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2013 Volume 31 Issue 12
2013, 31(12): 1599-1612
doi: 10.1007/s10118-013-1336-2
Abstract:
The simulation results on viscoelastic fluid flows in sudden expansion geometry with different expansion ratios are presented. Oldroyd-B, linear Phan-Thien-Tanner (L-PTT) and Finitely Extensible Nonlinear Elastic (FENE-P) based constitutive equations were applied in two-dimensional Cartesian coordinates. The governing equations in transient and fully developed regions were solved using open source software called OpenFOAM. The flow patterns, including velocity profiles, shear stresses and first normal stress differences in some horizontal and vertical sections are illustrated. In addition, effects of the fluid type, flow dynamics and expansion ratio on the flow and vortex patterns in transient and fully developed regions are presented and discussed. The presented results show that existences of vortices cause the inverse velocity and negative stresses in expansion regions of the channel which increase with increment of expansion ratio and Weissenberg number (We). Furthermore, some dead spaces can be observed at channel expansion regions close to the wall which are also increased. The results also show that at low We numbers all fluids show close behavior while at high We numbers the FENE-P fluid behavior shows high divergence from that of the two other fluids.
The simulation results on viscoelastic fluid flows in sudden expansion geometry with different expansion ratios are presented. Oldroyd-B, linear Phan-Thien-Tanner (L-PTT) and Finitely Extensible Nonlinear Elastic (FENE-P) based constitutive equations were applied in two-dimensional Cartesian coordinates. The governing equations in transient and fully developed regions were solved using open source software called OpenFOAM. The flow patterns, including velocity profiles, shear stresses and first normal stress differences in some horizontal and vertical sections are illustrated. In addition, effects of the fluid type, flow dynamics and expansion ratio on the flow and vortex patterns in transient and fully developed regions are presented and discussed. The presented results show that existences of vortices cause the inverse velocity and negative stresses in expansion regions of the channel which increase with increment of expansion ratio and Weissenberg number (We). Furthermore, some dead spaces can be observed at channel expansion regions close to the wall which are also increased. The results also show that at low We numbers all fluids show close behavior while at high We numbers the FENE-P fluid behavior shows high divergence from that of the two other fluids.
2013, 31(12): 1613-1622
doi: 10.1007/s10118-013-1348-y
Abstract:
Initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of acrylonitrile was first conducted at various ambient temperatures (30-45 ℃). The key to success is ascribed to the usage of an appropriate low temperature radical initiator (2,2'-azobis(2,4-dimethylvaleronitrile)) and a high reactivity catalytic system (CuBr2/Me6TREN). The molar ratio of Cu catalyst to AN as low as 1:20000 was used to prepare well-defined polyacrylonitrile with controlled molecular weight and a narrow polydispersity index range of 1.08-1.30, while the monomer conversion was up to ca. 98%. The apparent activation energy of the polymerization was calculated to be 128.45 kJ/mol, suggesting that the polymerization strongly depended on reaction temperature. The very high chain-end functionality of the resultant polymer was confirmed by 1H-NMR and GPC analyses as well as chain extension reaction.
Initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of acrylonitrile was first conducted at various ambient temperatures (30-45 ℃). The key to success is ascribed to the usage of an appropriate low temperature radical initiator (2,2'-azobis(2,4-dimethylvaleronitrile)) and a high reactivity catalytic system (CuBr2/Me6TREN). The molar ratio of Cu catalyst to AN as low as 1:20000 was used to prepare well-defined polyacrylonitrile with controlled molecular weight and a narrow polydispersity index range of 1.08-1.30, while the monomer conversion was up to ca. 98%. The apparent activation energy of the polymerization was calculated to be 128.45 kJ/mol, suggesting that the polymerization strongly depended on reaction temperature. The very high chain-end functionality of the resultant polymer was confirmed by 1H-NMR and GPC analyses as well as chain extension reaction.
2013, 31(12): 1623-1631
doi: 10.1007/s10118-013-1344-2
Abstract:
A new aromatic azo-polymer, poly(thiourea-azo-naphthyl) (PTAN), has been synthesized using 1-(5-thiocarbamoylaminonaphthyl)thiourea and diazonium salt solution of 2,6-diaminopyridine. PTAN was easily processable using polar solvents and had high molar mass 57103 g/mol. Electrically conducting, mechanically and thermally stable rubbery blends of poly(styrene-butadiene-styrene) (SBS) triblock copolymer and PTAN were produced by solution blending technique. FESEM of SBS/PTAN blends revealed nano-scale dispersion of the conducting filler showing good adhesion between the matrix and PTAN. Remarkable effects of azo-content on the conductivity of SBS-based blends have been observed. Accordingly, PTAN loading from 10 to 60 wt% increased the conductivity from 1.24 to 1.66 S/cm. Relationship between PTAN loading and thermal stability of the materials was also investigated. With increasing the PTAN content, 10% gravimetric loss was increased from 484 to 500 ℃, while glass transition was enhanced from 119 to 126 ℃. Thermal and conducting data of the blend showed better results relative to pure elastomer but were lower than those of the conducting filler. Similarly, the tensile strength (57.3562.33 MPa) of SBS/PTAN was improved relative to there of SBS. Fine balance of properties renders new materials fairly better than the existing elastomeric blends used in a number of applications.
A new aromatic azo-polymer, poly(thiourea-azo-naphthyl) (PTAN), has been synthesized using 1-(5-thiocarbamoylaminonaphthyl)thiourea and diazonium salt solution of 2,6-diaminopyridine. PTAN was easily processable using polar solvents and had high molar mass 57103 g/mol. Electrically conducting, mechanically and thermally stable rubbery blends of poly(styrene-butadiene-styrene) (SBS) triblock copolymer and PTAN were produced by solution blending technique. FESEM of SBS/PTAN blends revealed nano-scale dispersion of the conducting filler showing good adhesion between the matrix and PTAN. Remarkable effects of azo-content on the conductivity of SBS-based blends have been observed. Accordingly, PTAN loading from 10 to 60 wt% increased the conductivity from 1.24 to 1.66 S/cm. Relationship between PTAN loading and thermal stability of the materials was also investigated. With increasing the PTAN content, 10% gravimetric loss was increased from 484 to 500 ℃, while glass transition was enhanced from 119 to 126 ℃. Thermal and conducting data of the blend showed better results relative to pure elastomer but were lower than those of the conducting filler. Similarly, the tensile strength (57.3562.33 MPa) of SBS/PTAN was improved relative to there of SBS. Fine balance of properties renders new materials fairly better than the existing elastomeric blends used in a number of applications.
2013, 31(12): 1632-1646
doi: 10.1007/s10118-013-1361-1
Abstract:
Novel dyestuff polymers were successfully obtained through oxidative polymerization technique. The synthesized Schiff base and its polymer were soluble in alkaline aqueous medium and they have various colors in different solutions. Also, it can be said that the synthesized compounds are suitable as coloring agent (dyestuff) for textile applications. Fluorescence properties of the compounds were determined in DMF with different concentrations (mg/L). Poly-tris(4-aminophenyl)methanol (P-TAPM) has quite high emission and excitation intensity values. Optical and electrochemical band gaps of the polymers were lower than those of the monomers indicating the more conjugated structure of the polymers. The oxidized states of the novel dyestuff compounds were examined by cyclic voltammetry (CV) technique. The solid state conductivity measurements showed that the synthesized polymers were semiconductors when exposed to the iodine vapour their conductivities could be increased. P-TAPM had the highest undoped conductivity. Thermal characterizations of the synthesized compounds were carried out by TG-DTA and DSC methods.
Novel dyestuff polymers were successfully obtained through oxidative polymerization technique. The synthesized Schiff base and its polymer were soluble in alkaline aqueous medium and they have various colors in different solutions. Also, it can be said that the synthesized compounds are suitable as coloring agent (dyestuff) for textile applications. Fluorescence properties of the compounds were determined in DMF with different concentrations (mg/L). Poly-tris(4-aminophenyl)methanol (P-TAPM) has quite high emission and excitation intensity values. Optical and electrochemical band gaps of the polymers were lower than those of the monomers indicating the more conjugated structure of the polymers. The oxidized states of the novel dyestuff compounds were examined by cyclic voltammetry (CV) technique. The solid state conductivity measurements showed that the synthesized polymers were semiconductors when exposed to the iodine vapour their conductivities could be increased. P-TAPM had the highest undoped conductivity. Thermal characterizations of the synthesized compounds were carried out by TG-DTA and DSC methods.
2013, 31(12): 1647-1659
doi: 10.1007/s10118-013-1357-x
Abstract:
Copolymers of 1,3-butadiene and p-methylstyrene (p-MS) were synthesized via anionic polymerization. A benzophenone-potassium complex was added to tune the reactivity ratio of the two monomers, leading to random and gradient composition along the copolymer chain. The overall composition and microstructure could be controlled and well characterized by GPC and 1H-NMR. The p-MS was distributed from gradient to random with increasing the content of the benzophenone-potassium complex, and the 1,2-microstructure in the polybutadiene sequence increased at the same time. The hydrogenation of the copolymer of 1,3-butadiene and p-MS resulted in the corresponding saturated copolymer with well-defined structure and narrow molecular weight distribution.
Copolymers of 1,3-butadiene and p-methylstyrene (p-MS) were synthesized via anionic polymerization. A benzophenone-potassium complex was added to tune the reactivity ratio of the two monomers, leading to random and gradient composition along the copolymer chain. The overall composition and microstructure could be controlled and well characterized by GPC and 1H-NMR. The p-MS was distributed from gradient to random with increasing the content of the benzophenone-potassium complex, and the 1,2-microstructure in the polybutadiene sequence increased at the same time. The hydrogenation of the copolymer of 1,3-butadiene and p-MS resulted in the corresponding saturated copolymer with well-defined structure and narrow molecular weight distribution.
2013, 31(12): 1660-1669
doi: 10.1007/s10118-013-1362-0
Abstract:
A new polymeric reagent, cross-linked poly(4-vinylpyridine) supported azide ion, [P4-VP]N3, was introduced as polymeric reagents for efficient and regioselective conversion of epoxides to azidohydrins in the presence of cross-linked poly(4-vinylpyridine) supported sulfuric acid, [P4-VP]H2SO4, as a solid proton source and as catalyst under solvent-free conditions. The advantages of this polymeric reagent over some of those reported in the literature are easy work-up procedure and regeneration of the reagent.
A new polymeric reagent, cross-linked poly(4-vinylpyridine) supported azide ion, [P4-VP]N3, was introduced as polymeric reagents for efficient and regioselective conversion of epoxides to azidohydrins in the presence of cross-linked poly(4-vinylpyridine) supported sulfuric acid, [P4-VP]H2SO4, as a solid proton source and as catalyst under solvent-free conditions. The advantages of this polymeric reagent over some of those reported in the literature are easy work-up procedure and regeneration of the reagent.
2013, 31(12): 1670-1684
doi: 10.1007/s10118-013-1366-9
Abstract:
A graft copolymer of polyacrylonitrile (PAN) with sodium salt of partially carboxymethylated tamarind kernel powder (Na-PCMTKP,DS= 0.15) was synthesized by using ceric ammonium nitrate (CAN) as a redox initiator in an aqueous medium. The optimum reaction conditions for affording maximum percentage of grafting were established by successively varying reaction conditions such as concentrations of nitric acid, CAN, monomer (AN) as well as reaction time, temperature and amount of substrate. The influence of these reaction conditions on the grafting yields was discussed. The kinetic scheme of free radical graft copolymerization was proposed and the experimental results were found to agree very well with the proposed kinetic scheme. The graft copolymer (Na-PCMTKP-g-PAN, percentage of grafting G = 413.76% and percentage of grafting efficiency GE = 96.48%) sample synthesized under the established optimized reaction conditions was hydrolyzed by 0.7 molL-1 NaOH solution at 90-95 ℃ to yield the superabsorbent hydrogel, H-Na-PCMTKP-g-PAN. The swelling behavior of the hydrogel was studied by carrying out its absorbency measurements in low conductivity water, 0.15 molL-1 salt (NaCl, CaCl2 and AlCl3) solutions and simulated urine (SU) solution at different timings. FTIR, TGA and SEM techniques were used to characterize the products.
A graft copolymer of polyacrylonitrile (PAN) with sodium salt of partially carboxymethylated tamarind kernel powder (Na-PCMTKP,DS= 0.15) was synthesized by using ceric ammonium nitrate (CAN) as a redox initiator in an aqueous medium. The optimum reaction conditions for affording maximum percentage of grafting were established by successively varying reaction conditions such as concentrations of nitric acid, CAN, monomer (AN) as well as reaction time, temperature and amount of substrate. The influence of these reaction conditions on the grafting yields was discussed. The kinetic scheme of free radical graft copolymerization was proposed and the experimental results were found to agree very well with the proposed kinetic scheme. The graft copolymer (Na-PCMTKP-g-PAN, percentage of grafting G = 413.76% and percentage of grafting efficiency GE = 96.48%) sample synthesized under the established optimized reaction conditions was hydrolyzed by 0.7 molL-1 NaOH solution at 90-95 ℃ to yield the superabsorbent hydrogel, H-Na-PCMTKP-g-PAN. The swelling behavior of the hydrogel was studied by carrying out its absorbency measurements in low conductivity water, 0.15 molL-1 salt (NaCl, CaCl2 and AlCl3) solutions and simulated urine (SU) solution at different timings. FTIR, TGA and SEM techniques were used to characterize the products.
2013, 31(12): 1685-1696
doi: 10.1007/s10118-013-1364-y
Abstract:
In the present work, the blend of poly(butylene succinate) (PBS) and bisphenol A (BPA) was prepared by solution mixing, and the intermolecular interactions between the two components were characterized by a combination of nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The results showed that intermolecular hydrogen-bonding forms between the carbonyl group of PBS and phenol hydroxyl of BPA. With the increase of BPA content, more hydrogen bonds were formed. The effect of hydrogen bonding on the crystallization behavior of PBS was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results showed that the overall isothermal crystallization kinetics and the spherulite growth rate of PBS decrease with the increase of BPA content, while the PBS spherulite size increases with BPA content.
In the present work, the blend of poly(butylene succinate) (PBS) and bisphenol A (BPA) was prepared by solution mixing, and the intermolecular interactions between the two components were characterized by a combination of nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The results showed that intermolecular hydrogen-bonding forms between the carbonyl group of PBS and phenol hydroxyl of BPA. With the increase of BPA content, more hydrogen bonds were formed. The effect of hydrogen bonding on the crystallization behavior of PBS was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results showed that the overall isothermal crystallization kinetics and the spherulite growth rate of PBS decrease with the increase of BPA content, while the PBS spherulite size increases with BPA content.
2013, 31(12): 1697-1705
doi: 10.1007/s10118-013-1358-9
Abstract:
A series of biodegradable hydrogels based on dextran and poly(L-glutamic acid) were fabricated for effective vancomycin loading and release. The preparation of hydrogels was simply achieved by photo cross-linking of methacrylated dextran and poly(L-glutamic acid)-g-hydroxyethyl methacrylate (PGH) in the presence of photoinitiator I2959. The structures of hydrogels were characterized by FTIR and SEM. The swelling and enzymatic degradation behaviors of hydrogels were examined to be dependent on the poly(L-glutamic acid) content in the hydrogels. The higher content of poly(L-glutamic acid) in the gel, the higher swelling ratio and quicker degradation were observed. More interestingly, the hydrogel with higher PGH ratio showed higher vancomycin (VCM) loading content, which might be due to the electrostatic interaction between carboxylate groups in hydrogel and ammonium group of VCM. In vitro drug release from the VCM-loaded hydrogels in aqueous solution exhibited sustained release of VCM up to 72 h, while the in vitro antibacterial test based on the VCM-loaded hydrogel showed an efficient Methicillin-Resistant S. aureus (MRSA) inhibition extending out to 7 days. These results demonstrated that the biodegradable hydrogels which formed by in situ photo-cross linking would be promising as scaffolds or coatings for local antibacterial drug release in tissue engineering.
A series of biodegradable hydrogels based on dextran and poly(L-glutamic acid) were fabricated for effective vancomycin loading and release. The preparation of hydrogels was simply achieved by photo cross-linking of methacrylated dextran and poly(L-glutamic acid)-g-hydroxyethyl methacrylate (PGH) in the presence of photoinitiator I2959. The structures of hydrogels were characterized by FTIR and SEM. The swelling and enzymatic degradation behaviors of hydrogels were examined to be dependent on the poly(L-glutamic acid) content in the hydrogels. The higher content of poly(L-glutamic acid) in the gel, the higher swelling ratio and quicker degradation were observed. More interestingly, the hydrogel with higher PGH ratio showed higher vancomycin (VCM) loading content, which might be due to the electrostatic interaction between carboxylate groups in hydrogel and ammonium group of VCM. In vitro drug release from the VCM-loaded hydrogels in aqueous solution exhibited sustained release of VCM up to 72 h, while the in vitro antibacterial test based on the VCM-loaded hydrogel showed an efficient Methicillin-Resistant S. aureus (MRSA) inhibition extending out to 7 days. These results demonstrated that the biodegradable hydrogels which formed by in situ photo-cross linking would be promising as scaffolds or coatings for local antibacterial drug release in tissue engineering.
2013, 31(12): 1706-1716
doi: 10.1007/s10118-013-1363-z
Abstract:
The random copolymers of glutamic acid (LG) and aspartic acid (ASP), poly(LG-co-ASP), with designed compositions could be successfully synthesized via combination of N-carboxyanhydride ring opening copolymerization with debenzylation. Ring opening copolymerizations of g-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) and -benzyl-L-aspartate N-carboxyanhydride (BLA-NCA) were carried out by using different amines including triethylamine (TEA), diethylamine, n-hexylamine (NHA), triphenylamine, diphenylamine or aniline as initiators. All the 6 amines were highly efficient to get well-defined poly(BLG-co-BLA) copolymers with designed compositions although the polymerizations proceeded via different mechanisms (normal amine mechanism or/and activated monomer mechanism), which are based on chemical structure of amines. The molecular weights of poly(BLG-co-BLA) copolymers could be mediated by both TEA concentration and polymerization time. Then, debenzylation of poly(BLG-co-BLA) copolymers was conducted to prepare the corresponding hydrophilic random copolymers of poly(LG-co-ASP) with -subunit structure in ASP structural units. The contents of LG structural units in poly(LG-co-ASP) copolymers matched with those of BLG-NCA in NCA-monomer feeds in ring opening copolymerizations initiated by NHA or TEA and were closed to the theoretical line. The diblock copolymer of poly(BLG-b-BLA) could also be synthesized via living NCA ring opening copolymerization by sequential addition of BLG-NCA and BLA-NCA.
The random copolymers of glutamic acid (LG) and aspartic acid (ASP), poly(LG-co-ASP), with designed compositions could be successfully synthesized via combination of N-carboxyanhydride ring opening copolymerization with debenzylation. Ring opening copolymerizations of g-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) and -benzyl-L-aspartate N-carboxyanhydride (BLA-NCA) were carried out by using different amines including triethylamine (TEA), diethylamine, n-hexylamine (NHA), triphenylamine, diphenylamine or aniline as initiators. All the 6 amines were highly efficient to get well-defined poly(BLG-co-BLA) copolymers with designed compositions although the polymerizations proceeded via different mechanisms (normal amine mechanism or/and activated monomer mechanism), which are based on chemical structure of amines. The molecular weights of poly(BLG-co-BLA) copolymers could be mediated by both TEA concentration and polymerization time. Then, debenzylation of poly(BLG-co-BLA) copolymers was conducted to prepare the corresponding hydrophilic random copolymers of poly(LG-co-ASP) with -subunit structure in ASP structural units. The contents of LG structural units in poly(LG-co-ASP) copolymers matched with those of BLG-NCA in NCA-monomer feeds in ring opening copolymerizations initiated by NHA or TEA and were closed to the theoretical line. The diblock copolymer of poly(BLG-b-BLA) could also be synthesized via living NCA ring opening copolymerization by sequential addition of BLG-NCA and BLA-NCA.
2013, 31(12): 1717-1724
doi: 10.1007/s10118-013-1365-x
Abstract:
Lamellar crystals of diblock, triblock and four-arm poly(ethylene glycol)-b-poly(-caprolactone) (PEG-b-PCL) crystalline-crystalline copolymers were successfully obtained from their solution. Morphology and structure of lamellar crystals of crystalline-crystalline copolymers were investigated using tapping-mode atomic force microscopy (AFM) and selected area electron diffraction (SAED). All of these samples showed the truncated-lozenge multilayer basal shapes with central screw dislocation or central stack, which were all obtained simultaneously from the oil bath. The diffraction pattern of PEG block lamellar crystal is attributed to the (120) diffracting planes and the pattern of PCL block lamellar crystal is attributed to the (110) diffracting planes and (200) diffracting planes according to the SAED results. Four (110) crystal growth planes and two (200) crystal growth planes are discovered for the PCL blocks, but the (120) crystal growth planes of PEG blocks are hided in the figure of AFM. The crystalline structure of the four-arm copolymers (FA) is more disorder and confused than that of the diblock (DI) copolymer and the striated fold surface structures of lamellar crystals of four-arm copolymers (FA) are smoother than these of linear analogues, owing to the confused crystallization of blocks caused by the mutual restriction of blocks and the hindrance of the dendritic cores. In addition, the aspect ratio of FA is greater than that of the others. It is hypothesized that there are two reasons for the change of aspect ratios. First, the (200) diffracting planes of PCL crystals grew slowly compared to their (110) diffracting planes because of difference in the energy barrier. Secondly, edge dislocations on the (200) diffracting planes are also responsible for the variation of the aspect ratio. Consequently, the crystalline defects are augmented by the competing blocks crystallized simultaneously and the hindrance of the dendritic cores.
Lamellar crystals of diblock, triblock and four-arm poly(ethylene glycol)-b-poly(-caprolactone) (PEG-b-PCL) crystalline-crystalline copolymers were successfully obtained from their solution. Morphology and structure of lamellar crystals of crystalline-crystalline copolymers were investigated using tapping-mode atomic force microscopy (AFM) and selected area electron diffraction (SAED). All of these samples showed the truncated-lozenge multilayer basal shapes with central screw dislocation or central stack, which were all obtained simultaneously from the oil bath. The diffraction pattern of PEG block lamellar crystal is attributed to the (120) diffracting planes and the pattern of PCL block lamellar crystal is attributed to the (110) diffracting planes and (200) diffracting planes according to the SAED results. Four (110) crystal growth planes and two (200) crystal growth planes are discovered for the PCL blocks, but the (120) crystal growth planes of PEG blocks are hided in the figure of AFM. The crystalline structure of the four-arm copolymers (FA) is more disorder and confused than that of the diblock (DI) copolymer and the striated fold surface structures of lamellar crystals of four-arm copolymers (FA) are smoother than these of linear analogues, owing to the confused crystallization of blocks caused by the mutual restriction of blocks and the hindrance of the dendritic cores. In addition, the aspect ratio of FA is greater than that of the others. It is hypothesized that there are two reasons for the change of aspect ratios. First, the (200) diffracting planes of PCL crystals grew slowly compared to their (110) diffracting planes because of difference in the energy barrier. Secondly, edge dislocations on the (200) diffracting planes are also responsible for the variation of the aspect ratio. Consequently, the crystalline defects are augmented by the competing blocks crystallized simultaneously and the hindrance of the dendritic cores.
2013, 31(12): 1725-1732
doi: 10.1007/s10118-013-1312-x
Abstract:
Micron-sized cellulose microspheres were prepared through sol-gel method using NaOH/urea solution to dissolve cellulose, then cross-linked by 1,6-hexanylene diisocyanate (HDI), toluene 2,4-diisocyanate (TDI) and 1,4-phenylene diisocyanate (PDI), respectively. The reaction conditions for partial modification of the microspheres were studied. The degree of substitution (DS) in cellulose was controlled by adjusting the reaction conditions. HDI-crosslinked microspheres were partially modified with phenyl isocyanate to obtain chiral stationary phases (CSPs). The CSPs of a lower degree of crosslinking (DC) showed better chiral recognition ability than those of a higher DC. Meanwhile the CSPs prepared by pre-modification exhibited better chiral recognition ability than those prepared by pre-crosslinking.
Micron-sized cellulose microspheres were prepared through sol-gel method using NaOH/urea solution to dissolve cellulose, then cross-linked by 1,6-hexanylene diisocyanate (HDI), toluene 2,4-diisocyanate (TDI) and 1,4-phenylene diisocyanate (PDI), respectively. The reaction conditions for partial modification of the microspheres were studied. The degree of substitution (DS) in cellulose was controlled by adjusting the reaction conditions. HDI-crosslinked microspheres were partially modified with phenyl isocyanate to obtain chiral stationary phases (CSPs). The CSPs of a lower degree of crosslinking (DC) showed better chiral recognition ability than those of a higher DC. Meanwhile the CSPs prepared by pre-modification exhibited better chiral recognition ability than those prepared by pre-crosslinking.
