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2012 Volume 30 Issue 5
2012, 30(5): 613-622
doi: 10.1007/s10118-012-1178-3
Abstract:
A facile method is reported to controllably fabricate one dimensional (1D) polymer nanostructures via metallogel template polymerization. The metallogel was prepared through coordination interactions between silver ions and a ligand (L) bearing three pyridyl groups in tetrahydrofuran (THF). The diameters of the metallogel nanofibers could be tuned by the gel concentration (GC). Due to its high thermal stability and facility of removal, the metallogel was used as the template for radical polymerization of diacryolyl-2,6-diaminopyridine (DADAP) to form poly-diacryolyl-2,6-diaminopyridine (PDADAP) nanostructures. The gradually eroding of the templates by PDADAP provided us an effective way to fabricate various nanostructures of the polymer. We have demonstrated that different 1D nanostructures, including nanoribbons, nanotubes and nanowires, could be selectively fabricated by adjusting polymerization time, monomer concentration and GC. The rheological properties of the gel samples were tested by a rheometer. As prolonging the reaction time, more and more polymers were formed and the strength of the resulting polymer gels became higher and higher. The simple preparation process, easy controlled microstructures and adequate gel strength would make it a facile synthetic method for different 1D polymer nanosturctures.
A facile method is reported to controllably fabricate one dimensional (1D) polymer nanostructures via metallogel template polymerization. The metallogel was prepared through coordination interactions between silver ions and a ligand (L) bearing three pyridyl groups in tetrahydrofuran (THF). The diameters of the metallogel nanofibers could be tuned by the gel concentration (GC). Due to its high thermal stability and facility of removal, the metallogel was used as the template for radical polymerization of diacryolyl-2,6-diaminopyridine (DADAP) to form poly-diacryolyl-2,6-diaminopyridine (PDADAP) nanostructures. The gradually eroding of the templates by PDADAP provided us an effective way to fabricate various nanostructures of the polymer. We have demonstrated that different 1D nanostructures, including nanoribbons, nanotubes and nanowires, could be selectively fabricated by adjusting polymerization time, monomer concentration and GC. The rheological properties of the gel samples were tested by a rheometer. As prolonging the reaction time, more and more polymers were formed and the strength of the resulting polymer gels became higher and higher. The simple preparation process, easy controlled microstructures and adequate gel strength would make it a facile synthetic method for different 1D polymer nanosturctures.
2012, 30(5): 623-631
doi: 10.1007/s10118-012-1177-4
Abstract:
Atomic force microscopy (AFM), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry are used to analyze the crystallization morphology and melting behavior of 4-arm PEO-b-PCL under high-pressure CO2. It is demonstrated that CO2 has certain effect on the melting and crystallization behavior of the samples. After crystallization under CO2 at 4 MPa, spherulites with concentric ring-banded structure are formed which are composed of crystals with periodic thickness variation, and the band distance decreases with increasing treatment pressure. Due to the plasticization effect of CO2, depression of the melting temperature is observed with sorption of CO2 in polymers.
Atomic force microscopy (AFM), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry are used to analyze the crystallization morphology and melting behavior of 4-arm PEO-b-PCL under high-pressure CO2. It is demonstrated that CO2 has certain effect on the melting and crystallization behavior of the samples. After crystallization under CO2 at 4 MPa, spherulites with concentric ring-banded structure are formed which are composed of crystals with periodic thickness variation, and the band distance decreases with increasing treatment pressure. Due to the plasticization effect of CO2, depression of the melting temperature is observed with sorption of CO2 in polymers.
2012, 30(5): 632-641
doi: 10.1007/s10118-012-1149-8
Abstract:
Polypropylene (PP)/polybutene-1 (PB) alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were carried out to form isotactic polypropylene (#em/em#PP) particles containing active catalyst. Then, butene-1 was subsequently polymerized to form polybutene-1 phase inside the #em/em#PP particles. Finally, #em/em#PP/PB alloys with spherical shape and adjustable PB content were synthesized. The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed. The composition and physical properties of the PP alloys were characterized by FT-IR, 13C-NMR, SEM, DSC and XRD. It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly(butene-co-propylene) random copolymers and poly(butene-block-propylene) block copolymers. SEM measurements verified that the PB phases with size in the range of 300-400 nm dispersed in the PP matrix uniformly. The incorporation of PB upon the PP matrix affects the properties of final products greatly.
Polypropylene (PP)/polybutene-1 (PB) alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were carried out to form isotactic polypropylene (#em/em#PP) particles containing active catalyst. Then, butene-1 was subsequently polymerized to form polybutene-1 phase inside the #em/em#PP particles. Finally, #em/em#PP/PB alloys with spherical shape and adjustable PB content were synthesized. The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed. The composition and physical properties of the PP alloys were characterized by FT-IR, 13C-NMR, SEM, DSC and XRD. It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly(butene-co-propylene) random copolymers and poly(butene-block-propylene) block copolymers. SEM measurements verified that the PB phases with size in the range of 300-400 nm dispersed in the PP matrix uniformly. The incorporation of PB upon the PP matrix affects the properties of final products greatly.
2012, 30(5): 642-651
doi: 10.1007/s10118-012-1155-x
Abstract:
Poly[2-(4-chlorophenyl)-1,3-dioxolan-4-yl]methyl acrylate, poly(CPhDMA), was synthesized with radical polymerization process using 2,2￠-azobisisobutyronitrile as radical initiator in 1,4-dioxane at 60℃. The structure of poly(CPhDMA) was confirmed by means of UV-Vis, FT-IR, 1H-NMR, and 13C-NMR spectral techniques. The molecular weight distribution values of the polymer were determined with gel permeation chromatography (GPC). The number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of poly(CPhDMA) were determined to be 10300, 21600 and 2.097, respectively. The thermal degradation kinetics of the polymer was investigated by using TG/DTG-DTA and DSC analyses at different heating rates in dynamic nitrogen atmosphere. The apparent activation energy values obtained by Flynn-Wall-Ozawa and Friedman methods were found to be 91.68 and 85.23 kJ mol-1, respectively, for thermal decomposition of poly(CPhDMA). Also, the thermal degradation activation energy value of poly(CPhDMA) was calculated by using the Kissinger method based on the DTG, DTA and DSC data. Then the mechanism function of it was determined by master plots method. Finally, electrical and optical properties of poly(CPhDMA) were determined by four-point probe and UV-Vis techniques, respectively.
Poly[2-(4-chlorophenyl)-1,3-dioxolan-4-yl]methyl acrylate, poly(CPhDMA), was synthesized with radical polymerization process using 2,2￠-azobisisobutyronitrile as radical initiator in 1,4-dioxane at 60℃. The structure of poly(CPhDMA) was confirmed by means of UV-Vis, FT-IR, 1H-NMR, and 13C-NMR spectral techniques. The molecular weight distribution values of the polymer were determined with gel permeation chromatography (GPC). The number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of poly(CPhDMA) were determined to be 10300, 21600 and 2.097, respectively. The thermal degradation kinetics of the polymer was investigated by using TG/DTG-DTA and DSC analyses at different heating rates in dynamic nitrogen atmosphere. The apparent activation energy values obtained by Flynn-Wall-Ozawa and Friedman methods were found to be 91.68 and 85.23 kJ mol-1, respectively, for thermal decomposition of poly(CPhDMA). Also, the thermal degradation activation energy value of poly(CPhDMA) was calculated by using the Kissinger method based on the DTG, DTA and DSC data. Then the mechanism function of it was determined by master plots method. Finally, electrical and optical properties of poly(CPhDMA) were determined by four-point probe and UV-Vis techniques, respectively.
2012, 30(5): 652-663
doi: 10.1007/s10118-012-1152-0
Abstract:
Carbon black (CB)/polymer composites with high refractive index (RI) were fabricated from poly(vinyl alcohol) (PVA) and covalently functionalized nano-CB (PVA-es-CB) by simple esterification reaction. Transmission electron microscopy showed that uniform aggregates of PVA-es-CB nanoparticles with a size smaller than 100 nm formed in the nanocomposite films. Ellipsometric measurements indicated that the PVA-es-CB/PVA composite films had a RI in the range 1.520-1.598 linearly increased with the PVA-es-CB volume content. Theoretical equation based on Lorentz-Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values. The hybrid films also revealed relatively good surface planarity, thermal stability and optical transparency.
Carbon black (CB)/polymer composites with high refractive index (RI) were fabricated from poly(vinyl alcohol) (PVA) and covalently functionalized nano-CB (PVA-es-CB) by simple esterification reaction. Transmission electron microscopy showed that uniform aggregates of PVA-es-CB nanoparticles with a size smaller than 100 nm formed in the nanocomposite films. Ellipsometric measurements indicated that the PVA-es-CB/PVA composite films had a RI in the range 1.520-1.598 linearly increased with the PVA-es-CB volume content. Theoretical equation based on Lorentz-Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values. The hybrid films also revealed relatively good surface planarity, thermal stability and optical transparency.
2012, 30(5): 664-673
doi: 10.1007/s10118-012-1163-x
Abstract:
The molecular weight distributions were estimated for carbon fiber polymer precursors such as poly(acrylonitrile-co-itaconic acid) synthesized by semi batch solution polymerization in mixed solvents media with the azonitrile compounds as initiator under the different ratios of solvent and non solvent from 0.75 to 2.5 in weight. The copolymer was characterized by using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR) analyses. The molecular weight distributions were evaluated by Mv/Mn ratios estimated from viscosity and osmotic measurements, and Mw/Mn estimated from size exclusion chromatography. The molecular weight distributions of these polymers as determined from Mv/Mn and Mw/Mn are 2.9 to 3.2 and 2.0 to 2.5 respectively. The molecular distributions were close to a narrow distribution of 2.0 when the solvent/non-solvent ratio was varied between 1.4 and 2.0. Intrinsic viscosity [] as a function of molecular weight of poly(acrylonitrile-co-itaconic acid) was evaluated by means of low angle laser light scattering with size exclusion chromatography (SEC-LALLS) and viscometry with SEC (SEC-VISCO). The relationship between [] and Mw for poly(acrylonitrile-co-itaconic acid) in DMF at 50℃ was []=1.1 10-5 Mw0.79, where [] is obtained in dL/g.
The molecular weight distributions were estimated for carbon fiber polymer precursors such as poly(acrylonitrile-co-itaconic acid) synthesized by semi batch solution polymerization in mixed solvents media with the azonitrile compounds as initiator under the different ratios of solvent and non solvent from 0.75 to 2.5 in weight. The copolymer was characterized by using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR) analyses. The molecular weight distributions were evaluated by Mv/Mn ratios estimated from viscosity and osmotic measurements, and Mw/Mn estimated from size exclusion chromatography. The molecular weight distributions of these polymers as determined from Mv/Mn and Mw/Mn are 2.9 to 3.2 and 2.0 to 2.5 respectively. The molecular distributions were close to a narrow distribution of 2.0 when the solvent/non-solvent ratio was varied between 1.4 and 2.0. Intrinsic viscosity [] as a function of molecular weight of poly(acrylonitrile-co-itaconic acid) was evaluated by means of low angle laser light scattering with size exclusion chromatography (SEC-LALLS) and viscometry with SEC (SEC-VISCO). The relationship between [] and Mw for poly(acrylonitrile-co-itaconic acid) in DMF at 50℃ was []=1.1 10-5 Mw0.79, where [] is obtained in dL/g.
SYNTHESIS AND CHARACTERIZATION OF Fe(II)-COORDINATED PS-b-P[NIPAM-co-(VBC-Fe-DMAP)] BLOCK COPOLYMERS
2012, 30(5): 674-681
doi: 10.1007/s10118-012-1161-z
Abstract:
In this work, a new type of block polymers, polystyrene-b-poly[(N-isopropyl acrylamide)-co-(vinyl benzyl chloride)] (PS-b-P(NIPAM-co-VBC)), was prepared via reversible addition fragmentation transfer polymerization, then pentacyano(4-(dimethylamino pyridine))ferrate (Fe-DMAP) was attached to VBC units through a quaternization process. The Fe(II)-coordinated PS-b-P[NIPAM-co-(VBC-Fe-DMAP)] block copolymers were characterized by 1H-NMR, FT-IR and TGA. The self-assembly behavior of the block copolymers was also investigated and the micelle morphology was characterized by TEM. It was found that the PS-b-P(NIPAM-co-VBC) block polymer and Fe-coordinated block copolymer could both form spherical micelles in DMF/MeOH mixed solvent.
In this work, a new type of block polymers, polystyrene-b-poly[(N-isopropyl acrylamide)-co-(vinyl benzyl chloride)] (PS-b-P(NIPAM-co-VBC)), was prepared via reversible addition fragmentation transfer polymerization, then pentacyano(4-(dimethylamino pyridine))ferrate (Fe-DMAP) was attached to VBC units through a quaternization process. The Fe(II)-coordinated PS-b-P[NIPAM-co-(VBC-Fe-DMAP)] block copolymers were characterized by 1H-NMR, FT-IR and TGA. The self-assembly behavior of the block copolymers was also investigated and the micelle morphology was characterized by TEM. It was found that the PS-b-P(NIPAM-co-VBC) block polymer and Fe-coordinated block copolymer could both form spherical micelles in DMF/MeOH mixed solvent.
2012, 30(5): 682-693
doi: 10.1007/s10118-012-1143-1
Abstract:
The oligo(azomethine ether)s were synthesized via polycondensation of alkyl diamines with aromatic dialdehydes. Two series of dialdehydes, namely 2,2-[1,2-phenylenebis(methyleneoxy)]dibenzaldehyde [2,2-1,2-(PBMODB)] and 2,2-[1,4-phenylenebis(methyleneoxy)]dibenzaldehyde [2,2-1,4-(PBMODB)] were prepared from the condensation reactions of salicylaldehyde with o-xylenedibromide and p-xylenedibromide, respectively. The structures of dialdehydes and oligomers were determined by FT-IR, 1H-NMR and 13C-NMR. The thermal analyses of oligomers were conducted by DSC and TG/DTA techniques, respectively. Size exclusion chromatography (SEC) technique was also used to determine molecular weights and molecular weight distributions of oligomers. Electrochemical properties of the synthesized products were investigated.
The oligo(azomethine ether)s were synthesized via polycondensation of alkyl diamines with aromatic dialdehydes. Two series of dialdehydes, namely 2,2-[1,2-phenylenebis(methyleneoxy)]dibenzaldehyde [2,2-1,2-(PBMODB)] and 2,2-[1,4-phenylenebis(methyleneoxy)]dibenzaldehyde [2,2-1,4-(PBMODB)] were prepared from the condensation reactions of salicylaldehyde with o-xylenedibromide and p-xylenedibromide, respectively. The structures of dialdehydes and oligomers were determined by FT-IR, 1H-NMR and 13C-NMR. The thermal analyses of oligomers were conducted by DSC and TG/DTA techniques, respectively. Size exclusion chromatography (SEC) technique was also used to determine molecular weights and molecular weight distributions of oligomers. Electrochemical properties of the synthesized products were investigated.
2012, 30(5): 694-704
doi: 10.1007/s10118-012-1169-4
Abstract:
This article describes the synthesis of a series of aromatic amide-amines and their potential use as epoxy hardeners. These amines were synthesized by the reaction of L-phenylalanine (PA) with diamines of different structures i.e. 1,4-phenylene diamine (PD), 1,5-diamino naphthalene (N), 4,4'-(9-fluorenyllidene)-dianiline (F), 4,4'-diaminodiphenyl sulphide (DS) and 3,4'-oxydianiline (O) in a stoichiometric ratio (1:1). Structural characterization of synthesized amide-amines was done with the help of elemental analysis and spectroscopic techniques viz. FT-IR, 1H-NMR and 13C-NMR. An epoxy blend was prepared by mixing tris(glycidyloxy) phosphine oxide (TGPO) with conventional epoxy i.e. diglycidyl ether of bisphenol-A (DGEBA) in an equivalent ratio of 2:3 to incorporate phosphorous into the main chain. The curing kinetics of the epoxy blend with synthesized aromatic amide-amines was investigated by non-isothermal DSC technique using multiple heating rate method (5, 10, 15 and 20 K/min.). The activation energies were determined by fitting the experimental data into Kissinger and Ozawa kinetic models. The activation energies obtained through Ozawa method were slightly higher than those of Kissinger method but were comparable. However, both the energies were found to be dependent on the structure of amines. The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis (TGA) in nitrogen atmosphere. All the samples showed improved thermal stability in terms of char yield than using only amines as hardeners.
This article describes the synthesis of a series of aromatic amide-amines and their potential use as epoxy hardeners. These amines were synthesized by the reaction of L-phenylalanine (PA) with diamines of different structures i.e. 1,4-phenylene diamine (PD), 1,5-diamino naphthalene (N), 4,4'-(9-fluorenyllidene)-dianiline (F), 4,4'-diaminodiphenyl sulphide (DS) and 3,4'-oxydianiline (O) in a stoichiometric ratio (1:1). Structural characterization of synthesized amide-amines was done with the help of elemental analysis and spectroscopic techniques viz. FT-IR, 1H-NMR and 13C-NMR. An epoxy blend was prepared by mixing tris(glycidyloxy) phosphine oxide (TGPO) with conventional epoxy i.e. diglycidyl ether of bisphenol-A (DGEBA) in an equivalent ratio of 2:3 to incorporate phosphorous into the main chain. The curing kinetics of the epoxy blend with synthesized aromatic amide-amines was investigated by non-isothermal DSC technique using multiple heating rate method (5, 10, 15 and 20 K/min.). The activation energies were determined by fitting the experimental data into Kissinger and Ozawa kinetic models. The activation energies obtained through Ozawa method were slightly higher than those of Kissinger method but were comparable. However, both the energies were found to be dependent on the structure of amines. The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis (TGA) in nitrogen atmosphere. All the samples showed improved thermal stability in terms of char yield than using only amines as hardeners.
2012, 30(5): 705-718
doi: 10.1007/s10118-012-1167-6
Abstract:
The biocompatiable and low-toxic poly(thiophene-3-acetic acid) (PTAA) matrix was successfully electrosynthesized in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) in comparison with the electrosynthesis of PTAA matrix in acetonitrile (ACN). Ascorbate oxidase (AO) was used as a model for the development and application of biosensor. Vitamin C (VC) biosensors were facilely fabricated by the covalent immobilization of AO molecules on PTAA matrices electrosynthesized in ACN containing tetrabutylammonium tetrafluoroborate and BmimPF6, respectively. Electrochemical impedance spectroscopy, scanning electron microscopy and FTIR spectroscopy indicated that AO molecules were covalently immobilized on PTAA matrices. Parameters of the as-obtained biosensors such as working potential, pH and temperature have been optimized. The amperometric biosensor based on PTAA matrix electrosynthesized in BmimPF6 exhibited wider linear range, lower detection limit, higher sensitivity and bioaffinity, and better operational and storage stability than that electrosynthesized in ACN under optimal conditions. The as-obtained biosensor based on PTAA matrix electrosynthesized in BmimPF6 was employed for the detection of VC content in commercial juices, and the result was close to the data given by manufacturers. Excellent results indicate that the PTAA matrix electrosynthesized in ionic liquid is a promising platform for the covalent immobilization of biologically-active species and the development of biosensors.
The biocompatiable and low-toxic poly(thiophene-3-acetic acid) (PTAA) matrix was successfully electrosynthesized in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) in comparison with the electrosynthesis of PTAA matrix in acetonitrile (ACN). Ascorbate oxidase (AO) was used as a model for the development and application of biosensor. Vitamin C (VC) biosensors were facilely fabricated by the covalent immobilization of AO molecules on PTAA matrices electrosynthesized in ACN containing tetrabutylammonium tetrafluoroborate and BmimPF6, respectively. Electrochemical impedance spectroscopy, scanning electron microscopy and FTIR spectroscopy indicated that AO molecules were covalently immobilized on PTAA matrices. Parameters of the as-obtained biosensors such as working potential, pH and temperature have been optimized. The amperometric biosensor based on PTAA matrix electrosynthesized in BmimPF6 exhibited wider linear range, lower detection limit, higher sensitivity and bioaffinity, and better operational and storage stability than that electrosynthesized in ACN under optimal conditions. The as-obtained biosensor based on PTAA matrix electrosynthesized in BmimPF6 was employed for the detection of VC content in commercial juices, and the result was close to the data given by manufacturers. Excellent results indicate that the PTAA matrix electrosynthesized in ionic liquid is a promising platform for the covalent immobilization of biologically-active species and the development of biosensors.
2012, 30(5): 719-726
doi: 10.1007/s10118-012-1156-9
Abstract:
To improve the colloidal stability of bovine serum albumin (BSA) nanoparticles (NPs) in diverse mediums, poly(allylamine hydrochloride) (PAH)/sodium poly(4-styrene sulfonate) (PSS) multilayers and poly(allylamine hydrochloride)-graft-poly(ethylene glycol) (PAH-g-PEG) coating were coated on the surface of BSA NPs. Stabilities of the BSA NPs in diverse mediums with different surfaces were detected by dynamic light scattering (DLS). Multilayers and PAH-g-PEG coated BSA NPs can be well dispersed in various mediums with a narrow polydispersity index (PDI). The BSA NPs with the highest surface density of PEG show the best stability. The multilayers and PAH-g-PEG coating do not deter the pH-dependent loading and release property of BSA NPs. At pH 9, the encapsulation efficiency of doxorubicin reaches almost 99%, and the release rate at pH 5.5 is significantly higher than that at pH 7.4.
To improve the colloidal stability of bovine serum albumin (BSA) nanoparticles (NPs) in diverse mediums, poly(allylamine hydrochloride) (PAH)/sodium poly(4-styrene sulfonate) (PSS) multilayers and poly(allylamine hydrochloride)-graft-poly(ethylene glycol) (PAH-g-PEG) coating were coated on the surface of BSA NPs. Stabilities of the BSA NPs in diverse mediums with different surfaces were detected by dynamic light scattering (DLS). Multilayers and PAH-g-PEG coated BSA NPs can be well dispersed in various mediums with a narrow polydispersity index (PDI). The BSA NPs with the highest surface density of PEG show the best stability. The multilayers and PAH-g-PEG coating do not deter the pH-dependent loading and release property of BSA NPs. At pH 9, the encapsulation efficiency of doxorubicin reaches almost 99%, and the release rate at pH 5.5 is significantly higher than that at pH 7.4.
2012, 30(5): 727-734
doi: 10.1007/s10118-012-1174-7
Abstract:
This paper deals with the monitoring cyclo-addition of CO2 to methyl methacrylate (MMA)-glycidyl methacrylate (GMA) copolymers using spectral (1H-NMR and FTIR) and chemical (elemental analysis and titration) methods. Thus, poly(MMA-co-GMA), was first prepared via solution polymerization. The copolymer was then treated with CO2 gas flow in the presence of cetyltrimethyl ammoniumbromide as a catalyst. In terms of the carbonation reaction time, the terpolymer poly(MMA-co-GMA-co-2-oxo-1,3-dioxolane-4-yl-methyl methacrylate) was prepared in various yield of CO2 fixation ( 90%). The peak intensity changes in the 1H-NMR and FTIR spectra provided excellent demonstrative techniques to monitor the carbonation reaction progression. In a comparative analytical viewpoint, the NMR and elemental analysis were recognized to be the most accurate ways to follow the cyclo-addition reaction progression. However, titration was recognized to be the most preferred method, because it is a very inexpensive, facile and available method with a reasonable cost-accuracy balance.
This paper deals with the monitoring cyclo-addition of CO2 to methyl methacrylate (MMA)-glycidyl methacrylate (GMA) copolymers using spectral (1H-NMR and FTIR) and chemical (elemental analysis and titration) methods. Thus, poly(MMA-co-GMA), was first prepared via solution polymerization. The copolymer was then treated with CO2 gas flow in the presence of cetyltrimethyl ammoniumbromide as a catalyst. In terms of the carbonation reaction time, the terpolymer poly(MMA-co-GMA-co-2-oxo-1,3-dioxolane-4-yl-methyl methacrylate) was prepared in various yield of CO2 fixation ( 90%). The peak intensity changes in the 1H-NMR and FTIR spectra provided excellent demonstrative techniques to monitor the carbonation reaction progression. In a comparative analytical viewpoint, the NMR and elemental analysis were recognized to be the most accurate ways to follow the cyclo-addition reaction progression. However, titration was recognized to be the most preferred method, because it is a very inexpensive, facile and available method with a reasonable cost-accuracy balance.
2012, 30(5): 735-743
doi: 10.1007/s10118-012-1168-5
Abstract:
Partially exfoliated nanocomposite (2) has been synthesized by intercalation of poly(propylene carbonate) (PPC) into commercial clay, Cloisite 20B (PPC/C-20B). Nanocomposite 2 was characterized phiso-chemically and exhibited high thermal, mechanical and anti-water sorption properties as compared to PPC and intercalated nanocomposite (1) of PPC/C-20B having same amount of clay. TGA results revealed that the thermal decomposition temperature (Td, 50%) of 2 increased significantly, being 40 K and 17 K higher than that of pure PPC and 1, respectively, while DSC measurements indicated that the nano-filler dispersion of 2 increased the glass transition temperature from 21℃ to 31℃. Accordingly, 2 showed high elastic modulus, hardness and anti-water absorption capacity. These thermal, mechanical and anti-water absorption improvements are of great importance for the application of PPC as packaging and biomaterials.
Partially exfoliated nanocomposite (2) has been synthesized by intercalation of poly(propylene carbonate) (PPC) into commercial clay, Cloisite 20B (PPC/C-20B). Nanocomposite 2 was characterized phiso-chemically and exhibited high thermal, mechanical and anti-water sorption properties as compared to PPC and intercalated nanocomposite (1) of PPC/C-20B having same amount of clay. TGA results revealed that the thermal decomposition temperature (Td, 50%) of 2 increased significantly, being 40 K and 17 K higher than that of pure PPC and 1, respectively, while DSC measurements indicated that the nano-filler dispersion of 2 increased the glass transition temperature from 21℃ to 31℃. Accordingly, 2 showed high elastic modulus, hardness and anti-water absorption capacity. These thermal, mechanical and anti-water absorption improvements are of great importance for the application of PPC as packaging and biomaterials.
2012, 30(5): 744-758
doi: 10.1007/s10118-012-1164-9
Abstract:
Density functional theory has been employed to study the homogeneous catalytic copolymerization of styrene with carbon monoxide. The copolymerization reaction is catalyzed by Pd(II) coordinated with 2,2-bipyridine, a conventional nitrogen-containing bidentate ligand with achiral C2v symmetry. The chain propagation mechanism for the alternating copolymerization as well as the side reactions, including multiple insertions of CO and homopolymerization of styrene, has been investigated. This study focused exclusively on regioisomerism and stereoisomerism. We have demonstrated that the strictly alternating copolymerization is kinetically and thermodynamically favored over the side reactions (i.e., multiple insertions of CO and homopolymerization of styrene). The regiochemistry study indicates the 2,1 type. Furthermore, the stereochemistry study shows that the syndiotactic conformation is preferred over the isotactic or atactic conformations.
Density functional theory has been employed to study the homogeneous catalytic copolymerization of styrene with carbon monoxide. The copolymerization reaction is catalyzed by Pd(II) coordinated with 2,2-bipyridine, a conventional nitrogen-containing bidentate ligand with achiral C2v symmetry. The chain propagation mechanism for the alternating copolymerization as well as the side reactions, including multiple insertions of CO and homopolymerization of styrene, has been investigated. This study focused exclusively on regioisomerism and stereoisomerism. We have demonstrated that the strictly alternating copolymerization is kinetically and thermodynamically favored over the side reactions (i.e., multiple insertions of CO and homopolymerization of styrene). The regiochemistry study indicates the 2,1 type. Furthermore, the stereochemistry study shows that the syndiotactic conformation is preferred over the isotactic or atactic conformations.
2012, 30(5): 759-769
doi: 10.1007/s10118-012-1162-y
Abstract:
A novel conjugated hyperbranched polymer containing bithiazole rings (PBTADB) was synthesized by polycondensation of 1,3,5-benzenetricarboxaldehyde and 2,2-diamino-4,4-bithiazole (DABT). The structure of the hyperbranched polymer was confirmed by FT-IR and 1H-NMR. PBTADB dissolved in organic polar solvents such as DMSO and NMP. Bithiazole rings were introduced to provide bidentate N-donor sites for binding metal ions. The metal complexes were prepared by chelation of the polymer with Co2+ and Sm3+. The magnetic behavior of coordination compounds was measured as a function of magnetic field strength (0-4.8 106 A/m) at 5 K and as a function of temperature (5-300 K) at magnetic field strength of 2.4 106 A/m. The magnetic hysteresis loops of PBTADB-Sm3+ and PBTADB-Co2+ showed the typical S shape at 5 K with the Curie-Weiss temperature T= 96 K and 41 K respectively. The results show that they exhibit properties of soft ferromagnetic materials.
A novel conjugated hyperbranched polymer containing bithiazole rings (PBTADB) was synthesized by polycondensation of 1,3,5-benzenetricarboxaldehyde and 2,2-diamino-4,4-bithiazole (DABT). The structure of the hyperbranched polymer was confirmed by FT-IR and 1H-NMR. PBTADB dissolved in organic polar solvents such as DMSO and NMP. Bithiazole rings were introduced to provide bidentate N-donor sites for binding metal ions. The metal complexes were prepared by chelation of the polymer with Co2+ and Sm3+. The magnetic behavior of coordination compounds was measured as a function of magnetic field strength (0-4.8 106 A/m) at 5 K and as a function of temperature (5-300 K) at magnetic field strength of 2.4 106 A/m. The magnetic hysteresis loops of PBTADB-Sm3+ and PBTADB-Co2+ showed the typical S shape at 5 K with the Curie-Weiss temperature T= 96 K and 41 K respectively. The results show that they exhibit properties of soft ferromagnetic materials.
2012, 30(5): 770-776
doi: 10.1007/s10118-012-1179-2
Abstract:
Thermo-responsive block copolymers poly(ethylene glycol)-block-poly(N-acryloyl-2,2-dimethyl-1,3-oxazolidine), PEG-b-PADMO, based on linear PEG were prepared via a versatile reversible addition-fragmentation chain transfer (RAFT) polymerization. PEG22 (Mw=1000) was used as the hydrophilic component, whose dehydration was the main driving force for the phase transition of these copolymers, as demonstrated by the 1H-NMR spectra. Their lower critical solution temperatures (LCSTs) could be tuned in the range of 20℃ to 35℃, by adjusting the degree of polymerization (DP) of PADMO between 14-27. Furthermore, a sharp phase transition at ca. 33℃, close to the physiological temperature with minimal hysteresis, was observed for the PEG22-b-PADMO14 copolymer. Moreover, excellent reversibility and reproducibility were displayed for the same copolymer over 10 cycles of repeated temperature change between 25℃ (below the LCST) and 40℃ (above the LCST).
Thermo-responsive block copolymers poly(ethylene glycol)-block-poly(N-acryloyl-2,2-dimethyl-1,3-oxazolidine), PEG-b-PADMO, based on linear PEG were prepared via a versatile reversible addition-fragmentation chain transfer (RAFT) polymerization. PEG22 (Mw=1000) was used as the hydrophilic component, whose dehydration was the main driving force for the phase transition of these copolymers, as demonstrated by the 1H-NMR spectra. Their lower critical solution temperatures (LCSTs) could be tuned in the range of 20℃ to 35℃, by adjusting the degree of polymerization (DP) of PADMO between 14-27. Furthermore, a sharp phase transition at ca. 33℃, close to the physiological temperature with minimal hysteresis, was observed for the PEG22-b-PADMO14 copolymer. Moreover, excellent reversibility and reproducibility were displayed for the same copolymer over 10 cycles of repeated temperature change between 25℃ (below the LCST) and 40℃ (above the LCST).
