Diffusion and sorption of benzene vapor through polybutadiene‐, polybutadiene/styrene‐, and polybutadiene/acrylonitrile‐based polyurethanes

A series of polyurethane (PU) films made from toluene diisocyanate (TDI), 1,4‐butanediol (BDO), and hydroxyl‐terminated polybutadiene (HTPB), hydroxyl terminated polybutadiene/styrene (HTBS), or hydroxyl terminated polybutadiene/acrylonitrile (HTBN) was synthesized by solution polymerization. The absorption of benzene vapor was found mainly in the soft phase. The equilibrium adsorption (M_∞) was reduced with increasing hard segment content for all the PUs. The values of M_∞ were in the sequence of HTBN‐PUs > HTBS‐PUs > HTPB‐PUs, which could be explained by the different interaction parameters between soft segments and benzene. The HTBN‐PU film showed the lowest degree of phase segregation and had more hard segments intermixed in the soft phase, restricting the movement of soft segments, and therefore resulted to non‐Fickian behavior, while the HTPB‐PU is antithetical. FTIR and atomic force microscopy were utilized to identify the hydrogen bonding behavior and morphology change of the PU films before and after the absorption of benzene vapor. The tensile strength of the HTBN‐PUs showed a greater decrease than that of HTBS‐PUs and HTPB‐PUs after absorbing benzene vapor. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2984–2991, 2004     

Measurements of monomer partitioning in emulsion copolymerization systems

A new apparatus to measure the equilibrium solvent activity in a multiphase system containing a particulated polymer is presented. An experimental procedure to determine the monomer partitioning in typical emulsion copolymerization systems is developed; the method is devised in a way that no phase separation between water and swollen polymer particles is required in order to determine the monomer content in each phase. The analytical technique used is quantitative gas chromatography, either of the vapor or of the liquid phases. Different monomers (styrene, methyl methacrylate, and vinyl acetate) and polymeric matrices (polystyrene and methyl methacrylate–vinyl acetate copolymer) are examined both above and below saturation conditions (corresponding to intervals II and III of an emulsion polymerization process). The experimental results are compared with predictions of a literature model. © 1996 John Wiley & Sons, Inc.     

Bulk polymer/solvent interactions for polyethylene and EVA copolymers,below their melting temperatures

In this work, the Flory–Huggins parameters corresponding to the amorphous phase of a polyethylene (PE) and two ethylene–vinyl acetate (EVA) copolymers (with 18 and 33 % vinyl acetate content, respectively) samples, with different solvents have been determined below the melting temperature of the polymers, in order to quantify the bulk interactions of these polymer/solvent systems. The employed solvents were a dispersion solvent (cyclohexane), a polar solvent (vinyl acetate) and an association solvent (methanol). Initially, the inverse gas chromatography measurements allowed obtaining the retention volumes, activity coefficients and overall Flory–Huggins parameters of every polymer/solvent system. According to these parameters, in all cases, the more compatible solvent was cyclohexane, so it was selected as the probe to calculate the percentages of crystallinity at room temperature, whose results were in agreement the literature data (35 % for PE, 29 % for EVA18, and 12 % for EVA33). The percentage of crystallinity allowed determining the amorphous Flory–Huggins parameters which are the ones which take into account just the bulk interactions in a polymer/solvent mixture. The Flory–Huggins parameter results show that, to accurately study the vapor–liquid equilibrium between a polymer and a solvent (bulk interactions), when the range of studied temperatures is below the melting point of the polymer, it is crucial to calculate the amorphous contribution (χ _amorphous) on the overall Flory–Huggins parameter. In the case of this study, the lower the vinyl acetate content (higher crystallinity), the higher the difference between the overall and amorphous Flory–Huggins parameters is. Analyzing the interactions between the three polymeric materials and the solvents it can be noticed that, for the most compatible solvent (cyclohexane), χ _amorphous represents the less contribution, or the highest correction, to the overall Flory–Huggins parameter (around 50 % for PE and EVA18, and 79 % for EVA33, the less crystalline polymer).     

Application of cubic equation of state models in prediction of vapor–liquid equilibria for binary polyvinyl acetate/solvent solutions

The cubic equation of state (CEoS) is a powerful method for calculation of (vapor + liquid) equilibrium (VLE) in polymer solutions. Using CEoS for both the vapor and liquid phases allows one to calculate the non‐ideality of polymer solutions based on a single EoS approach. In this research, vapor–liquid equilibria calculations of polyvinyl acetate (PVAc)/solvent solutions were performed. In this approach, eight models containing PRSV and SRK CEoS separately combined with four mixing rules namely vdW1, vdW2, Wong–Sandler (WS), and Zhong–Masuoka (ZM) were applied to calculations of bubble point pressure. For the better prediction, the adjustable binary interaction parameters existing in any mixing rule were optimized. The results were very acceptable and satisfactory. Absolute average deviations (%AAD) between predicted results and experimental bubble point pressure data were calculated and presented. The capability of two cubic equations of state had a good agreement with experimental data and predict the correct type of phase behavior in all cases, but the performance of the PRSV + vdW2 was more reliable than the other models with 2.65% in AAD for total of solution systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40651.     

Preparation and characterization of high‐impact polystyrene using different types of polybutadiene

The mechanical, morphological, and rheological properties of polymer blends based on polystyrene (PS) and three different types of polybutadiene (PB) were studied. The polymer blends containing 20% of PB were processed in a Haake mixer at 180°C and 60 rpm for 6 min. The materials exhibited impact strength superior to that of the PS. An increase was observed in the impact strength of 138, 208, and 823%, when low‐cis polybutadiene (PB_l), high‐cis polybutadiene (PB_h), and styrene–butadiene block copolymer (PB_co), were respectively used. The materials presented dispersed morphology with polybutadiene domains, with sizes inferior to 1 μm, randomly distributed in the PS matrix. The viscous and storage moduli increased as the applied frequency increased. The flow activation energy, calculated by Arrhenius equation, varied from 34 to 71 kJ/mol. In the rheological experiments all polymer blends presented pseudoplastic behavior, showing decreasing viscosities as the shear rate increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase behaviors of binary polymer solutions: The extended lattice fluid model

The generalized lattice–fluid (GLF) model is extended to predict phase behaviors of polymer/solvent systems. The GLF model gives some difficulties in describing liquid–liquid equilibria (LLE) of binary polymer solution systems due to general assumptions on its derivation. An extended lattice–fluid (ELF) model is proposed by introducing a new universal constant (C₀) and a model parameter (κ₁₁). The proposed model is then compared with experimental data for polymer/solvent systems and polymer1/polymer2 systems, which exhibit lower critical solution temperature (LCST) behaviors. Theoretical predictions and experimental results are in good agreement. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1143–1150, 1998     

Determination of the methyl methacrylate monomer in its polymer latex by headspace gas chromatography

This article reports a headspace gas chromatography (GC) method for the determination of the residual monomer in a methyl methacrylate polymer latex or emulsion. Because of the multiphase nature of a polymer latex, the level of the residual monomer cannot be quantified by headspace GC on the basis of its vapor–liquid equilibrium (VLE) without significant thermodynamic assumptions. With a significant dilution of a polymer latex sample followed by vapor–liquid equilibration at an elevated temperature, the monomer droplets are completely dissolved in the aqueous phase, and monomer absorption in the polymer particles can be minimized. Thus, VLE is established in the diluted latex, and a linear relationship between the monomer concentration in the vapor and aqueous phases can be obtained. This technique eliminates sample pretreatment procedures such as solvent extraction in the conventional GC method, and it avoids the risk of polymer deposition on the GC column caused by a direct injection of a monomer‐containing solvent. It also eliminates the possibility of solvent interference in the conventional GC monomer analysis. This method is simple, accurate, and automated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 392–397, 2006     

Novel methods for the characterization of water-soluble polymers

The liquid chromatography of four water-soluble polymers [pullulan, polyacrylamide, poly(ethylene glycol), and poly(ethylene oxide)] have been investigated and used to categorize separation processes which couple enthalpic and entropic mechanisms. Experiments were carried out with a binary mobile phase which combined a thermodynamically good solvent (water or aqueous 0.02M Na₂SO₄) and nonsolvent (methanol). The polymer solute was injected in a good solvent. By varying the solvent–nonsolvent ratio in the eluent, conditions could be obtained where the free energies of exclusion and solvation were balanced. This has been given the nomenclature “liquid chromatography under limiting conditions of solubility” (LC-LCS) since the polymer elutes just in front of the system peak at the “limit” of its solubility. Conditions can also be identified where exclusion is balanced with adsorption (“liquid chromatography under limiting conditions of adsorption,” or LC-LCA). To our knowledge, these are the first experimental reports of LC-LCS for any polymer and the first LC-LCA observation on water-soluble macromolecules. All measurements were carried out over a poly(hydroxymethylacrylate) sorbent. Cloud point curves were found to generally distinguish the regions where LC-LCA or LC-LCS dominate. The data illustrate the need to consider the polymer when analyzing LC-LCA. Conversely, polymer adsorption may play an important role in LC-LCS. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2549–2557, 1998     

Synthesis and characterization of polybutadiene with monotitanocene/methylaluminoxane catalyst

Butadiene was polymerized using a monotitanocene complex of η⁵‐pentamethylcyclopentadienyltribenzyloxy titanium [Cp*Ti(OBz)₃] in the presence of four types of modified methylaluminoxanes (mMAO), which contained different amounts of residual trimethylaluminum (TMA). The titanium oxidation states in Cp*Ti(OBz)₃/mMAO and Cp*Ti(OBz)₃/mMAO/triisobutylaluminum (TIBA) catalytic systems were determined by redox titration method. The effects of various oxidation states of titanium active species on butadiene polymerization were investigated. It was found that Ti(III) active species is more effective for preparing polybutadiene with high molecular weight. The addition of TIBA to the Cp*Ti(OBz)₃/mMAO system could reduce a greater number of Ti(IV) complexes to Ti(III) species and lead to significant increases of polymerization activity and molecular weight of polymer, whereas the polybutadiene microstructure was only slightly changed. On the basis of microstructure and property characterization by FTIR, ¹³C‐NMR, DSC, and WAXD, all resultant polymers were proved to be amorphous polybutadiene with mixed 1,2; cis‐1,4; and trans‐1,4 structures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2494–2500, 2004     

Sulfonated polybutadiene ionomer‐templated nanocopper composites

New composites based on nanosize particles provide a promising route to the fabrication of novel materials for advanced technology applications in the 21st century. To prepare desired materials, it is important to control the composition and distribution of nanoclusters within the bulk or surface coating of nanostructured materials. To achieve this aim, we developed a novel method of preparing nanocopper–ionomer thermoplastic composite material with sulfonated cis‐1,4‐polybutadiene random ionomer as a matrix and a capping polymer in organic solvent. The effect of sonication on stabilized nanocopper colloid was studied. The self‐assembled composite film was characterized by ultraviolet–visible spectroscopy, transmission electron microscopy, ¹H‐NMR, and thermogravimetric analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3180–3184, 2002     

Thermodynamic modeling of vapor–liquid equilibrium for binary polyethylene glycol/solvent solutions using cubic equations of state: optimization and comparison of CEoS models

The cubic equation of state (CEoS) is a powerful method for calculation of (vapor + liquid) equilibrium in polymer solutions. Using CEoS for both the vapor and liquid phases allows one to calculate the non-ideality of polymer solutions based on a single EoS approach. In this research, vapor–liquid equilibrium calculations of Polyethylene glycol(Polyethylene oxide)/solvent solutions were carried out. In this approach eight models containing PRSV and SRK CEoS separately combined with four mixing rules namely one-parameter van der Waals one-fluid, two-parameter van der Waals one-fluid (vdW2), Wong–Sandler, and Zhong–Masuoka were applied to calculations of bubble point pressure. For the better prediction, the adjustable binary interaction parameters existing in any mixing rule were optimized. The results were very acceptable and satisfactory. The results of absolute average deviations between predicted results and experimental bubble point pressure data were calculated and presented. Although the capability of two cubic equations of state had a good agreement with experimental data and predict the correct type of phase behavior in all cases, the performance of the PRSV+vdW2 was more reliable than the other models.     

Synthesis and kinetic behavior of stereotriblock polybutadiene using dilithium as initiator

Anionic polymerization of butadiene was conducted in cyclohexane using 1,1,4,4‐tetraphenyl‐1,4‐dilithium butane (TPB–DiLi) as initiator and dipiperidinoethane (DPE) as modifier. The polymer design effects of DPE/TPB–DiLi (simplified as DPE/Li) and polymerization temperature on the 1,2 content of polybutadiene (PB) were examined and 1,2‐polybutadiene (1,2‐PB) with a nearly 100% 1,2 content was obtained. 1,2–1,4–1,2‐Stereotriblock polybutadiene (STPB) can be synthesized easily by means of one feed reaction. DSC and DMA analyses showed that STPB with the designed molecular structure (molecular weight, block ratio, and 1,2 content in 1,2 blocks) has two T_g's and two loss moduli and exhibits microphase separation. Studies on reaction kinetics established the polymerization kinetics equation of 1,4‐PB as ?d[M]/dt = 0.356[C]^0.5[M], indicating the first‐order relationship between polymerization rate and monomer concentration. At 50°C, the addition of the strong polar modifier DPE into the system increased the reaction rate. The apparent propagating activating energies before and after DPE addition were also determined in this study. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1049–1054, 2003     

The effect of heating rate on the thermal degradation of polybutadiene

Using derivative thermogravimetric analysis (DTG), polybutadiene is shown to degrade by two distinct weight loss events when heated dynamically. The volatile products of the first stage are almost exclusively depolymerization products (butadiene and vinylcyclohexene). The residue—cyclized and crosslinked polybutadiene—degrades in the second stage. Increasing the heating rate or sample size results in increased depolymerization; and at a 100°C/min heating rate, up to 50% of the initial sample weight is converted to depolymerization products. Differential scanning calorimetry (DSC) indicates that degradation is exothermic in the temperature range of the first weight loss stage. The determined exothermicity (0.95 kJ/g polybutadiene) is independent of heating rate. Infrared observations show cis—trans isomerization in the same temperature range. Kinetic analysis of the DTG data yields an apparent activation energy of 251 kJ/mole for depolymerization, while for the overall reactions is the first stage, DSC data yield 170 kJ/mole. Why the exothermicity of the degradation is independent of the depolymerization/cyclization ratio is not clear.     

Vapor treatment,liquid crystal formation,magnetic orientation,and crystallization (VLMC) to form helical polyisocyanides with oriented crystal-like structure

We describe a four-step process [solvent vapor treatment, liquid crystal formation, magnetic orientation, and crystallization (VLMC)] for producing oriented helical polyisocyanides with crystal-like structure. We synthesized a series of ortho-alkyl groups substituted with poly(phenyl isocyanide), and characterized the polymer structure using polarizing optical microscopy, scanning electron microscopy, and X-ray diffraction. The results demonstrated that the polymer has a crystal-like structure and the sample forms cholesteric liquid crystal phase. Vapor treatment of polymer films under a magnetic field produced an aligned fiber structure at the submicron level and demonstrated magnetic alignment and formation of a solvent vapor-induced polymer crystal. These results demonstrated formation of a polymer with a one-handed helical structure, formation of a liquid crystal and polymer crystal via solvent vapor treatment, and magnetic alignment of a textile-like polymer crystal domain.     

Compatibility studies of polystyrene–polybutadiene blends by thermal analysis

In order to examine the behavior of incompatible blends of polystyrene and polybutadiene, the glass transition temperature, the melting point, and the specific heat increment at the glass transition temperature for atactic polystyrene (a-PS), isotactic polystyrene (i-PS), polybutadiene (PBD), and blends of a-PS/PBD and i-PS/PBD were determined by use of a differential scanning calorimeter. Blends were prepared by solution casting, freeze-drying, and milling. Weight fractions of polystyrene in the blends ranged from 0.95 to 0.05. The glass transition temperature of polystyrene changed with weight fraction in the blends, and with blending preparation methods; the glass transition temperature of polybutadiene remained essentially unchanged. The specific heat increment at the glass transition temperature of PBD decreases linearly with increasing proportions of PS in the PS/PBD blend for the broad and narrow molecular weight distribution polybutadience polymers, whereas the specific heat increment for PS did not decrease with increasing proportions of PBD in the PS/PBD blend. These results suggest that the polybutadiene dissolves more in the polystyrene phase than does the polystyrene in the polybutadiene phase.     

Thermal conductivity of polyethylene/polystyrene blends containing SEBS block copolymer

We measured the thermal conductivity of a polyethylene/polystyrene blend containing SEBS block copolymer, which has two components of polystyrene block and hydrogenated polybutadiene block, and discussed the effect of phase inversion on the thermal conductivity by observing the morphorogy of the blend. Further, we examined the applicability of the thermal conduction model for composites, which was proposed in our previous reports, to this blend system. By plotting the logarithm of the thermal conductivities of the blends vs. the weight content of polyethylene, it was found that the experimental data lie approximately on a straight line with an increase in polyethylene until the range of dual–phase continuity (phase inversion), and then the data move on another straight line beyond the range of dual–phase continuity. Thus, our model to explain the thermal conductivity of the polymer blend was proved. Further, both coefficients A and B in our model took linear relations with the weight content of the block copolymer, and the model was, thus, more strongly confirmed to be applicable to thermal conductivity of polymer blends.     

Ultrasonic investigations of linear and star shaped polybutadiene polymers in solutions of cyclohexane,hexane and ethylbenzene

Ultrasonic attenuation and velocity measurements are reported on solutions of linear and star shaped polybutadiene in cyclohexane, hexane and ethylbenzene. The linear polymers exhibit viscosity and ultrasonic attenuation characterics typical of linear polymers. In contrast, the star-shaped polymers exhibit viscosities which are considerably lower than those for the equivalent linear polymer. The ultrasonic attenuation is larger in the star shaped polymers than in the corresponding linear materials and this additional contribution to the attenuation is ascribed to the effects of relaxation of the chemical crosslink. In contrast, the adiabatic compressibilities of the linear and star shaped polymers are essentially independent of molecular weight and structure of the polymer and only a function of the solvent. Analysis of the data presented leads to the conclusion that in this system the excess attenuation is associated with the relaxation of the crosslinks and that the major contribution to such a relaxation comes from entropic rather than volume or enthalpic processes.     

Thin‐film nanostructure and polymer architecture in semicrystalline syndiotactic poly(p‐methylstyrene)–(cis‐1,4‐polybutadiene) multiblock copolymers

The thin‐film morphology of stereoregular syndiotactic poly(p‐methylstyrene)–(cis‐1,4‐polybutadiene) (sP(pMS–B)) multiblock copolymers has been investigated using tapping mode atomic force microscopy with variation of the polymer composition and monomer block lengths. The morphology of the thin films ranges from isolated circular domains of sP(pMS) embedded into a matrix of polybutadiene (PB) to isolated domains of PB embedded into a matrix of sP(pMS), passing through bicontinuous (jagged) lamellae when the pMS concentration is in the range 20–67 mol%. Multiple folding of the polymer segments, i.e. where reciprocal inclusions of polymer segments to each other phase are able to generate greater domain, has been postulated and validated by considerations on the polymer architecture and the thermal and crystalline behaviour. © 2019 Society of Chemical Industry     

Phase equilibria in SBR/polybutadiene elastomer blends: Application of Flory–Huggins theory

Blends of anionically-polymerized polybutadiene (BR) and styrene–butadiene copolymer (SBR) must be treated as mixtures of terpolymers and tetrapolymers, due to the presence of three different BR isomers: cis-1,4, trans-1,4, and vinyl-1,2. Moreover, in the absence of specific interactions or chemical reactions that strongly influence miscibility, structural characteristics of the component polymers, such as BR isomer content, SBR styrene content, monomer sequence distribution, molecular weight, and molecular weight distribution, are expected to have an increased role in determining the blend miscibility characteristics. Small angle neutron scattering (SANS) studies of SBR/BR blends have resulted in the computation of the monomer–monomer segmental interaction energetics via a Flory–Huggins treatment. This allows quantitative prediction of miscibility behavior as a function of polymer structure. We have used the Flory–Huggins chi parameters, describing the styrene/cis-1,4, styrene/trans-1,4, and cis-1,4/trans-1,4 segmental interactions, to identify certain blend combinations expected to exhibit phase transitions in an experimentally accessible temperature range. The appropriate polymers were synthesized, solution blended, and the blends analyzed via optical microscopy and thermal analysis. Our results show that the blend behavior, observed experimentally, is consistent with the calculated cloud point curves. © 1994 John Wiley & Sons, Inc.     

Characterization of hydroxyl-terminated polybutadiene

¹H and ¹³C NMR spectra were used to study the structure of hydroxyl-terminated polybutadiene (HTPB) obtained by using hydrogen peroxide as initiator and an alcohol as solvent. This alcohol was introduced into the polymer chain, forming a hydroxylated end group. The subject has aroused some argument in the literature and is considered further in our discussion of reaction mechanisms. Received: 29 November 1996/Revised: 4 December 1996/Accepted: 9 December 1996