Determination of the critical concentration of partially hydrolyzed polyacrylamide by potentiometry in an acidic medium

The literature presents different methods for quantifying and characterizing partially hydrolyzed polyacrylamide (HPAM) in solution. However, only a few of these are suitable for determining the critical overlap concentration (C*). The evaluation of C* is important for describing the transition from the dilute to the semidilute regime, that is, when the solution depicts a characteristic viscosity at concentrations above C*. This article describes the determination of C* for HPAM in solution by potentiometry. The molecular weight, degree of hydrolysis, and polymerization degree are determined by mathematical manipulation of the constant of formation of aggregates, which is based on the law of mass action. The potentiometric curves were initially linear; asymptotic behavior followed. The inflection point was determined by the intersection, and the resulting equation of mathematical development statistically satisfied the experimental data and described the number of moles of monomers, the equilibrium constant for the formation of the aggregate, C*, and the acidity constant of the polymer. The results for C*, the degree of copolymerization, and the molecular weight proved that this method is a good alternative for the characterization of polymers with ionizable monomers and that are soluble in water. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of poly(ethylene terephthalate)‐based proton‐exchange membranes through the ultraviolet‐induced graft copolymerization of allyl methacrylate for applications in fuel cells

The ultraviolet‐induced graft copolymerization of allyl methacrylate into poly(ethylene terephthalate) films and the subsequent sulfonation of the grafted film were performed to prepare a polymer electrolyte membrane (PEM). The sulfonation reaction occurred at the grafted chain under mild conditions; that is, the grafted film was easily transformed into a PEM. The mechanical, chemical, and thermal properties of the prepared PEM (i.e., the ion‐exchange capacity, water uptake, tensile strengths at different water uptakes and temperatures, stability in hydrogen peroxide solutions, and proton conductivity) were measured with titrimetric and gravimetric analyses; most were found to be better than those of Nafion. The maximum ion‐exchange capacity and proton conductivity of the PEM were observed to be 0.072 mmol/g and 0.0458 S/cm, respectively. Because this PEM is inexpensive to prepare with available raw materials and has the properties required for fuel cells, it could be an attractive and suitable device for use in fuel‐cell technology. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

粘度法间接测定聚磷酸铵聚合度研究

提出了粘度法间接测定聚磷酸铵（APP）聚合度的一种方法。采用离子交换法把常温下没有溶剂的APP转化成聚磷酸钠（NaPP）或其复盐并溶于水中。利用Strauss和Pfanstiel分别针对聚磷酸钠、聚磷酸钾确定的Mark-Houwink方程及经验公式，测定聚磷酸钠及其复盐的相对分子质量或聚合度，间接获得APP的聚合度。结果表明，2种方法结果差别很大，Pfanstiel法结果比Strauss法结果小很多。分析了造成2种方法测定结果差别很大的原因，讨论了2种方法结果之间的关系，认为Pfanstiel法可以用来测定APP相对分子质量，Strauss法可以用来比较用一种方法制备的APP相对分子质量的大小。     

Kinetic study of the free‐radical polymerization of vinyl acetate in the presence of deuterated chloroform by 1H‐NMR spectroscopy

The free‐radical polymerization of vinyl acetate was performed in the presence of deuterated chloroform (CDCl₃) as a chain‐transfer agent (telogen) and 2,2′‐azobisisobutyronitrile as an initiator. The effects of the initiator and solvent concentrations (or equivalent monomer concentration) and the reaction temperature on the reaction kinetics were studied by real‐time ¹H‐NMR spectroscopy. Data obtained from analysis of the ¹H‐NMR spectra were used to calculate some kinetic parameters, such as the initiator decomposition rate constant (k_d), k_p(f/k_t)^1/2 ratio (where k_p is the average rate constant for propagation, f is the initiator efficiency, and k_t is the average rate constant for termination), and transfer constant to CDCl₃ (C). The results show that k_d and k_p(f/k_t)^1/2 changed significantly with the solvent concentration and reaction temperature, whereas they remained almost constant with the initiator concentration. C changed only with the reaction temperature. Attempts were made to explain the dependence of k_p(f/k_t)^1/2 on the solvent concentration. We concluded from the solvent‐independent C values that the solvent did not have any significant effect on the k_p values. As a result, changes in the k_p(f/k_t)^1/2 values with solvent concentration were attributed to the solvent effect on the f and/or k_t values. Individual values of f and k_t were estimated, and we observed that both the f and k_t values were dependent on the solvent (or equivalent monomer) concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Modified frontal polymerization of poly(methyl methacrylate)

In this work, we propose a modified frontal polymerization method to build a uniform reaction front by gradually immersing the reacting mixture in a thermal bath. This scheme allows uniform materials to be obtained with nearly constant molecular weights and polydispersities and a low residual monomer concentration. A comparative study of the molecular weight distributions of poly(methyl methacrylate)s obtained by bulk polymerization, frontal polymerization, and frontal polymerization with the proposed gradual immersion is presented. Samples obtained by these methods show that materials obtained by bulk polymerization and by frontal polymerization are less uniform than those obtained by frontal polymerization with gradual immersion in a thermal bath. The obtained uniformity is directly related to a stabilizing effect of the reaction front by the gradual immersion of the reactor in a constant‐temperature bath and to a reduction in the reaction rate promoted by a moderate transfer agent concentration. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of the new derivatives of cellulose and oligomeric species of cellulose containing magneson II chromophore

Fully acetylated cellulose triacetate (CTA) was hydrolyzed in the presence of hydronium ions in a solution of acetic acid and concentrated sulfuric acid to give a hydroxyl‐terminated cellulose triacetate oligomers (HCTA). By using gel permeation chromatography (GPC) analysis, the molecular weight of the isolated oligomeric product was calculated to be 3748 Da. HCTA was converted to their new derivatives having 4‐(4‐nitrophenylazo)‐1‐naphthol (magneson II) as a chromophore. Then 4′‐bromobutoxy‐4‐(4‐nitrophenylazo) naphthalene was synthesized from the reaction of 4‐(4‐nitrophenylazo)‐1‐naphthol with 1,4‐dibromobutane. The synthesized alkylated chromophore was reacted with oligomeric cellulose and cellulose itself in the solution of dimethyl sulfoxide to produce cellulose ethers containing the desired chromophore. In the last step, the isolated compounds were used for the preparation of new polymers and oligomers, which contain both of dodecane and butoxy‐4‐(4‐nitrophenylazo)naphthalene as the alkyl side chains in their backbone. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of poly(vinyl acetate) by degenerative transfer polymerization in the presence of iodine

A new curing agent containing maleimide and biphenyl moieties (MIBP) was synthesized by the condensation polymerization of 4,4′-bismethoxymethylbiphenyl and N-(4-hydroxyphenyl)maleimide (HPM). The chemical structure was characterized with Fourier transform infrared (FTIR) spectroscopy, and the molecular weight of the new curing agent was determined by gel permeation chromatography. Curing reactions of O-cresol formaldehyde epoxy (CNE) resin with MIBP were investigated under nonisothermal differential scanning calorimetry, and the exotherm exhibited two overlapping exothermic peaks during the curing process; this was demonstrated by FTIR traces. The Flynn–Wall–Ozawa and Friedman methods were used to examine the kinetic parameters and the kinetic models of the curing processes of the CNE/MIBP mixtures. Both reactions turned out to be nth-order curing mechanisms. Values of the reaction order (n) = 1.42 and activation energy (E_a) = 91.2 kJ/mol were obtained for the first reaction of the curing of the CNE/MIBP system, and values of n = 1.11 and E_a = 78.7 kJ/mol were obtained for the second reaction. The thermal properties of the cured resin were measured with thermogravimetric analysis, and the results show a high glass-transition temperature (T_g = 155°C), good thermal stability (temperature at 10% weight loss, under nitrogen and in air, ≈ 400 and 408°C, respectively), and high char yield (temperature = 800°C, char residue = 44.5% under nitrogen). These excellent thermal properties were due to the introduction of the maleimide and biphenyl groups of MIBP into the polymer structure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

高聚合度聚氯乙烯的共混改性及加工应用

综述了近年来我国内外高聚合度聚氯乙烯（HPVC）的共混改性和加工应用情况,对软质材料、硬质材料的力学性能、加工改性的发展方向及加工过程的凝胶化行为进行了系统阐述,展望了HPVC制品的应用前景。     

Effect of degree of polymerization on gelation and flow processability of poly(vinyl chloride)

The effect of degree of polymerization (DP) on the gelation and flow processability of poly(vinyl chloride) (PVC) was studied. Sheets with adjusted degree of gelation were prepared by rolling rigid pipe formulation suspension PVC compounds with DPs of 800, 1050 and 1300 by changing the milling temperature. Their degrees of gelation were measured with DSC and their capillary flow properties were measured with a capillary rheometer at 150, 170 and 190°C and the effect of DP on the relation between gelation and flow processabilities was studied. Because of the higher shearing heat during milling, the sample with the higher DP had a higher history temperature and thus tended to show a higher degree of gelation. The viscosity increased as the gelation increased. The dependency of viscosity on DP was higher at higher milling and extrusion temperatures and thus at a higher degree of gelation and a lower shear rate. This was assumed to be attributed to the more prominent uniform molecular flow as against the particle flow. The die swell increased with increasing the milling and extrusion temperatures and hence with increasing the gelation. A sample with a lower DP tended to show a larger die swell and this tendency was even more pronounced at the higher extrusion temperature. The melt fracture easily occurred when a sample with advanced gelation was extruded at low temperature. Whereas at low milling temperatures a sample with the lower DP showed a lower critical shear rate at onset of melt fracture, and thus easily generating melt fracture, at high milling temperatures it showed a higher critical shear rate and hence scarcely generated melt fracture. These experimental results were explained by the fact and concept that a sample with a lower DP shows a higher increase in the gelation during extrusion and/or the slighter feature of particle flow as against the uniform molecular flow at the same gelation level. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1915–1938, 2004     

Characterization of poly(vinyl alcohol) films with various molecular parameters

The effects of three major molecular parameters of poly(vinyl alcohol)—the number‐average degree of polymerization, degree of saponification, and syndiotactic dyad content—on the characteristics of poly(vinyl alcohol) films were investigated. Various poly(vinyl alcohol) films were prepared by a casting method. Then, the films were characterized with atomic force microscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, Fourier transform infrared spectroscopy, and Instron instrumentation. On the basis of atomic force microscopy images and calculated average roughness values, it was determined that the surface roughness of poly(vinyl alcohol) films increased with increasing molecular parameters. The crystallinities obtained with differential scanning calorimetry and wide‐angle X‐ray diffraction analyses were also enhanced with increasing molecular parameters, especially the degree of saponification. The tensile properties were improved with higher molecular parameters. This might be ascribed to the fact that the higher the molecular parameters were, the stronger the hydrogen bonding was. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Continuous polymerization of ε‐caprolactone initiated by titanium phenoxide in a twin‐screw extruder

The continuous polymerization of ε‐caprolactone initiated by titanium phenoxide was carried out in both an internal mixer and a twin‐screw extruder. The polymerization was performed under different processing conditions, including various temperatures and screw speeds. To perform a kinetic study, samples were collected along the time axis (internal mixer) and along the screw axis (extruder). Size exclusion chromatography and proton nuclear magnetic resonance were used to study the evolution of the conversion degree with mixing time and with the extruder. The rheological behavior was also characterized. Temperature had a strong effect on conversion in the internal mixer, whereas in the twin‐screw extruder, both temperature and screw speed played major roles. The specificity of the titanium phenoxide to lead to high‐molar‐mass poly(ε‐caprolactone) under these processing conditions was also confirmed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Applying Tikhonov regularization to process the kinetic data of polymerization

Most experimental polymerization kinetic data are in the form of degree of polymerization versus time plots. However, to explore kinetic models it is more useful to have the data as polymerization rate versus degree of polymerization plots. Converting degree of polymerization into rate is an ill‐posed problem in that if inappropriate methods are used the noise in the data will be amplified, leading to unreliable results. This paper describes a procedure, based on Tikhonov regularization, to perform this conversion. The procedure is independent of kinetic models and keeps noise amplification under control. Its performance is demonstrated using several sets of published polymerization kinetic data. In each case the computed rates are used to determine the parameters in the rate expression proposed in the original papers. Modified rate expressions will also be explored. The ease with which such investigations can be performed highlights the advantages of this new procedure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1625–1633, 2004     

Synthetic resin. XII. Synthesis and characterization of new terpolymer resins derived from 8‐hydroxyquinoline 5‐sulfonic acid,melamine, and formaldehyde

Terpolymers 8‐hydroxyquinoline 5‐sulphonic acid–melamine–formaldehyde (8‐HQ5‐SAMF) were synthesized through the condensation of 8‐hydroxyquinoline 5‐sulfonic acid and melamine with formaldehyde in the presence of an acid catalyst. Four different terpolymers were synthesized with various molar proportions of the reacting monomers. The terpolymer resin compositions were determined on the basis of elemental analysis. The number‐average molecular weights of these resins were determined by conductometric titration in a nonaqueous medium; viscometric measurements in dimethyl sulfoxide were carried out to ascertain the characteristic functions and constants. Ultraviolet–visible, Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR spectroscopy and thermogravimetric analysis were used to elucidate the structures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrochemical behaviors of poly(ferrocenylsilane) solutions

The electrochemical behaviors of two kinds of poly(ferrocenylsilanes) (PFS) with different substituent groups in CH₂Cl₂ solutions were investigated by means of cyclic voltammetry (CV) and electrochemical quartz crystal microbalance. The results demonstrated that the CV processes of the PFS on the glass carbon electrode surface in CH₂Cl₂ solutions are the diffusion‐controlled reversible processes. The oxidative state of PFS forms an adsorption layer on the electrode surface during the oxidation process. The interaction of active ferrocene centers along the main chain induces the stepwise redox process, and makes the CV waves of the PFS solutions present two couples of peaks. The diffusion coefficients of PFS in CH₂Cl₂ solution are much larger than those of PFS in films. The different electrochemical behaviors of the two PFS solutions indicated that the molecular structure of polymer has influence on the electrochemical properties of the PFS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 789–794, 2007     

Electrochemical polymerization of β‐naphthalene sulfonic acid

β‐Naphthalene sulfonic acid (β‐NSA) has been electrochemically polymerized in a mixed electrolyte of boron trifluoride diethyl etherate (BFEE) solution mixed with a certain amount of trifluoroacetic acid (TFA) or concentrated sulfuric acid (SA). The poly(β‐naphthalene sulfonic acid) (PNSA) film prepared from the medium of BFEE+TFA was partly soluble in methanol. On the other hand, the polymer obtained from the system of BFEE+SA was soluble in water and general polar organic solvents such as methanol, alcohol, and acetone. The structure of PNSA was examined by infrared and UV spectra. Fluorescent spectral studies indicate that the polymer is a blue light emitter with fluorescence quantum efficiency of ～ 4%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1939–1944, 2004     

Preparation of porous polyacrylamide hydrogels by frontal polymerization

Polyacrylamide hydrogels with defined porous structure were synthesized through frontal polymerization (FP) in the presence of NaHCO₃ as a foaming agent. Pore properties were analyzed using scanning electron microscopy and mercury intrusion porosimetry. The as‐prepared hydrogels displayed a small cell diameter of ca 2 µm. The dissolved foaming agent dispersing at the level of molecules and the polymerization front propagating step by step should be responsible for the small uniform cell structure. The pore volume varied from 0.63 to 3.65 cm³ g^?1 and the bulk density changed from 0.48 to 0.28 g cm^?3 for a foaming agent content from 0 to 18%. The hydrogels synthesized by FP exhibited higher swelling rate and swelling ratio with respect to conventional batch polymerization. The highest swelling ratio and rate were obtained at a foaming agent concentration of 12% based on monomer. Copyright © 2007 Society of Chemical Industry     

Gelation in the radical polymerization of dimethyl diallyl ammonium chloride

Within the framework of an irreversible aggregation model on a sample of polydimethyl diallyl ammonium chloride, we demonstrated that gelation occurred on a transient part from the autoacceleration stage until the dopolymerization stage. During part of the autoacceleration, the polymer solution was in a sol state on the segment of autoacceleration. Therefore, the use of the term gel effect in reference to the beginning of the reaction did not seem quite justified. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1394–1396, 2004     

Benzylated modification and dyeing of ramie fiber in supercritical carbon dioxide

The effects of pretreatment conditions, including the addition of a phase‐transfer catalyst, on the benzylation of ramie fiber were investigated in this study. Raw and benzylated ramie fibers were dyed in supercritical carbon dioxide, and the color strength (K/S) of the ramie fiber was measured by ultraviolet–visible spectroscopy. An obviously improved dyeing capability of the benzylated ramie fiber, that is, a better level‐dyeing property and a higher K/S, was achieved. Moreover, the color strength of the ramie fiber, indexed as the value of K/S, increased significantly with the degree of substitution of the benzylated ramie fiber. The raw and modified ramie fibers were characterized with Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

EWOD‐Driven translational movement of a liquid polyelectrolyte droplet

Controlled transportation of air‐ and electrochemically stable materials is of interest in many areas of science. Herein, we report the synthesis and characterization of an ionic liquid monomer and its corresponding polyelectrolyte. The translational movement of these ionic liquid droplets across a substrate using the mechanism of electrowetting on a dielectric (EWOD) is demonstrated with emphasis given to electrode design and selective switching in the device construction. Directional control of a 2 mm sized polyelectrolyte droplet is shown to laterally move across the substrate surface on the order of 10s of minutes due to its increased viscosity, whereas its ionic liquid monomer also transverses but at a much faster pace‐on the order of 10s of seconds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008