Simple modification by thermal treatment is the commonly used approach to enhance the performance... more Simple modification by thermal treatment is the commonly used approach to enhance the performance of electrospun fibers. This was investigated in the thermal treatment of polybenzoxazine (PBz) fibers blended with sulfur copolymers (SDIB) to determine the effect of varying treatment conditions on the microstructure and morphology of PBz fibers with the effect of incorporating sulfur functional groups on resulting properties. Mechanical properties of PBz are greatly improved by thermally-induced ring-opening polymerization (ROP) of the oxazine ring. Blending with sulfur copolymers (SDIB) could have beneficial effects on endowed features on fibers but could also affect the resulting properties of SDIB-blended PBz fibers during crosslinking reactions. Fiber mats were fabricated by electrospinning of PBz (10 wt%) blended with SDIB (10 wt%). Physical modification with varying conditions of sequential thermal treatment were evaluated and compared to the conditions applied on pristine PBz f...
Functionalization of PBz by electrospinning of nanofibers then thermal crosslinking followed by d... more Functionalization of PBz by electrospinning of nanofibers then thermal crosslinking followed by direct sulfonation process.
This study demonstrated the processability of sulfur copolymers (SDIB) into polymer blend with po... more This study demonstrated the processability of sulfur copolymers (SDIB) into polymer blend with polybenzoxazines (PBz) and their compatibility with the electrospinning process. Synthesis of SDIB was conducted via inverse vulcanization using elemental sulfur (S8). Polymer blends produced by simply mixing with varying concentration of SDIB (5 and 10 wt%) and fixed concentration of PBz (10 wt%) exhibited homogeneity and a single-phase structure capable of forming nanofibers. Nanofiber mats were characterized to determine the blending effect on the microstructure and final properties. Fiber diameter increased and exhibited non-uniform, broader fiber diameter distribution with increased SDIB. Microstructures of mats based on SEM images showed the occurrence of partial aggregation and conglutination with each fiber. Incorporation of SDIB were confirmed from EDX which was in agreement with the amount of SDIB relative to the sulfur peak in the spectra. Spectroscopy further confirmed that SDI...
On the basis of the reaction between ketene and alcohol groups to result in an ester linkage and ... more On the basis of the reaction between ketene and alcohol groups to result in an ester linkage and Meldrum's acid as an effective precursor of ketene group, a bifunctional aliphatic Meldrum's acid compound (BisMA) is synthesized and used as a monomer to react with ethylene glycol and glycerol for the preparation of linear and cross-linked aliphatic polyesters, respectively. A 62 and 35 wt % of biodegradation fraction have been recorded on the linear and cross-linked aliphatic polyesters after an 8 week biodegradation test, respectively, to demonstrate the good biodegradability of the synthesized polyesters. In addition to conventional linear biodegradable polyesters, this synthetic route also provides a new and convenient method for preparation of cross-linked biodegradable polyesters. The types of the required monomers and reaction methods for preparation of the cross-linked biodegradable polyesters are similar to those used for conventional thermosetting resins. An integration of biodegradable polymers and thermosetting resins in polymer chemistry has been demonstrated.
Nafion-initiated atom transfer radical polymerization to prepare graft copolymers of Nafion for p... more Nafion-initiated atom transfer radical polymerization to prepare graft copolymers of Nafion for proton exchange membranes.
Flower-like CuO spheres anchored on electrospun PVDF fiber surfaces as catalytic membranes for th... more Flower-like CuO spheres anchored on electrospun PVDF fiber surfaces as catalytic membranes for the photodegradation of rhodamine B aqueous solutions.
A new class of thermosetting resins are developed through the ketene chemistry with in situ forma... more A new class of thermosetting resins are developed through the ketene chemistry with in situ formation of cavities in the resins so as to reduce the dielectric constants of the resins to about 2.0.
We explore an approach to effectively enhance the properties of cost-effective hydrocarbon proton... more We explore an approach to effectively enhance the properties of cost-effective hydrocarbon protonexchange membranes for application in the direct methanol fuel cell (DMFC). This approach utilizes sulfonated silica nanoparticles (SA-SNP) as additives to modify sulfonated poly(arylene ether ether ketone ketone) (SPAEEKK). The interaction between the sulfonic acid groups of SA-SNP and those of SPAEEKK combined with hydrophilic-hydrophobic phase separation induce the formation of proton conducting channels, as evidenced by TEM images, which contribute to increases in the proton conductivity of the SPAEEKK/SA-SNP nanocomposite membrane. The presence of SA-SNP nanoparticles also reduces methanol crossover in the membrane. Therefore, the SPAEEKK/SA-SNP nanocomposite membrane shows a high selectivity, which is 2.79-fold the selectivity of Nafion ® 117. The improved selectivity of the SPAEEKK/SNP nanocomposite membrane demonstrates potential of this approach in providing hydrocarbon-based PEMs as alternatives to Nafion in direct methanol fuel cells.
Journal of Polymer Science Part A: Polymer Chemistry, 2006
Epoxy/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were obtained from octakis(glyci... more Epoxy/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were obtained from octakis(glycidyldimethylsiloxy)octasilsesquioxane (OG) and diglycidyl ether of bisphenol A cured with small-molecule curing agents of diethylphosphite (DEP) and dicyandiamide (DICY). An increase in the POSS contents of the nanocomposites and an improvement in the nanocomposite homogeneity were observed with the use of the small-molecule curing agents. Phosphorus in DEP and nitrogen in DICY also performed synergism with POSS for thermal stability enhancement and flammability improvement in the nanocomposites. The nanocomposites possessing high OG contents exhibited good thermal stability, improved flammability, and high storage moduli. V
Organic/inorganic urea/malonamide dendron-POSS nanohybrids with different generations of dendrons... more Organic/inorganic urea/malonamide dendron-POSS nanohybrids with different generations of dendrons and peripheral groups were prepared. Chemical structures of the nanohybrids were characterized with FTIR, 1 H NMR, molecular mass spectrometry, and elemental analysis. The nanohybrids exhibited better solubility in organic solvents as compared to their corresponding dendrons. Self-assembled layered dendron/POSS structures were observed for the nanohybrids with the low generation dendrons, as evidenced by TEM analysis. The nanohybrids also exhibited amphiphilic property because of the hydrophilicity of urea/malonamide dendrons. Moreover, the morphologies of the nanohybrids could be tailored via using various casting solvents.
Nanocomposite proton exchange membranes were prepared from sulfonated poly(phthalazinone ether ke... more Nanocomposite proton exchange membranes were prepared from sulfonated poly(phthalazinone ether ketone) (sPPEK) and various amounts of sulfonated silica nanoparticles (silica-SO 3 H). The use of silica-SO 3 H compensates for the decrease in ion exchange capacity of membranes observed when non-sulfonated nano-fillers are utilized. The strong-SO 3 H/-SO 3 H interaction between sPPEK chains and silica-SO 3 H particles leads to ionic cross-linking in the membrane structure, which increases both the thermal stability and methanol resistance of the membranes. The membrane with 7.5 phr of silica-SO 3 H (phr = g of silica-SO 3 H/100 g of sPPEK in membranes) exhibits low methanol crossover, high bound-water content, and a proton conductivity of 3.6 fold increase to that of the pristine sPPEK membrane.
X-Ray diffraction (XRD) measurements XRD measurements were performed with an instrument of Rigaku... more X-Ray diffraction (XRD) measurements XRD measurements were performed with an instrument of Rigaku D/max-3C OD-2988N wide angle XRD using Cu K α line (λ = 0.15418 nm) as a radiation source. The Fe 3 O 4 structure is characterized with the peaks at about 30 o (111), 36 o (311), 48 o (400), 57 o (511), and 62.5 o
Two series of novel phosphorus-containing poly(alkylene) amines with or without aromatic groups w... more Two series of novel phosphorus-containing poly(alkylene) amines with or without aromatic groups were synthesized via reacting phosphoryl chloride derivatives with commercially available polyetheramines, ethylenediamine and N-phenyl-1,4phenylenediamine, respectively. Chemical structures of the amines were characterized with FTIR, NMR, P (phosphorus) content measurement, and amine content titration. These amines were then utilized as curing agents to react with diglycidyl ether of bisphenol A for preparing phosphorus containing epoxy polymers. The introduction of soft OPOOO linkage, polyalkyene, and hard aromatic group into the backbones of the synthesized phosphorus-containing amine (PCA) provides epoxy resins with tunable flexibility. Thermal analysis of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveals that these resulted epoxy resins possess moderate T g 's and thermal stability. Furthermore, high char yields in TGA and high limited oxygen index (LOI) values indicate that these phosphorus-containing epoxy (PCE) resins are capable of exhibiting excellent flame retardant properties. These polymers can be potentially utilized in flame retardant epoxy coatings and other applications.
To achieve highly efficient proton conduction, microphase-separated morphological structure is cr... more To achieve highly efficient proton conduction, microphase-separated morphological structure is crucial for proton exchange membranes (PEMs). Herein, we report a novel fully aromatic triblock copolymer, sulfonated poly(2,6-phenyl-1,4-phenylene oxide)-b-poly(arylene ether sulfone)-b-sulfonated poly(2,6-phenyl-1,4-phenylene oxide) (SPPO-b-PAES-b-SPPO) with highly sulfonated PPO blocks. This molecular design for a PEM was implemented to promote the nanophase separation between the hydrophobic polymer chain and hydrophilic ionic groups that are responsible for the water uptake and conduction. Morphological investigations and electrochemical measurements reveal that the proton-conducting systems derived from this triblock copolymer architecture exhibit nanoscale-organized phase separated morphology Submitted to 2 with well-connected hydrophilic nanochannels, and thus show a dramatic enhancement in proton conductivity under partially hydrated conditions, relative to other hydrocarbon-based PEMs. The results suggest that nanoscale organization of proton-conducting functionalities is a key consideration in obtaining efficient proton transport in a partly hydrated operating environment.
Meldrum's acid (MA) is utilized as a monomer to polymerize with diisocyanates to result in polyam... more Meldrum's acid (MA) is utilized as a monomer to polymerize with diisocyanates to result in polyamides, containing MA moieties at polymer chains. This reaction is also employed to prepare isocyanate-terminated polyamide segments which are utilized as a precursor for preparation of MA-containing polyurethanes. Based on the thermolysis reaction of MA groups, followed by ketene dimerization reaction, the reactive polyamides and polyurethanes show selfcross-linkable features. The cross-linked polyurethanes exhibit good film formability, thermal stability, and mechanical properties. A new MA-based polymerization method and a novel synthesis route for preparation of reactive polyamides and polyurethanes are demonstrated.
Epoxy-melamine hybrid resins were obtained from in situ polymerization of siliconized (SE500) and... more Epoxy-melamine hybrid resins were obtained from in situ polymerization of siliconized (SE500) and phosphorylated (PE690) epoxy resins with hexakis-(methoxymethyl)melamine (HMMM). The hybrid resins having HMMM contents less than 15 wt % exhibited high transparency and homogeneity. The compatibilities between SE500 and melamine as well as that between PE690 and melamine were poor than the compatibility between general bisphenol-A epoxy and melamine. Incorporation of HMMM altered the degradation mechanisms and enhanced the thermal stability of the epoxy resins, especially for PE690 based resins. Excellent flame retardant property was observed with the hybrid resins because of the SiON and PON synergisms of flame retardation.
Simple modification by thermal treatment is the commonly used approach to enhance the performance... more Simple modification by thermal treatment is the commonly used approach to enhance the performance of electrospun fibers. This was investigated in the thermal treatment of polybenzoxazine (PBz) fibers blended with sulfur copolymers (SDIB) to determine the effect of varying treatment conditions on the microstructure and morphology of PBz fibers with the effect of incorporating sulfur functional groups on resulting properties. Mechanical properties of PBz are greatly improved by thermally-induced ring-opening polymerization (ROP) of the oxazine ring. Blending with sulfur copolymers (SDIB) could have beneficial effects on endowed features on fibers but could also affect the resulting properties of SDIB-blended PBz fibers during crosslinking reactions. Fiber mats were fabricated by electrospinning of PBz (10 wt%) blended with SDIB (10 wt%). Physical modification with varying conditions of sequential thermal treatment were evaluated and compared to the conditions applied on pristine PBz f...
Functionalization of PBz by electrospinning of nanofibers then thermal crosslinking followed by d... more Functionalization of PBz by electrospinning of nanofibers then thermal crosslinking followed by direct sulfonation process.
This study demonstrated the processability of sulfur copolymers (SDIB) into polymer blend with po... more This study demonstrated the processability of sulfur copolymers (SDIB) into polymer blend with polybenzoxazines (PBz) and their compatibility with the electrospinning process. Synthesis of SDIB was conducted via inverse vulcanization using elemental sulfur (S8). Polymer blends produced by simply mixing with varying concentration of SDIB (5 and 10 wt%) and fixed concentration of PBz (10 wt%) exhibited homogeneity and a single-phase structure capable of forming nanofibers. Nanofiber mats were characterized to determine the blending effect on the microstructure and final properties. Fiber diameter increased and exhibited non-uniform, broader fiber diameter distribution with increased SDIB. Microstructures of mats based on SEM images showed the occurrence of partial aggregation and conglutination with each fiber. Incorporation of SDIB were confirmed from EDX which was in agreement with the amount of SDIB relative to the sulfur peak in the spectra. Spectroscopy further confirmed that SDI...
On the basis of the reaction between ketene and alcohol groups to result in an ester linkage and ... more On the basis of the reaction between ketene and alcohol groups to result in an ester linkage and Meldrum's acid as an effective precursor of ketene group, a bifunctional aliphatic Meldrum's acid compound (BisMA) is synthesized and used as a monomer to react with ethylene glycol and glycerol for the preparation of linear and cross-linked aliphatic polyesters, respectively. A 62 and 35 wt % of biodegradation fraction have been recorded on the linear and cross-linked aliphatic polyesters after an 8 week biodegradation test, respectively, to demonstrate the good biodegradability of the synthesized polyesters. In addition to conventional linear biodegradable polyesters, this synthetic route also provides a new and convenient method for preparation of cross-linked biodegradable polyesters. The types of the required monomers and reaction methods for preparation of the cross-linked biodegradable polyesters are similar to those used for conventional thermosetting resins. An integration of biodegradable polymers and thermosetting resins in polymer chemistry has been demonstrated.
Nafion-initiated atom transfer radical polymerization to prepare graft copolymers of Nafion for p... more Nafion-initiated atom transfer radical polymerization to prepare graft copolymers of Nafion for proton exchange membranes.
Flower-like CuO spheres anchored on electrospun PVDF fiber surfaces as catalytic membranes for th... more Flower-like CuO spheres anchored on electrospun PVDF fiber surfaces as catalytic membranes for the photodegradation of rhodamine B aqueous solutions.
A new class of thermosetting resins are developed through the ketene chemistry with in situ forma... more A new class of thermosetting resins are developed through the ketene chemistry with in situ formation of cavities in the resins so as to reduce the dielectric constants of the resins to about 2.0.
We explore an approach to effectively enhance the properties of cost-effective hydrocarbon proton... more We explore an approach to effectively enhance the properties of cost-effective hydrocarbon protonexchange membranes for application in the direct methanol fuel cell (DMFC). This approach utilizes sulfonated silica nanoparticles (SA-SNP) as additives to modify sulfonated poly(arylene ether ether ketone ketone) (SPAEEKK). The interaction between the sulfonic acid groups of SA-SNP and those of SPAEEKK combined with hydrophilic-hydrophobic phase separation induce the formation of proton conducting channels, as evidenced by TEM images, which contribute to increases in the proton conductivity of the SPAEEKK/SA-SNP nanocomposite membrane. The presence of SA-SNP nanoparticles also reduces methanol crossover in the membrane. Therefore, the SPAEEKK/SA-SNP nanocomposite membrane shows a high selectivity, which is 2.79-fold the selectivity of Nafion ® 117. The improved selectivity of the SPAEEKK/SNP nanocomposite membrane demonstrates potential of this approach in providing hydrocarbon-based PEMs as alternatives to Nafion in direct methanol fuel cells.
Journal of Polymer Science Part A: Polymer Chemistry, 2006
Epoxy/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were obtained from octakis(glyci... more Epoxy/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were obtained from octakis(glycidyldimethylsiloxy)octasilsesquioxane (OG) and diglycidyl ether of bisphenol A cured with small-molecule curing agents of diethylphosphite (DEP) and dicyandiamide (DICY). An increase in the POSS contents of the nanocomposites and an improvement in the nanocomposite homogeneity were observed with the use of the small-molecule curing agents. Phosphorus in DEP and nitrogen in DICY also performed synergism with POSS for thermal stability enhancement and flammability improvement in the nanocomposites. The nanocomposites possessing high OG contents exhibited good thermal stability, improved flammability, and high storage moduli. V
Organic/inorganic urea/malonamide dendron-POSS nanohybrids with different generations of dendrons... more Organic/inorganic urea/malonamide dendron-POSS nanohybrids with different generations of dendrons and peripheral groups were prepared. Chemical structures of the nanohybrids were characterized with FTIR, 1 H NMR, molecular mass spectrometry, and elemental analysis. The nanohybrids exhibited better solubility in organic solvents as compared to their corresponding dendrons. Self-assembled layered dendron/POSS structures were observed for the nanohybrids with the low generation dendrons, as evidenced by TEM analysis. The nanohybrids also exhibited amphiphilic property because of the hydrophilicity of urea/malonamide dendrons. Moreover, the morphologies of the nanohybrids could be tailored via using various casting solvents.
Nanocomposite proton exchange membranes were prepared from sulfonated poly(phthalazinone ether ke... more Nanocomposite proton exchange membranes were prepared from sulfonated poly(phthalazinone ether ketone) (sPPEK) and various amounts of sulfonated silica nanoparticles (silica-SO 3 H). The use of silica-SO 3 H compensates for the decrease in ion exchange capacity of membranes observed when non-sulfonated nano-fillers are utilized. The strong-SO 3 H/-SO 3 H interaction between sPPEK chains and silica-SO 3 H particles leads to ionic cross-linking in the membrane structure, which increases both the thermal stability and methanol resistance of the membranes. The membrane with 7.5 phr of silica-SO 3 H (phr = g of silica-SO 3 H/100 g of sPPEK in membranes) exhibits low methanol crossover, high bound-water content, and a proton conductivity of 3.6 fold increase to that of the pristine sPPEK membrane.
X-Ray diffraction (XRD) measurements XRD measurements were performed with an instrument of Rigaku... more X-Ray diffraction (XRD) measurements XRD measurements were performed with an instrument of Rigaku D/max-3C OD-2988N wide angle XRD using Cu K α line (λ = 0.15418 nm) as a radiation source. The Fe 3 O 4 structure is characterized with the peaks at about 30 o (111), 36 o (311), 48 o (400), 57 o (511), and 62.5 o
Two series of novel phosphorus-containing poly(alkylene) amines with or without aromatic groups w... more Two series of novel phosphorus-containing poly(alkylene) amines with or without aromatic groups were synthesized via reacting phosphoryl chloride derivatives with commercially available polyetheramines, ethylenediamine and N-phenyl-1,4phenylenediamine, respectively. Chemical structures of the amines were characterized with FTIR, NMR, P (phosphorus) content measurement, and amine content titration. These amines were then utilized as curing agents to react with diglycidyl ether of bisphenol A for preparing phosphorus containing epoxy polymers. The introduction of soft OPOOO linkage, polyalkyene, and hard aromatic group into the backbones of the synthesized phosphorus-containing amine (PCA) provides epoxy resins with tunable flexibility. Thermal analysis of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveals that these resulted epoxy resins possess moderate T g 's and thermal stability. Furthermore, high char yields in TGA and high limited oxygen index (LOI) values indicate that these phosphorus-containing epoxy (PCE) resins are capable of exhibiting excellent flame retardant properties. These polymers can be potentially utilized in flame retardant epoxy coatings and other applications.
To achieve highly efficient proton conduction, microphase-separated morphological structure is cr... more To achieve highly efficient proton conduction, microphase-separated morphological structure is crucial for proton exchange membranes (PEMs). Herein, we report a novel fully aromatic triblock copolymer, sulfonated poly(2,6-phenyl-1,4-phenylene oxide)-b-poly(arylene ether sulfone)-b-sulfonated poly(2,6-phenyl-1,4-phenylene oxide) (SPPO-b-PAES-b-SPPO) with highly sulfonated PPO blocks. This molecular design for a PEM was implemented to promote the nanophase separation between the hydrophobic polymer chain and hydrophilic ionic groups that are responsible for the water uptake and conduction. Morphological investigations and electrochemical measurements reveal that the proton-conducting systems derived from this triblock copolymer architecture exhibit nanoscale-organized phase separated morphology Submitted to 2 with well-connected hydrophilic nanochannels, and thus show a dramatic enhancement in proton conductivity under partially hydrated conditions, relative to other hydrocarbon-based PEMs. The results suggest that nanoscale organization of proton-conducting functionalities is a key consideration in obtaining efficient proton transport in a partly hydrated operating environment.
Meldrum's acid (MA) is utilized as a monomer to polymerize with diisocyanates to result in polyam... more Meldrum's acid (MA) is utilized as a monomer to polymerize with diisocyanates to result in polyamides, containing MA moieties at polymer chains. This reaction is also employed to prepare isocyanate-terminated polyamide segments which are utilized as a precursor for preparation of MA-containing polyurethanes. Based on the thermolysis reaction of MA groups, followed by ketene dimerization reaction, the reactive polyamides and polyurethanes show selfcross-linkable features. The cross-linked polyurethanes exhibit good film formability, thermal stability, and mechanical properties. A new MA-based polymerization method and a novel synthesis route for preparation of reactive polyamides and polyurethanes are demonstrated.
Epoxy-melamine hybrid resins were obtained from in situ polymerization of siliconized (SE500) and... more Epoxy-melamine hybrid resins were obtained from in situ polymerization of siliconized (SE500) and phosphorylated (PE690) epoxy resins with hexakis-(methoxymethyl)melamine (HMMM). The hybrid resins having HMMM contents less than 15 wt % exhibited high transparency and homogeneity. The compatibilities between SE500 and melamine as well as that between PE690 and melamine were poor than the compatibility between general bisphenol-A epoxy and melamine. Incorporation of HMMM altered the degradation mechanisms and enhanced the thermal stability of the epoxy resins, especially for PE690 based resins. Excellent flame retardant property was observed with the hybrid resins because of the SiON and PON synergisms of flame retardation.
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Papers by Ying-Ling Liu