Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements Part 4. Radical polymerization of acrylic acid in the presence of poly(vinyl alcohol): characterization of resulting polymer blends

The radical polymerization of acrylic acid in the presence of poly(vinyl alcohol) as a template in aqueous solution has been studied using conductimetry, which shows template influences on the reaction rate. A comparison is made between data obtained by differential scanning calorimetry and infrared spectroscopy for poly(acrylic acid)–poly(vinyl alcohol) blends prepared either by template polymerization or by casting of the preformed polymers. Evidence for more significant interpolymer interactions in blends prepared by template polymerization than in those obtained by simple mixing is given. © 2001 Society of Chemical Industry     

Novel mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of silk sericin

A novel mucoadhesive polymer was prepared by template polymerization of acrylic acid in the presence of sericin for a transmucosal drug‐delivery (TMD) system. FTIR results indicated that a polymer complex was formed between poly(acrylic acid) (PAA) and sericin through hydrogen bonding. The glass transition temperatures (T_g's) of sericin and PAA in the PAA/sericin polymer complex were inner‐shifted compared with the T_g's of sericin and PAA themselves. This may be due to the increased miscibility of PAA with sericin through hydrogen bonding. The dissolution rate of the PAA/sericin interpolymer complex was dependent on the pH. The mucoadhesive force of the PAA/sericin polymer complex was similar to that of a commercial product, Carbopol 971P NF. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 274–280, 2001     

A mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poly(ethylene glycol) macromer

A new mucoadhesive polymer complex was prepared by the template polymerization of acrylic acid with poly(ethylene glycol) macromer (PEGM) as a template polymer. Fourier transform infrared results showed that the poly(acrylic acid) (PAA)/PEGM mucoadhesive polymer complex was formed by hydrogen bonding between the carboxyl groups of PAA and the ether groups of PEGM. The glass‐transition temperature of the PAA/PEGM mucoadhesive polymer complexes was shifted to a lower temperature as the repeating unit ratio of PAA/PEGM in the complex decreased. The dissolution rate of the PAA/PEGM mucoadhesive polymer complex was much slower than that of the PAA/poly(ethylene glycol) (PEG) mucoadhesive polymer complex and was dependent on the pH and molecular weight of PEGM. The mucoadhesive force of the PAA/PEGM mucoadhesive polymer complexes was stronger than that of commercial Carbopol 971P NF and almost the same as that of the PAA/PEG mucoadhesive polymer complex. The PAA/PEGM interpolymer complex seemed to be a better mucoadhesive polymer matrix than the PAA/PEG interpolymer complex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1904–1910, 2002     

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     

Crosslinking reaction of poly(vinyl alcohol) with poly(acrylic acid) (PAA) by heat treatment: Effect of neutralization of PAA

The crosslinking reaction of poly(vinyl alcohol) (PVA) by esterification using poly(acrylic acid) (PAA) as a crosslinking reagent was investigated to obtain highly insoluble PVA materials. Blend films of PVA and PAA (PVA/PAA = 8/2) were prepared to examine the effect of degree of neutralization (DN) in PAA and heat‐treatment conditions on the degree of crosslinking reaction. The degree of crosslinking reaction varied significantly when the DN of PAA changed. The optimum DN for the crosslinking reaction was in the range of 5 to 10 mol %. In the case of unneutralized PAA, the degree of crosslinking reaction was at most 15 mol % by heat treatment for 20 min at 200°C. Applying partially neutralized PAA (DN = 10 mol %) raised the degree to about 40 mol % under the same heat‐treatment conditions. FTIR analysis revealed that the hydroxyl group of PVA in the film blended with unneutralized PAA was degraded to a greater degree than that with partially neutralized PAA as a result of heat treatment. It was found that heat treatment at a low pH condition enhances the degradation of the hydroxyl group of PVA, resulting in a decrease of the number of crosslinking sites by esterification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2420–2427, 2003     

Preparation of poly(acrylic acid)/poly(vinyl alcohol) membrane for the facilitated transport of CO2

Poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) membrane was prepared for the facilitated transport of CO₂. The carrier of CO₂ was monoprotonated ethylenediamine and was introduced in the membrane by ion exchange. The ion‐exchange capacity of the membrane was 4.5 meq/g, which was much higher than that of the Nafion 117 membrane. The membrane was highly swollen by the aqueous solution. Much higher selectivity of CO₂ over N₂ and higher CO₂ permeability were obtained in the PAA/PVA membrane than in the Nafion membrane because of the higher ion‐exchange capacity and solvent content. The highest selectivity was more than 1900 when the CO₂ partial pressure in the feed gas was 0.061 atm. Effects of ion‐exchange capacity, membrane thickness, and annealing temperature in conditions of membrane preparation on membrane performance were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 936–942, 2001     

Drug release behavior of electrical responsive poly(vinyl alcohol)/poly(acrylic acid) IPN hydrogels under an electric stimulus

The electrically modulated properties of interpenetrating polymer networks (IPN) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) under electric field were investigated for drug delivery systems. PVA/PAAc IPNs with various compositions were synthesized by a sequential method, that is, ultraviolet polymerization of AAc in the mixture of PVA and aqueous AAc monomer solution, followed by a freeze‐thawing process to prepare elastic hydrogels. The amount of loaded drug significantly increased with the content of PAAc containing ionizable groups in IPN. The amount of introduced ionic drug (cefazoline) was greater than that of the nonionic drug (theophylline). Release behaviors of drug molecules from negatively charged PVA/PAAc IPN were switched on and off in a pulsatile pattern depending on the applied electric stimulus. The released amount and the release rate of drug were influenced significantly by the applied voltage, ionic group contents in IPN, ionic properties of drug solute, and the ionic strength of release medium. In addition, the ionic properties of drug molecules dramatically affected release behaviors, thus the release of ionic drug was much more enhanced than that of the nonionic drug. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1752–1761, 1999     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry     

Synthesis and characterization of an interpenetrating polymer network composed of poly(methacrylic acid) and poly(vinyl alcohol)

Temperature and pH‐responsive interpenetrating polymer network (IPN) hydrogels, constructed with poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA), by a sequential IPN method, were studied. The characterization of IPN hydrogels was investigated by Fourier‐transform infrared spectroscopy, differential scanning calorimetry (DSC) and swelling under various conditions. The IPN hydrogels exhibited relatively high swelling ratios, in the range 230–380 %, at 25 °C. The swelling ratios of the PMAA/PVA IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the amounts of freezing and non‐freezing water. The amount of free water increased with increasing PMAA content in the IPN hydrogels. Copyright © 2004 Society of Chemical Industry     

A study of blending and complexation of poly(acrylic acid)/poly(vinyl pyrrolidone)

Poly(acrylic acid) (PAA) and poly(vinyl pyrrolidone) (PVP) were chosen to prepare polymer complex and blends. The complex was prepared from ethanol solution and the blends were prepared from 1-methyl-2-pyrrolidone solution. DSC results show that the T_gs of the PAA/PVP blends lie between those of the two constituent polymers, whereas T_g of the PAA/PVP complex is higher than both blends and the two constituent polymers. TGA results show that degradation temperature, T_d, of PAA increases upon adding PVP in the blend, but thermal stability of the complex is higher than that of the blends as reflected by the higher T_d. Both FTIR and high-resolution solid state NMR show strong hydrogen bonding between PAA and PVP by showing significant chemical shift. The T_1ρ(H) measurement shows that the homogeneity scale for the blend is at ∼20 Å and that for the complex is ∼15 Å.     

Characteristics of poly(vinyl pyrrolidone)/poly(acrylic acid) interpolymer complex prepared by template polymerization of acrylic acid: Effect of reaction solvent and molecular weight of template

Poly(vinyl pyrrolidone) (PVP)/poly(acrylic acid) (PAA) interpolymer complexes were prepared, in ethanol or dimethylformamide (DMF), by template polymerization of acrylic acid in the presence of PVP (MW: 42.5 or 1100 K) used as the template. FTIR analysis showed that the complexes were formed through hydrogen bonding between the carboxyl groups of the PAA and the carbonyl groups of the PVP. The glass‐transition temperature (T_g) of the complex, prepared in ethanol, was higher than that of the component polymers, whereas the T_g of the complex, prepared in DMF, was located between that of the component polymers. The dissolution rate of the complex was affected by the molecular weight of the PVP and the reaction solvent. The release rate of ketoprofen from the complexes showed a pH dependency, and was slower at a lower pH. The ketoprofen release rate from the complex was controlled mainly by the dissolution rate of the complex above the pK_a of PAA (4.75) and by the diffusion rate below the pK_a. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2390–2394, 2004     

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.     

Effects of the tacticities of poly(vinyl alcohol) on the structure and morphology of poly(vinyl alcohol) nanowebs prepared by electrospinning

The effects of tacticities on the characteristics of poly(vinyl alcohol) (PVA) nanowebs prepared by an electrospinning technique were investigated. PVA webs composed of uniform nanofibers with syndiotactic dyad (s‐dyad) contents of 53.5 and 57.3% were successfully obtained with electrospinning. By changing processing parameters such as the initial polymer concentration, applied voltage, and tip‐to‐collector distance, we found suitable conditions for forming PVA webs with uniform nanofibers. PVAs of higher s‐dyad contents were prepared at a lower solution concentration and at a higher applied voltage because of the easy formation of syndiotactic PVA chain entanglements at a very low polymer concentration. The average diameter of the nanofibers in a PVA web with the higher s‐dyad content of 57.3% (ca. 240 nm) was thinner than that of the nanofibers in a PVA web with the lowers‐dyad content of 53.5% (ca. 270 nm). In addition, the crystallinity and thermal stability were greatly increased with an increase in the s‐dyad content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Swelling and morphological properties of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) hydrogels in solution with high salt concentration

Understanding the swelling properties of hydrogels and how they affect the hydrogel's morphology is of fundamental importance in the development of hydrogel-based artificial muscles, bio-actuators, sensors and other devices. In this paper, the swelling behavior of PVA-PAA hydrogel films in saline water and in buffer solutions of different pH values was investigated. It was observed that the swelling factor of the hydrogel decreases when the ionic strength of the solvent solution increases. Scanning Electron Microscopy (SEM) revealed structures with different pore shapes and sizes depending on the type of solution used for hydration. In saline water, Energy Dispersive X-Ray (EDS) analysis indicated the formation of NaCl crystals within the polymeric network. Finally, the PVA-PAA hydrogel was used as an actuator to strain a fiber Bragg grating sensor, thus providing an indirect measurement of the pH value of the surrounding solution.     

Bending behaviour of electroresponsive poly(vinyl alcohol)/poly(acrylic acid) semi‐interpenetrating network hydrogel fibres under an electric stimulus

Poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) composite fibres were prepared via solution spinning and subsequently, semi‐interpenetrating networks (SIPN) were obtained by crosslinking the fibres with glutaraldehyde. The hydrogel fibres exhibited bending behaviour under DC electric stimulation. The effects of a number of factors have been systematically studied, including the PAA content within the network, electric voltage imposed across the fibre, the fibre diameter, concentration of the crosslinking agent, pH and ionic strength of the bath solution. Our experimental results show a stable reversibility of bending behaviour under the applied electric field. The degree of bending at equilibrium and the bending speed of the hydrogel fibre increased with the intensity of the applied electric voltage and the PAA content having negatively charged ionic groups within the SIPN. The electroresponsive behaviour of the present SIPN hydrogel fibre was also affected by the aforementioned extrinsic factors. These observations are interpreted in terms of fibre stiffness, fixed charge density and swelling pressure, which depend on the hydrogel equilibrium states in different pH and ionic environments together with the electrochemical reactions under DC electric field. © 2002 Society of Chemical Industry     

Glass polyalkenoate dental cements based on physical blends of poly(acrylic acid) and poly(vinyl phosphonic acid)

Physical blends of spray-dried poly(acrylic acid), PAA, with poly(vinyl phosphonic acid), PVPA, have been prepared and used in experimental dental cements by mixing them with basic sub-45 μm acid-degradable fluoroaluminosilicate glass powders and adding water. The effect of varying the ratio of PAA to PVPA, of altering the molar mass of PAA, and of using glasses of differing basicity have been investigated. The compressive strengths of the best of the cements formed from these blends were comparable to those formed from the individual polyacids, i.e. about 160 MPa.     

聚乳酸/聚乙烯醇纳米纤维的制备及结构

以二甲基亚砜为溶剂,制备不同配比的聚乳酸(PLLA)和聚乙烯醇(PVA)的混合溶液,静电纺丝制得PLLA/PVA纳米纤维。采用红外光谱仪、原子力显微镜等对PLLA/PVA纳米纤维结构与性能进行了表征。结果表明:PLLA/PVA纳米纤维中PVA上的羟基与PLLA上的羰基形成了氢键,PLLA与PVA之间存在一定的相互作用,但PLLA/PVA纳米纤维存在相分离现象;混合溶液的PLLA质量分数为11%,PVA质量分数为8%时可以得到较好的PLLA/PVA纳米纤维,但PVA质量分数为6%时出现液滴及珠丝,PVA质量分数为4%时,不能制得纳米纤维。     

Soluble and crosslinked hydrophilic films based on compositions of poly(acrylic acid) and poly(2‐hydroxyethyl vinyl ether) for controlled drug release

Soluble and crosslinked films based on compositions of poly(acrylic acid) and poly(2‐hydroxyethyl vinyl ether) were prepared. Solubility, morphology, mechanical characteristics, and swelling properties of the films were investigated. Potential applications of the polymer complex films in controlled drug delivery were also examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 137–142, 2003     

Thermal behavior of poly(acrylic acid)–poly(vinyl pyrrolidone) and poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

Thermal analysis (TGA and DTA) of samples of PAA, PVP, PAA–PVP complexes, containing different weight fractions of PAA and ternary polymer–metal–polymer complexes, were studied. The activation energy parameters for the thermal degradation were also calculated. The study of the effect of FeCl₃, NiCl₂, and Ni(NO₃)₂ on the TGA and DTA curves of the complexes showed that the decompositions are dependent on the concentrations and the nature of the metal ions. The DTA traces of PAA–PVP complex containing FeCl₃, NiCl₂, and Ni(NO₃)₂ showed that the treatment of the complex with these metal ions causes considerable changes in the thermal decomposition of PAA–PVP complex. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4049–4057, 2006