR composites were studied. FTIR results confirmed that the clay was chemically modified by IPPD and changed into an organoclay. X-ray diffraction (XRD) results confirmed the increase in interlayer distance of the clay due to the insertion of IPPD. Rheological and cure characteristics of SBR compounds were determined using RPA (Rubber Process Analyzer) and rheometer. Scorch time and cure time of SBR compounds decreased with introduction of the organoclay. Mechanical properties and heat aging resistance of the SBR composites were improved significantly by incorporation of the organoclay.
2011, 29(2): 197-202
doi: 10.1007/s10118-010-1013-7
Abstract:
The ring-opening polymerization of 5-methyl-1,3-dioxolane-2,4-dione (lactic O-carboxylic anhydride, LacOCA) using organometallic complexes, including Co(III) complexes with Schiff base ligands, Tin(II) alphatates and Al(III) complexes with Schiff base ligands, was explored. The polymerization was carried out by treatment of the organometallic complexes with LacOCA in toluene under mild conditions. The corresponding poly(lactic acid) was characterized by spectroscopy and thermal analyses, which revealed insight into the structure of the effective catalyst for the polymerization of LacOCA.
The ring-opening polymerization of 5-methyl-1,3-dioxolane-2,4-dione (lactic O-carboxylic anhydride, LacOCA) using organometallic complexes, including Co(III) complexes with Schiff base ligands, Tin(II) alphatates and Al(III) complexes with Schiff base ligands, was explored. The polymerization was carried out by treatment of the organometallic complexes with LacOCA in toluene under mild conditions. The corresponding poly(lactic acid) was characterized by spectroscopy and thermal analyses, which revealed insight into the structure of the effective catalyst for the polymerization of LacOCA.
2011, 29(2): 203-213
doi: 10.1007/s10118-010-1010-x
Abstract:
The response factors of refractive index (RI) and ultraviolet (UV) detectors of size exclusion chromatography (SEC) defined as the ratio of area of output signal to the mass of injected sample are studied and analyzed by using five narrowly distributed polystyrene (PS) standard samples with known molar masses. It is found that the individual response factor for a given sample varies with the concentration of the injected solution within a limited range bounded by an upper and a lower limiting response factor values. This variation reveals the conformational change of the polymer chains with the concentration of the injected solution. The dynamic contact concentrations cs of the PS samples derived from the response factor data are in good accordance with those reported earlier by other methods. The physical meanings of the signals of the two detectors are further analyzed and theoretically formulated. The solvation of the polymer chain and the conformation changes play an important role in these detecting systems. Both of the solvation number of the structural repeating unit and the extra embedded solvent due to cluster forming in higher concentrations could be deduced from the variation of response factor with the concentration of the injected solution.
The response factors of refractive index (RI) and ultraviolet (UV) detectors of size exclusion chromatography (SEC) defined as the ratio of area of output signal to the mass of injected sample are studied and analyzed by using five narrowly distributed polystyrene (PS) standard samples with known molar masses. It is found that the individual response factor for a given sample varies with the concentration of the injected solution within a limited range bounded by an upper and a lower limiting response factor values. This variation reveals the conformational change of the polymer chains with the concentration of the injected solution. The dynamic contact concentrations cs of the PS samples derived from the response factor data are in good accordance with those reported earlier by other methods. The physical meanings of the signals of the two detectors are further analyzed and theoretically formulated. The solvation of the polymer chain and the conformation changes play an important role in these detecting systems. Both of the solvation number of the structural repeating unit and the extra embedded solvent due to cluster forming in higher concentrations could be deduced from the variation of response factor with the concentration of the injected solution.
2011, 29(2): 215-244
doi: 10.1007/s10118-010-1015-5
Abstract:
Biodegradable porous nanocomposite scaffolds of poly(lactide-co-glycolide) (PLGA) and L-lactic acid(LAc) oligomer surface-grafted hydroxyapatite nanoparticles (op-HA) with a honeycomb monolith structure were fabricated with the single-phase solution freeze-drying method. The effects of different freezing temperatures on the properties of the scaffolds, such as microstructures, compressive strength, cell penetration and cell proliferation were studied. The highly porous and well interconnected scaffolds with a tunable pore structure were obtained. The effect of different freezing temperature (4C, -20C, -80C and -196C) was investigated in relation to the scaffold morphology, the porosity varied from 91.2% to 83.0% and the average pore diameter varied from (167.2 62.6) m to (11.9 4.2) m while the s10 increased significantly. The cell proliferation were decreased and associated with the above-mentioned properties. Uniform distribution of op-HA particles and homogeneous roughness of pore wall surfaces were found in the 4C frozen scaffold. The 4C frozen scaffold exhibited better cell penetration and increased cell proliferation because of its larger pore size, higher porosity and interconnection. The microstructures described here provide a new approach for the design and fabrication of op-HA/PLGA based scaffold materials with potentially broad applicability for replacement of bone defects.
Biodegradable porous nanocomposite scaffolds of poly(lactide-co-glycolide) (PLGA) and L-lactic acid(LAc) oligomer surface-grafted hydroxyapatite nanoparticles (op-HA) with a honeycomb monolith structure were fabricated with the single-phase solution freeze-drying method. The effects of different freezing temperatures on the properties of the scaffolds, such as microstructures, compressive strength, cell penetration and cell proliferation were studied. The highly porous and well interconnected scaffolds with a tunable pore structure were obtained. The effect of different freezing temperature (4C, -20C, -80C and -196C) was investigated in relation to the scaffold morphology, the porosity varied from 91.2% to 83.0% and the average pore diameter varied from (167.2 62.6) m to (11.9 4.2) m while the s10 increased significantly. The cell proliferation were decreased and associated with the above-mentioned properties. Uniform distribution of op-HA particles and homogeneous roughness of pore wall surfaces were found in the 4C frozen scaffold. The 4C frozen scaffold exhibited better cell penetration and increased cell proliferation because of its larger pore size, higher porosity and interconnection. The microstructures described here provide a new approach for the design and fabrication of op-HA/PLGA based scaffold materials with potentially broad applicability for replacement of bone defects.
2011, 29(2): 225-231
doi: 10.1007/s10118-011-1029-7
Abstract:
A new approach was developed to prepare high-performance isobutylene-isoprene rubber/swollen organoclay nanocomposites by shear mixing. Compared with traditional melt compounding method, better dispersion of nanoclay layers in rubber matrix was verified through transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nanocomposites also exhibit significantly improved mechanical properties and gas barrier property. As a mechanism, the molecules of organic swelling agent play a vital role in accelerating the diffusion and intercalation of the matrix molecules.
A new approach was developed to prepare high-performance isobutylene-isoprene rubber/swollen organoclay nanocomposites by shear mixing. Compared with traditional melt compounding method, better dispersion of nanoclay layers in rubber matrix was verified through transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nanocomposites also exhibit significantly improved mechanical properties and gas barrier property. As a mechanism, the molecules of organic swelling agent play a vital role in accelerating the diffusion and intercalation of the matrix molecules.
2011, 29(2): 233-240
Abstract:
The poly(lactide-co-glycolide) (PLGA) sponge fabricated by a gelatin porogen leaching method was filled with fibrin gel to obtain a hybrid scaffold for chondrocytes culture in vitro. The fibrin gel evenly distributed in the hybrid scaffold with visible fibrinogen fibers after drying. In vitro culture it was found that in the hybrid scaffold the chondrocytes distributed more evenly and kept a round morphology as that in the normal cartilage. Although the chondrocytes seeded in the control PLGA sponges showed similar proliferation behavior with that in the hybrid scaffolds, they were remarkably elongated, forming a fibroblast-like morphology. Moreover, a larger amount of glycosaminoglycans was secreted in the hybrid scaffolds than that in the PLGA sponges after in vitro culture of chondrocytes for 4 weeks. The results suggest that the fibrin/PLGA hybrid scaffold may be favorably applied for cartilage tissue engineering.
The poly(lactide-co-glycolide) (PLGA) sponge fabricated by a gelatin porogen leaching method was filled with fibrin gel to obtain a hybrid scaffold for chondrocytes culture in vitro. The fibrin gel evenly distributed in the hybrid scaffold with visible fibrinogen fibers after drying. In vitro culture it was found that in the hybrid scaffold the chondrocytes distributed more evenly and kept a round morphology as that in the normal cartilage. Although the chondrocytes seeded in the control PLGA sponges showed similar proliferation behavior with that in the hybrid scaffolds, they were remarkably elongated, forming a fibroblast-like morphology. Moreover, a larger amount of glycosaminoglycans was secreted in the hybrid scaffolds than that in the PLGA sponges after in vitro culture of chondrocytes for 4 weeks. The results suggest that the fibrin/PLGA hybrid scaffold may be favorably applied for cartilage tissue engineering.
2011, 29(2): 241-250
doi: 10.1007/s10118-011-1030-1
Abstract:
The amphiphilic multiarm copolymers were synthesized through the modification of commercially available hyperbranched polyesters (Boltorn H40) with N--carbobenzoxy-L-Lysine N-carboxyanhydride (ZLys-NCA). After being condensed with N-Boc-phenylalanine (Boc-NPhe) and deprotected the Boc-groups in trifluoroacetic acid (TFA), the original terminal hydroxyl groups were transformed into the amino groups and then initiated the ring-opening polymerization of ZLys-NCA. The hydrophilic poly(L-lysine) was grafted to the surface of Boltorn H40 successfully after the protecting benzyl groups were removed by the HBr solution in glacial acetic acid (33 wt%). The resulting multiarm copolymers were characterized by the 1H-NMR, GPC and FTIR. The arm length calculated by NMR and GPC analysis was about 3 and 13 lysine-units for H40-Phe-PLys1 and H40-Phe-PLys2 respectively. Due to the amphiphilic molecular structure, they displayed ability to self-assemble into spherical micelles in aqueous solution with the average diameter in the range from 70 nm to 250 nm. The CMC of H40-Phe-PLys1 and H40-Phe-PLys2 was 0.013 mg/mL and 0.028 mg/mL, respectively, indicating that H40-Phe-PLys1 with shorter arm length is easier to self-assemble than H40-Phe-PLys2 with longer arm length.
The amphiphilic multiarm copolymers were synthesized through the modification of commercially available hyperbranched polyesters (Boltorn H40) with N--carbobenzoxy-L-Lysine N-carboxyanhydride (ZLys-NCA). After being condensed with N-Boc-phenylalanine (Boc-NPhe) and deprotected the Boc-groups in trifluoroacetic acid (TFA), the original terminal hydroxyl groups were transformed into the amino groups and then initiated the ring-opening polymerization of ZLys-NCA. The hydrophilic poly(L-lysine) was grafted to the surface of Boltorn H40 successfully after the protecting benzyl groups were removed by the HBr solution in glacial acetic acid (33 wt%). The resulting multiarm copolymers were characterized by the 1H-NMR, GPC and FTIR. The arm length calculated by NMR and GPC analysis was about 3 and 13 lysine-units for H40-Phe-PLys1 and H40-Phe-PLys2 respectively. Due to the amphiphilic molecular structure, they displayed ability to self-assemble into spherical micelles in aqueous solution with the average diameter in the range from 70 nm to 250 nm. The CMC of H40-Phe-PLys1 and H40-Phe-PLys2 was 0.013 mg/mL and 0.028 mg/mL, respectively, indicating that H40-Phe-PLys1 with shorter arm length is easier to self-assemble than H40-Phe-PLys2 with longer arm length.
2011, 29(2): 251-258
doi: 10.1007/s10118-010-1014-6
Abstract:
The early stage of polymer crystallization may be viewed as physical gelation process, i.e., the phase transition of polymer from liquid to solid. Determination of the gel point is of significance in polymer processing. In this work, the gelation behavior of poly(butylene succinate) (PBS) at different temperatures has been investigated by rheological method. It was found that during the isothermal crystallization process of PBS, both the storage modulus (G) and the loss modulus (G) increase with time, and the rheological response of the system varies from viscous-dominated (G G) to elastic-dominated (G G), meaning the phase transition from liquid to solid. The physical gel point was determined by the intersection point of loss tangent curves measured under different frequencies. The gel time (tc) for PBS was found to increase with increasing crystallization temperature. The relative crystallinity of PBS at the gel point is very low (2.5%-8.5%) and increases with increasing the crystallization temperature. The low crystallinity of PBS at the gel point suggests that only a few junctions are necessary to form a spanning network, indicating that the network is loosely connected, in another word, the critical gel is soft. Due to the elevated crystallinity at gel point under higher crystallization temperature, the gel strength Sg increases, while the relaxation exponent n decreases with increasing the crystallization temperature. These experimental results suggest that rheological method is an effective tool for verifying the gel point of biodegradable semi-crystalline polymers.
The early stage of polymer crystallization may be viewed as physical gelation process, i.e., the phase transition of polymer from liquid to solid. Determination of the gel point is of significance in polymer processing. In this work, the gelation behavior of poly(butylene succinate) (PBS) at different temperatures has been investigated by rheological method. It was found that during the isothermal crystallization process of PBS, both the storage modulus (G) and the loss modulus (G) increase with time, and the rheological response of the system varies from viscous-dominated (G G) to elastic-dominated (G G), meaning the phase transition from liquid to solid. The physical gel point was determined by the intersection point of loss tangent curves measured under different frequencies. The gel time (tc) for PBS was found to increase with increasing crystallization temperature. The relative crystallinity of PBS at the gel point is very low (2.5%-8.5%) and increases with increasing the crystallization temperature. The low crystallinity of PBS at the gel point suggests that only a few junctions are necessary to form a spanning network, indicating that the network is loosely connected, in another word, the critical gel is soft. Due to the elevated crystallinity at gel point under higher crystallization temperature, the gel strength Sg increases, while the relaxation exponent n decreases with increasing the crystallization temperature. These experimental results suggest that rheological method is an effective tool for verifying the gel point of biodegradable semi-crystalline polymers.
2011, 29(2): 259-266
doi: 10.1007/s10118-010-1009-3
Abstract:
Polyurethanes (PU) were prepared using toluene diisocyanate, polypropylene glycol, ethylene glycol, dimethylolpropionic acid and triethylamine, and a siloxane modified PU (PSU) was obtained through reaction of the PU prepolymers with bis(3-(1-methoxy-2-hydroxypropoxy)propyl) terminated polysiloxanes (PMTS) of different molecular weight, specifically designed for this purpose. Results showed that, with increases in molecular weight of PMTS and its content, viscosity of the final PSU latexes decreased; phase separation of the incorporated PMTS in PSU films increased; the average particle sizes of the latexes varied between 110 nm and 330 nm, and the surface tension in the final latexes was relatively constant regardless of PMTS amount and its molecular weight. It was likely that copolymerized polysiloxanes had trend to enrich on top of the film when PMTS molecular weight was around 2000 and its content above 5 wt%. In general, PMTS modified polyurethane films showed higher performance than those from unmodified waterborne polyurethane latexes.
Polyurethanes (PU) were prepared using toluene diisocyanate, polypropylene glycol, ethylene glycol, dimethylolpropionic acid and triethylamine, and a siloxane modified PU (PSU) was obtained through reaction of the PU prepolymers with bis(3-(1-methoxy-2-hydroxypropoxy)propyl) terminated polysiloxanes (PMTS) of different molecular weight, specifically designed for this purpose. Results showed that, with increases in molecular weight of PMTS and its content, viscosity of the final PSU latexes decreased; phase separation of the incorporated PMTS in PSU films increased; the average particle sizes of the latexes varied between 110 nm and 330 nm, and the surface tension in the final latexes was relatively constant regardless of PMTS amount and its molecular weight. It was likely that copolymerized polysiloxanes had trend to enrich on top of the film when PMTS molecular weight was around 2000 and its content above 5 wt%. In general, PMTS modified polyurethane films showed higher performance than those from unmodified waterborne polyurethane latexes.
2011, 29(2): 267-273
doi: 10.1007/s10118-010-1025-3
Abstract:
Monodispersed microspheres with polystyrene as the core and poly(acrylamide-co-N-acryloxysuccinimide) as the shell were synthesized by a two-step surfactant-free emulsion copolymerization. The core-shell morphology of the microspheres was shown by scanning electron microscopy and transmission electron microscopy. Rabbit immunoglobulin G (as antigen) was covalently coupled onto the microspheres by the reaction between succinimide-activated ester groups on the shell of the microspheres and amino groups of the antigen molecules. The size of particles was characterized by dynamic light scattering technique and was found to vary upon bioconjugation and interaction with proteins. The binding process was shown to be specific to goat anti-rabbit immunoglobulin G (as antibody) and reversible upon the addition of free antigen into the system.
Monodispersed microspheres with polystyrene as the core and poly(acrylamide-co-N-acryloxysuccinimide) as the shell were synthesized by a two-step surfactant-free emulsion copolymerization. The core-shell morphology of the microspheres was shown by scanning electron microscopy and transmission electron microscopy. Rabbit immunoglobulin G (as antigen) was covalently coupled onto the microspheres by the reaction between succinimide-activated ester groups on the shell of the microspheres and amino groups of the antigen molecules. The size of particles was characterized by dynamic light scattering technique and was found to vary upon bioconjugation and interaction with proteins. The binding process was shown to be specific to goat anti-rabbit immunoglobulin G (as antibody) and reversible upon the addition of free antigen into the system.
