Properties of branched and network poly(vinyl alcohols) prepared with poly(vinyl alcohol) having aldehyde groups at the chain ends

Branched and network poly(vinyl alcohols) (PVAs) were prepared with inter-acetalization of the PVA with aldehyde groups at the chain ends which was prepared by the cleavage of 1,2 glycol bonds in commercial PVA. The numbers of branches estimated from molecular weights were compared with those estimated by theory. Huggins' constant and crystallinity decreased with increasing branch number. Dissolution of branched PVAs into dimethylsulphoxide was not so easy compared with commercial PVA. The colour of branched PVA–iodine complex decreased rapidly with standing while that of commercial PVA decreased gradually. Network PVAs with Young's modulus of 1–8 MPa were prepared.     

Synthesis of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) and poly(vinyl alcohol)‐graft‐poly(lactide) in melt with magnesium hydride as catalyst

Grafting of poly(ε‐caprolactone) (PCL) and poly(lactide) (PLA) chains on poly(vinyl alcohol) backbone (PVA degree of hydrolysis 99%) was investigated using MgH₂ environmental catalyst and melt‐grown ring‐opening polymerization (ROP) of ε‐caprolactone (CL) and L ‐lactide (LA), that avoiding undesirable toxic catalyst and solvent. The ability of MgH₂ as catalyst as well as yield of reaction were discussed according to various PVA/CL/MgH₂ and PVA/LA/MgH₂ ratio. PVA‐g‐PCL and PVA‐g‐PLA were characterized by ¹H‐ and ¹³C‐NMR, DSC, SEC, IR. For graft copolymers easily soluble in tetrahydrofuran (THF) or chloroform, wettability and surface energy of cast film varied in relation with the length and number of hydrophobic chains. Aqueous solution of micelle‐like particles was realized by dissolution in THF then addition of water. Critical micelle concentration (CMC) decreased with hydrophobic chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Contributions to characterization of poly(vinyl chloride)–lignin blends

The present study evaluates the impact of blending organosolv and kraft lignins, which are natural polymer by‐products in the pulp and paper industry, with plasticized poly(vinyl chloride) (PVC) in flooring formulations. Also examined is the impact of replacing dioctyl phthalate, a PVC industry general‐purpose plasticizer, with diethylene glycol dibenzoate (Benzoflex 2‐45), tricresyl phosphate (Lindol), or alkyl sulfonic phenyl ester (Mesamoll) in these formulations. The influence of the different types of lignins and plasticizers on the processibility, thermal, and mechanical properties of the blends is discussed. These properties demonstrate that partial replacement of PVC (20 parts) with different lignins is feasible for some formulations that can be successfully used as matrices for a high level of calcium carbonate filler in flooring products. In addition, the data demonstrate that the presence of certain plasticizers, which interfere with the intramolecular interactions existing in lignins, may allow the lignin molecules to have more molecular mobility. The morphology and the properties of PVC plasticized lignin blends are strongly influenced by the degree and mode of the lignin plasticization and its dispersion within the PVC matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2732–2748, 2006     

Phase transformations of some poly(vinyl alcohol)–NiCl2 composites

Samples of poly(vinyl alcohol)–NiCl₂ composites containing up to 30 wt% NiCl₂ were prepared by casting in order to study phase transformation–structural change relationships of these samples before and after heat treatment. Differential thermal analysis (DTA) thermograms were recorded at 10, 15, 20 and 30 °C min^?1. For untreated samples four endotherms were assigned as: rotation of hydroxyl groups in the glassy state, glass transition, structural transition in the rubber‐like state, and melting transition. Ultrasonic attenuation measurements were carried out to confirm these transitions in the glassy and rubber‐like states. In the glassy state, the effect of NiCl₂ addition is explained in terms of chain stiffness due to the creation of local crosslinked regions in amorphous parts of the polymer. Average values of activation energies for glass transition were calculated using both methods of Kissinger and Ozawa. However, addition of NiCl₂ had an opposite effect on the heating rate independent crystallization melting temperature (T_m), relative to that on T_g. The DTA thermograms of heat‐treated samples indicated that square planar NiCl₂ molecules were embedded in the polymer matrix with no local crosslinking role due to the formation of conjugated polyenes along the polymer chains by thermal treatment. Copyright © 2003 Society of Chemical Industry     

Preparation and characterization of poly(vinyl alcohol)‐poly(vinyl pyrrolidone) blend: A biomaterial with latent medical applications

Aqueous solutions of poly(vinyl alcohol) and poly(vinyl pyrrolidone) are blended and films are produced by casting method with the further intention of being used as bio‐materials with latent medical application. Glutaraldehyde, 4,4′‐diazido‐2,2′‐stilbenedisulfonic acid disodium salt tetra‐hydrate are used as crosslinker agents, whereas lactic acid is the plasticizer in the blend. The obtained films are characterized by differential scanning calorimetry (DSC), mechanical properties, swelling and solubility behavior. DSC measurements show that the blends exhibit a single glass transition temperature indicating that they are miscible, even in the presence of the plasticizer and crosslinker agents. By the combination of all mentioned additives, a relevant enhancement of the swelling is observed, accompanied by a stabilization of the solubility during the tested time. Finally, mechanical properties show an appropriate performance in the studied parameters. As a consequence, the obtained films could be suitable for use as medium or long‐term implants. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enzyme-based bioartificial polymeric materials: the α-amylase–poly(vinyl alcohol) system

The possibility of realizing bioartificial polymeric materials from blends of the enzyme α-amylase (EC 3.2.1.1) and poly(vinyl alcohol), in the form of film and hydrogel, was investigated. The interactions at molecular level between the enzyme and the synthetic polymer have been studied by calorimetry, X-ray diffractometry and morphological analysis. A certain degree of interaction through which the α-amylase molecules influence the crystallinity of the poly(vinyl alcohol) was observed. The thermal stability of the enzyme in the blends was enhanced, while its biological activity did not vary significantly. In addition, hydrogels prepared by a freeze–thawing method can be considered suitable for manufacturing delivery systems capable of releasing enzymes which maintain their full biological activity. ©1997 SCI     

Formation of poly(vinyl alcohol)–iodine complex in aqueous solution: a SEM study of the freeze-dried substances

The freeze-dried samples prepared from dilute PVA aqueous solutions and PVA–iodine complex aqueous solutions have been examined using a scanning electron microscope. The samples prepared from syndiotacticity-rich PVA (S-PVA) solutions were found to have a network structure due to the formation of intermolecular hydrogen bonds, whereas in the case of atactic PVA (A-PVA) a network structure was not found. The network structure became more finely structured with increasing syndiotacticity. The structure of the freeze-dried sample of the complex solution prepared from S-PVA having a syndiotactic diad content of 63·8%, and iodine, was coarse in comparison with that of the freezedried sample of the S-PVA solution. In addition, the formation of spherical bulges, which are considered to correspond to microgels in the aqueous solution, were observed in several places. In the S-PVA having a syndiotactic diad content of 57·8%, the spherical bulges were not observed, whereas the absorbance of the aqueous solution was the highest. Although A-PVA did not form a PVA– iodine complex at 30°C in solution, the frozen solution turned blue due to the formation of aggregates. These phenomena were confirmed by the degree of crystallinity estimated from IR spectra, and the amount of iodine estimated from X-ray microanalysis of the freeze-dried samples. The PVA–iodine complexes are formed by the interaction of the aggregates of PVA molecules with iodine molecules. However, the PVA microgels do not interact with iodine. © 1998 Society of Chemical Industry     

Thermal and mechanical behaviors of poly(vinyl alcohol)–lactose blends

Thermal and mechanical behaviors of poly(vinyl alcohol) (PVA)–lactose blends were studied by differential scanning calorimetry, thermal gravimetric analysis, and stress–strain analysis. The increase in glass transition temperature of the PVA–lactose blends with lactose contents suggests the formation of hydrogen‐bonded PVA–lactose complex in the PVA matrix. The hydrogen bonding interactions can improve thermal and mechanical properties of the blends. Results of this study demonstrate that lactose, a byproduct of dairy industry, can be used directly and in substantial quantity (33%) as a modifier to enforce the physical properties of PVA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 929–935, 2002     

Thermal characteristics of poly(vinyl alcohol) and poly(vinylpyrrolidone) IPNs

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and 1‐vinyl‐2‐pyrrolidone (VP) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone (DMPAP) and methylene bisacrylicamide (MBAAm) as initiator and crosslinker, respectively. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depressions of the melting temperatures of PVA segments in IPNs were observed with increasing VP content via the DSC. The DEA was employed to ascertain the glass transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_gs indicating the presence of phase separation in the IPN. The thermal decomposition of IPNs was investigated using TGA and appeared at near 270°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1844–1847, 2002     

Application of FTIR spectroscopy for structural characterization of ternary poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

The FTIR spectroscopic technique was used in the study of ternary polymer–metal complexes containing two polyelectrolytes of opposite charge and metal ions. The structure of the ternary (PAA‐Fe³⁺‐PVP) complexes was examined by following the changes in their infrared spectra. It was found that the shapes of the absorption bands of the resultant compounds are influenced by the presence of Fe³⁺. According to this result it was suggested that two types of structure which differ in the composition are formed, one of which results from the coordination of Fe³⁺ with PAA‐PVP complex and the other is due to the formation of Fe³⁺ polycarboxylate. Comparison between the spectrum of PAA‐PVP complex and those of the compounds resulted from the reaction between the two opposite charged electrolytes, PAA and PVP and each of the divalent metal chlorides NiCl₂, CoCl₂, CuCl₂, and ZnCl₂) led to the conclusion that a reaction took place between the divalent transition metal chlorides and the extent of reaction depends on the nature of metal ions and PAA‐PVP complex. The FTIR spectra of the precipitate resulted from the mixtures of PAA‐PVP and Ni(NO₃)₂ or Sr(NO₃)₂ were investigated. It was noted that the addition of Ni(NO₃)₂ or Sr(NO₃)₂ to the mixture of the electrolytes of PAA and PVP provoked appreciable changes in the characteristic spectral features of the complex resulting from the interaction of the metal ions with the polymer–polymer complex. The FTIR spectra of the precipitate resulted from the reaction between CeCl₃, ErCl₃, and LaCl₃ were also investigated. It was concluded that a reaction took place between the rare earth metals and the PPC. This means that ternary polymer–metal–polymer complexes were formed. The extent of changes in the spectral features differs from metal to metal according to the nature of metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Biodegradable poly(vinyl alcohol)‐graft‐ poly(ε‐caprolactone) comb‐like polyester: Microwave synthesis and its characterization

Poly(vinyl alcohol)‐initiated microwave‐assisted ring opening polymerization of ε‐caprolactone in bulk was investigated, and a series of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) (PVA‐g‐PCL) copolymers were prepared, with the degree of polymerization (DP) of PCL side chains and the degree of substitution (DS) of PVA by PCL being in the range of 3–24 and 0.35–0.89, respectively. The resultant comb‐like PVA‐g‐PCL copolymers were confirmed by means of FTIR, ¹H NMR, and viscometry measurement. The introduction of hydrophilic backbone resulted in the decrease in both melting point and crystallization property of the PVA‐g‐PCL copolymers comparing with linear PCL. With higher microwave power, the DP of PCL side chains and DS of PVA backbone were higher, and the polymerization reaction proceeded more rapidly. Both the DP and monomer conversion increased with irradiation time, while the DS increased first and then remained constant. With initiator in low concentration, the DP and DS were higher, while the monomer was converted more slowly. Microwaves dramatically improved the polymerization reaction in comparison of conventional heating method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3973–3979, 2007     

Poly(acrylic acid)–poly(vinyl alcohol) copolymers with superabsorbent properties

Biodegradable polyacrylates were produced by a series of novel copolymerization and/or crosslinking techniques using poly(vinyl alcohol) (PVA) moieties modified by the incorporation of olefinic structures. PVA was modified by a tosylation and/or detosylation reaction. The functionalized PVA was copolymerized and/or crosslinked with acrylic acid or its partially neutralized form to give crosslinked polyacrylates that could swell in water. Their swelling behavior was determined under load. Degradation studies were performed in α-chymotrypsin, trypsin, and papain solutions. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 817–829, 1998     

Influence of Syndiotacticity on Poly(vinyl alcohol)–Iodine Complex Formation

The extent of colour development in an aqueous poly(vinyl alcohol) (PVA)–iodine complex solution increased with increasing syndiotacticity up to a certain syndiotactic content, then decreased with increasing syndiotacticity. The complex formation depended on the content of the syndiotactic pentad sequence length in the PVA molecules. The most suitable content of the syndiotactic pentad for forming complexes was around 12% in the case of reaction at 30°C. A 0·5% solution of syndiotactic PVA (S-PVA) with an syndiotactic diad (s-(diad)) content of 63·8% changed into a sol, whereas that with an s-(diad) content of 58% did not change after standing for 2h at 30°C, and the colour due to the iodine complex in the latter was deeper than in the former. The gel prepared from the 0·5% solution of S-PVA with an s-(diad) content of 63·8% was hardly coloured. In the solutions containing two kinds of s-PVA having different syndiotacticities, additivity for the extent of colour development did not hold, and the extent was lower than the sum of that of the components. The decrease in the extent of colour development at higher syndiotacticity was due to the formation of microgels. The absorption maximum shifted to a longer wavelength with increasing syndiotacticity. The length of polyiodine increased with increasing syndiotacticity. © of SCI.     

Thermal properties of poly(vinyl alcohol)–solute blends studied by TMDSC

A thermal analysis study of blends of semicrystalline poly(vinyl alcohol) (PVA) with a pharmaceutical substance, buflomedil pyridoxal phosphate (BPP) is presented. Temperature‐modulated DSC (TMDSC) was used to determine the T_g as well as the crystallinity of blends with various polymer to drug ratios, for different annealing procedures. Positive deviations from a simple expression for the composition dependence of the glass transition of the blend were found. This result, together with the increased thermal stability of PVA–BPP blends, evidenced by TGA analysis, indicates the existence of specific interactions between the polar groups of the two components. The incorporation of dispersed BPP in the PVA matrix results in a composition‐dependent lowering of the polymer's T_m and degree of crystallinity. In addition, we found that, while melting of pure PVA is predominantly reversing, its melting in the blends acquires an increasingly higher nonreversing component with increasing BPP content in the blend. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1151–1156, 2004     

Kinetics of ligand exchange reaction of Cu(II)-ammine complex with poly(vinyl alcohol) in aqueous solution

The kinetics of the ligand exchange reaction of the Cu(II)-ammine complex with poly(vinyl alcohol) (PVA) has been studied by a stopped-flow method at pH 9–10, at μ=0.1 (NH₄Cl) and at 25°C. The reaction is initiated by the formation of unstable [Cu(NH₃)₃]²⁺ by the attack of H⁺ on Cu(II)-ammine complex, and proceeds through the mixed complex {[Cu(NH₃)₃(O?PVA)]²⁺}. This step may be rate-determining, followed by a rapid reaction. Finally, the Cu(II) ion is taken up by PVA. The rate is given by d[Cu(II)?PVA]/dt=k[H⁺]{[Cu(NH₃)₄]²⁺}[PVA]/[NH₄Cl], where k=k₁ + k′₂[H⁺], k₁=4.25× 10s^?1 and k′₂=5.20× 10¹¹l mol^?1s^?1.     

Preparation and characterization of biocompatible spongy cryogels of poly(vinyl alcohol)–gelatin and study of water sorption behaviour

Porous biocompatible spongy hydrogels of poly(vinyl alcohol) (PVA)–gelatin were prepared by the freezing–thawing method and characterized by infrared and differential scanning calorimetry. The prepared so‐called ‘cryogels’ were evaluated for their water‐uptake potential and the influence of various factors, such as the chemical architecture of the spongy hydrogels, pH and the temperature of the swelling bath, on the degree of water sorption by the cryogels was investigated. It was found that the water sorption capacity constantly decreased with increasing concentration of PVA while initially an increase and thereafter a decrease in swelling was obtained with increasing amounts of gelatin in the cryogel. The water sorption capacity decreased with an increase in the number of freeze–thaw cycles. The hydrogels were also swollen in salt solutions and various simulated biological fluids and a fall in swelling ratio was noticed. The effect of the drying temperature of the cryogel on its water sorption capacity was also investigated, and a decrease in swelling was obtained with increasing temperature of drying. The biocompatibility of the prepared materials was assessed by in vitro methods of blood‐clot formation, platelet adhesion, and per cent haemolysis. It was noticed that with increasing concentration of PVA and gelatin the biocompatibility increased, while a reduced biocompatibility was noted with an increasing number of freeze–thaw cycles. Copyright © 2005 Society of Chemical Industry     

Physical and biological stability of dehydro-thermally crosslinked α-amylase–poly(vinyl alcohol) blends

A dehydro-thermal treatment has been used to crosslink α-amylase (EC 3.2.1.1)–poly(vinyl alcohol) blends in order to reduce their water solubility and to favour their potential use as bio-artificial polymeric materials based on enzymes. The influence of a thermal treatment on the thermal and biological stability of the enzyme blended with a synthetic polymer was carefully studied by means of calorimetry and biological assays. The values of the kinetic parameters obtained from the biological assays indicate that the enzyme specificity for the substrate in all the blends examined is not affected by the thermal treatment. In addition, the results of the releasing tests showed that the thermally crosslinked α-amylase–poly(vinyl alcohol) blends can be considered suitable for manifacturing delivery systems able to release enzymes. © 1998 Society of Chemical Industry     

Synthesis of poly(vinyl propionate) from poly(vinyl alcohol) in nonaqueous medium using ethyl nitrate dimethyl sulfoxide as a catalyst

Poly(vinyl alcohol) (PVA) can be dissolved in a nonaqueous medium in the presence of catalytic concentration of ethyl nitrate dimethyl sulfoxide, C₂H₅ONO₂·DMSO. From the PVA solution, poly(vinyl propionate), PVPR was prepared by the homogeneous esterification of PVA with propionic acid. The ester thus formed contained some unconverted hydroxyl group. The formation of the ester was confirmed by the IR and ¹H‐NMR spectra. The molecular weight of the ester was determined by GPC and intrinsic viscosity (η) was determined by viscometric method. Glass transition temperature, T_g, was obtained from differential scanning calorimetric (DSC) analysis. Thermal stabilities of the ester were checked by thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) analysis. The efficiency of the ester as a flow improver of crude oil was also examined. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5675–5679, 2006     

Poly(vinyl alcohol) and poly(vinyl amine) blend membranes for isopropanol dehydration

Blended membranes of hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(vinyl amine) (PVAm) were prepared and crosslinked with glutaraldehyde. The prepared membranes were characterized using infrared (attenuated total reflection mode) spectroscopy, differential scanning calorimetry, X‐ray diffractometry, and scanning electron microscopy measurements. Pervaporation performances of the membranes were evaluated for the separation of water‐isopropanol (IPA) mixtures. As the PVAm content increased from PVAm0 to PVAm1.5, the flux through a 70 μm film increased from 0.023 to 0.10 kg/m² h at an IPA/water feed ratio of 85/15 at 30 °C. The driving force for permeation of water increased due to the temperature but it has no effect on IPA permeation. Activation energies for the permeation of IPA and water were calculated to be 17.11 and 12.46 kJ/mol, respectively. Controlling the thickness of the blend membrane could improve the permeation flux with only a marginal reduction in the separation factor. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45572.