Principal component analysis of polymer–solvent and filler–solvent interactions by inverse gas chromatography

Polymers (polyethylene, polyurethane), silica and modified silicas (modified with: N-2-aminoethyl-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-merkaptopropyltrimethoxysilane, triethoxyoctylsilane) were examined by inverse gas chromatography at four different temperatures: 363, 383, 393 and 403 K. The modifiers of silica were applied at five different concentrations. Small amounts of the following test solutes were injected to achieve the infinite dilution conditions: pentane, hexane, heptane, octane, nonane, dichloromethane, chloroform, carbon tetrachloride, and 1,2-dichloroethane.

The retention times for these test solutes were determined and Flory–Huggins parameters were calculated. Values of these physico-chemical parameters characterizing the examined materials were arranged in a matrix form: in the rows the supports and modifiers were enumerated at different temperatures whereas the columns contained the test solutes. The input matrix was subject to principal component analysis after standardization. Three principal components explain more than 93% of the total variance in the data. Four test solutes (hexane, heptane, chloroform and carbon tetrachloride) carry very similar information. Therefore, it is justified to eliminate any three of them from the series of test solutes. Modifiers, supports and various temperatures were classified and different groups were observed according to the dominant interactions. Type of modifier, its content, and temperature can change and shift the properties from the dominant clusters to the neighboring clusters. Unambiguous separation was observed in cases of silica modified with 5 and 10 parts of triethoxyoctylsilane at all examined temperatures.     

The use of Flory–Huggins parameters as a measure of interactions in polymer‐filler systems

Any quantitative information on the strength of interactions between inorganic filler and polymer is substantial for the future application of the composite. The magnitude of adhesion of two phases may be deduced from results collected by various experimental techniques. Polyether‐urethane/modified carbonate‐silicate fillers systems containing different amount of filler (5, 10, and 20 wt %) were the materials investigated. We propose to express the magnitude of modified filler/polymer interactions by Flory–Huggins χ parameter. It may be deduced from the results collected by inverse gas chromatographic (IGC) experiment. We have also tried to explain the influence of the solvent on values of the evaluated parameters and to check the usefulness of some of presented methods to minimize Δχ effect. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1853–1862, 2006     

Swelling of poly(N-isopropylacrylamide) gels in water-aprotic solvent mixtures

The swelling volume of poly(N-isopropylacrylamide) (PIPAAm) gel in aprotic solvents (acetonitrile (AcN)-, tetrahydrofuran (THF)-, 1,4-dioxane (DO)- and dimethylsulfoxide (DMSO))-water mixtures was measured at 25°C. The gel swollen in water shrank first and then reswelled with addition of the aprotic solvents. At an intermediate mole fraction (XDMSO) range of DMSO-water mixtures, the gel demonstrated a reentrant swelling phenomenon the hydrated gel shrank first on addition of a small amount of solvent, showed a typical wide reentrant transition, and gradually reswelled in the range near pure solvent. On the other hand, the gels in AcN-, THF-, and DO-water mixtures demonstrated a reentrant-convex swelling phenomenon: the gels reswelled after a reentrant phase transition in low Xorg (XAcN, XTHF and XDO), showed a maximum swelling in the intermediate Xorg region, and shrank again gradually in the high Xorg region. Such a swelling behavior of the gel was interpreted by correlating with solution properties of the aqueous aprotic solvent mixtures.The strength of hydrogen bonding around amide groups of the homopolymer was examined in pure solvents (water, THF, and DMSO) and in all proportion of aqueous THF to observe the relation with swelling behavior of gel by spectrum analysis of the amide I and II bands of Fourier Transform Infrared Spectroscopy (FT-IR). The swelling properties of gels in solvents and the aqueous mixtures were well correlated with the peak shifts of amide groups of the homopolymer.     

Construction of ternary phase diagrams in nonsolvent/solvent/PMMA systems

In this work, the ternary phase diagrams in three nonsolvent/solvent/PMMA systems (n-hexane/n-butyl acetate/PMMA, water/acetone/PMMA, and n-hexane/acetone/PMMA) were constructed by theoretical calculation and experimental measurement. Binodal curves were calculated by using the Flory–Huggins theory for three-component systems and measured by titrating the PMMA solution with nonsolvent until the onset of turbidity. By using concentration-dependent nonsolvent/solvent and solvent/PMMA interaction parameters and constant nonsolvent/PMMA interaction parameters, good agreement has been obtained between the calculation and the measurement. The values of nonsolvent/solvent interaction parameters were taken from the literature sources, and the values of solvent/PMMA and nonsolvent/PMMA interaction parameters were measured by vapor sorption and swelling equilibrium, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 607–615, 1998     

Specific swelling behaviors of alkali‐metal poly(styrene sulfonate) gels in aqueous solvent mixtures

Counterion‐ and solvent‐specific swelling behaviors were investigated for alkali‐metal poly(styrene sulfonate) (PSSM) gels having different degrees of sulfonation in aqueous organic solvent mixtures [water plus methanol, ethanol, 2‐propyl alcohol, t‐butyl alcohol, dimethyl sulfoxide (DMSO), acetone, acetonitrile, tetrahydrofuran, or dioxane]. With an increasing organic solvent concentration, most gel systems, except for DMSO, showed a volume phase transition. The transition abruptly occurred without significant deswelling in the lower solvent concentration region. Such swelling behavior contrasted with that of other common charged gel systems, including alkali‐metal polyacrylate (PAAM) gels, which showed gel collapse after gradual deswelling with an increasing organic solvent concentration. The dielectric constant at the critical transition point (D_cr) for most mixed solvent systems decreased in the order of PSSK ≥ PSSCs ≥ PSSNa > PSSLi; that is, larger counterion systems were favorable for the transition. The counterion specificity also contrasted with our previous results for PAAM gels: PAANa > PAAK > PAALi ～ PAACs. On the other hand, the solvent specificity for the PSSM gels was similar to that for the PAAM gels; the higher the dielectric constant was of the organic solvent, the higher the D_cr value was at which the transition occurred. These specificities were examined on the basis of the solvation properties of the counterions and polymer charged groups and the solvent properties such as the Gutmann–Mayer donor number and acceptor number. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1166–1175, 2007     

Self‐Assembly of Poly(vinylpyridine‐b‐oligo(ethylene glycol) methyl ether methacrylate) Diblock Copolymers

Poly(oligoethylene glycol)‐poly(2‐vinylpyridine) is a model diblock for studying the effect of block‐localized charge on block copolymer self‐assembly because in the absence of charge the polymers are perfectly miscible, and upon protonation of the vinylpyridine block the polymer undergoes an order–disorder transition. Seven model block copolymers with molecular weights of approximately 60 kDa containing poly(2‐vinylpyridine) volume fractions spanning 0.069–0.700 were synthesized using reversible addition fragmentation transfer polymerization and then studied to understand the effect of protonation level, diblock composition, and temperature on the location of the ordering transition and the type of nanostructures formed in a charge asymmetric system. All of the polymers displayed lower critical solution‐type behavior, with the order–disorder transition temperature decreasing with increasing acid content. Polymers with symmetric compositions showed the highest degree of incompatibility for a given degree of protonation, and the observed morphologies for all polymers were consistent with those observed at similar compositions for classical hydrophobic block copolymers. The observed protonation‐induced phase transition can be explained by the shift of the Flory–Huggins parameter due to the alternation of the identity of monomers, consistent with the prediction of Nakamura and Wang's theory. The use of polyvalent ions promotes self‐assembly at lower concentrations, consistent with ionic crosslinking effects between polymer chains that are promoted at high concentration due to exchange entropy in crosslinked polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1181–1190     

Determination of interactions between aryl polyesters and poly(ether imide) via glass transition temperatures of separated phases in immiscible blends

Phase behavior in domains of immiscible blends of poly(pentamethylene terephthalate)/poly(ether imide) (PPT/PEI) and poly(hexamethylene terephthalate)/poly(ether imide) (PHT/PEI) were investigated using differential scanning calorimetry (DSC). The measured glass transition temperature (T _g) reveals that aryl polyesters dissolve more in the PEI-rich phase than the PEI does in the aryl polyester-rich phase, for both PPT/PEI and PHT/PEI systems. Additionally, optical microscopy supports the conclusion that PPT (or PHT) dissolves more in the PEI-rich phase than PEI does in the PPT-rich (or PHT-rich) phase in the aryl polyester/PEI blends. Furthermore, the Flory–Huggins interaction parameters (χ₁₂) for the PPT/PEI and the PHT/PEI blends were calculated to be 0.12 and 0.17, respectively. For the blend systems comprising of PEI and homologous aryl polyesters, the value of χ₁₂ exhibits a trend of variation with respect to structure of aryl polyesters. For the PPT/PEI and PHT/PEI blends, investigated in this study, value of the polymer–polymer interaction parameter (χ₁₂) between the aryl polyester and the PEI was found to be positive, which increases with the number of methylene moieties in the repeating unit of the aryl polyester, ultimately resulting in phase separation observed.     

Preparation of poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) core–shell nanoparticles

Poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) (PMMA–NBR) core–shell structured nanoparticles were prepared using a two‐stage semibatch microemulsion polymerization system with PMMA and NBR as the core and shell, respectively. The Gemini surfactant 12‐3‐12 was used as the emulsifier and found to impose a pronounced influence on the formation of core–shell nanoparticles. The spherical morphology of core–shell nanoparticles was observed. It was found that there exists an optimal MMA addition amount, which can result in the minimized size of PMMA–NBR core–shell nanoparticles. The formation mechanism of the core–shell structure and the interaction between the core and shell domains was illustrated. The PMMA–NBR nanosize latex can be used as the substrate for the following direct latex hydrogenation catalyzed by Wilkinson's catalyst to prepare the PMMA–HNBR (hydrogenated NBR) core–shell nanoparticles. The hydrogenation rate is rapid. In the absence of any organic solvent, the PMMA–HNBR nanoparticles with a size of 30.6 nm were obtained within 3 h using 0.9 wt % Wilkinson's catalyst at 130 °C under 1000 psi of H₂. This study provides a new perspective in the chemical modification of NBR and shows promise in the realization of a “green” process for the commercial hydrogenation of unsaturated elastomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Statistical thermodynamics evaluation of polymer–polymer miscibility

The Simha and Somcynsky (S–S) statistical thermodynamics theory was used to compute the solubility parameters as a function of temperature and pressure [δ = δ(T, P)], for a series of polymer melts. The characteristic scaling parameters required for this task, P*, T*, and V*, were extracted from the pressure–temperature–volume (PVT) data. To determine the potential polymer–polymer miscibility, the dependence of δ versus T (at ambient pressure) was computed for 17 polymers. Close proximity of the δ versus T curves for four miscible polymer pairs: PPE/PS, PS/PVME, and PC/PMMA signaled the usefulness of this approach. It is noteworthy, that the tabulated solubility parameters (derived from the solution data under ambient conditions) propounded the immiscibility of the PVC/PVAc pair. The computed values of δ also suggested miscibility for polymer pairs of unknown miscibility, namely PPE/PVC, PPE/PVAc, and PET/PSF. In recognizing the limitations of the solubility parameter approach (the omission of several thermodynamic contributions), these preliminary results are auspicious because they indicate a new route for estimating the miscibility of any polymeric material at a given temperature and pressure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2909–2915, 2004     

Temperature and crosslinking effects on the swelling of poly(isoprene) in isopiestic conditions

Isopiestic measurements of solvent uptake have been made in the synthetic isoprene/benzene system for both crosslinked and uncrosslinked polymers in order to revisit the question of the swelling activity parameter S. Both the nonzero value of S at zero swelling and the appearance of a peak in S vs. degree of swelling have been observed in some solvent/rubber pairs and we here investigate both the crosslink and temperature dependencies of these phenomena. The data analysis is an extension of prior work from this laboratory using continuum thermodynamics concepts and avoiding molecular models in an attempt to establish the fundamental phenomenology of the process and the validity or lack of validity of the hypothesis that the mixing and elastic contributions to the free energy of networks are separable. We present results from measurements in benzene vapors at temperatures between 10 and 55°C for an uncrosslinked rubber and rubbers crosslinked with 1, 5, 10, and 15 parts per hundred dicumyl peroxide. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 817–826, 1997     

Phase diagrams of poly(dimethylsiloxane) and 5CB blends

The phase diagrams of poly(dimethylsiloxane) (PDMS) and 4‐cyano‐4′‐n‐pentyl‐biphenyl (5CB) mixtures are studied for two systems of different molecular weights of the polymer. The experimental diagrams are established by polarized optical microscopy (POM), and analyzed using a combination of the Flory–Huggins theory of isotropic mixing and the Maier–Saupe theory of nematic order. The results are compared with those of polystyrene (PS) and 4‐cyano‐4′‐n‐octyl‐biphenyl (8CB) with analogous molecular weight of the polymer. This investigation could be useful for the choice of systems in electro‐optical devices. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 581–588, 2001     

Poly(ethylene glycol)–poly(L‐lactide) star block copolymer hydrogels crosslinked by metal–ligand coordination

The aqueous solution behavior and thermoreversible gelation properties of pyridine‐end‐functionalized poly(ethylene glycol)–poly(L ‐lactide) (PEG–(PLLA)₈–py) star block copolymers in the presence of coordinating transition metal ions were studied. In aqueous solutions, the macromonomers self‐assembled into micelles and micellar aggregates at low concentrations and formed physically crosslinked, thermoreversible hydrogels above a critical gel concentration (CGC) of 8% w/v. In the presence of transition metal ions like Cu(II), Co(II), or Mn(II), the aggregate dimensions increased. Above the CGC, the gel–sol transition shifted to higher temperatures due to the formation of additional crosslinks from intermolecular coordination complexes between metal ions and pyridine ligands. Furthermore, as an example, PEG–(PLLA)₈–py hydrogels stabilized by Mn(II)–pyridine coordination complexes were more resistant against degradation/dissolution when placed in phosphate buffered saline at 37 °C when compared with hydrogels prepared in water. Importantly, the stabilizing effect of metal–ligand coordination was noticeable at very low Cu(II) concentrations, which have been reported to be noncytotoxic for fibroblasts in vitro. These novel PEG–(PLLA)₈–py metallo‐hydrogels, which are the first systems to combine metal–ligand coordination with the advantageous properties of PEG–PLLA copolymer hydrogels, are appealing materials that may find use in biomedical as well as environmental applications like the removal of heavy metal ions from waste streams. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Composite thin films of poly(phenylene oxide)/poly(styrene) and PPO/silver via vapor phase deposition

We report fabrication of thin (100～300 nm) poly(phenylene oxide) (PPO) films and their composites with poly (styrene) (PS) and silver (Ag) nanoparticles using a one‐step electron beam‐assisted vapor phase co‐deposition technique. Surface morphology and the structure of the deposited polymer thin film composites were characterized by FTIR, Raman, X‐ray spectroscopy, and contact angle measurements. As‐deposited PPO films and PPO/Ag composites were of porous nature and contrary to solvent casting techniques were free from nodular growth. In the case of PPO/PS thin film polymer composites, however, film morphology displayed nodular growth of PPO with nodule diameters of about ～200 nm and height of approximately 50 nm. Unique morphological changes on the porous PPO thin film surface were noticed at different Ag filling ratios. Further, the capacitance of PPO/Ag composites (<16 wt%) were measured under radio‐frequency conditions and they were functional up to 100 MHz with an average capacitance density of about 2 nF/cm². The fabricated PPO‐based composite systems are discussed for their potential applications including embedded capacitor technology. Copyright © 2008 John Wiley & Sons, Ltd.     

Molecular weight dependent structure and charge transport in MAPLE‐deposited poly(3‐hexylthiophene) thin films

In this work, poly(3‐hexylthiophene) (P3HT) films prepared using the matrix‐assisted pulsed laser evaporation (MAPLE) technique are shown to possess morphological structures that are dependent on molecular weight (MW). Specifically, the structures of low MW samples of MAPLE‐deposited film are composed of crystallites/aggregates embedded within highly disordered environments, whereas those of high MW samples are composed of aggregated domains connected by long polymer chains. Additionally, the crystallite size along the side‐chain (100) direction decreases, whereas the conjugation length increases with increasing molecular weight. This is qualitatively similar to the structure of spin‐cast films, though the MAPLE‐deposited films are more disordered. In‐plane carrier mobilities in the MAPLE‐deposited samples increase with MW, consistent with the notion that longer chains bridge adjacent aggregated domains thereby facilitating more effective charge transport. The carrier mobilities in the MAPLE‐deposited simples are consistently lower than those in the solvent‐cast samples for all molecular weights, consistent with the shorter conjugation length in samples prepared by this deposition technique. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 652–662     

A continuous polydisperse thermodynamic algorithm for a modified flory–Huggins model: The (polystyrene + nitroethane) example

A modified Flory–Huggins model is presented, considering a concentration‐ and temperature‐dependent interaction parameter, and using the methodology of Continuous Thermodynamics to take into account both polydispersity and its effect on phase equilibrium of polymeric systems. This model describes all commonly found, as well as other unusual polymer + solvent and polymer + polymer, liquid–liquid phase diagrams and is easily extended to take all possible pressure effects into consideration. Modeling and least‐squares fit of polystyrene + nitroethane liquid–liquid cloud‐point data have produced results in good accord with the experimental ones by using meaningfully physical parameters. These results have been used to discuss polystyrene molecular weight, pressure, and isotopic substitution effects on polystyrene + nitroethane systems. A first‐order interpretation of phase equilibrium isotopic substitution effect has also been applied. It combines the simplest form of the Flory–Huggins model with the statistical theory of condensed phase isotope effects. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 632–651, 2000     

Intrinsic viscosities of sodium carboxymethylcellose in acetonitrile–water mixed solvent media using isoionic dilution method

Precise measurements on the viscosities of the solutions of sodium carboxymethylcellulose in water and in two acetonitrile–water mixtures containing 10 and 20 vol % of acetonitrile have been reported at 35, 40 and 50 °C. Isoionic dilutions were performed with the total ionic strengths of the solutions maintained with sodium chloride at ～4.20 × 10^?4 and 1.45 × 10^?3 mol dm^?3 of NaCl to obtain the intrinsic viscosities. The Huggins constants were also obtained from the experimental results. The influences of the medium, the temperature, and the total ionic strength on the intrinsic viscosities as well as on the Huggins constants have been interpreted from the points of view of the solvodynamic and thermodynamic interactions prevailing in the polyelectrolyte solution under investigation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1765–1770, 2007     

Morphology control of poly(3‐hexylthiophene)‐b‐poly(ethylene oxide) block copolymer by solvent blending

The use of mixed solvents provided an effective way to control the self‐assembly behavior and photophysical properties of a conjugated rod–coil block copolymer, poly(3‐hexylthiophene)‐b‐poly(ethylene oxide) (P3HT‐b‐PEO). It was shown that the balance between the π–π stacking of the P3HT and microphase separation of the copolymer could be dynamically controlled and shifted by solvent blending. Depending on the mixed solvent ratio (i.e., chloroform/methanol, anisole/chloroform, or anisole/methanol), the copolymer chains experienced different kinetic pathways, yielding a series of nanostructures such as disordered wormlike pattern, densely packed nanofibrils, and isolated nanofibrils. With the varying solvent selectivity, the P3HT‐b‐PEO chains displayed a hybrid photophysical property depending on the competition between intrachain and interchain excitonic coupling, resulting in the transformation between J‐ and H‐aggregation. Overall, this work offered an effective way to demonstrate the correlation and transformation between π–π stacking of P3HT and microphase separation, and how the conformation of P3HT chains influenced the photophysical properties of the copolymer during solvent blending. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 544–551     

Conductivity of Poly(pyrrole)‐Poly(styrene sulfonate) Core–Shell Nanoparticles

The dielectric properties of poly(styrene) nanoparticles decorated at their surfaces with poly(styrene sulfonate) [PSS] brushes and subsequently loaded with polypyrrole (PPy) were studied. These film‐forming materials which may serve as hole‐injection layers in organic light‐emitting diodes, exhibit a core–shell‐type morphology with a core of electrically insulating poly(styrene) and a shell consisting of a corona of PSS chains which form the matrix in which the electrically conducting complex of PPy and PSS is embedded. This conducting complex exists in form of domains of nanoscale dimensions. Thin compressed pellets of these nanoparticles were studied using mainly impedance spectroscopy. Measurements were carried out in the temperature range between 123 and 453 K and frequency range from 10^?1 to 10⁶ Hz. While earlier studies were centered around the effect of polypyrrole volume fraction on the conductivity films and pellets composed of these nanoparticles, the present study reveals in which way the conductivity can be modified by exchange of the mobile inorganic counter ions of PSS. Besides the free‐acid form (H⁺), the Li⁺‐, Na⁺‐ and Cs⁺‐salts of PSS were investigated. The PPy volume fraction was the same for all PPy/PSS core–shell nanoparticles. The distance for phonon‐assisted hopping between next‐neighbor polypyrrolium chains is influenced by the presence of these inorganic cations. For all samples containing PPy, a transition from insulating to conducting behavior in the range of 300‐350 K was found. Using the fluctuation‐induced tunneling model, the average tunneling distance, as well as the potential energy barrier separating neighboring conducting grains was estimated. Finally, a detailed analysis of the dielectric spectra suggests the localization length of the charge carriers to be about 0.33 nm.