Synthesis,characterization, and flocculation characteristics of hydrolyzed and unhydrolyzed polyacrylamide grafted xanthan gum

The partial hydrolysis of xanthan gum‐g‐polyacrylamide was carried out in alkaline medium. Four grades of partially hydrolyzed products were synthesized by varying the reaction parameters. The neutralization equivalents of these products were determined by titration with standard sodium hydroxide solution. The flocculation characteristics of all the hydrolyzed graft copolymers and the unhydrolyzed xanthan gum‐g‐polyacrylamide were determined in 5 wt % iron ore and kaolin suspensions. The partially hydrolyzed product with neutralization equivalent of 1000 g showed better performance than that of other partially hydrolyzed products, but all hydrolyzed products exhibited poorer performance than that of the unhydrolyzed product in flocculation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1411–1419, 2004     

Asymmetric oxidation of poly(vinyl sulfides) with percamphoric acid,aspergillus niger,and penicillium notatum

The asymmetric oxidation of poly(phenylvinyl sulfide) (poly-Ph VS) and poly(t-butylvinyl sulfide) (poly-t-BuVS) was carried out with optically active percamphoric acid, and the optically active polysulfoxides were obtained. The values of the specific rotation for the oxidation products of poly-PhVS and poly-t-BuVS were + 1.0 (having 56% of sulfoxide unit contents) and +9.1 (49%), respectively. The specific rotation of the product increased with increasing the contents of sulfoxide units. The optical rotatory dispersion curves of the oxidation products of poly-PhVS and poly-t-BuVS were positive curves and were found to fit the simple Drude equation. The λ_c values of the oxidation products (poly-PhVS, 271 mμ; poly-t-BuVS, 212 mμ) suggested that the chromophore which caused optically activity was the sulfoxide group. Similarly, the asymmetric oxidation of t-BuVS–MMA copolymer, t-BuVS–styrene copolymer, and PhVS–MMA copolymer was carried out, and the optically active copolysulfoxides were obtained. Furthermore, the biosynthetic oxidation of poly-PhVS and PhVS–maleic anhydride copolymer treated with aqueous KOH was carried out using Aspergillus niger or Penicillium notatum in Czapeck solution, and the optically active polymers were obtained.     

A Remarkable Titanium‐Catalyzed Asymmetric Strecker Reaction using Hydrogen Cyanide at Room Temperature

Close to perfect enantioselectivity (up to 98% ee) is obtained for the formation of amino nitriles using hydrogen cyanide (HCN) as the cyanide source at room temperature for the first time. In an operationally simple process, the catalyst generated from a partially hydrolyzed titanium alkoxide (PHTA) and (S)‐N‐salicyl‐β‐amino alcohol ligand, catalyzes the cyanation of imines in a short reaction time.     

Complexation of Titanium Alkoxides with Cis-2-butene-1,4-diol and Hydrolysis of Their Products

Reaction of Ti(OEt)₄ and Ti(OBu ⁿ )₄ with cis-2-butene-1,4-diol (B.diol-2H) in 1:1 molar ratio was studied at room temperature using the sol-gel process. ¹³C{¹H}- and ¹H-NMR data showed that all the B.diol-2H completely reacted with both titanium alkoxides. Each of the products was hydrolyzed by water. The new hydrolyzed products were characterized by ¹³C- and ¹H-NMR spectroscopy and Karl–Fischer Titration. Thermogravimetric and differential thermal analyses (TGA-DTA) of the hydrolyzed-products were also studied.     

A novel type of chiral titanium phosphonates and hybrid titanium phosphonates for heterogeneous asymmetric catalysis

(1R, 2S)-(?)-2-amino-1, 2-diphenylethanol and (1S, 2R)-(+)-2-amino-1, 2-diphenylethanol had been immobilized on the layered titanium phosphonates 4a–d and hybrid titanium phosphonates 5a–c in spheroid form with interlayer space 20.845–19.407 Å which can be used as heterogeneous catalysts in the enantioseletive addition of diethylzinc to benzaldehyde to obtain optically active (R)-or (S)-1-phenylpropan-1-ol for the first time. It was shown that the titanium phosphonate 4a led to active heterogeneous catalysis for asymmetric additions of diethylzinc to benzaldehydes in 88.5% yield and ee value of up to 40.8% which decreased at 16% ee lower than corresponding chiral ligand in homogeneous asymmetric catalysis. AFM showed that the distribution of 1,2-dipenyl-2-aminoethanol organic moieties on the surface of titanium phosphonates irregularly lined like flow mark.     

Microwave‐assisted and classical heating polycondensation reaction of bis(p‐amido benzoic acid)‐N‐trimellitylimido‐L‐leucine with diisocyanates as a new method for preparation of optically active poly(amide imide)s

A new class of optically active poly(amide imide)s were synthesized via direct polycondensation reaction of diisocyanates with a chiral diacid monomer. The step‐growth polymerization reactions of monomer bis(p‐amido benzoic acid)‐N‐trimellitylimido‐L‐leucine (BPABTL) (5) as a diacid monomer with 4,4′‐methylene bis(4‐phenylisocyanate) (MDI) (6) was performed under microwave irradiation, solution polymerization under gradual heating and reflux condition in the presence of pyridine (Py), dibuthyltin dilurate (DBTDL), and triethylamine (TEA) as a catalyst and without a catalyst, respectively. The optimized polymerization conditions according to solvent and catalyst for each method were performed with tolylene‐2,4‐diisocyanate (TDI) (7), hexamethylene diisocyanate (HDI) (8), and isophorone diisocyanate (IPDI) (9) to produce optically active poly(amide imide)s by the diisocyanate route. The resulting polymers have inherent viscosities in the range of 0.09–1.10 dL/g. These polymers are optically active, thermally stable, and soluble in amide type solvents. All of the above polymers were fully characterized by IR spectroscopy, ¹H NMR spectroscopy, elemental analyses, specific rotation, and thermal analyses methods. Some structural characterization and physical properties of this new optically active poly(amide imide)s are reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1647–1659, 2004     

Complexation of Titanium Alkoxides with Cis-2-butene-1,4-diol and Hydrolysis of Their Products

Reaction of Ti(OEt)₄ and Ti(OBu ⁿ )₄ with cis-2-butene-1,4-diol (B.diol-2H) in 1:1 molar ratio was studied at room temperature using the sol-gel process. ¹³C{¹H}- and ¹H-NMR data showed that all the B.diol-2H completely reacted with both titanium alkoxides. Each of the products was hydrolyzed by water. The new hydrolyzed products were characterized by ¹³C- and ¹H-NMR spectroscopy and Karl–Fischer Titration. Thermogravimetric and differential thermal analyses (TGA-DTA) of the hydrolyzed-products were also studied.     

Effects of Silanes Alone and Their Blends with HEMA on Resin–Titanium Bonding

Abstract

Two organofunctional silane coupling agents alone and two silane blend systems with HEMA were evaluated in vitro as adhesion promoters for bonding bis-GMA resin to a silica-coated titanium surface. The silanes were applied onto tribochemically silica-coated titanium surfaces. Experimental bis-GMA resin stubs were applied and photo-polymerized onto titanium. The specimens were subjected to three different conditions: (1) dry storage for 24 h, (2) storage in de-ionized water at 37°C for six months and (3) alternating storage in de-ionized water at 37°C and thermocycling (6000 cycles, 5–55°C) for 6 months. Shear bond strengths of the resin to titanium were measured using a universal testing machine. Surface examination was made with a scanning electron microscope (SEM) after the bond strength test. Highest shear bond strength was obtained with 3-acryloxypropyltrimethoxysilane stored in dry condition (20.2 ± 3.2MPa), and the lowest value was obtained with 3-methacryloxypropyltrimethoxysilane (ESPE Sil) in alternating water storage and thermocycling condition (1.4 ± 0.6 MPa). The type of storage condition affected significantly the shear bond strength (p < 0.05). The shear bond strength obtained from dry storage was the highest, while the shear bond strength obtained from alternating water storage and thermocycling condition was the lowest. Interfacial failure was the main failure mode (87.2%) followed by mixed failure (9.4%) and cohesive failure (3.4%). The addition of 0.5 vol%. HEMA into silane primers did not improve the shear bond strength between the experimental resin and silica-coated titanium.     

Synthesis and characterization of novel poly(amide imide)s based on bis(p‐amidobenzoic acid)‐n‐trimellitylimido‐L‐leucine

N‐Trimellitylimido‐L ‐leucine was reacted with thionyl chloride, and N‐trimellitylimido‐L ‐leucine diacid chloride was obtained in a quantitative yield. The reaction of this diacid chloride with p‐aminobenzoic acid was performed in dry tetrahydrofuran, and bis(p‐amidobenzoic acid)‐N‐trimellitylimido‐L ‐leucine (5) was obtained as a novel optically active aromatic imide–amide diacid monomer in a high yield. The direct polycondensation reaction of the monomer imide–amide diacid 5 with 4,4′‐diaminodiphenylsulfone, 4,4′‐diaminodiphenylether, 1,4‐phenylenediamine, 1,3‐phenylenediamine, 2,4‐diaminotoluene, and benzidine (4,4′‐diaminobiphenyl) was carried out in a medium consisting of triphenyl phosphite, N‐methyl‐2‐pyrolidone, pyridine, and calcium chloride. The resulting novel poly(amide imide)s (PAIs), with inherent viscosities of 0.22–0.52 dL g^?1, were obtained in high yields, were optically active, and had moderate thermal stability. All of the compounds were fully characterized with IR spectroscopy, elemental analyses, and specific rotation. Some structural characterization and physical properties of these new optically active PAIs are reported. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 35–43, 2002; DOI 10.1002/app.10181     

Complexation of titanium alkoxides with pentenoic acid and allylacetoacetate and their hydrolysis and addition reactions with H‐silanes

Complexation reactions of titanium tetraethoxide [Ti(OEt)₄] and titanium tetra‐n‐butoxide [Ti(OBuⁿ)₄] with 3‐pentenoic acid (PA) and allylacetoacetate (AAA), in a 1 : 1M ratio, were studied in ethanol solution at room temperature. ¹³C‐NMR and FTIR spectra showed that all PA and AAA completely reacted with both titanium alkoxides. Hydridosilane compounds such as triethoxysilane and triethylsilane were added to titanium chelate complexes in a 1 : 1M ratio. The investigation of products by ¹³C‐ and ²⁹Si‐NMR and FTIR showed additions of ? SiH to the C?C double bond. The hydrolysis of titanium–PA and AAA complexes, by water in 1 : 4 ratios, resulted in released PA in an amount of 10% and AAA of 20%. The stability of hydrolyzed products was investigated by ¹³C‐NMR, ²⁹Si‐NMR, and FTIR. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 790–796, 2005     

Mass‐Spectrometric and Kinetic Studies on the Mechanism and Degradation Pathways of Titanium Salalen Catalysts for Asymmetric Epoxidation with Aqueous Hydrogen Peroxide

The composition and degradation of a highly active and enantioselective titanium salalen in situ catalyst for the asymmetric epoxidation of olefins with aqueous hydrogen peroxide was investigated. Kinetic data and ESI‐MS studies point to a mononuclear titanium salalen as the catalytically active species. By means of ESI‐MS and selective monodeuteration of the salalen ligand, the oxidative degradation was studied. Upon exposure to aqueous hydrogen peroxide, the amine functionality of the salalen ligand is converted to the hydroxylamine, followed by loss of water and generation of the inactive titanium‐salen complex. This transformation limits the activity of the catalyst in the epoxidation of less electron‐rich olefins, such as 1‐octene.     

Synthesis and characterization of new optically active segmented poly(amide imide urethane)s based on different diacids via an isocyanate route

A new class of optically active poly(amide imide urethane)s (PAIUs) was synthesized via a two-step diisocyanate route. In the first step, 4,4′-methylenebis(phenyl isocyanate) (MDI) was reacted with different diacids to produce an isocyanate-terminated oligo(amide imide). The chain extension of the previous hard segment with poly (ethylene glycol) diols with a molecular weight of 400 was the second step for furnishing a series of new PAIUs. N-Trimellitylimido-L -leucine was used as a diacid monomer for polycondensation reactions. Polymerization reactions were performed without any catalysts or with pyridine or dibutyltin dilaurate as a catalyst. The optimized reaction conditions were used for the reaction of N-trimellitylimido-L -isoleucine, N-trimellitylimido-L -methionine, N-trimellitylimido-S -valine, and N-trimellitylimido-L -phenylalanine as diacid monomers with MDI. The resulting multiblock copolymers had inherent viscosities of 0.25–0.78 dL/g. These multiblock copolymers were optically active, thermally stable, and soluble in amide-type solvents. All these polymers were fully characterized with Fourier transform infrared spectroscopy, ¹H-NMR and ultraviolet–visible spectroscopy, specific rotation measurements, and thermal analyses. Some structural characteristics and physical properties of these new optically active PAIUs were examined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Partially hydrolyzed polyacrylamide–poly(N-vinylpyrrolidone) copolymers as superabsorbents synthesized by gamma irradiation

Partially hydrolyzed polyacrylamide-co-poly(n-vinyl pyrrolidone) used as a superabsorbent was prepared from acrylamide monomers exposed to γ-rays to become polyacrylamide that was subsequently partially hydrolyzed and was then copolymerized with n-vinylpyrrolidone to obtain a terpolymeric superabsorbent with a water retention value of 1100 times its dried weight. The total dose and dose rate along with the appropriate degree of hydrolysis were investigated for percentage conversion in each polymerization and the extent of water absorption. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:191–203, 1998     

Effects of preparation method on microstructure and properties of UV‐curable nanocomposite coatings containing silica

UV‐curable nanocomposites were prepared by the blending method or the in situ method with nanosilica obtained from a sol–gel process. The microstructure and properties of the nanocomposite coatings were investigated using ²⁹Si‐NMR cross‐polarization/magic‐angle spinning, transmission electron microscopy (TEM), Fourier transform IR (FTIR), differential scanning calorimetry (DSC), and UV–visible (UV–vis) spectra, respectively. The NMR and TEM showed that during the blending method, tetraethyl orthosilicate (TEOS) completely hydrolyzed to form nanosilica particles, which were evenly dispersed in the polymer matrix. However, for the in situ method, TEOS partially hydrolyzed to form some kind of microstructure and morphology of inorganic phases intertwisted with organic molecules. FTIR analysis indicated that the nanocomposites prepared from the in situ method had much higher curing rates than those from the blending method. DSC and UV–vis measurements showed that the blending method caused higher glass‐transition temperatures and UV absorbance than the in situ method. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1119–1124, 2005     

Simplified hydrolysis of cellulose and substituted cellulose: Observations on trifluoroacetic acid hydrolyses

Hydrolyses of selected soluble polysaccharides (e.g., polyoses) and disordered and crystalline celluloses, each bearing 2-diethylaminoethyl (DEAE) substituents at low degree of substitution (DS < 0.05) were explored in 100% and 2N trifluoroacetic acid (TFA). Analyses were evaluated relative to hydrolysis with 72% sulfuric acid. DEAE–polyoses hydrolyzed readily in 100% and 2 N TFA during extended reaction periods with complete liberation of DEAE–glucoses. Hydrolyses of cellulose and DEAE–celluloses in 100% TFA were critically dependent upon cautious incremental dilution of the TFA during stepwise reaction to avoid precipitation of incompletely hydrolyzed products. DEAE–celluloses were partially solubilized and hydrolyzed in heterogeneous reaction in 2N TFA at 121°C. Complete liberation of DEAE-glucoses in the solubilized components was achieved after supplementary hydrolysis at 121°C. In all hydrolyses, including those with 72% sulfuric acid, extended hydrolyses were essential for complete liberation of the 2-O- and 6-O-DEAE–glucoses. Under optimum conditions, results of hydrolyses in 100% TFA were comparable to those in 72% sulfuric acid. Ease of release of DEAE-glucopyranoses in hydrolyses of DEAE-cellulose in 2N TFA was in the same order (3-O- > 6-O-> 2-O-) as in homogeneous hydrolyses in sulfuric acid and in 100% TFA. Differences in release of isomeric DEAE–glucoses were greater in the heterogenous system. Degradation of glucose and DEAE–glucopyranoses occurred in extended periods of reaction in all acidic media. Rates of degradation of glucose and DEAE–glucopyranoses in dilute acid at 100°C were similar for glucose and 6-O-DEAE–glucose. The rates were about half as fast for 3-O-DEAE–glucose and an order of magnitude lower for 2-O-DEAE–glucose.     

Supported titanium–magnesium catalysts with different titanium content: Kinetic peculiarities at ethylene homopolymerization and copolymerization and molecular weight characteristics of polyethylene

The effect of Ti content on the activity of titanium–magnesium catalysts (TMC) and molecular weight distribution (MWD) of polyethylene (PE) produced has been studied. It was found that the activity enhances sharply as Ti content decreases from 0.6 to 0.07 wt %, and shows no significant changes in the Ti content range of 0.6–5.0 wt %. The maximum activity (36 kg PE/mmol Ti × h × bar C₂H₄) was observed for TMC with the lowest Ti content. The catalyst with low titanium content (～ 0.1 wt % of Ti) produced PE with narrower MWD (M_w/M_n = 3.1–3.5) as compared to catalysts with higher titanium content (3–5 wt % of Ti; M_w/M_n = 4.8–5.0). New data on the effect of hydrogen on MWD of PE have been found. Increasing hydrogen concentration results in broadening the MWD of PE, especially in the case of TMC with high titanium content. The data presented indicate the heterogeneity of active centers of TMC in the reaction of chain transfer with hydrogen. The data on the ethylene–hexene‐1 copolymerization over TMC with different titanium content are presented. Comonomer reactivity ratios were shown to be independent of the Ti content in TMC. Presumably the difference in activity of these catalysts is mainly caused by the difference in the number of active centers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5436–5442, 2006     

New optically active poly(amide–imide–urethane) thermoplastic elastomers derived from poly(ethylene glycol diols), 4,4′‐methylene‐bis(4‐phenylisocyanate), and a diacid based on an amino acid by a two‐step method under microwave irradiation

A new class of optically active poly(amide–imide–urethane)s (PAIUs) was synthesized via a two‐step diisocyanate route under microwave irradiation. In these reactions, 4,4′‐methylene‐bis(4‐phenylisocyanate) was reacted with bis(p‐amido benzoic acid)‐N‐trimellitylimido‐L ‐leucine and poly(ethylene glycol diol)s (PEGs), such as PEG‐400, PEG‐600, PEG‐1000, and PEG‐2000, to furnish a series of new PAIUs. The effects of different reaction conditions, such as the method of preparation (polyol or acid chain extension), the prepolymerization step (NCO‐terminated oligoamide or NCO‐terminated polyether polyol), the irradiation time and power, the reaction solvent, the soft‐segment length, and the presence or absence of reaction catalysts (e.g., triethylamine, pyridine, and dibutyltin dilaurate), on the properties of the copolymers, including the solubility, viscosity, and thermal behavior, were investigated. The resulting multiblock copolymers had inherent viscosities of 0.15–0.53 dL/g. These multiblock copolymers were optically active, thermally stable, and soluble in amide‐type solvents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1781–1792, 2005     

Solvent Effect on Complexation of Titanium Tetraethoxide with Allylacetoacetate

The effect of the solvent butanol on the complexation reaction of allylacetoacetate (AAA) with titanium tetraethoxide. (Ti(OEt)₄) in molar ratio Ti(OEt)₄:AAA = 1:1 was investigated by ¹³C-NMR, FT-IR spectroscopy and elemental analysis. The investigation shows that some ethoxy groups that are attached to the titanium are substituted with butoxy groups. The hydrolytic stability of the allylacetoacetate–Ti complex in a molar ratio Ti(OEt)₄:H₂O = 1:4 was also characterized by spectroscopic techniques and elemental analysis. The result of this characterization shows that almost 20% of the AAA and some ethoxy groups are released from the hydrolyzed product.     

Optically active poly(ester‐amide)s: synthesis and characterization

The synthesis and characterization of a new series of chiral poly(ester‐amide)s are reported. They were prepared by the simple reaction of diacid chlorides with biphenolic azo chromophores and optically active dihydroxy compound (isosorbide) in dimethyl acetamide at 100 °C. The polymers containing isosorbide units were optically active. The polymers showed T_g between 100 and 190 °C and were stable up to 400 °C. These poly(ester‐amide)s showed a positive solvatochromism in UV–visible absorption spectra. Second harmonic generation activities were measured by the powder method. © 2001 Society of Chemical Industry     

Synthesis and characterization of new optically active poly(amide‐imide‐urethane) thermoplastic elastomers,derived from 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L‐leucine‐p‐aminobenzoic acid) and PEG‐MDI

A new class of optically active poly(amide‐imide‐urethane) was synthesized via two‐step reactions. In the first step, 4,4′‐methylene‐bis(4‐phenylisocyanate) (MDI) reacts with several poly(ethylene glycols) (PEGs) such as PEG‐400, PEG‐600, PEG‐2000, PEG‐4000, and PEG‐6000 to produce the soft segment parts. On the other hand, 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine‐p‐amidobenzoic acid) (2) was prepared from the reaction of 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine) diacid chloride with p‐aminobenzoic acid to produce hard segment part. The chain extension of the above soft segment with the amide‐imide 2 is the second step to give a homologue series of poly(amide‐imide‐urethanes). The resulting polymers with moderate inherent viscosity of 0.29–1.38 dL/g are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses, and specific rotation. Some structural characterization and physical properties of this new optically active poly(amide‐imide‐urethanes) are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2288–2294, 2004