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2008 Volume 26 Issue 6
2008, 26(6): 653-657
Abstract:
Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS). Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures, i.e. the cloud points and the dynamic crystallization temperatures, respectively. It was found that the cloud points were coincident with the crystallization temperatures, indicating that a solid-liquid phase separation occurred during thermal quenching of the UHMWPE/LP solution, while, no liquid-liquid phase separation above the crystallization temperature was observed. The effects of the content and the molecular weight of UHMWPE on the morphology and average pore size were investigated with field emission scanning electron microscopy (FE-SEM) and mercury porosimetry. With the increase of the content of UHMWPE, the average pore size of the microporous material decreased and the molecular weight of UHMWPE could also influence the pore size slightly.
Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS). Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures, i.e. the cloud points and the dynamic crystallization temperatures, respectively. It was found that the cloud points were coincident with the crystallization temperatures, indicating that a solid-liquid phase separation occurred during thermal quenching of the UHMWPE/LP solution, while, no liquid-liquid phase separation above the crystallization temperature was observed. The effects of the content and the molecular weight of UHMWPE on the morphology and average pore size were investigated with field emission scanning electron microscopy (FE-SEM) and mercury porosimetry. With the increase of the content of UHMWPE, the average pore size of the microporous material decreased and the molecular weight of UHMWPE could also influence the pore size slightly.
2008, 26(6): 659-668
Abstract:
A series of nanofiltration (NF) membranes were prepared with poly(amido-amine) (PAMAM) and trimesoyl chloride (TMC) via in situ interfacial polymerization. The effects of the generation number and concentration of PAMAM on the properties of NF membranes were discussed. Fourier transform infrared spectroscopy (FTIR-ATR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle measurements were employed to characterize the resulting membranes. The nanofiltration performances were evaluated with solutions of NaCl, Na2SO4, MgCl2 and MgSO4, respectively. FTIR-ATR spectra indicated that TMC reacted more sufficiently with the higher generation PAMAM. The salts rejection of the resulting membranes increased with increasing the generation number of PAMAM, which was mainly attributed to the concentration difference of terminal amino-groups among the different generation PAMAM. The MgCl2 (2000 mg/L) rejection of NF-G5 reached 90.3% under the pressure of 0.6 MPa in a cross-flow method measurement. The rejection of MgCl2 increased with increasing concentration of PAMAM. The salts rejection order of NF membranes with high rejection is MgCl2 MgSO4 Na2SO4 NaCl. It was also found that the NF-Gx (x = 4, 5, 6, 7) membranes became more hydrophilic with increasing the generation number of PAMAM.
A series of nanofiltration (NF) membranes were prepared with poly(amido-amine) (PAMAM) and trimesoyl chloride (TMC) via in situ interfacial polymerization. The effects of the generation number and concentration of PAMAM on the properties of NF membranes were discussed. Fourier transform infrared spectroscopy (FTIR-ATR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle measurements were employed to characterize the resulting membranes. The nanofiltration performances were evaluated with solutions of NaCl, Na2SO4, MgCl2 and MgSO4, respectively. FTIR-ATR spectra indicated that TMC reacted more sufficiently with the higher generation PAMAM. The salts rejection of the resulting membranes increased with increasing the generation number of PAMAM, which was mainly attributed to the concentration difference of terminal amino-groups among the different generation PAMAM. The MgCl2 (2000 mg/L) rejection of NF-G5 reached 90.3% under the pressure of 0.6 MPa in a cross-flow method measurement. The rejection of MgCl2 increased with increasing concentration of PAMAM. The salts rejection order of NF membranes with high rejection is MgCl2 MgSO4 Na2SO4 NaCl. It was also found that the NF-Gx (x = 4, 5, 6, 7) membranes became more hydrophilic with increasing the generation number of PAMAM.
2008, 26(6): 669-678
Abstract:
Organoclay-modified hydroxylterminated polysulfone (PSF)/epoxy interpenetrating network nanocomposites (oM-PSF/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polysulfone and epoxy resin (PSF/EP) using diaminodiphenylmethane (DDM) as curing agent. The mechanical properties like tensile strength, tensile modulus, flexural strength, flexural modulus and impact properties of the nanocomposites were studied as per ASTM standards. Differential scanning calorimetry (DSC) analysis, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) analysis showed that PSF was compatible with EP, and the glass transition temperature (Tg) of the oM-PSF/EP nanocomposites decreased with increasing the oMMT content. Water absorption tests showed that the PSF/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM-PSF/EP nanocomposites.
Organoclay-modified hydroxylterminated polysulfone (PSF)/epoxy interpenetrating network nanocomposites (oM-PSF/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polysulfone and epoxy resin (PSF/EP) using diaminodiphenylmethane (DDM) as curing agent. The mechanical properties like tensile strength, tensile modulus, flexural strength, flexural modulus and impact properties of the nanocomposites were studied as per ASTM standards. Differential scanning calorimetry (DSC) analysis, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) analysis showed that PSF was compatible with EP, and the glass transition temperature (Tg) of the oM-PSF/EP nanocomposites decreased with increasing the oMMT content. Water absorption tests showed that the PSF/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM-PSF/EP nanocomposites.
2008, 26(6): 679-687
Abstract:
The use of new food grade polysaccharides (mucilage) obtained from Hibiscus esculentus and Trigonella foenum graceum, commonly called Okra and Fenugreek, respectively, as flocculants was described. These polysaccharides were used for removal of solids (suspended solids (SS) and total dissolved solids (TDS)) and dyes from real textile effluents and aqueous solutions of different class of synthetic dyes. Influences of varying polysaccharide concentration, contact time and pH on removal of pollutant from the textile wastewater were investigated. Results showed that polysaccharides (mucilage) obtained from Okra and Fenugreek were capable of removing 90%-94% of SS, 30%-44% of TDS and 30%-35% of dye using a very low concentration of polysaccharide. X-ray diffraction (XRD) patterns of solid waste material obtained before and after the treatment with polysaccharides were used as a supportive evidence to explain the mechanism of flocculation.
The use of new food grade polysaccharides (mucilage) obtained from Hibiscus esculentus and Trigonella foenum graceum, commonly called Okra and Fenugreek, respectively, as flocculants was described. These polysaccharides were used for removal of solids (suspended solids (SS) and total dissolved solids (TDS)) and dyes from real textile effluents and aqueous solutions of different class of synthetic dyes. Influences of varying polysaccharide concentration, contact time and pH on removal of pollutant from the textile wastewater were investigated. Results showed that polysaccharides (mucilage) obtained from Okra and Fenugreek were capable of removing 90%-94% of SS, 30%-44% of TDS and 30%-35% of dye using a very low concentration of polysaccharide. X-ray diffraction (XRD) patterns of solid waste material obtained before and after the treatment with polysaccharides were used as a supportive evidence to explain the mechanism of flocculation.
2008, 26(6): 689-696
Abstract:
Two master-batches, polyamide 66 (PA66)/organo-montmorillonite (OMMT) and polyamide 6 (PA6)/OMMT, prepared by melt compounding with methyl methacrylate (MMA) as co-intercalation agent, have been used to prepare nearly exfoliated PA66/montmorillonite (MMT) nanocomposites. The resulting nanocomposites are compared in view of their morphology and properties. Nano-scale dispersion of OMMT is realized in both types of nanocomposites, as revealed by XRD, TEM and Molau tests. PA66/MMT nanocomposites having superior mechanical properties and heat distortion temperature (HDT) can be obtained from either PA66/OMMT or PA6/OMMT master-batch. Those from PA6/OMMT have lower tensile and flexural properties, and HDT than those from PA66/OMMT due to the presence of less stiff and less thermal resistant PA6. The crystallization behavior and crystal structure of the matrix in both types of PA66/MMT nanocomposites are also investigated by DSC and WAXD.
Two master-batches, polyamide 66 (PA66)/organo-montmorillonite (OMMT) and polyamide 6 (PA6)/OMMT, prepared by melt compounding with methyl methacrylate (MMA) as co-intercalation agent, have been used to prepare nearly exfoliated PA66/montmorillonite (MMT) nanocomposites. The resulting nanocomposites are compared in view of their morphology and properties. Nano-scale dispersion of OMMT is realized in both types of nanocomposites, as revealed by XRD, TEM and Molau tests. PA66/MMT nanocomposites having superior mechanical properties and heat distortion temperature (HDT) can be obtained from either PA66/OMMT or PA6/OMMT master-batch. Those from PA6/OMMT have lower tensile and flexural properties, and HDT than those from PA66/OMMT due to the presence of less stiff and less thermal resistant PA6. The crystallization behavior and crystal structure of the matrix in both types of PA66/MMT nanocomposites are also investigated by DSC and WAXD.
2008, 26(6): 697-703
Abstract:
The spherulitic structure and morphology development of poly(ethylene succinate)/poly(ethylene oxide) (PES/PEO) blends with one-step crystallization behavior were observed by means of polarizing optical microscope. It was found that the pure PES spherulite in which the adequate quantity of PEO melt existed in the interlamellar regions, and the blending spherulite formed by both PES and PEO lamellae could form simultaneously. When the two types of spherulites contacted with each other the front of the blending spherulite could penetrate into the pure PES spherulite to grow continually. This penetration growth behavior was also observed when the mini-crystal particles of the PES component were formed at lower crystallization temperatures. The kinetics analysis showed that the penetration growth rate was faster than that in the original melt. It was evidenced that the increasing of growth rate and the formation of new growth site should be the typical characteristics of interpenetrated growth in binary crystalline polymer blends.
The spherulitic structure and morphology development of poly(ethylene succinate)/poly(ethylene oxide) (PES/PEO) blends with one-step crystallization behavior were observed by means of polarizing optical microscope. It was found that the pure PES spherulite in which the adequate quantity of PEO melt existed in the interlamellar regions, and the blending spherulite formed by both PES and PEO lamellae could form simultaneously. When the two types of spherulites contacted with each other the front of the blending spherulite could penetrate into the pure PES spherulite to grow continually. This penetration growth behavior was also observed when the mini-crystal particles of the PES component were formed at lower crystallization temperatures. The kinetics analysis showed that the penetration growth rate was faster than that in the original melt. It was evidenced that the increasing of growth rate and the formation of new growth site should be the typical characteristics of interpenetrated growth in binary crystalline polymer blends.
2008, 26(6): 705-712
Abstract:
Five kinds of polyimides were synthesized using five dianhydrides (including 2,2-bis[4-(3,4-dicarboxyphenoxy)-phenyl] propane dianhydride (BPADA), 3,3′,4,4′-diphenylsulfone-tetracarboxylic dianhydride (DSDA), 4,4#61602;-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA), 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA), and 4,4′-oxydiphthlic dianhydride (ODPA)) and 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane (BDAF) via the two-step method that included polyaddition to form the polyamic acid and subsequent chemical imidization at ambient temperature. The structures of polyimides were characterized by FTIR and NMR. The thermal properties were characterized by DSC and TGA. All five kinds of polyimides showed good thermal properties and solubility in organic solvents such as DMF, DMAc, NMP and THF at room temperature. The pervaporation (PV) experiments of polyimides for toluene/n-heptane mixture were carried out, and all the polyimides showed selective permeation towards toluene. The fluxes of 6FDA-BDAF, DSDA-BDAF, HQDPA-BDAF and ODPA-BDAF at 80#61616;C were 1.08, 0.96, 1.77 and 0.10 kg#8226;μm/(m2#8226;h), and the separation factors were 5.44, 1.64, 1.28 and 11.44, respectively. The increasing feed temperature resulted in higher flux and lower separation factor of the 6FDA-BDAF membrane.
Five kinds of polyimides were synthesized using five dianhydrides (including 2,2-bis[4-(3,4-dicarboxyphenoxy)-phenyl] propane dianhydride (BPADA), 3,3′,4,4′-diphenylsulfone-tetracarboxylic dianhydride (DSDA), 4,4#61602;-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA), 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA), and 4,4′-oxydiphthlic dianhydride (ODPA)) and 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane (BDAF) via the two-step method that included polyaddition to form the polyamic acid and subsequent chemical imidization at ambient temperature. The structures of polyimides were characterized by FTIR and NMR. The thermal properties were characterized by DSC and TGA. All five kinds of polyimides showed good thermal properties and solubility in organic solvents such as DMF, DMAc, NMP and THF at room temperature. The pervaporation (PV) experiments of polyimides for toluene/n-heptane mixture were carried out, and all the polyimides showed selective permeation towards toluene. The fluxes of 6FDA-BDAF, DSDA-BDAF, HQDPA-BDAF and ODPA-BDAF at 80#61616;C were 1.08, 0.96, 1.77 and 0.10 kg#8226;μm/(m2#8226;h), and the separation factors were 5.44, 1.64, 1.28 and 11.44, respectively. The increasing feed temperature resulted in higher flux and lower separation factor of the 6FDA-BDAF membrane.
2008, 26(6): 713-721
Abstract:
A new adsorbent (JN-01) was prepared by modifying resin NDA-1800 with nitro functional groups. The adsorption capacities of resins XAD-4, NDA-1800 and JN-01 were investigated, and the results indicated that the modified resin JN-01 was much better in adsorbing phenol, p-nitrophenol and p-cresol. The adsorption capacities of the resin JN-01 were higher than those of the resins XAD-4 and NDA-1800 within a temperature range of 283#61485;323 K, which might be attributed to the higher surface area and the partial polarity on its matrix. The new adsorbent could be widely used in wastewater treatment.
A new adsorbent (JN-01) was prepared by modifying resin NDA-1800 with nitro functional groups. The adsorption capacities of resins XAD-4, NDA-1800 and JN-01 were investigated, and the results indicated that the modified resin JN-01 was much better in adsorbing phenol, p-nitrophenol and p-cresol. The adsorption capacities of the resin JN-01 were higher than those of the resins XAD-4 and NDA-1800 within a temperature range of 283#61485;323 K, which might be attributed to the higher surface area and the partial polarity on its matrix. The new adsorbent could be widely used in wastewater treatment.
2008, 26(6): 723-732
Abstract:
A study has been conducted on the synthesis and characterization of a kind of novel polyrotaxanes comprising #61537;-cyclodextrins α-CDs) threaded on triblock copolymers with poly(ethylene glycol) (PEG) as a central axle and flanked by two low molecular weight polystyrenes as outer stoppers. Styrene was allowed to telomerize with polypseudorotaxanes as chain transfer agents made from the self-assembly of a distal thiol-capped PEG with a varying amount of #61537;-CDs in the presence of a redox initiation system at 40°C in aqueous solutions. The resulting polyrotaxanes were characterized in detail by 1H-NMR, FTIR, XRD, TG and DSC analyses. The findings from the study demonstrated that the low molecular weight polystyrenes were successfully attached to two axle terminals of polypseudorotaxanes, and the number of #61537;-CDs threaded onto the PEG backbone was tunable by varying its molar feeding ratio to some extent, while the polymerization degree of PS nearly remained constant in this radical telomerization process.
A study has been conducted on the synthesis and characterization of a kind of novel polyrotaxanes comprising #61537;-cyclodextrins α-CDs) threaded on triblock copolymers with poly(ethylene glycol) (PEG) as a central axle and flanked by two low molecular weight polystyrenes as outer stoppers. Styrene was allowed to telomerize with polypseudorotaxanes as chain transfer agents made from the self-assembly of a distal thiol-capped PEG with a varying amount of #61537;-CDs in the presence of a redox initiation system at 40°C in aqueous solutions. The resulting polyrotaxanes were characterized in detail by 1H-NMR, FTIR, XRD, TG and DSC analyses. The findings from the study demonstrated that the low molecular weight polystyrenes were successfully attached to two axle terminals of polypseudorotaxanes, and the number of #61537;-CDs threaded onto the PEG backbone was tunable by varying its molar feeding ratio to some extent, while the polymerization degree of PS nearly remained constant in this radical telomerization process.
2008, 26(6): 733-740
Abstract:
The fractionated crystallization behavior of the minor dispersed HDPE phase in PS/POE/HDPE/SBS quaternary blends was investigated by differential scanning calorimetry (DSC). Interestingly, we found that the fractionated crystallization behavior of HDPE was molecular weight dependent. At a fixed composition, HDPE with lower molecular weight showed more obvious fractionated crystallization behavior than HDPE with higher molecular weight. This was ascribed to a finer dispersion of HDPE with lower molecular weight, as evidenced by SEM observations. The fractionated crystallization behavior of HDPE in the blends became less obvious with increasing of its content, due to a change of phase morphology from droplet to co-continuous structure. Correspondingly, a change of tensile toughness of the blends from brittle to ductile mode was observed.
The fractionated crystallization behavior of the minor dispersed HDPE phase in PS/POE/HDPE/SBS quaternary blends was investigated by differential scanning calorimetry (DSC). Interestingly, we found that the fractionated crystallization behavior of HDPE was molecular weight dependent. At a fixed composition, HDPE with lower molecular weight showed more obvious fractionated crystallization behavior than HDPE with higher molecular weight. This was ascribed to a finer dispersion of HDPE with lower molecular weight, as evidenced by SEM observations. The fractionated crystallization behavior of HDPE in the blends became less obvious with increasing of its content, due to a change of phase morphology from droplet to co-continuous structure. Correspondingly, a change of tensile toughness of the blends from brittle to ductile mode was observed.
2008, 26(6): 741-749
Abstract:
The mean-square radius of gyrationS2 , the mean-square dipole moment D2, the mean-square end-to-end distanceR2 and their temperature coefficients of unsymmetrical disubstituted poly(methylphenylsiloxane) (PMPS) chains, as a function of stereochemical structure, confomational energies and length of polymers, were studied by using an improved configurational-confomational statistical method based on the rotational-isomeric-state theory. It is found that the increase in isotacticity of PMPS chains causes a significant decrease in the unperturbed dimensions and increase in their temperature coefficients. This correlation of the properties of PMPS and its stereochemical structure is different from that of vinyl monosubstituted polystyrene and disubstituted poly(α-methylstyrene) chains. Dependence of the characteristic ratio of S2on conformational energy Eω’ of C6H5…C6H5 four-bond interactions increases markedly with the degree of isotacticity increasing, the dependence on the conformational energy Eδ and dEσ decreases with increasing the degree of isotacticity. It is also found that the characteristic ratios of R2and its temperature coefficients are in agreement with corresponding experimental results in the degree of isotacticity of about 0-40%. Moreover, the C6H5…C6H5 four-bond interactions play a dominant role in regard to the dimensions of high syndiotactic chains. In addition, the effect of large side groups on unperturbed dimensions is investigated further by the improved expressions ofS2 .
The mean-square radius of gyrationS2 , the mean-square dipole moment D2, the mean-square end-to-end distanceR2 and their temperature coefficients of unsymmetrical disubstituted poly(methylphenylsiloxane) (PMPS) chains, as a function of stereochemical structure, confomational energies and length of polymers, were studied by using an improved configurational-confomational statistical method based on the rotational-isomeric-state theory. It is found that the increase in isotacticity of PMPS chains causes a significant decrease in the unperturbed dimensions and increase in their temperature coefficients. This correlation of the properties of PMPS and its stereochemical structure is different from that of vinyl monosubstituted polystyrene and disubstituted poly(α-methylstyrene) chains. Dependence of the characteristic ratio of S2on conformational energy Eω’ of C6H5…C6H5 four-bond interactions increases markedly with the degree of isotacticity increasing, the dependence on the conformational energy Eδ and dEσ decreases with increasing the degree of isotacticity. It is also found that the characteristic ratios of R2and its temperature coefficients are in agreement with corresponding experimental results in the degree of isotacticity of about 0-40%. Moreover, the C6H5…C6H5 four-bond interactions play a dominant role in regard to the dimensions of high syndiotactic chains. In addition, the effect of large side groups on unperturbed dimensions is investigated further by the improved expressions ofS2 .
2008, 26(6): 751-757
Abstract:
The dynamic rheological properties of a composite composed of solution-polymerized styrene butadiene rubber (SSBR) filled with starch/silica (SiO2) compound fillers were studied by means of temperature, frequency and strain sweeps, respectively, and the influence of the starch content in the compound fillers (SCCF) on the rheological behaviors was discussed. It is found from frequency sweeps that a maximum of loss tangent (tanδ) appears at 20 rad/s, which is independent of SCCF. G’ of the composites decreases whereas tanδ and critical strain (γc) of Payne effect increase with increasing SCCF. The reasons for these are believed to be that both SiO2 and starch could form filler networks due to interaction of hydrogen bounding between them, and the interactions between SiO2 and SSBR are stronger than those between starch and SSBR. Moreover, increasing SCCF in the compound fillers is in favor of improving the stability of the filler networks. Furthermore, tanδ values at 0oC and 60oC representing the properties for the wet traction and the rolling resistance of SSBR composites respectively can be improved by partial replacing SiO2 with starch. However, the reinforcement effect of starch to SSBR is weaker than that of SiO2 due to starch agglomeration.
The dynamic rheological properties of a composite composed of solution-polymerized styrene butadiene rubber (SSBR) filled with starch/silica (SiO2) compound fillers were studied by means of temperature, frequency and strain sweeps, respectively, and the influence of the starch content in the compound fillers (SCCF) on the rheological behaviors was discussed. It is found from frequency sweeps that a maximum of loss tangent (tanδ) appears at 20 rad/s, which is independent of SCCF. G’ of the composites decreases whereas tanδ and critical strain (γc) of Payne effect increase with increasing SCCF. The reasons for these are believed to be that both SiO2 and starch could form filler networks due to interaction of hydrogen bounding between them, and the interactions between SiO2 and SSBR are stronger than those between starch and SSBR. Moreover, increasing SCCF in the compound fillers is in favor of improving the stability of the filler networks. Furthermore, tanδ values at 0oC and 60oC representing the properties for the wet traction and the rolling resistance of SSBR composites respectively can be improved by partial replacing SiO2 with starch. However, the reinforcement effect of starch to SSBR is weaker than that of SiO2 due to starch agglomeration.
2008, 26(6): 759-766
Abstract:
In the weak segregation limit, the structure evolution of the hexagonal cylindrical phase of diblock copolymers in films was investigated. Employing the Landau-Brazovskii mean field theory, we obtained three amplitude parameters as functions of temperature, surface field strength and film thickness. By controlling confinement size and surface field strength, lamellae and undulated lamellae appear in the cylindrical bulk phase of diblock copolymers. “Phase diagrams” of confinement-induced structures are constructed at different surface field strengths. The obtained theoretical results are in agreement with relevant theoretical and experimental results.
In the weak segregation limit, the structure evolution of the hexagonal cylindrical phase of diblock copolymers in films was investigated. Employing the Landau-Brazovskii mean field theory, we obtained three amplitude parameters as functions of temperature, surface field strength and film thickness. By controlling confinement size and surface field strength, lamellae and undulated lamellae appear in the cylindrical bulk phase of diblock copolymers. “Phase diagrams” of confinement-induced structures are constructed at different surface field strengths. The obtained theoretical results are in agreement with relevant theoretical and experimental results.
2008, 26(6): 767-774
Abstract:
The title block copolymer (defined as PSUEA) containing pendant, self-complementary quadruple hydrogen bonding sites has been prepared successfully by three steps. First, poly(styrene-b-2-hydroxyethyl acrylate) (defined as PSHEA) was prepared by living radical polymerizing 2-hydroxyethyl acrylate (HEA) initiated by polystyrene (PSt) macro-initiator, which was prepared via nitroxide-mediated polymerization (NMP) technique. After treated by excessive 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), PSHEA was transferred into an intermediate polymer (defined as PSIEA) with isocyanate groups in the second block. Finally, PSIEA was reacted with excessive 2-amino-4-hydroxy-6-methyl-pyrimidone (MIS) to obtain PSUEA bearing pendant quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidone (Upy) units. Based on 1H-NMR, FT-IR and GPC analysis, all the polymers with well controlled structures were obtained. Preliminary thermal analysis of the block polymers indicated that the introduction of Upy units significantly increased the glass transition temperature. The possibility to form quadruple hydrogen bonding should make PSUEA suitable as new building component for supramolecular assembling.
The title block copolymer (defined as PSUEA) containing pendant, self-complementary quadruple hydrogen bonding sites has been prepared successfully by three steps. First, poly(styrene-b-2-hydroxyethyl acrylate) (defined as PSHEA) was prepared by living radical polymerizing 2-hydroxyethyl acrylate (HEA) initiated by polystyrene (PSt) macro-initiator, which was prepared via nitroxide-mediated polymerization (NMP) technique. After treated by excessive 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), PSHEA was transferred into an intermediate polymer (defined as PSIEA) with isocyanate groups in the second block. Finally, PSIEA was reacted with excessive 2-amino-4-hydroxy-6-methyl-pyrimidone (MIS) to obtain PSUEA bearing pendant quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidone (Upy) units. Based on 1H-NMR, FT-IR and GPC analysis, all the polymers with well controlled structures were obtained. Preliminary thermal analysis of the block polymers indicated that the introduction of Upy units significantly increased the glass transition temperature. The possibility to form quadruple hydrogen bonding should make PSUEA suitable as new building component for supramolecular assembling.
2008, 26(6): 775-781
Abstract:
A high molecular weight (Mw = 1.85 × 107) polystyrene (PS) with narrow distribution was prepared by high vacuum anionic polymerization in tetrahydrofuran. By use of dynamic light scattering, the dynamics of PS chains in cyclohexane was studied around the θ temperature. For the first time, we have observed the internal motion of polymer chains in solutions below the θ temperature by using dynamic light scattering at smaller angles (even qRg 1).
A high molecular weight (Mw = 1.85 × 107) polystyrene (PS) with narrow distribution was prepared by high vacuum anionic polymerization in tetrahydrofuran. By use of dynamic light scattering, the dynamics of PS chains in cyclohexane was studied around the θ temperature. For the first time, we have observed the internal motion of polymer chains in solutions below the θ temperature by using dynamic light scattering at smaller angles (even qRg 1).
2008, 26(6): 783-792
Abstract:
The typical immiscible PP/PS blend based clay nanocomposites were prepared via melt blending. The dispersion of clay was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and dynamic mechanical properties were measured by thermogravimetrical analysis (TGA) and dynamic mechanical analysis (DMA), respectively. Preferential intercalation behavior of clay in PP/PS blends was found. The dispersion of clay is significantly influenced by the polarity of PP and PS, meanwhile the location of clay can be controlled by the alternation of the polarity of PP and PS through chemical modification. The clay migrates from PS phase to PP phase with the improvement of the polarity of PP. However, when the PS is sulfonated, clay migrates back to the dispersed PS phase again. The dispersion and location of clay have profound influence on the thermal and dynamic mechanical behavior of PP/PS blends. The better the dispersion of clay in either continuous phase or disperse phase, the higher the thermal stability of the blends. Besides, samples with clay located in the continuous phase can display the best strengthening effect.
The typical immiscible PP/PS blend based clay nanocomposites were prepared via melt blending. The dispersion of clay was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and dynamic mechanical properties were measured by thermogravimetrical analysis (TGA) and dynamic mechanical analysis (DMA), respectively. Preferential intercalation behavior of clay in PP/PS blends was found. The dispersion of clay is significantly influenced by the polarity of PP and PS, meanwhile the location of clay can be controlled by the alternation of the polarity of PP and PS through chemical modification. The clay migrates from PS phase to PP phase with the improvement of the polarity of PP. However, when the PS is sulfonated, clay migrates back to the dispersed PS phase again. The dispersion and location of clay have profound influence on the thermal and dynamic mechanical behavior of PP/PS blends. The better the dispersion of clay in either continuous phase or disperse phase, the higher the thermal stability of the blends. Besides, samples with clay located in the continuous phase can display the best strengthening effect.
2008, 26(6): 793-797
Abstract:
Aromatic copolyamides were synthesized by the Yamazaki phosphorylation method starting from bis(4-carboxyphenyl) phenyl phosphine oxide, terephthalic acid and 4,4'-diaminodiphenyl methane. The copolymers with inherent viscosities of 0.52-0.99 dL/g were obtained. The structures of the copolyamides were characterized by elemental analysis, FTIR and NMR. The glass transition temperatures were measured by DSC and DMA, respectively, and the results showed that the Tgs of the polymers were higher than 287oC. Thermal decomposition temperatures of the copolyamides at 5% weight loss were found in the range of 423-469oC by TGA. Most of the copolymers were readily soluble in a variety of organic solvents such as NMP, DMAc, m-cresol and so on. The tensile experiments of the thin films showed that the polymers had good mechanical properties.
Aromatic copolyamides were synthesized by the Yamazaki phosphorylation method starting from bis(4-carboxyphenyl) phenyl phosphine oxide, terephthalic acid and 4,4'-diaminodiphenyl methane. The copolymers with inherent viscosities of 0.52-0.99 dL/g were obtained. The structures of the copolyamides were characterized by elemental analysis, FTIR and NMR. The glass transition temperatures were measured by DSC and DMA, respectively, and the results showed that the Tgs of the polymers were higher than 287oC. Thermal decomposition temperatures of the copolyamides at 5% weight loss were found in the range of 423-469oC by TGA. Most of the copolymers were readily soluble in a variety of organic solvents such as NMP, DMAc, m-cresol and so on. The tensile experiments of the thin films showed that the polymers had good mechanical properties.
2008, 26(6): 799-801
Abstract:
A rare earth Schiff base complex: lanthanum tris(N-phenylethyl-3,5-di-t-butylsalicylaldiminato)s [La(OPEBS)3] was successfully applied as single component initiator for the ring-opening polymerization of 1,4-dioxan-2-one (PDO) in bulk. The influence of reaction conditions, such as polymerization temperature, the molar ratio of the monomer to initiator (M/I) on the monomer conversion and molecular weight of the polymer has been investigated. Poly(1,4-dioxan-2-one) with a viscosity-average molecular weight (Mv) of 8. 29 × 104 and yield of 91.5% was prepared.
A rare earth Schiff base complex: lanthanum tris(N-phenylethyl-3,5-di-t-butylsalicylaldiminato)s [La(OPEBS)3] was successfully applied as single component initiator for the ring-opening polymerization of 1,4-dioxan-2-one (PDO) in bulk. The influence of reaction conditions, such as polymerization temperature, the molar ratio of the monomer to initiator (M/I) on the monomer conversion and molecular weight of the polymer has been investigated. Poly(1,4-dioxan-2-one) with a viscosity-average molecular weight (Mv) of 8. 29 × 104 and yield of 91.5% was prepared.
