Characterization and Morphology of Nanocomposite Hydrogels with a 3D Network Structure Prepared Using Attapulgite-Enhanced Polyvinyl Alcohol.

In this investigation, purified attapulgite (ATT) and polyvinyl alcohol (PVA) were utilized to fabricate nanocomposite hydrogels and a xerogel, with a focus on studying the impact of minor additions of ATT on the properties of the PVA nanocomposite hydrogels and xerogel. The findings demonstrated that at a concentration of 0.75% ATT, the water content and gel fraction of the PVA nanocomposite hydrogel reached their peak. Conversely, the nanocomposite xerogel with 0.75% ATT reduced its swelling and porosity to the minimum. SEM and EDS analyses revealed that when the ATT concentration was at or below 0.5%, nano-sized ATT could be evenly distributed in the PVA nanocomposite xerogel. However, when the concentration of ATT rose to 0.75% or higher, the ATT began to aggregate, resulting in a decrease in porous structure and the disruption of certain 3D porous continuous structures. The XRD analysis further affirmed that at an ATT concentration of 0.75% or higher, a distinct ATT peak emerged in the PVA nanocomposite xerogel. It was observed that as the content of ATT increased, the concavity and convexity of the xerogel surface, as well as the surface roughness, decreased. The results also confirmed that the ATT was evenly distributed in the PVA, and a combination of hydrogen bonds and ether bonds resulted in a more stable gel structure. The tensile properties exhibited that when compared with pure PVA hydrogel, the maximum tensile strength and elongation at break were achieved at an ATT concentration of 0.5%, indicating increases of 23.0% and 11.8%, respectively. The FTIR analysis results showed that the ATT and PVA could generate an ether bond, further confirming that ATT could enhance the PVA properties. The TGA analysis showed that the thermal degradation temperature peaked when the ATT concentration was at 0.5%, providing further evidence that the compactness of the nanocomposite hydrogel and the dispersion of the nanofiller was superior, contributing to a substantial increase in the mechanical properties of the nanocomposite hydrogel. Finally, the dye adsorption results displayed a significant rise in dye removal efficiency for methylene blue with the increase in the ATT concentration. At an ATT concentration of 1%, the removal efficiency rose by 103% compared with that of the pure PVA xerogel.

Enhanced Piezoelectric Properties of Poly(Vinylidenefluoride-Co-Trifluoroethylene)/Carbon-Based Nanomaterial Composite Films for Pressure Sensing Applications.

In this study, heat and polarization treatments were applied to poly(vinylidenefluoride-co-trifluoroethylene (PVDF-TrFE) films to improve their crystallinity and piezoelectric effect. Carbon-based nanomaterials (CBNs) of multiple dimensions (i.e., modified zero-dimensional (0D) carbon black (OCB), one-dimensional (1D) modified carbon nanotubes (CNT-COOH) and two-dimensional (2D) graphene oxide (GO)) were added to the copolymer to study the effects of different CBN dimensions on the crystallinity and piezoelectric effect of PVDF-TrFE films. Additionally, amphiphilic polymeric dispersants were added to improve the dispersibility of CBNs; the dispersant was synthesized by the amidation, and imidization reactions of styrene-maleic anhydride copolymer (SMAz) and polyoxyalkylene amine (M1000). Polymer solutions with different ratios of CBN to dispersant (z = 10:1, 5:1, 1:1, 1:5, 1:10) were prepared. The enhanced dispersibility enabled the fluorine atoms in the PVDF-TrFE molecular chain to more efficiently form hydrogen bonds with the -COOH group in the CBN, thereby increasing the content of the ß crystal phase (the origin of the piezoelectric effect) of the film. Therefore, the resulting film exhibited a higher output voltage on the application side and better sensitivity on the sensing element. The addition of CNT-COOH and polymeric dispersants increased the ß-phase content in PVDF-TrFE from 73.6% to 86.4%, which in turn raised the piezoelectric coefficient from 19.8 ± 1.0 to 26.4 ± 1.3 pC/N. The composite film-based pressure sensor also exhibited a high degree of sensitivity, which is expected to have commercial potential in the future.

Characterization of network bonding created by intercalated functionalized graphene and polyvinyl alcohol in nanocomposite films for reinforced mechanical properties and barrier performance.

Graphene that consists of less than 10 layers is expensive; moreover, it tends to agglomerate. These disadvantages restrict its utility. In this regard, the present study aimed to reduce the number of layers of a functionalized graphene (FG) with 10-30 layers to less than 10 layers by using an ultrasonic processor. We prepared nanocomposite films of polyvinyl alcohol (PVA) incorporated with FG by a simple hydrothermal method and ultrasonic dispersion. Oxygen transmission rate and water vapor permeability were considerably increased on account of modifying PVA with FG. Furthermore, the mechanical properties, thermostability, and barrier properties were improved. The barrier efficiency of the nanocomposites at different temperatures remained high for long periods of operation because of the network bonding. A simple procedure involving relatively low-cost nanomaterials could unlock the potential of nanocomposite FG/PVA films in the fields of coating, packaging, and semiconductor materials.

Controlling the Structures, Flexibility, Conductivity Stability of Three-Dimensional Conductive Networks of Silver Nanoparticles/Carbon-Based Nanomaterials with Nanodispersion and their Application in Wearable Electronic Sensors.

This research has successfully synthesized highly flexible and conductive nanohybrid electrode films. Nanodispersion and stabilization of silver nanoparticles (AgNPs) were achieved via non-covalent adsorption and with an organic polymeric dispersant and inorganic carbon-based nanomaterials-nano-carbon black (CB), carbon nanotubes (CNT), and graphene oxide (GO). The new polymeric dispersant-polyisobutylene-b-poly(oxyethylene)-b-polyisobutylene (PIB-POE-PIB) triblock copolymer-could stabilize AgNPs. Simultaneously, this stabilization was conducted through the addition of mixed organic/inorganic dispersants based on zero- (0D), one- (1D), and two-dimensional (2D) nanomaterials, namely CB, CNT, and GO. Furthermore, the dispersion solution was evenly coated/mixed onto polymeric substrates, and the products were heated. As a result, highly conductive thin-film materials (with a surface electrical resistance of approximately 10-2 Ω/sq) were eventually acquired. The results indicated that 2D carbon-based nanomaterials (GO) could stabilize AgNPs more effectively during their reductNion and, hence, generate particles with the smallest sizes, as the COO- functional groups of GO are evenly distributed. The optimal AgNPs/PIB-POE-PIB/GO ratio was 20:20:1. Furthermore, the flexible electrode layers were successfully manufactured and applied in wearable electronic sensors to generate electrocardiograms (ECGs). ECGs were, thereafter, successfully obtained.

Synthetic Environmentally Friendly Castor Oil Based-Polyurethane with Carbon Black as a Microphase Separation Promoter.

This study created water polyurethane (WPU) prepolymer by using isophorone diisocyanate, castor oil, dimethylolpropionic acid, and triethanolamine (TEA) as the hard segment, soft segment, hydrophilic group, and neutralizer, respectively. TEA, deionized water, and carbon black (CB) were added to the prepolymer under high-speed rotation to create an environmentally friendly vegetable-oil-based polyurethane. CB served as the fortifier and promoter of microphase separation. Fourier transform infrared spectroscopy was performed to elucidate the role of H-bond interactions within the CB/WPUs. Additionally, atomic force microscopy was conducted to determine the influence of H-bond interactions on the degree of microphase separation in the WPU. Furthermore, this study used four-point probe observation to discover the materials' conductivity of CB in the WPU. Thermogravimetric analysis and dynamic mechanical analysis were performed to measure the thermal properties of the CB/WPUs. The mechanical properties of CB/WPUs were measured using a tensile testing machine. The CB/WPUs were also soaked in 1 wt.% NaOH solution for different amounts of time to determine the degradation properties of the CB/WPUs. Finally, scanning electron microscopy was performed to observe the topography of the CB/WPUs after degradation.

Properties and degradation of castor oil-based fluoridated biopolyurethanes with different lengths of fluorinated segments.

To develop a durable, biodegradable polymer, this study successfully synthesized a castor-oil-based prepolymer by using methylene diphenyl diisocyanate as a hard segment, polycaprolactone as a soft segment, and castor oil as a functional monomer. We added perfluorinated alkyl segments with varying chain lengths into the castor-oil-based polymer to synthesize castor-oil-based fluoridated biopolyurethanes (FCOPUs) with different fluorinated segment lengths. The castor-oil-based polyurethanes with different fluorinated segment lengths had similar molecular weights, which enabled accurate analysis of the effect of the lengths of fluorinated segments on FCOPUs. Nuclear magnetic resonance (NMR) was used to perform 1H NMR, 19F NMR, 19F-19F COSY, 1H-19F COSY, and HMBC analyses on the FCOPU structures. The results of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy curve fitting verified the interaction between C-F⋯H-N and C-F⋯C[double bond, length as m-dash]O. This interaction increased as the fluorinated segments became longer. Regarding the thermal properties of the FCOPUs, the thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis results revealed that long fluorinated segments were associated with increased thermal stability in the FCOPUs. The atomic force microscopy and tensile strength test suggested that long fluorinated segments contained in the FCOPUs increased the degree of phase separation and tensile strength in FCOPUs. Finally, we dipped the FCOPUs in a 3 wt% NaOH solution, calculated the weight loss of the FCOPUs, and observed their surface structure by using scanning electron microscopy.

Synthesis and properties of shape memory polyurethanes generated from schiff-base chain extender containing benzoyl and pyridyl rings.

In this study, 4,4'-diphenylmethane diisocyanate and polytetramethylene glycol were used to prepare a prepolymer; N,N'-bis(4-hydroxybenzylidene)-2,6-diaminopyridine (BHBP) was used as a chain extender; and these elements were combined to prepare a novel polyurethane, BHBP/PU. Gel permeation chromatography revealed that the molecular weight of the BHBP/PU samples increased as the BHBP content was increased. Fourier transform infrared spectroscopy demonstrated that high BHBP content facilitated strong hydrogen bonding in the samples. Differential thermogravimetry indicated that the initial decomposition temperature of BHBP/PU-3 was approximately 10 °C higher than that of BHBP/PU-1. Differential scanning calorimetry and dynamic mechanical analysis revealed that increasing the BHBP content substantially increased both the glass transition and dynamic glass transition temperatures of the BHBP/PU samples. The tensile strengths of BHBP/PU-1, BHBP/PU-2, and BHBP/PU-3 were 7.7, 10.9, and 21.6 MPa, respectively, with corresponding Young's moduli of 0.7, 1.9, and 3.3 MPa. These results demonstrated that both the tensile strength and Young's modulus of the BHBP/PU samples increased as the BHBP content was increased. Moreover, the BHBP/PU samples exhibited excellent shape recovery of >90%.

Synthesis and Properties of Novel Polyurethanes Containing Long-Segment Fluorinated Chain Extenders.

In this study, novel biodegradable long-segment fluorine-containing polyurethane (PU) was synthesized using 4,4'-diphenylmethane diisocyanate (MDI) and 1H,1H,10H,10H-perfluor-1,10-decanediol (PFD) as hard segment, and polycaprolactone diol (PCL) as a biodegradable soft segment. Nuclear magnetic resonance (NMR) was used to perform ¹H NMR, 19F NMR, 19F⁻19F COSY, ¹H⁻19F COSY, and HMBC analyses on the PFD/PU structures. The results, together with those from Fourier transform infrared spectroscopy (FTIR), verified that the PFD/PUs had been successfully synthesized. Additionally, the soft segment and PFD were changed, after which FTIR and XPS peak-differentiation-imitating analyses were employed to examine the relationship of the hydrogen bonding reaction between the PFD chain extender and PU. Subsequently, atomic force microscopy was used to investigate the changes in the microphase structure between the PFD chain extender and PU, after which the effects of the thermal properties between them were investigated through thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. Finally, the effects of the PFD chain extender on the mechanical properties of the PU were investigated through a tensile strength test.

Antibacterial Property and Cytotoxicity of a Poly(lactic acid)/Nanosilver-Doped Multiwall Carbon Nanotube Nanocomposite.

A novel method was used to synthesize a nanosilver-doped multiwall carbon nanotube (MWCNT-Ag), and subsequently, the novel poly(lactic acid) (PLA)- and MWCNT-Ag-based biocompatible and antimicrobial nanocomposites were prepared by melt blending. Based on energy dispersive X-ray spectrometry images, an MWCNT-Ag was successfully synthesized. The effect of the MWCNT-Ag on the PLA bionanocomposites was investigated by evaluating their thermal and mechanical properties, antifungal activity, and cytotoxicity. The nanocomposites exhibited a high degree of biocompatibility with the MWCNT-Ag content, which was less than 0.3 phr. Furthermore, tensile strength testing, thermogravimetric analysis, differential scanning calorimetry, and antibacterial evaluation revealed that the tensile strength, thermostability, glass transition temperature, and antibacterial properties were enhanced by increasing the MWCNT-Ag content. Finally, hydrolysis analysis indicated that the low MWCNT-Ag content could increase the packing density of PLA.

Biocompatibility and characterization of polylactic acid/styrene-ethylene-butylene-styrene composites.

Polylactic acid (PLA)/styrene-ethylene-butylene-styrene (SEBS) composites were prepared by melt blending. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WXRD) were used to characterize PLA and PLA/SEBS composites in terms of their melting behavior and crystallization. Curves from thermal gravimetric analysis (TGA) illustrated that thermostability increased with SEBS content. Further morphological analysis of PLA/SEBS composites revealed that SEBS molecules were not miscible with PLA molecules in PLA/SEBS composites. The tensile testing for PLA and PLA/SEBS composites showed that the elongation at the break was enhanced, but tensile strength decreased with increasing SEBS content. L929 fibroblast cells were chosen to assess the cytocompatibility; the cell growth of PLA was found to decrease with increasing SEBS content. This study proposes possible reasons for these properties of PLA/SEBS composites.

Preparation and Characterization of Bioplastic-Based Green Renewable Composites from Tapioca with Acetyl Tributyl Citrate as a Plasticizer.

Granular tapioca was thermally blended with poly(lactic acid) (PLA). All blends were prepared using a plasti-corder and characterized for tensile properties, thermal properties and morphology. Scanning electron micrographs showed that phase separation occurred, leading to poor tensile properties. Therefore, methylenediphenyl diisocyanate (MDI) was used as an interfacial compatibilizer to improve the mechanical properties of PLA/tapioca blends. The addition of MDI could improve the tensile strength of the blend with 60 wt% tapioca, from 19.8 to 42.6 MPa. In addition, because PLA lacked toughness, acetyl tributyl citrate (ATBC) was added as a plasticizer to improve the ductility of PLA. A significant decrease in the melting point and glass-transition temperature was observed on the basis of differential scanning calorimetry, which indicated that the PLA structure was not dense after ATBC was added. As such, the brittleness was improved, and the elongation at break was extended to several hundred percent. Therefore, mixing ATBC with PLA/tapioca/MDI blends did exhibit the effect of plasticization and biodegradation. The results also revealed that excessive plasticizer would cause the migration of ATBC and decrease the tensile properties.

Tetra-kis[µ-1,3-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene-κ(2)N:N']tris-ilver(I) tris-(hexa-fluoridophosphate).

In the title compound, [Ag(3)(C(12)H(12)N(2)O(2))(4)](PF(6))(3), one Ag(I) ion, lying on a twofold rotation axis, is coordinated by four N atoms from four 1,3-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene (L) ligands in a distorted tetra-hedral geometry and the other Ag(I) ion is coordinated by two N atoms from two L ligands in a bent arrangement [N-Ag-N = 169.03 (17)°]. Two L ligands adopt a syn conformation, while the other two adopt an anti conformation. They bridge adjacent Ag(I) ions, forming a trinuclear complex. One of the PF(6) (-) anions is half-occupied, with the P atom located on a twofold rotation axis. The PF(6) (-) anions link the complex mol-ecules via Ag⋯F inter-actions [2.80 (2) and 2.85 (2) Å] into a polymeric chain along [100].

Poly[[µ-(3-amino-pyridine)-κ(2)N:N'-µ-chlorido-chlorido(N,N'-dimethyl-formamide-κO)nickel(II)] N,N'-dimethyl-formamide monosolvate].

The title compound, {[NiCl(2)(C(5)H(6)N(2))(C(3)H(7)NO)]·C(3)H(7)NO}(n), is a two-dimensional polymer in which the Ni(II) atom is coordinated by two N atoms from two 3-amino-pyridine ligands, one O atom from a dimethyl-formamide (DMF) group, one terminal Cl and two bridging Cl atoms in a distorted octa-hedral geometry. The Ni(II) atoms are bridged by the 3-amino-pyridine ligands [Ni⋯N = 6.7048 (3) Å] and Cl(-) atoms [Ni⋯N = 3.5698 (3) Å], forming (4,4) two-dimensional nets. The DMF solvent mol-ecule and the non-bridged Cl(-) ions participate in N-H⋯O and N-H⋯Cl hydrogen bonds with the amino groups.

Poly[(µ(3)-quinoline-6-carboxyl-ato-κ(3)N:O:O')silver(I)].

In the title coordination polymer, [Ag(C(10)H(6)NO(2))](n), the Ag(I) cation is coordinated by two O atoms and one N atom from three 6-quinoline-carboxyl-ate anions in a distorted T-shaped AgNO(2) geometry, in which the O-Ag-O angle is 160.44 (9)°. The 6-quinoline-carboxyl-ate anion bridges three Ag(+) cations, forming a nearly planar polymeric sheet parallel to (101). The distance between Ag(+) cations bridged by the carboxyl group is 2.9200 (5) Å. In the crystal, π-π stacking is observed between parallel quinoline ring systems, the centroid-centroid distance being 3.7735 (16) Å.

catena-Poly[[silver(I)-µ-1,2-bis-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)ethane-κ(2)N:N'] perchlorate hemihydrate].

In the title coordination polymer, {[Ag(C(12)H(20)N(2)O(2))]ClO(4)·0.5H(2)O}(n), the Ag(I) cation is coordinated by two N atoms from two 1,2-bis-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)ethane (L) ligands in a nearly linear geometry [N-Ag-N = 171.07 (8)°]. The L ligand bridges adjacent Ag(+) cations, forming a polymeric chain running along the c axis. The lattice water mol-ecule is situated on a twofold rotation axis, and links to the perchlorate anion via an O-H⋯O hydrogen bond. The long Ag⋯O separation of 3.200 (4) Šindicates a weak inter-action between the perchlorate anion and the Ag(I) cation. Weak C-H⋯O hydrogen bonding occurs between the chain and the lattice water mol-ecule and between the chain and perchlorate anions. Both five-membered rings of the L ligand display envelope conformations; in one five-membered ring, the flap C atom is disordered on opposite sides of the ring with occupancies of 0.65 and 0.35.

Tetra-kis[µ-1,4-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene-κN:N']tetra-kis-(µ-methano-lato-κO:O)bis-(µ-perchlorato-κO:O')tetra-copper(II) bis-(perchlorate).

The title tetra-nuclear Cu(II) complex, [Cu(4)(C(12)H(12)N(2)O(2))(4)(CH(3)O)(4)(ClO(4))(2)](ClO(4))(2), is located around an inversion center. Each Cu(II) atom is coordinated by two cis-O atoms from two bridging methano-late anions and two cis-N atoms from two bridging 1,4-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene (L) ligands in the basal plane, and is further coordinated by one O atom of the bridging perchlorate anion, forming a distorted square-pyramidal geometry. The Cu⋯Cu separations in the recta-ngular core are 2.9878 (11) and 6.974 (1) Å. In the asymmetric unit, there are two L ligands with a syn conformation. In one L ligand, the dihedral angles between the central benzene ring and the terminal 4,5-dihydro-1,3-oxazol-2-yl mean planes are 22.1 (4) and 33.1 (4)°, and in the other L ligand the corresponding dihedral angles are 29.3 (4) and 29.9 (4)°. The uncoordinated perchlorate anion is linked with the complex mol-ecules via weak C-H⋯O hydrogen bonds.

catena-Poly[(µ-2-amino-1,3,4-thia-diazole-κN:N)di-µ-chlorido-cadmium].

In the title coordination polymer, [CdCl(2)(C(2)H(3)N(3)S)](n), the Cd(II) cation is coordinated by four Cl(-) anions and two N atoms from two trans 2-amino-1,3,4-thia-diazole (L) ligands in a distorted octa-hedral geometry. The L ligand and Cl(-) anions bridge adjacent Cd cations, forming a polymeric chain along the b axis; the separation between adjacent Cd cations is 3.619 (1) Å. In the crystal, the polymeric chains are inter-linking through N-H⋯Cl hydrogen bonds between the L ligands and Cl(-) anions.

Poly[[µ(2)-1,4-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene-κN:N']di-µ(2)-chlorido-cadmium].

In the title coordination polymer, [CdCl(2)(C(12)H(12)N(2)O(2))](n), the Cd(II) ion, situated on an inversion center, is coordinated by four bridging Cl atoms and two N atoms from two 1,4-bis-(4,5-dihydro-1,3--oxazol-2-yl)benzene (L) ligands in a distorted octa-hedral geometry. Each L ligand also lies across an inversion center and bridges two Cd(II) ions, forming infinite two-dimensional recta-ngular layers running parallel to (010).

Poly[[µ-1,4-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene-κN:N']di-µ-bromido-cadmium].

In the title coordination polymer, [CdBr(2)(C(12)H(12)N(2)O(2))](n), the Cd(II) ion, situated on an inversion centre, is coordinated by four bridging Br atoms and two N atoms from two 1,4-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene (L) ligands in a distorted octa-hedral geometry. The L ligand, which also lies across an inversion centre, bridges two Cd(II) ions, forming layers parallel to (010).

catena-Poly[[bis-(nitrato-κO)copper(II)]-µ-1,4-bis-(4,5-dihydro-1,3-oxazol-2-yl)-benzene-κN:N'].

In the title coordination polymer, [Cu(NO(3))(2)(C(12)H(12)N(2)O(2))](n), the Cu(II) ion, situated on an inversion center, is coordinated by two O atoms from two nitrate anions and two N atoms from two 1,4-bis-(4,5-dihydro-1,3-oxazol-2-yl)benzene (L) ligands in a distorted square-planar geometry. Each L ligand also lies across an inversion center and bridges two Cu(II) ions, forming a polymeric chain running along the [101] direction. The three O atoms of the nitrate group are disordered over two positions in a 3:2 ratio.