Login In
2010 Volume 28 Issue 2
2010, 28(2): 137-145
doi: 10.1007/s10118-010-8223-x
Abstract:
A series of hydrophobically associating polyacrylamides modified by small amounts ( 3 mol%) of a self-associative cationic monomer 4-(2-(acryloyloxy) ethoxy) benzyl tri-ethyl ammonium bromide (AEBA) as hydrophobe were synthesized by radical copolymerization in aqueous solutions without external surfactants. The resulting copolymers containing a multiblock structure exhibited a high tendency for hydrophobic association and a high thickening capacity. Solution properties and aggregation structures were investigated by viscometry and fluorescence technique. The high viscosity enhancement was found as the polymer concentration beyond a critical value c* and strongly depended on the copolymer microstructures. The number and length of hydrophobic microblocks within the copolymer backbones could be controlled by changing the AEBA concentration in copolymerization system. Addition of salt induced more hydrophobic association and viscosity enhancement. The synthesis method used was simple and environmentally friendly without any external surfactant contamination in comparison with the conventional micellar copolymerization.
A series of hydrophobically associating polyacrylamides modified by small amounts ( 3 mol%) of a self-associative cationic monomer 4-(2-(acryloyloxy) ethoxy) benzyl tri-ethyl ammonium bromide (AEBA) as hydrophobe were synthesized by radical copolymerization in aqueous solutions without external surfactants. The resulting copolymers containing a multiblock structure exhibited a high tendency for hydrophobic association and a high thickening capacity. Solution properties and aggregation structures were investigated by viscometry and fluorescence technique. The high viscosity enhancement was found as the polymer concentration beyond a critical value c* and strongly depended on the copolymer microstructures. The number and length of hydrophobic microblocks within the copolymer backbones could be controlled by changing the AEBA concentration in copolymerization system. Addition of salt induced more hydrophobic association and viscosity enhancement. The synthesis method used was simple and environmentally friendly without any external surfactant contamination in comparison with the conventional micellar copolymerization.
2010, 28(2): 147-155
doi: 10.1007/s10118-010-8231-x
Abstract:
Aromatic/aliphatic polyamides were synthesized from a diamine monomer, 2,3-bis-p-aminophenylquinoxaline (IV), based on quinoxaline and various dicarboxylic acids of aliphatic, aromatic and heterocyclic. The diamine and polyamides were characterized by elemental analysis, FTIR and 1H-NMR. The solubility of the polyamides was affected by the quinoxaline and heterocyclic groups in the polymer chain. They were all soluble in common organic solvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF) and N-methylpyrolidone (NMP). The polyamides showed inherent viscosity in the range of 0.25-0.3 dL/g in DMSO at 25°C and good thermal stability with the char yields in the range of 65%-82% at 600°C in nitrogen.
Aromatic/aliphatic polyamides were synthesized from a diamine monomer, 2,3-bis-p-aminophenylquinoxaline (IV), based on quinoxaline and various dicarboxylic acids of aliphatic, aromatic and heterocyclic. The diamine and polyamides were characterized by elemental analysis, FTIR and 1H-NMR. The solubility of the polyamides was affected by the quinoxaline and heterocyclic groups in the polymer chain. They were all soluble in common organic solvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF) and N-methylpyrolidone (NMP). The polyamides showed inherent viscosity in the range of 0.25-0.3 dL/g in DMSO at 25°C and good thermal stability with the char yields in the range of 65%-82% at 600°C in nitrogen.
2010, 28(2): 157-164
doi: 10.1007/s10118-010-8238-3
Abstract:
Neodymium chloride isopropanol complex (NdCl3·3iPrOH) activated by modified methylaluminoxane (MMAO) was examined in isoprene polymerization in hexane, with regards to Nd compounds, aluminum (Al) compounds, [Al]/[Nd] ratio, polymerization temperature and time. NdCl3·3iPrOH exhibited high activity producing polymers featuring high cis-1,4 stereospecificity ( 96%), very high molecular weight (Mn 1.0×106) and fairly narrow molecular weight distribution (MWD, Mw/Mn 2.0) simultaneously. In comparison, neodymium isopropoxide also showed high activity providing polymers with narrow MWD (Mw/Mn = 2.07), but somewhat low cis-1,4 content (ca. 92%), while neodymium chloride had no activity under present polymerization conditions. The Al compounds affected the polymer yield in the order of Al(i-Bu)3 MMAO Al(i-Bu)2H. MMAO as cocatalyst afforded polyisoprene with high Mn over 1.0×106, whereas as stronger chain transfer agent than MMAO, Al(i-Bu)3 and Al(i-Bu)2H yielded polymers with low Mn (1.0×105-8.0×105). NdCl3·3iPrOH/MMAO catalyst showed a fairly good catalytic activity even at relatively low [Al]/[Nd] ratio of 30, and the produced polymer remained high cis-1,4 content of 95.8% along with high Mn over 1.0×106 even at elevated temperatures up to 70οC. The polymerization rate is of the first order with respect to the concentration of isoprene. The mechanism of active species formation was discussed preliminarily.
Neodymium chloride isopropanol complex (NdCl3·3iPrOH) activated by modified methylaluminoxane (MMAO) was examined in isoprene polymerization in hexane, with regards to Nd compounds, aluminum (Al) compounds, [Al]/[Nd] ratio, polymerization temperature and time. NdCl3·3iPrOH exhibited high activity producing polymers featuring high cis-1,4 stereospecificity ( 96%), very high molecular weight (Mn 1.0×106) and fairly narrow molecular weight distribution (MWD, Mw/Mn 2.0) simultaneously. In comparison, neodymium isopropoxide also showed high activity providing polymers with narrow MWD (Mw/Mn = 2.07), but somewhat low cis-1,4 content (ca. 92%), while neodymium chloride had no activity under present polymerization conditions. The Al compounds affected the polymer yield in the order of Al(i-Bu)3 MMAO Al(i-Bu)2H. MMAO as cocatalyst afforded polyisoprene with high Mn over 1.0×106, whereas as stronger chain transfer agent than MMAO, Al(i-Bu)3 and Al(i-Bu)2H yielded polymers with low Mn (1.0×105-8.0×105). NdCl3·3iPrOH/MMAO catalyst showed a fairly good catalytic activity even at relatively low [Al]/[Nd] ratio of 30, and the produced polymer remained high cis-1,4 content of 95.8% along with high Mn over 1.0×106 even at elevated temperatures up to 70οC. The polymerization rate is of the first order with respect to the concentration of isoprene. The mechanism of active species formation was discussed preliminarily.
2010, 28(2): 165-170
doi: 10.1007/s10118-010-8243-6
Abstract:
The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.
The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.
2010, 28(2): 171-179
doi: 10.1007/s10118-010-8239-2
Abstract:
Zein/chitosan composite fibrous membranes were fabricated from aqueous ethanol solutions by electrospinning. Poly(vinyl pyrrolidone) (PVP) was introduced to facilitate the electrospinning process of zein/chitosan composites. The as-spun zein/chitosan/PVP composite fibrous membranes were characterized by scanning electron microscopy (SEM) and tensile tests. SEM images indicated that increasing zein and PVP concentrations led to an increase in average diameters of the composite fibers. In order to improve stability in wet stage and mechanical properties, the composite fibrous membranes were crosslinked by hexamethylene diisocyanate (HDI). The crosslinked composite fibrous membranes showed slight morphological change after immersion in water for 24 h. Mechanical tests revealed that tensile strength and elongation at break of the composite fibrous membranes were increased after crosslinking, whereas Young’s modulus was decreased.
Zein/chitosan composite fibrous membranes were fabricated from aqueous ethanol solutions by electrospinning. Poly(vinyl pyrrolidone) (PVP) was introduced to facilitate the electrospinning process of zein/chitosan composites. The as-spun zein/chitosan/PVP composite fibrous membranes were characterized by scanning electron microscopy (SEM) and tensile tests. SEM images indicated that increasing zein and PVP concentrations led to an increase in average diameters of the composite fibers. In order to improve stability in wet stage and mechanical properties, the composite fibrous membranes were crosslinked by hexamethylene diisocyanate (HDI). The crosslinked composite fibrous membranes showed slight morphological change after immersion in water for 24 h. Mechanical tests revealed that tensile strength and elongation at break of the composite fibrous membranes were increased after crosslinking, whereas Young’s modulus was decreased.
2010, 28(2): 181-189
doi: 10.1007/s10118-010-8245-4
Abstract:
After tentative ring-opening cross metathesis (ROCM) of endo-bicyclo[3.2.0]hept-6-en-3-yl 4-bromobenzoate with PhCH＝CH2 initiated by (Cy3P)2Cl2Ru＝CHPh in CH2Cl2, ring-opening metathesis polymerization (ROMP) of a series of endo-bicyclo[3.2.0]hept-6-en-3-yl benzoates was achieved under the same conditions, furnishing a variety of the corresponding polymers. Then some of them were selected to hydrogenate the C＝C double bonds in their backbone with p-tosylhydrazide, affording saturated and thus more flexible polymers. All of these polymers were well characterized by spectroscopic means including GPC, UV-Vis, NMR and IR, based on which the tacticity of these polymers was investigated together with nonlinear optical (electric-field-induced second-harmonic generation, EFISH)) analysis.
After tentative ring-opening cross metathesis (ROCM) of endo-bicyclo[3.2.0]hept-6-en-3-yl 4-bromobenzoate with PhCH＝CH2 initiated by (Cy3P)2Cl2Ru＝CHPh in CH2Cl2, ring-opening metathesis polymerization (ROMP) of a series of endo-bicyclo[3.2.0]hept-6-en-3-yl benzoates was achieved under the same conditions, furnishing a variety of the corresponding polymers. Then some of them were selected to hydrogenate the C＝C double bonds in their backbone with p-tosylhydrazide, affording saturated and thus more flexible polymers. All of these polymers were well characterized by spectroscopic means including GPC, UV-Vis, NMR and IR, based on which the tacticity of these polymers was investigated together with nonlinear optical (electric-field-induced second-harmonic generation, EFISH)) analysis.
CHEMICAL SYNTHESIS, SPECTRAL CHARACTERIZATION AND STABILITY OF SOME ELECTRICALLY CONDUCTING POLYMERS
2010, 28(2): 191-197
doi: 10.1007/s10118-010-9004-2
Abstract:
The synthesis, characterization, thermal degradation and stability of polyaniline (PANI), poly(m-nitroaniline), poly(m-chloroaniline) and poly(o-methylaniline) were reported. Different properties were measured and compared with PANI to find out the effect of electron donating groups (―CH3) and electron withdrawing groups (―Cl, ―NO2). It was found that the presence of any type of substitution in the benzene ring of aniline increased the solubility but reduced the yield, thermal stability and electrical conductivity. Two probe methods were used to measure the electrical conductivity of these polymers. The structural properties of these polymers were characterized by using FTIR and UV-Vis spectroscopic methods. Thermal degradation and stability of these polymers were explained by using thermogravimetric analysis (TGA) and conductivity measurements.
The synthesis, characterization, thermal degradation and stability of polyaniline (PANI), poly(m-nitroaniline), poly(m-chloroaniline) and poly(o-methylaniline) were reported. Different properties were measured and compared with PANI to find out the effect of electron donating groups (―CH3) and electron withdrawing groups (―Cl, ―NO2). It was found that the presence of any type of substitution in the benzene ring of aniline increased the solubility but reduced the yield, thermal stability and electrical conductivity. Two probe methods were used to measure the electrical conductivity of these polymers. The structural properties of these polymers were characterized by using FTIR and UV-Vis spectroscopic methods. Thermal degradation and stability of these polymers were explained by using thermogravimetric analysis (TGA) and conductivity measurements.
2010, 28(2): 199-207
Abstract:
A series of poly[(methylsilylene ethynylenephenyleneethynylene)-co-(dimethylsilylene ethynylenephenylenee-thynylene)]s were synthesized by the incorporation of various ratios of methylsilylene to dimethylsilylene units into the polymer chain backbone. The resultant copolymers were soluble in a variety of common organic solvents at room temperature. The copolymers were characterized by FT-IR, 1H-NMR, GPC, rheological analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that the copolymers exhibited good processability and cured at low temperatures like 200°C. The curing reactions involved in hydrosilylation of Si―H and alkyne groups and the polymerization of alkynes. Td5 (5% weight loss) of the cured copolymers ranged from 629°C to 686°C, and the decomposition residues of cured copolymers at 1000°C ranged from 88.1% to 90.9% under nitrogen. Thermal stability of the copolymers increased with the introduction of methylsilylene units into polymer chains. The cured copolymers were sintered at 1450°C, and the results of X-ray diffraction analysis showed that β-SiC was formed in the sintered products.
A series of poly[(methylsilylene ethynylenephenyleneethynylene)-co-(dimethylsilylene ethynylenephenylenee-thynylene)]s were synthesized by the incorporation of various ratios of methylsilylene to dimethylsilylene units into the polymer chain backbone. The resultant copolymers were soluble in a variety of common organic solvents at room temperature. The copolymers were characterized by FT-IR, 1H-NMR, GPC, rheological analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that the copolymers exhibited good processability and cured at low temperatures like 200°C. The curing reactions involved in hydrosilylation of Si―H and alkyne groups and the polymerization of alkynes. Td5 (5% weight loss) of the cured copolymers ranged from 629°C to 686°C, and the decomposition residues of cured copolymers at 1000°C ranged from 88.1% to 90.9% under nitrogen. Thermal stability of the copolymers increased with the introduction of methylsilylene units into polymer chains. The cured copolymers were sintered at 1450°C, and the results of X-ray diffraction analysis showed that β-SiC was formed in the sintered products.
2010, 28(2): 209-217
doi: 10.1007/s10118-010-8250-7
Abstract:
The number of configurations, c(n, m), of a single chain with length n attached to a flat surface with m monomers contacting the surface is exactly enumerated. A function of c(n, m) about m and n is obtained. From the function, a scaling law for mean energy of chain is derived, and we estimate the critical point εc = 0.276 and the crossover exponent f = 0.5. The free energy difference between tethered chain and free chain in dilute solution is also studied, which shows the critical adsorption point is about 0.272 for infinite long chain with f = 0.5.
The number of configurations, c(n, m), of a single chain with length n attached to a flat surface with m monomers contacting the surface is exactly enumerated. A function of c(n, m) about m and n is obtained. From the function, a scaling law for mean energy of chain is derived, and we estimate the critical point εc = 0.276 and the crossover exponent f = 0.5. The free energy difference between tethered chain and free chain in dilute solution is also studied, which shows the critical adsorption point is about 0.272 for infinite long chain with f = 0.5.
2010, 28(2): 219-229
Abstract:
A series of stable waterborne polysiloxaneurethane (WPSUR) dispersions were prepared using amino-terminated polydimethylsiloxane (NS), dimethylolpropionic acid (DMPA), castor oil, polypropylene glycol and toluene diisocyanate. Meanwhile, NS with different molecular weights was synthesized and used as the soft co-segment. Effects of types and contents of soft co-segments as well as chain extenders on the thermal degradation and stability for WPSUR films were examined. Results reveal that WPSUR films exhibit excellent water resistance and mechanical properties as compared with pure polyurethane (PU) films, and the NS soft co-segment possesses a remarkable effect on the second stage (stage II), while the content of the hard segment is propitious to the initial stage (stage I). Moreover, the highest temperature of stage II (T2m) for WPSUR films using NS as soft co-segment is 413οC, approximately being 30οC higher than that of those typical PUs using HDA and APDMS as the chain extenders, respectively.
A series of stable waterborne polysiloxaneurethane (WPSUR) dispersions were prepared using amino-terminated polydimethylsiloxane (NS), dimethylolpropionic acid (DMPA), castor oil, polypropylene glycol and toluene diisocyanate. Meanwhile, NS with different molecular weights was synthesized and used as the soft co-segment. Effects of types and contents of soft co-segments as well as chain extenders on the thermal degradation and stability for WPSUR films were examined. Results reveal that WPSUR films exhibit excellent water resistance and mechanical properties as compared with pure polyurethane (PU) films, and the NS soft co-segment possesses a remarkable effect on the second stage (stage II), while the content of the hard segment is propitious to the initial stage (stage I). Moreover, the highest temperature of stage II (T2m) for WPSUR films using NS as soft co-segment is 413οC, approximately being 30οC higher than that of those typical PUs using HDA and APDMS as the chain extenders, respectively.
2010, 28(2): 231-239
doi: 10.1007/s10118-010-9003-3
Abstract:
Tannic acid and its related compounds are known as refractory organic pollutants, and it can create serious problems for the environment. The adsorption and desorption studies of tannic acid on commercial resins XAD-7 and D-201 are performed, and all data indicates resin XAD-7 can be used as an effective adsorbent for removing tannic acid during water/wastewater treatment. Furthermore, adsorption thermodynamics studies indicate different adsorption mechanisms for TA on XAD-7 and D-201. FT-IR and solid state 13C-NMR spectroscopy are used to explain the adsorption force between XAD-7 and TA. It suggests that hydrogen bonding is the main adsorption force for TA. Finally, XAD-7’s adsorption capacity in the presence of different metal ions is investigated, which indicates that heavy metal ions in solutions can decrease the adsorption capacity for TA on ester resin XAD-7.
Tannic acid and its related compounds are known as refractory organic pollutants, and it can create serious problems for the environment. The adsorption and desorption studies of tannic acid on commercial resins XAD-7 and D-201 are performed, and all data indicates resin XAD-7 can be used as an effective adsorbent for removing tannic acid during water/wastewater treatment. Furthermore, adsorption thermodynamics studies indicate different adsorption mechanisms for TA on XAD-7 and D-201. FT-IR and solid state 13C-NMR spectroscopy are used to explain the adsorption force between XAD-7 and TA. It suggests that hydrogen bonding is the main adsorption force for TA. Finally, XAD-7’s adsorption capacity in the presence of different metal ions is investigated, which indicates that heavy metal ions in solutions can decrease the adsorption capacity for TA on ester resin XAD-7.
2010, 28(2): 241-248
doi: 10.1007/s10118-010-8249-0
Abstract:
Two hypercrosslinked polymeric adsorbents (ZH-01 and Amberlite XAD-4 resin) were employed to remove three kinds of phenolic compounds including phenol, 4-nitrophenol and 2,4-dinitrophenol from aqueous solutions. The study was focused on the static equilibrium adsorption behavior, the column dynamic adsorption and desorption profiles. The Freundlich model gave a perfect fitting to the isotherm data. The adsorbing capacities for these three compounds on ZH-01 were higher than those on Amberlite XAD-4 within the temperature range 288-318 K, which was attributed to the large micropore area and 2-carboxybenzoyl functional groups on the network of ZH-01 resin. The adsorption for phenol and 4-nitrophenol on ZH-01 was a physical adsorption process, while for 2,4-dinitrophenol it was a coexistence process of physical adsorption and chemisorption’s transitions. The column test showed the advantages of ZH-01 in the dynamic adsorption processes of phenolic compounds. Being used as the desorption reagent, sodium hydroxide solution showed an excellent performance.
Two hypercrosslinked polymeric adsorbents (ZH-01 and Amberlite XAD-4 resin) were employed to remove three kinds of phenolic compounds including phenol, 4-nitrophenol and 2,4-dinitrophenol from aqueous solutions. The study was focused on the static equilibrium adsorption behavior, the column dynamic adsorption and desorption profiles. The Freundlich model gave a perfect fitting to the isotherm data. The adsorbing capacities for these three compounds on ZH-01 were higher than those on Amberlite XAD-4 within the temperature range 288-318 K, which was attributed to the large micropore area and 2-carboxybenzoyl functional groups on the network of ZH-01 resin. The adsorption for phenol and 4-nitrophenol on ZH-01 was a physical adsorption process, while for 2,4-dinitrophenol it was a coexistence process of physical adsorption and chemisorption’s transitions. The column test showed the advantages of ZH-01 in the dynamic adsorption processes of phenolic compounds. Being used as the desorption reagent, sodium hydroxide solution showed an excellent performance.
2010, 28(2): 249-255
doi: 10.1007/s10118-010-9013-1
Abstract:
The phase morphology and thermal behavior of various isotactic polypropylene (PP)/linear low density polyethylene (LLDPE) blends were investigated with aid of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The effect of barrel (melt) temperature on the morphology, thermal behavior and the resultant mechanical properties of the injection molded bars was the research focus, and the influence of LLDPE composition was also taken into account. It was found that the mechanical properties, especially the tensile ductility and the impact strength, were greatly affected by the processing temperature. The samples obtained at low temperatures had the highest elongation at break and impact strength, while those molded at high temperatures had the poorest toughness. Two reasons were responsible for that: first, the phase size in the samples increased with the processing temperature; second, possible orientation existed in the samples obtained at low processing temperatures.
The phase morphology and thermal behavior of various isotactic polypropylene (PP)/linear low density polyethylene (LLDPE) blends were investigated with aid of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The effect of barrel (melt) temperature on the morphology, thermal behavior and the resultant mechanical properties of the injection molded bars was the research focus, and the influence of LLDPE composition was also taken into account. It was found that the mechanical properties, especially the tensile ductility and the impact strength, were greatly affected by the processing temperature. The samples obtained at low temperatures had the highest elongation at break and impact strength, while those molded at high temperatures had the poorest toughness. Two reasons were responsible for that: first, the phase size in the samples increased with the processing temperature; second, possible orientation existed in the samples obtained at low processing temperatures.
2010, 28(2): 257-267
doi: 10.1007/s10118-010-9038-5
Abstract:
A novel dualfunctional monomer, 2-(2,2,6,6-tetramethyl-piperidinyl-1-oxy)methylbenzene-1,4-dioyl chloride hydrochloride, with two acid chloride groups for step-growth polymerization and a nitroxide group for the mediation of living radical polymerization was synthesized. It was first copolymerized with terephthaloyl chloride and p-phenylenediamine at a feed molar ratio of 1:3:4 in N-methyl-2-pyrrolidone containing 10 wt% calcium chloride at -10C to yield a poly(p-phenylene terephthalamide) based macroinitiator, which initiated radical polymerization of styrene at 125C to obtain a series of poly(p-phenylene terephthalamide)-g-polystyrenes. A combinatory analysis of proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elementary analysis, thermogravimetry and gel permeation chromatography indicated that the macroinitiator induced the radical polymerization of styrene to proceed in a well-controlled way. The molecular weight of side-chains increased with an increase of monomer conversion, and the molecular weight distribution index remained lower than 1.5. The graft copolymers showed a remarkably improved solubility in N-methyl-2-pyrrolidone and much depressed crystallinity in bulk.
A novel dualfunctional monomer, 2-(2,2,6,6-tetramethyl-piperidinyl-1-oxy)methylbenzene-1,4-dioyl chloride hydrochloride, with two acid chloride groups for step-growth polymerization and a nitroxide group for the mediation of living radical polymerization was synthesized. It was first copolymerized with terephthaloyl chloride and p-phenylenediamine at a feed molar ratio of 1:3:4 in N-methyl-2-pyrrolidone containing 10 wt% calcium chloride at -10C to yield a poly(p-phenylene terephthalamide) based macroinitiator, which initiated radical polymerization of styrene at 125C to obtain a series of poly(p-phenylene terephthalamide)-g-polystyrenes. A combinatory analysis of proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elementary analysis, thermogravimetry and gel permeation chromatography indicated that the macroinitiator induced the radical polymerization of styrene to proceed in a well-controlled way. The molecular weight of side-chains increased with an increase of monomer conversion, and the molecular weight distribution index remained lower than 1.5. The graft copolymers showed a remarkably improved solubility in N-methyl-2-pyrrolidone and much depressed crystallinity in bulk.
2010, 28(2): 269-275
doi: 10.1007/s10118-010-9066-1
Abstract:
Nanomechanical properties of multilayer films constructed of polyaniline (PANI) and azobeneze-containing polyelectrolytes (PNACN and PPAPE) were studied by using nanoindentation method. The multilayer films were prepared by the electrostatic layer-by-layer self-assembly through alternately dipping in the polymer solutions. The multilayer films deposited onto the glass slides after proper dry were used for the nanomechanical property testing. The nanomechanical measurement indicated that the PANI/PNACN and PANI/PPAPE multilayers possessed the mean elastic modulus of 5.42 GPa and 4.35 GPa, and hardness of 0.26 GPa and 0.18 GPa, respectively. The nanoscratch properties of the PANI/PNACN and PANI/PPAPE multilayer films were also measured. The critical loads of PANI/PNACN and PANI/PPAPE films were 103.52 mN and 100.59 mN. The degree of electrostatic cross-linking in the multilayers could be altered by exposing the films to aqueous solutions with different pH values. As a result, the modulus and hardness of the multilayer films were changed through the solvent treatment. Both modulus and hardness of the PANI/PNACN films obviously increased after dipping the multilayer films in solutions with pH in a range from 9 to 11.
Nanomechanical properties of multilayer films constructed of polyaniline (PANI) and azobeneze-containing polyelectrolytes (PNACN and PPAPE) were studied by using nanoindentation method. The multilayer films were prepared by the electrostatic layer-by-layer self-assembly through alternately dipping in the polymer solutions. The multilayer films deposited onto the glass slides after proper dry were used for the nanomechanical property testing. The nanomechanical measurement indicated that the PANI/PNACN and PANI/PPAPE multilayers possessed the mean elastic modulus of 5.42 GPa and 4.35 GPa, and hardness of 0.26 GPa and 0.18 GPa, respectively. The nanoscratch properties of the PANI/PNACN and PANI/PPAPE multilayer films were also measured. The critical loads of PANI/PNACN and PANI/PPAPE films were 103.52 mN and 100.59 mN. The degree of electrostatic cross-linking in the multilayers could be altered by exposing the films to aqueous solutions with different pH values. As a result, the modulus and hardness of the multilayer films were changed through the solvent treatment. Both modulus and hardness of the PANI/PNACN films obviously increased after dipping the multilayer films in solutions with pH in a range from 9 to 11.
2010, 28(2): 277-285
doi: 10.1007/s10118-010-9089-7
Abstract:
Monodisperse hollow polymer microspheres having various functional groups on the shell-layer, such as carboxylic acid, pyridyl and amide, were prepared by two-stage distillation precipitation polymerization in neat acetonitrile in the absence of any stabilizer or additive, during which monodisperse poly(methacrylic acid) (PMAA) afforded from the first-stage polymerization was utilized as the seeds for the second-stage polymerization. The shell layer with different functional groups was formed during the second-stage copolymerization of either divinylbenzene (DVB) or ethyleneglycol dimethacrylate (EGDMA) as crosslinker and the functional comonomers, in which the hydrogen-bonding interaction between the carboxylic acid group of PMAA core and the functional groups of the corresponding comonomers, including carboxylic acid, amide and pyridyl, played an essential role for the formation of monodisperse core-shell functional microspheres. The hollow polymer microspheres were then developed after the subsequent removal of PMAA cores by dissolution in ethanol under basic condition. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the morphology of the resultant PMAA core, functional core-shell microspheres and the corresponding hollow polymer microspheres with different functional groups. FT-IR spectra confirmed the successful incorporation of the various functional groups on the shell layer of the hollow polymer microspheres.
Monodisperse hollow polymer microspheres having various functional groups on the shell-layer, such as carboxylic acid, pyridyl and amide, were prepared by two-stage distillation precipitation polymerization in neat acetonitrile in the absence of any stabilizer or additive, during which monodisperse poly(methacrylic acid) (PMAA) afforded from the first-stage polymerization was utilized as the seeds for the second-stage polymerization. The shell layer with different functional groups was formed during the second-stage copolymerization of either divinylbenzene (DVB) or ethyleneglycol dimethacrylate (EGDMA) as crosslinker and the functional comonomers, in which the hydrogen-bonding interaction between the carboxylic acid group of PMAA core and the functional groups of the corresponding comonomers, including carboxylic acid, amide and pyridyl, played an essential role for the formation of monodisperse core-shell functional microspheres. The hollow polymer microspheres were then developed after the subsequent removal of PMAA cores by dissolution in ethanol under basic condition. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the morphology of the resultant PMAA core, functional core-shell microspheres and the corresponding hollow polymer microspheres with different functional groups. FT-IR spectra confirmed the successful incorporation of the various functional groups on the shell layer of the hollow polymer microspheres.
2010, 28(2): 287-290
doi: 10.1007/s10118-010-9151-5
Abstract:
Based on several unsymmetrical, twist, noncoplanar phthalazinone-containing monomers 2a-2e and an active bis(4-fluorophenyl)phenyl phosphine oxide (BFPPO) monomer, a series of novel poly(phthalazinone ether phosphine oxide)s (PPEPO) was synthesized by anhydrous K2CO3 mediated N―C coupling reaction in DMAc. The polymers exhibited good thermal properties with Tgs ranging from 267°C to 306°C and 5% weight loss temperatures in nitrogen higher than 430°C, together with high char yield upon prolonged heating at 800°C (35%-56%). Moreover, the polymers were readily soluble in common organic solvents, such as N-methyl-2-pyrrolidone, chloroform and m-cresol. These polymers had inherent viscosities in the range of 0.45-0.72 dL/g and could be cast into flexible and colorless films by spin coating or casting approach.
Based on several unsymmetrical, twist, noncoplanar phthalazinone-containing monomers 2a-2e and an active bis(4-fluorophenyl)phenyl phosphine oxide (BFPPO) monomer, a series of novel poly(phthalazinone ether phosphine oxide)s (PPEPO) was synthesized by anhydrous K2CO3 mediated N―C coupling reaction in DMAc. The polymers exhibited good thermal properties with Tgs ranging from 267°C to 306°C and 5% weight loss temperatures in nitrogen higher than 430°C, together with high char yield upon prolonged heating at 800°C (35%-56%). Moreover, the polymers were readily soluble in common organic solvents, such as N-methyl-2-pyrrolidone, chloroform and m-cresol. These polymers had inherent viscosities in the range of 0.45-0.72 dL/g and could be cast into flexible and colorless films by spin coating or casting approach.
