Carbon‐13 nuclear magnetic resonance investigation of styrene–α‐methylstyrene copolymers

A copolymer based on α‐methylstyrene (AMS) was investigated by nuclear magnetic resonance (NMR). The styrene‐co‐α‐methylstyrene (SAMS) was analyzed by solution and solid‐state NMR techniques. Three copolymers of SAMS with different compositions presented a particular behavior. The solution results showed the copolymer microstructure and the AMS content. The carbon‐13 spectra of SAMS C indicated that the AMS CH₃ signal was detected at three distinct chemical shifts, because of the different comonomer‐sequences distribution. The proton spin–lattice relaxation time in the rotating frame (Tρ) parameter was chosen because it permits the evaluation of changes in the molecular mobility. The values of Tρ found for the copolymers confirmed the random distribution in the samples. The copolymer with a low quantity of AMS (1.7%), when analyzed by this relaxation parameter, showed lower values that were interpreted as an antiplasticization effect. The SAMS copolymer with a higher AMS quantity showed a plasticization effect. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 261–266, 2001     

Study on the thermal stability of heterogeneous nucleation effect of polypropylene nucleated by different nucleating agents

The thermal stability of the heterogeneous nucleation effect of polypropylene (PP) nucleated with an organic phosphate (A) and two kinds of sorbitol derivatives (B and D) was investigated by DSC multiscanning. For pure PP, the peak temperature of crystallization (T) was little changed with an increasing number of DSC scans, indicating that nucleation of PP is thermally stable. For the PP nucleated with an organic phosphate (PPA), the temperatures at the onset of crystallization (T) and at the completion of crystallization (T); the peak temperature of crystallization (T) and melting (T); and the heat of crystallization (ΔH_c) and fusion (ΔH_m) of PP are higher than those of pure PP and were little influenced with an increasing number of DSC scans. For PP nucleated with the sorbitol derivatives (PPB and PPD), the T, T, T, and T decreased with an increasing the number of scans. These results indicated that the thermal stability of heterogeneous nucleation effect of the nucleating agent A is higher than that of nucleating agents B and D. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1643–1650, 2002     

Mass transport process for the adsorption of Cr(VI) onto water‐insoluble cationic starch synthetic polymers in aqueous systems

Dynamic adsorption behaviors between Cr(VI) ion and water‐insoluble amphoteric starches was investigated. It was found that the HCrO ion predominates over the initial pH ∼ 2–4, the CrO ion predominates over the initial pH ∼ 10–12, and both ions coexist over the initial pH ∼ 6–8. The sorption process occurs in two stages: the external mass transport process occurs in the early stage and the intraparticle diffusion process occurs in the long‐term stage. The diffusion coefficient of the early stage (D₁) is larger than that of the long‐term stage (D₂) for the initial pH 4 and pH 10. The diffusion rate of HCrO ion is faster than that of CrO ion for both processes. The D₁ and D₂ values are ∼ 1.38 × 10⁻⁷–10.1 × 10⁻⁷ and ∼ 0.41 × 10⁻⁷–1.60 × 10⁻⁷ cm² s⁻¹, respectively. The ion diffusion rate in both processes is concentration dependent and decreases with increasing initial concentration. The diffusion rate of HCrO ion is more concentration dependent than that of CrO ion for the external mass transport process. In the intraparticle diffusion process, the concentration dependence of the diffusion rate of HCrO and CrO ions is about the same. The external mass transport and intraparticle diffusion processes are endothermic and exothermic, respectively, for the initial pH 4 and pH 10. The k_d values of the external mass transport and intraparticle diffusion processes are ∼ 15.20–30.45 and ∼ −3.53 to −12.67 kJ mol⁻¹, respectively. The diffusion rate of HCrO ion is more temperature dependent than that of CrO ion for both processes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2409–2418, 1999     

The influence of the equilibrium melting temperature on the supermolecular morphology of several polymers

At a constant isothermal crystallization temperature (T_c), the crystalline morphologies of several polymers have been found to be a function of the melt-liquid temperature (T₁). At a constant T_c below a critical crystallization temperature (T [about 0.9 T(K)], a transition from a nonspherulitic to a spherulitic morphology occurs when the melt liquid is heated above a melt-liquid transition temperature, (T_lt) [approximately 1.03 T_m (K)], where T_m is the observed melting temperature of the sample. The melt-liquid transition temperature, T_lt, which experimentally affects the visible morphology of a semicrystalline polymer, is apparently indistinguishable from the thermodynamic melting temperature, T, determined by the Hoffman-Weeks procedure. The X-ray powder diffraction patterns of spherulitic and nonspherulitic morphologies were identical, independent of the heating-cooling cycle. This suggests that the transition that occurs at T_It does not affect the arrangement of polymer molecules in the crystallite, but only the manner in which the crystallites are arranged in the supermolecular morphology. The evidence suggests, at least for the polymers studied, that a residual order exists in the melt until the T or T_It of the particular polymer is reached. © 1993 John Wiley & Sons, Inc.     

Synthesis,characterization, and thermodynamic properties of poly(3‐mesityl‐2‐hydroxypropyl methacrylate)

Poly(3‐mesityl‐2‐hydroxypropyl methacrylate) (PMHPMA) was synthesized in a 1,4‐dioxane solution with 2,2′‐azobisisobutyronitrile as the initiator at 60°C. The homopolymer and its monomer were characterized with ¹H‐ and ¹³C‐NMR, Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and elemental analysis techniques. According to size exclusion chromatography analysis, the number‐average molecular weight, weight‐average molecular weight, and polydispersity index of PMHPMA were 65,864 g/mol, 215,375 g/mol, and 3.275, respectively. According to thermogravimetric analysis, the carbonaceous residue value of PMHPMA was 14% at 500°C. The values of the specific retention volume, adsorption enthalpy, sorption enthalpy, sorption free energy, sorption entropy, partial molar free energy, partial molar heat of mixing, weight fraction activity coefficient of solute probes at infinite dilution (Ω), and Flory–Huggins interaction parameter (χ) were calculated for the interactions of PMHPMA with selected alcohols and alkanes by the inverse gas chromatography method at various temperatures. According to Ω and χ, selected alcohols and alkanes were nonsolvents for PMHPMA at 423–453 K. Also, the solubility parameter of PMHPMA (δ₂) was found to be 24.24 and 26.33 (J/cm³)^0.5 from the slope and intercept of (δ/RT) ? χ/V₁ = (2δ₂/RT)δ₁ ? δ/RT at 443 K, respectively [where δ₁ is the solubility parameter of the probe, V₁ is the molar volume of the solute, T is the column temperature (K), and R is the universal gas constant]. The glass‐transition temperature of PMHPMA was found to be 386 and 385 K by inverse gas chromatography and differential scanning calorimetry techniques, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 101–109, 2006     

Elastic characteristics of branched-network polymers

The computed dependencies of elastic characteristics of branched-network polymers were obtained on the basis of the Takayanagi series model. The moduli ratio (λ) for branched-network and branched polymers increases as a result of an increase of the moduli ratio of network and branched phases (E/E) and the network phase fraction (V_net). The λ-increase as a function of V_net is larger than in the case of the E/E dependence. On the basis of computed dependencies, the experimental results for the radiation crosslinked SBS block copolymer were considered. The experimental results agree with the computed de-pendencies for the hetergeneous branched-network polymers with E/E ≈︁ 20. The influence of entanglements on the elastic characteristics of branched-network polymers is discussed. © 1996 John Wiley & Sons, Inc.     

Adsorption of a gold‐iodide complex (AuI2−) onto cellulose acetate‐polyaniline membranes: Equilibrium experiments

The adsorption of AuI complex onto acetate cellulose‐polyaniline membranes was investigated. Kinetic experiments showed a rapid adsorption of this complex, which was attributed to an ion‐exchange mechanism. Equilibrium adsorption results were represented by the Langmuir model, showing a correlation coefficient of 0.9852. Langmuir parameters K and Q_m were found to be 0.2937 L mg^?1 and 1.2394 mg g^?1, respectively. Approximately 94% of AuI was adsorbed when a solid/liquid ratio of 40 g L^?1 (grams of membrane/ liter of solution) was used. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Determination of crystallinity ratio and some physicochemical properties of poly(4‐methyl‐1‐pentene)

It was determined that the thermal stability of poly(4‐methyl‐1‐pentene) (P4MP) was maintained up to 424°C in an inert atmosphere by thermogravimetric analysis. The retention diagrams of ethyl acetate, tert‐butyl acetate, and benzene on P4MP were plotted at temperatures between 30 and 280°C by inverse gas chromatography (IGC) technique. Melting temperature of the polymer was determined as 230 and 239.5°C by IGC and differential scanning calorimetry (DSC), respectively. The percent crystallinity of P4MP was obtained from the retention diagrams at temperatures below melting point. The percent crystallinity obtained by IGC is in good agreement with the ones obtained by DSC. Then, specific retention volume, V, weight fraction activity coefficient, Ω, Flory‐Huggins polymer‐solvent interaction parameter, χ, equation‐of‐state polymer‐solvent interaction parameter, χ, and effective exchange energy parameter, X_eff of octane, nonane, decane, undecane, dodecane, tridecane, n‐butyl acetate, isobutyl acetate, isoamyl acetate with P4MP, were determined between 240 and 280°C by IGC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Melting behavior of poly(trimethylene terephthalate)

In this study, the melting behavior of isothermally crystallized polytri‐ methylene terephthalate (PTT) was investigated. Multiple melting behaviors in DSC heating trace were found because two populations of lamellar stacks were formed during primary crystallization and the recrystallization at heating process, respectively. This fact could be also confirmed from the result of optical microscopy observation. The Hoffman–Weeks equation was applied to obtain equilibrium melting temperature (T). The T value of PTT is about 525 K, which is 10 K higher than that reported. Combining the enthalpy of fusion from the DSC result and the degree of crystallinity from WAXD result, the value of the equilibrium‐melting enthalpy ΔH was deduced to be approximately 28.8 kJ mol^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2426–2433, 2002     

Influence of anionic form on thermal degradation of TMAHP–cellulose

Trimethylammoniumhydroxypropyl (TMAHP)–cellulose in 10 anionic forms (F^?, Cl^?, Br^?, I^?, HSO, NO, OH^?, HCO, H₂PO, CH₃COO^?) was prepared, and the influence of each anion on thermal degradation in inert atmosphere was studied. With the help of dynamic and isothermal thermogravimetry (TG) it was found that H₂PO ions had the greatest retarding effect on TMAHP–cellulose degradation. From the values of rate constants it can be seen that all ionic forms of TMAHP–cellulose have the starting rate of thermal degradation greater than unmodified cellulose. The calculated values of activation energy of thermal degradation for different ionic forms are decreasing in following sequence: H₂PO > F^? > NO > I^? > Br^? > HCO > Cl^? > HSO > OH^? > unmodified cellulose > CH₃COO^?. From the results of pyrolyse measurements in combination with gas chromatography and mass spectrometry (Py–GC–MS) it follows that the products of the elimination of quarternary ammonium salts are trimethylamine, 3-hydroxy-2-propanone, and, in the case of OH^? form, water. In all other ionic forms the third product is the corresponding acid.     

Synthesis and electrochemistry of grafted copolymers of cellulose with 4-vinylpyridine, 1-vinylimidazole, 1-vinyl-2-pyrrolidinone,and 9-vinylcarbazole

Some new cellulosic materials, suitable for the adsorption of noble metal ions, were syn-thesized by chemical and electrochemical modification of cellulose. The polymerizable groups were introduced in cellulose with ∼ 80% yield of substitution by esterification with acryloyl chloride. The vinyl monomers (4-vinylpyridine, 1-vinylimidazole, 1-vinyl-2-pyrrolidinone, and 9-vinylcarbazole) were readily grafted into cellulose acrylate via radical polymerization in acetonitrile. The grafted copolymers of cellulose with 4-vinylpyridine and 4-vinylimidazole were reacted with methyl iodide and the corresponding 1-methylpyridinium iodide ( 6 ) and 3-methylimidazolium iodide ( 7 ) copolymers of cellulose were obtained. Copolymers 6 and 7 were transformed into new polymeric regents, differing in anions (ClO, CF₃COO⁻, NO, p-TsO⁻, BF, PF) by using a supporting electrolyte carrying the desired anions through the ion-exchange-electrochemical oxidation of the released iodide at a controlled anodic potential. © 1996 John Wiley & Sons, Inc.     

Surface activity and micellar behavior of dimethylamino‐ and trimethylammonium‐ tipped oxyethylene–oxybutylene diblock copolymers in aqueous media

Surface activity and micellar behavior in aqueous media in the temperature range 20–50°C of the two block copolymers, Me₂N(CH₂)₂OE₃₉B₁₈, (DE₄₀B₁₈) and I^?Me₃N⁺(CH₂)₂OE₃₉B₁₈, (TE₄₀B₁₈) in the premicellar and postmicellar regions have been studied by surface tensiometry, viscometry, and densitometry. Where E represents an oxyethylene unit while B an oxybutylene unit. Various fundamental parameters such as, surface excess concentrations (Γ_m), area per molecule (a) at air/water interface and standard Gibbs free energy for adsorption, ΔG have been investigated for the premicellar region at several temperatures. The thermodynamic parameters of micellization such as, critical micelle concentrations, CMC, enthalpy of micellization, ΔH, standard free energy of micellization ΔG, and entropy of micellization ΔS have also been calculated from surface tension measurements. Dilute solution viscosities have been used to estimate the intrinsic viscosities, solute‐solvent interaction parameter and hydration of micelle. Partial specific volume and density of the micelle were obtained from the density measurements at various temperatures. The effect of modifying the end group of the hydrophilic block was investigated by comparing the behavior of trimethylammonium‐ and dimethylamino‐tipped copolymers, designated TE₄₀B₁₈, and DE₄₀B₁₈, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrochemical synthesis and properties of poly(3‐methylthiophene): Novel synthesis of poly(3‐methylthiophene) with pentachlorostannate and hexachloroantimonate

Poly(3‐methylthiophene) (P3‐MeT) doped with different anions were prepared electrochemically in the presence of tetraalkylammonium salts. The new poly(3‐methylthiophene) SnCl and SbCl (P3‐MeT SnCl₅ and P3‐MeT SbCl₆) were prepared electrochemically using tetra‐n‐butylammonium pentachlorostannate and tetra‐n‐butylammonium hexachloroantimonate as the supporting electrolytes. The effect of current density, salt concentration, reaction temperature, and the nature of solvents on the polymer yield and polymer conductivities have been investigated. Cyclic voltammetry of poly(3‐methylthiophene) has been examined at platinum electrode in 1,2‐dichloroethane medium containing n‐Bu₄NSnCl₅, Bu₄NSbCl₆, and Bu₄NClO₄ as the supporting electrolytes in the range of −1.0 to 1.7 V versus SCE in the presence and absence of 3‐methylthiophene. Electrical conductivity, magnetic susceptibility measurements, and structural determination by elemental analysis and infrared studies were also made. Scanning electron microscopy revealed a globular, branched, fibrous and a spongy, fibrous morphology of poly(3‐methylthiophene) SnCl, ClO, and SbCl, respectively. The thermal analysis of the polymers was also investigated. Possible causes for the observed lower conductivity of these polymers have also been discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 91–102, 1999     

Preparation and glass transition temperature of hyperbranched poly[allyl methyl maleate‐co‐N‐propyl maleimide]

The kinetics and molecular weight averages of the hyperbranched polymers formed by the alternating copolymerization of equimolar allyl methyl maleate (AMM) and N‐n‐propyl maleimide (PMI) were investigated. The yields, molecular weight averages, and polydispersity indices as well as the branching degrees of the produced copolymers increased with increasing initiator concentrations and prolonged polymerization time. The trends of the experimental molecular weights as determined by size exclusion chromatography were in good agreement with the theoretical predictions. The molecular weight distribution indices fit the curve given by M_w/M_n = 1/(1‐x_D), and the molecular weights fit the curve given by M_w = 4076/(1‐x_D)², where x_D was the conversion of vinyl groups. DSC studies demonstrated a nonlinear relation of T_g values to the reciprocal of molecular weight (M), and T_g values decreased with the increase of molecular weight. For the T_g values of highly branched polymers in high molecular weight range, a relation of T_g = T + k/M was obtained, where T was obtained by extrapolating to infinite molecular weight and k was a constant. T was 136°C, and k = 2.9 for this work. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1941–1947, 2005     

Nonisothermal crystallization and melting behavior of β‐nucleated isotactic polypropylene and polyamide 66 blends

A highly novel nano‐CaCO₃ supported β‐nucleating agent was employed to prepare β‐nucleated isotactic polypropylene (iPP) blend with polyamide (PA) 66, β‐nucleated iPP/PA66 blend, as well as its compatibilized version with maleic anhydride grafted PP (PP‐g‐MA), maleic anhydride grafted polyethylene‐octene (POE‐g‐MA), and polyethylene‐vinyl acetate (EVA‐g‐MA), respectively. Nonisothermal crystallization behavior and melting characteristics of β‐nucleated iPP and its blends were investigated by differential scanning calorimeter and wide angle X‐ray diffraction. Experimental results indicated that the crystallization temperature (T) of PP shifts to high temperature in the non‐nucleated PP/PA66 blends because of the α‐nucleating effect of PA66. T of PP and the β‐crystal content (K_β) in β‐nucleated iPP/PA66 blends not only depended on the PA66 content, but also on the compatibilizer type. Addition of PP‐g‐MA and POE‐g‐MA into β‐nucleated iPP/PA66 blends increased the β‐crystal content; however, EVA‐g‐MA is not benefit for the formation of β‐crystal in the compatibilized β‐nucleated iPP/PA66 blend. It can be relative to the different interfacial interactions between PP and compatibilizers. The nonisothermal crystallization kinetics of PP in the blends was evaluated by Mo's method. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Spherulitic crystallization behavior of linear low‐density polyethylene

In this study the crystallization behavior of linear low‐density polyethylenes (LLDPEs) (ethylene‐α‐olefin copolymers) was studied by polarized light microscopy. A modified Hoffman‐Lauritzen (MHL) expression is proposed whereby the equilibrium melting temperature, T (T), is replaced with the melting temperature of the crystal stem is replaced with the maximum possible stem length, T. It successfully describes the crystalline spherulitic growth kinetics for both homogeneous and heterogeneous LLDPEs. In addition to regimes III and II, another regime (IM) was found in the high crystallization temperature range. Linear growth behavior of crystalline spherulites was observed in regime III, and nonlinear growth behavior was found in regimes II and IM. The basal surface free energy can be estimated from the short chain branching polydispersity (SCBP) for LLDPEs with excluded comonomers. Polym. Eng. Sci. 45:74–83, 2005. © 2004 Society of Plastics Engineers.     

Curie transition and piezoelectricity of the blends of a ferroelectric VDF/TrFE copolymer and PMMA

The Curie transition, even though the conformational change at the Curie transition primarily arises from intermolecular interaction, is highly dependent on the crystallization conditions. A slower cooling rate from the melt during paraelectric crystallization lowers T_c, increases the portion of F_β at the expense of F_α reduction, and produces a more unstable ferroelectric phase. T is rarely dependent upon the amount of PMMA, but T is increased with the PMMA content. PMMA has a favorable action in forming a more stable ferroelectric phase in the P(VDF/TrFE)/PMMA blend and elevating the Curie transition point because of the all-trans sequence conformation of PMMA and a specific intermolecular interaction with P(VDF/TrFE) in the melt state. However, PMMA reduces the total amount of the crystalline phase, the electric response, and the piezoelectricity. © 1993 John Wiley & Sons, Inc.     

Isothermal crystallization behavior and melting characteristics of injection sample of nucleated polypropylene

The isothermal crystallization behavior and melting characteristics of pure polypropylene (PP) and PPs nucleated with a phosphate nucleating agent (A) and a sorbitol derivative (D) have been studied by differential scanning calorimetry (DSC). Compared with pure PP, nucleated PPs show a shorter half‐times of crystallization. Dependence of crystallization rate of nucleated PP on the crystallization temperature is stronger than that of pure PP at the higher crystallization temperature, whereas the opposite results are obtained at the lower crystallization temperature. Addition of nucleating agent shifts the temperature at the deviation from the baseline of DSC melting curve, T, and the temperature at the completion of melting, T, to higher temperatures, indicating that nucleated PPs exhibit a higher perfection of PP crystals. A shoulder peak in the high temperature range of melting peak of nucleated PP and a wider low temperature region in the melting peak of pure PP are observed. Obviously, PP and nucleated PPs form different distribution of crystal perfection in the isothermal crystallization process. According to the half‐time of crystallization, nucleating agent A is more effective than D. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2547–2553, 2000     

Fundamental studies on a new series of SPSEBS‐PVA‐QPSEBS bipolar membrane: Membrane preparation and characterization

A sulfonated polystyrene ethylene butylene polystyrene (SPSEBS)‐poly(vinyl alcohol) (PVA)‐Quaternized polystyrene ethylene butylene polystyrene (QPSEBS) bipolar membrane (BPM) was prepared by lamination method using PSEBS as the starting material, the functionalization of which was modified by sulfonation and amination while PVA was used as the intermediate layer to enhance the water splitting efficiency. The cross section view of SPSEBS‐PVA‐QPSEBS BPM was studied by SEM. Fourier transform infra‐red spectroscopy (FTIR) studies indicated that the prepared BPM contained –SO, –NR, and –C‐N functional groups. The thermal stability of the prepared BPM was studied by thermogravimetric analysis (TGA). Some of the BPM characteristics results showed that the co‐ion fluxes was greater for t(0.065) when compared with t(0.051) along with a water splitting capacity value of 0.88 for SPSEBS‐PVA‐QPSEBS BPM. The water dissociation flux was 2.8 × 10^?5 mol/m²/s and 2.2 × 10^?5 mol/m²/s for the acid (H⁺) and base (OH^?), respectively. The other essential current‐voltage characteristics and permeate flux across the membrane were also evaluated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci 2013