Binary Polymer Systems Research Articles

Miscibility between PS and PSAN affected by solvent and temperature of the system

The influence of solvent on the miscibility of polystyrene (PS) and poly (styrene-co-acrylonitrile) (PSAN) blends has been investigated viscometrically. The miscibility of different PS/PSAN blend (30/70, 50/50 and 70/30) compositions in acetone and benzene at 20, 30, and 40 °C was investigated on the basis of the sign of Chee (ΔB and µ), and Sun’s (α) criteria. The values of these parameters were evaluated from the analyses of reduced viscosity data of binary (solvent/polymer) and ternary (solvent/polymer1/polymer2) polymer systems. These investigations indicated partial miscibility for both the blend systems. However, PS/PSAN/acetone blend system showed somewhat higher partial miscibility than the PS/PSAN/Benzene blend system highlighting the impact of solvent over the polymer-polymer interactions and hence their miscibility. The results obtained through viscometry were also corroborated by the refractive index and density results for the blends under study. The effect of temperature on miscibility in both the cases was almost negligible.

Structure and selection in an autocatalytic binary polymer model

An autocatalytic binary polymer system is studied as an abstract model for a chemical reaction network capable to evolve. Due to autocatalysis, long polymers appear spontaneously and their concentration is shown to be maintained at the same level as that of monomers. When the reaction starts from a pool of monomers, highly ordered populations with particular sequence patterns are dynamically selected out of a vast number of possible states. The interplay between the selected microscopic sequence patterns and the macroscopic cooperative structures is examined both analytically and in simulation. Stability, fluctuations, and dynamic selection mechanisms are investigated for the involved self-organizing processes.

Study on the Properties of Blends between Acrylonitrile-Butadiene Rubber and Acrylonitrile-Butadiene-Styrene or Poly(Styrene-co-Acrylonitrile)

Acrylonitrile-butadiene rubber (NBR) or nitrile rubber is an unsaturated copolymer of butadiene and acrylonitrile. NBR has been widely used for fuel hoses, seals and gaskets due to its excellent oil and fuel resistance. Aiming to develop NBR which has resistance to oxygenated solvent, NBR with acrylonitrile content of 34 wt%, was blended with Acrylonitrile-butadiene-styrene (ABS) and Poly (Styrene-co-Acrylonitrile) (SAN) as binary polymer systems. The NBR/ABS and SAN blends were prepared by mechanical blending in the composition of 80/20, 70/30 and 60/40 w/w. The effects of ABS or SAN content on mechanical, morphological and thermal properties were investigated and compared with commercials NBR. Mechanical properties were determined using the tensile testing machine. The morphologies of polymer blends were investigated using scanning electron microscope (SEM). The thermal properties were examined using differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). It has been found that percent compatibility of ABS and SAN into NBR rich phase are 2.69 and 1.53 wt% respectively.

Phase field study on the effect of shear flow on polymer phase separation

Shear flow is the main external condition during the preparation of polymer materials. In this paper, microstructural evolution and the size of equilibrium phase during different shear flow in binary polymer systems were investigated via phase field simulation, using Flory-Huggins model and Cahn-Hilliard method. It is found that shear flow greatly affected the microstructure of polymer materials, and anisotropy materials can be prepared by controlling the shear flow.

Bulk heterojunction polymer solar cells based on binary and ternary blend systems

Polymer solar cells (PSCs) were fabricated using a ternary blend film consisting two conjugated polymers and a soluble fullerene derivative as the donor and acceptor materials, respectively. And, to compare ternary blend system, the single-component copolymers consisting of the repeating units of each of the copolymers, used in ternary blend solar cells, were designed and synthesized for use as the electron donor materials in binary blend solar cells. We systematically investigated the field-effect carrier mobilities and the optical, electrochemical, and photovoltaic properties of the copolymers. Under optimized conditions, the binary blend polymer systems showed power conversion efficiencies (PCEs) for the PSCs in the range 3.87–4.16% under AM 1.5 illumination (100 mW cm−2). All polymers exhibited similar PCEs that did not depend on the ratio of repeating units. The binary blend solar cell containing a single-component copolymer as the electron donor material performed better than the ternary blend solar cell in this work. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Preparation and characterization of bioadhesive systems containing propolis or sildenafil for dental pulp protection

Purpose: Binary polymeric systems containing poloxamer 407 (P407) and Carbopol 934P (C934P) were designed to deliver propolis extract (PE) or sildenafil citrate for the endodontic treatment (pulp protection).Methods: Gelation temperature, rheology (flow), bioadhesion, and in vitro drug release of formulations were determined.Results: Formulations showed thermoresponsive behavior, existing as a liquid at room temperature and gel at 34–37°C. In addition, they exhibited pseudoplastic flow and low degrees of thixotropy or rheopexy. The greatest bioadhesion was noted in the formulation containing 20% P407 (w/w) and 0.10% C934P (w/w). PE release from formulation containing 15% P407 (w/w) and 0.25% C934P (w/w) was controlled by the phenomenon of relaxation of polymer chains. Moreover, sildenafil release from formulation containing 20% P407 (w/w) and 0.10% C934P (w/w) was controlled by Fickian diffusion.Conclusion: The data obtained on these formulations indicate a potentially useful role in the endodontic treatment (pulp protection) and suggest they are worthy of clinical evaluation.

Stimuli‐Responsive Polymers in Solution Investigated by NMR and Infrared Spectroscopy

AbstractSummary: Temperature‐induced and solvent composition‐induced phase separation in solutions of poly(N‐isopropylmethacrylamide) (PIPMAm) and other thermoresponsive polymers as studied by NMR and infrared (IR) spectroscopy is discussed. The fraction p of phase‐separated units (units with significantly reduced mobility) and subsequently, e.g., thermodynamic parameters characterizing the coil‐globule phase transition induced by temperature, were determined from reduced integrated intensities in high‐resolution 1H NMR spectra. This approach can be especially useful in investigations of phase separation in solutions of binary polymer systems. Information on behaviour of water during temperature‐induced phase transition was obtained from measurements of 1H NMR relaxation times of HDO molecules. NMR and IR spectroscopy were used to investigate PIPMAm solutions in water/ethanol (D2O/EtOH) mixtures where the phase separation can be induced by solvent composition (cononsolvency). Some differences in globular‐like structures induced by temperature and solvent composition were revealed by these methods.

Predicting microstructures in polymer blends under two-step quench in two-dimensional space

The formation of nanostructures during two-step quench in binary polymer systems having various types of liquid miscibility gaps are investigated systematically via computer simulations using the phase field method. Coupled liquid spinodal decomposition and fluid flow processes are considered by solving simultaneously the Cahn-Hilliard and Navier-Stokes equations. Various interesting phenomena and morphological patterns are predicted. It is found that the primary microstructures developed at the first quench and isothermal holding temperature greatly affect the secondary microstructures developed during the second quench and isothermal holding. Depending on the morphology and scale of the primary microstructure, either multicore and multishell or unicore and unishell structures are predicted. The breakup of annuluses in a core-shell structure in two dimensions is analyzed. The effects of viscosity on the formation of core-shell structure and on the growth and coarsening behaviors of bimodal droplets produced by the two-step quench in systems are also investigated.

Flow behavior in a corotating twin‐screw extruder of pure polymers and blends: Characterization by fluorescence monitoring technique

AbstractThe objective of this work was to investigate the flow behavior of pure polymers and blends, especially miscible polymer/polymer systems, in a corotating twin‐screw extruder (TSE) using an online fluorescence monitoring device. An immiscible blend was also studied for the sake of comparison. The fluorescence signal was obtained by using synthesized fluorescence tracers added to the melt at very low concentrations. These tracers consisted of two styrene‐maleic anhydride copolymers (SMA) labeled with anthracene. The investigated blends were SMA8 (8 wt % of MA in SMA)/polystyrene (PS), SMA14 (14 wt % of MA in SMA)/styrene acrylonitrile copolymer (SAN), and poly(methyl methacrylate) (PMMA)/ethyl acrylate‐methyl methacrylate copolymer (PMMAEA). The residence time distribution (RTD), the mean residence time (t), the dimensionless variance (σθ2), the Peclet number (Pe) and the fluorescence peak intensity distribution of pure polymers and binary polymer systems were investigated and interpreted in terms of polymers rheological properties. It was observed that polymers presenting higher viscosity or higher pressure showed longer residence time. A difference in behavior was also observed for the RTD of miscible and immiscible blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Rheological, mechanical and mucoadhesive properties of thermoresponsive, bioadhesive binary mixtures composed of poloxamer 407 and carbopol 974P designed as platforms for implantable drug delivery systems for use in the oral cavity

This study described the formulation and characterisation of the viscoelastic, mechanical and mucoadhesive properties of thermoresponsive, binary polymeric systems composed of poloxamer (P407) and poly(acrylic acid, C974P) that were designed for use as a drug delivery platform within the oral cavity. Monopolymeric and binary polymeric formulations were prepared containing 10, 15 and 20% (w/w) poloxamer (407) and 0.10–0.25% (w/w) poly(acrylic acid, 934P). The flow rheological and viscoelastic properties of the formulations were determined using controlled stress and oscillatory rheometry, respectively, the latter as a function of temperature. The mechanical and mucoadhesive properties (namely the force required to break the bond between the formulation and a pre-hydrated mucin disc) were determined using compression and tensile analysis, respectively. Binary systems composed of 10% (w/w) P407 and C934P were elastoviscous, were easily deformed under stress and did not exhibit mucoadhesion. Formulations containing 15 or 20% (w/w) Pluronic P407 and C934P exhibited a sol–gel temperature T sol/gel, were viscoelastic and offered high elasticity and resistance to deformation at 37 °C. Conversely these formulations were elastoviscous and easily deformed at temperatures below the sol–gel transition temperature. The sol–gel transition temperatures of systems containing 15% (w/w) P407 were unaffected by the presence of C934P; however, increasing the concentration of C934P decreased the T sol/gel in formulations containing 20% (w/w) P407. Rheological synergy between P407 and C934P at 37 °C was observed and was accredited to secondary interactions between these polymers, in addition to hydrophobic interactions between P407 micelles. Importantly, formulations composed of 20% (w/w) P407 and C934P exhibited pronounced mucoadhesive properties. The ease of administration (below the T sol/gel) in conjunction with the viscoelastic (notably high elasticity) and mucoadhesive properties (at body temperature) render the formulations composed of 20% (w/w) P407 and C934P as potentially useful platforms for mucoadhesive, controlled topical drug delivery within the oral cavity.

Glass transition temperatures in binary polymer blends

AbstractKnowledge of the glass transition temperatures (Tgs) as function of composition reflects miscibility (or lack of it) and is decisive for virtually all properties of polymer‐based materials. In this article, we analyze single blend‐average and effective Tgs of miscible polymer blends in full concentration ranges. Shortcomings of the extant equations are discussed to support the need for an alternative. Focusing on the deviation from a linear relationship, defined as ΔTg = Tg − φ1Tg,1 − φ2Tg,2 (where φi and Tg,i are, respectively, the weight fraction and the Tg of the i‐th component), a recently proposed equation for the blend Tg as a function of composition is tested extensively. This equation is simple; a quadratic polynomial centered around 2φ1 − 1 = 0 is defined to represent deviations from linearity, and up to three parameters are used. The number of parameters needed to describe the experimental data, along with their magnitude and sign, provide a measure of the system complexity. For most binary polymer systems tested, the results obtained with the new equation are better than those attained from existing Tg equations. The key parameter of the equation a0 is related to parameters commonly used to represent intersegmental interactions and miscibility in binary polymer blends. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 80–95, 2008

Assessment of thermodynamic properties in pure polymers

The thermodynamic properties including enthalpy, entropy and Gibbs free energy of 15 types of pure polymers were derived from experimental data of heat capacity, as a function of temperature. The calculated results are presented in both polynomial expressions and graphs. This database of pure polymers will provide basic parameters in assessments of phase diagrams in binary, ternary and higher-order polymer systems.

Interaction Between P(VC-VA) and SAN Copolymer Blends Investigated by Thermal Analysis

Miscibility and activation energy of the binary polymer system consisting of Poly (vinyl chloride-vinyl acetate)/Poly (styrene-acrylonitrile) of various compositions (100/0, 85/15, 75/25, 50/50, 25/75, 15/85, 0/100) has been investigated by Differential Scanning Calorimeter (DSC). The interaction parameters were calculated from the measurements based on glass transition temperature of the blends. The thermal stability and activation energy of the blends was calculated using Doyle's method. The results suggest that the extent of partial miscibility of the two components is very limited.

Estimation of Miscibility and Interaction for Cellulose Acetate and Butyrate Blends with N‐Vinylpyrrolidone Copolymers

AbstractThe miscibility of CA/P(VP‐co‐MMA) blends was examined as a function of DS of CA and the VP fraction in the copolymer composition, in an extension of the previous studies on cellulose ester blends using P(VP‐co‐VAc) as a counter component. It was observed by DSC thermal analysis that when CA of DS ≤ 2.5 and P(VP‐co‐MMA) of VP > 30 mol‐% were two blending components, most of the binary polymer systems were miscible, whereas the other combinations of DS and VP values led to an immiscible series of blends, a possible exception being the miscible pair of DS = 2.70 and VP = 100 mol‐%. Results of FT‐IR and solid‐state 13C CP/MAS NMR spectra measurements suggested the miscibility to be driven by the hydrogen‐bonding interaction between the residual hydroxyls of CA and the carbonyls of VP units in P(VP‐co‐MMA), as in the case of CA/P(VP‐co‐VAc) blends where the range of miscible pairing of acetyl DS and VP fraction was rather wide. From evaluations of proton spin‐lattice relaxation times in the NMR study, it was confirmed that the homogeneity of the miscible blends of CA/P(VP‐co‐MMA) was substantially on a scale within a few nanometers. To interpret the difference in the DS‐ and copolymer composition‐dependence of the miscibility behavior between three blend systems, CA/P(VP‐co‐MMA), CA/P(VP‐co‐VAc), and CB/P(VP‐co‐VAc), Krigbaum‐Wall intermolecular interaction parameters were estimated by solution viscometry for different polymer pairs pertinent to those blends. In particular, discussion took into consideration the effectiveness of an intramolecular repulsive action between the two units (VP and VAc, or VP and MMA) constituting the vinyl copolymers.magnified image

Rheological Characterization of Bioadhesive Binary Polymeric Systems Designed as Platforms for Drug Delivery Implants

This study describes the formulation and characterization of binary interactive polymeric systems, designed as platforms for improved drug delivery to mucosal sites. Binary interactive systems were manufactured containing hydroxyethylcellulose (HEC; 1-5% w/w) and polycarbophil (PC; 1-5% w/w) at pH 7, and their rheological (flow and dynamic), mechanical, and mucoadhesive properties were characterized, both before and after dilution with phosphate buffered saline (designed to mimic dilution by biological fluids). Physical interactions between HEC and PC were confirmed by the observed rheological synergy. Within the binary interactive systems increasing polymer concentration increased the storage modulus (G'), loss modulus (G' '), dynamic viscosity (eta'), hardness, compressibility, consistency, and mucoadhesion yet decreased the loss tangent. This was attributed to enhanced entanglements and interactions between adjacent polymer chains. Dilution with PBS altered the above properties; however, the binary interactive systems, particularly those containing higher concentrations of HEC, still exhibited predominantly elastic properties (high G', low tan delta). In light of this, it is suggested that the rheological and mucoadhesive properties of binary interactive systems composed of HEC (5% w/w) and PC (1-3% w/w) offered particular promise as platforms for topical mucosal drug delivery systems.

Intimate blending of binary polymer systems from their common cyclodextrin inclusion compounds

AbstractA procedure for the formation of intimate blends of three binary polymer systems polycarbonate (PC)/poly(methyl methacrylate) (PMMA), PC/poly(vinyl acetate) (PVAc) and PMMA/PVAc is described. PC/PMMA, PC/PVAc, and PMMA/PVAc pairs were included in γ‐cyclodextrin (γ‐CD) channels and were then simultaneously coalesced from their common γ‐CD inclusion compounds (ICs) to obtain intimately mixed blends. The formation of ICs between polymer pairs and γ‐CD were confirmed by wide‐angle X‐ray diffraction (WAXD), fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). It was observed [solution 1H nuclear magnetic resonance (NMR)] that the ratios of polymers in coalesced PC/PMMA and PC/PVAc binary blends are significantly different than the starting ratios, and PC was found to be preferentially included in γ‐CD channels when compared with PMMA or PVAc. Physical mixtures of polymer pairs were also prepared by coprecipitation and solution casting methods for comparison. DSC, solid‐state 1H NMR, thermogravimetric analysis (TGA), and direct insertion probe pyrolysis mass spectrometry (DIP‐MS) data indicated that the PC/PMMA, PC/PVAc, and PMMA/PVAc binary polymer blends were homogeneously mixed when they were coalesced from their ICs. A single, common glass transition temperature (Tg) recorded by DSC heating scans strongly suggested the presence of a homogeneous amorphous phase in the coalesced binary polymer blends, which is retained after thermal cycling to 270 °C. The physical mixture samples showed two distinct Tgs and 1H T1ρ values for the polymer components, which indicated phase‐separated blends with domain sizes above 5 nm, while the coalesced blends exhibited uniform 1H spin‐lattice relaxation values, indicating intimate blending in the coalesced samples. The TGA results of coalesced and physical binary blends of PC/PMMA and PC/PVAc reveal that in the presence of PC, the thermal stability of both PMMA and PVAc increases. Yet, the presence of PMMA and PVAc decreases the thermal stability of PC itself. DIP‐MS observations suggested that the degradation mechanisms of the polymers changed in the coalesced blends, which was attributed to the presence of molecular interactions between the well‐mixed polymer components in the coalesced samples. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2578–2593, 2005

Characterizations of Multiphase Biogenic Polymer Blends from Poly(L-lactide) and Poly(methyl methacrylate)

AbstractMelt processing of binary immiscible polymer systems has been a focus of our group as an economical and scalable route to achieve synergistic or superior mechanical properties at and around the co-continuous region without the need of compatibilization. System of poly(L-lactide) (PLLA) and poly(methyl methacrylate) (PMMA) was selected to target bio-related applications, including bone fillers and scaffolds, where the biodegradability of PLLA will enable the integration of native tissue into the material over time. Tunable properties such as morphology, interconnectivity, resorbability and interfacial bonding control the long-term integrity of the new material and influence the interaction and integration of new tissue. Binary blends of PLLA and PMMA has been prepared and characterized over a large range of compositions in which regions of co-continuity are of special interest. Such regions exhibit a well interconnected structure that ensures controlled release of resorbable PLLA. Modulated differential scanning calorimetry (MDSC) detected a broad and unexpected transition between 70 °C and 100 °C. The magnitude of this transition is greatest within co-continuous regions, suggesting the presence of a complex or other derivative of the two primary phases. This complex appears to provide a degree of compatibilization between the phases, thus inducing mechanical property synergism which has been confirmed by flexural and nano-indentation analyses.

Miscibility and Phase Behavior in Melt Blends of Thermoplastic Polyurethane and Styrene Acrylonitrile Copolymers

Phase behavior of the binary polymer system consisting of thermoplastic polyurethane (TPU) and styrene acrylonitrile (SAN) copolymers of various compositions (100/0, 90/10, 70/30, 50/50, 30/70, 0/100) has been investigated by differential scanning calorimeter (DSC). The phase separation on heating, i.e., lower critical solution temperature (LCST) behavior, was found to occur when these blends were heated to elevated temperatures. The cloud‐point temperature or phase separation was found to vary with TPU/SAN blend compositions. The interaction parameters were calculated from the measurements based on glass transition temperature of the blends. The results suggest that the extent of partial miscibility of the two components is very limited.

The Effect of Transreactions on the Structure and Dynamic Mechanical Properties of 1:1 Poly(ethylene terephthalate)/Poly(ethylene 2,6‐naphthalate) Blends Produced by Cryogenic Mechanical Alloying

AbstractCryogenically alloyed poly(ethylene terephthalate) (PET)/poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) blends (1:1 w/w) were subjected to melt pressing at 300 °C for various times. The binary polymer systems so obtained were studied by means of atomic force microscopy (AFM), dynamic mechanical analysis (DMA) and proton NMR. A high level of homogenization at the nanometer scale was achieved. By changing the time of melt pressing in the range of 1–35 min, PET‐PEN block copolymers with average block lengths decreasing between 10 and 2 repeat units were produced. This copolymer formation was accompanied by significant changes in the dynamic mechanical properties as revealed by the variations in the temperature dependence of the loss factor, tan δ, in the region of the glass transition. Particularly, with the increase of annealing time a transition from double to single alpha‐relaxation was observed. The traditional two‐phase Takayanagi model applied to these alpha‐relaxation data did not provide an adequate description of the viscoelastic behavior as a function of annealing time. The results were discussed in terms of the Adam‐Gibbs theory of the cooperatively rearranging regions. magnified image

Alumina‐based water‐dispersible conducting nanocomposites of polypyrrole and polypyrrole with poly(N‐vinylcarbazole)

AbstractWater‐dispersible nanocomposites of polypyrrole with Al2O3 (PPYAl2O3) and of poly(N‐vinylcarbazole) with Al2O3 (PNVCAl2O3) were prepared in an aqueous medium. Nanocomposites involving binary polymer systemsPNVC(PPYAl2O3) and PPY(PNVCAl2O3)were prepared by precipitating PNVC or PPY onto a suspension of PPYAl2O3 or PNVCAl2O3, respectively. The incorporation of the polymers in the composites was confirmed by Fourier transform infrared analyses. Scanning electron microscopy analyses revealed distinct morphological features of the composites. Transmission electron microscopy analyses of the PPYAl2O3, PNVCAl2O3, and PPY(PNVC Al2O3) composites confirmed the formation of spherical particles in the nanometer range. Thermogravimetric and differential thermal analyses revealed the stability order as: PNVCAl2O3 > PNVC(PPYAl2O3) > PPY(PNVCAl2O3) > PPYAl2O3. Direct current conductivity values of the PPYAl2O3, PNVC(PPYAl2O3), and PPY(PNVCAl2O3) composites were on the order of 2.8 × 10−4, 1.7 × 10−5, and 4.5 × 10−6 (S/cm), respectively. These nanocomposites dispersed in water, with stability decreasing in the order: PPYAl2O3 (∼40 h) > PNVC(PPYAl2O3) (30 h) > PPY(PNVCAl2O3) (20 h), and in the presence of polyvinylpyrrolidone a permanently stable suspension was obtained in all cases. The dispersibility appeared to be higher when the polymerization was conducted in a suspension containing a higher amount of Al2O3. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1058–1065, 2003