Unified analysis of thermodynamic and rheological properties of high polymer solutions. II. Ternary systems

We extend to ternary solutions our previous study of conformational, thermodynamic, and rheological properties of semidilute polymer solutions in good solvent. Osmotic pressure and viscosity measurements were performed in several mixtures of two compatible polymers in a common solvent. Renormalization group results were used to analyze the data, using de Gennes's blobs model to connect dynamic and conformational properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1071–1079, 2002     

Effect of operation parameters on temperature rising elution fractionation and crystallization analysis fractionation

Crystallization analysis fractionation and temperature rising elution fractionation are two techniques used to estimate the chemical composition distributions of semicrystalline copolymers. This study investigates the cooling rate and cocrystallization effects for both techniques with a series of ethylene/1‐olefin copolymers and their blends. Ideally, both techniques should operate in the vicinity of thermodynamic equilibrium so that crystallization kinetic effects are avoided. The results show that, in fact, crystallization kinetic effects play an important role at the typical cooling rate used with both techniques. Cocrystallization is significant when fast cooling rates are used. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1762–1778, 2003     

Constitutional isomerism in polyamides derived from isophthaloyl chloride and 1,3‐diamine‐4‐chlorobenzene

Polyamides from isophthaloyl chloride and 1,3‐diamino‐4‐chlorobenzene with diverse constitutional order were obtained in a one‐stage synthesis varying the polymerization temperature and the monomer mixing modes. The constitutional order was calculated by ¹H and ¹³C NMR spectroscopies. A model to determine the constitutional isomerism in these polycondensates was applied with the relevant kinetic reaction parameters obtained from the model reactions. The Monte Carlo technique was used to model the constitution along the polycondensation reaction as a function of the average polymerization degree. Constitution was determined by kinetic factors and not by thermodynamic ones. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1202–1215, 2003     

Unified analysis of thermodynamic and rheological properties of high polymer solutions. I. Binary systems

We present a comprehensive experimental study of thermodynamic and rheological properties of semidilute polymer solutions in good solvent. Osmotic pressure and viscosity measurements have been done in several polymer‐solvent systems at different temperatures. A renormalization group technique was applied to analyze the data using de Gennes's blobs model to connect dynamic and conformational quantities. The behavior of polymer systems in the whole range from dilute to semidilute solutions can be satisfactorily described using only a few nonuniversal quantities experimentally determined. An adequate agreement between experiments and theory was found, showing universal behavior with a system‐dependent constant β that does not depend on molecular weight or concentration. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 290–301, 2002     

Conformational analysis of dipeptide‐derived polyisocyanides

The conformational properties of polymers derived from isocyanodipeptides have been investigated with a combination of model calculations, X‐ray diffraction, and circular dichroism spectroscopy. Depending on the configuration of the side chains, defined arrays of hydrogen bonds along the polymeric backbone are formed. This leads to a well‐defined conformation as, for example, expressed in the formation of lyotropic liquid‐crystalline phases and increased helical stability. Upon the disruption of the hydrogen bonds by a strong acid, a less well‐defined macromolecular conformation is observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1725–1736, 2003     

Anisotropic elastic moduli and Poisson's ratios of a poly(ethylene terephthalate) film

Expressions for the directional dependence of Young's modulus and Poisson's ratio were derived for a general material under plane‐stress conditions. Experiments with a laser extensometer to measure the Young's modulus and Poisson's ratio directly by a tension test are described, and the results are compared with the theoretical expressions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 260–266, 2004     

Life—a complex polymer system

After a discussion of the different levels of macromolecules, the phenomenon of life is regarded as a complex polymer system. The thermodynamic basis of general system theory is explained as well as the character of system laws. The important notion of emergent system properties is stressed, and life is explained as a system property of a sufficiently complex system. The general applicability of the systemic approach is pointed out, and some examples are provided. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 471–478, 2004     

Molecular characterization of a hyperbranched polyester. II. Small‐angle neutron scattering

A series of fractions of a hyperbranched polyester in deutero tetrahydrofuran solution were investigated by small‐angle neutron scattering. Concentrations of polymer from 2 to 5% w/v were used, and the molecular parameters were obtained from Zimm plots of the data. Second virial coefficients were positive, and these values were confirmed by dilute‐solution light scattering on a small number of fractions with deutero tetrahydrofuran as a solvent. The small‐angle neutron scattering data exhibited the general features predicted for the particle scattering functions of nonrandomly branched polymers, but an exact fit of the theoretical equation to the data could not be obtained for all fractions of the hyperbranched polymer, particularly those of high molecular weight. Excluded volume effects were cited as a possible cause for this disagreement. A fractal dimension of ～2.5 was obtained from the scattering vector dependence of the differential scattering cross section of the polymer in deutero tetrahydrofuran solution, which agreed with the scaling exponent for the dependence of the radius of gyration on weight‐average molecular weight. Hydrogenous tetrahydrofuran solutions of the hyperbranched polymer exhibited negative second virial coefficients that were attributed to isotopic influences on the thermodynamic properties of the polymer–solvent combination. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1352–1361, 2003     

Theoretical modeling of the relationship between Young's modulus and formulation variables for segmented polyurethanes

We describe a new modeling approach to prediction of Young's modulus of segmented polyurethanes. This approach combines micromechanical models with thermodynamic considerations based on the theory of block copolymers. The resulting model predicts both the equilibrium morphology and the “ideal” Young's modulus of a segmented polyurethane polymer as a function of its formulation (hard segment chemical structure, hard segment weight fraction, soft segment equivalent weight) and temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2123–2135, 2007     

New materials for optical rectification and electrooptic sampling of ultrashort pulses in the terahertz regime

The synthesis and nonlinear optical characterization of new electrooptic (EO) materials useful for terahertz (THz) applications is presented. Semiempirical calculations were used to guide the development of a series of chromophores on the basis of 2‐dicyanomethylen‐3‐cyano‐4,5,5‐trimethyl‐2,5‐dihydrofuran acceptors acting as guests in polymer films used in the generation of THz radiation via optical rectification. Amorphous films, 65–250 μm thick, with EO coefficients as high as 52 pm/V at 785 nm were used to generate sub‐picosecond pulses with bandwidths up to 3 THz. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2492–2500, 2003     

Nucleation ability of multiwall carbon nanotubes in polypropylene composites

The nonisothermal crystallization of multiwall carbon nanotube (MWNT)/isotactic polypropylene (iPP) nanocomposites was investigated. The results derived from the differential scanning calorimetry curves (onset temperature, melting point, supercooling, peak temperature, half‐time of crystallization, and enthalpy of crystallization) were compared with those of neat iPP. The data were also processed according to Ozawa's theory and Dobreva's approach. These results and X‐ray diffraction data showed that the MWNTs acted as α‐nucleating agents in iPP. Accordingly, MWNT/iPP was significantly different from neat iPP: A fibrillar morphology was observed instead of the usual spherulites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 520–527, 2003     

Theoretical and experimental X-ray photoelectron spectroscopy investigation of ion-implanted nafion

The membrane properties of a Nafion surface can be modified by ion implantation with N⁺ or F⁺. The results are presented of an X-ray photoelectron spectroscopy (XPS) study of implanted surfaces. For the interpretation of the XPS spectra, calculations using a semiempirical quantum chemical formalism (AM1) have been applied, in conjunction with a charge-potential model, to predict the C_1s core electron binding energies. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 551–556, 2004     

Kinetics of thermally induced phase separation in ternary polymer solutions. II. Comparison of theory and experiment

Light‐scattering measurements and spinodal decomposition modeling have been used to quantify the kinetics of pore growth in thermally quenched polymer‐solvent–nonsolvent [poly(methyl methacrylate) (PMMA)/1‐methyl‐2‐pyrrolidinone (NMP)/glycerin] solutions. Solutions of fixed composition were quenched to a series of temperatures and light‐scattering measurements and model calculations were performed to determine the temperature dependence of the pore growth rate. Both the experimental results and the model calculations show that the growth rate exhibits a maximum at an intermediate quench temperature that is related to an interplay between the thermodynamic and transport effects that govern pore growth. A similar growth‐rate maximum is also observed when a series of solutions of varying nonsolvent composition are all quenched to the same temperature. The relevance of these experiments to the dynamics of pore growth and the eventual locking‐in of the two‐phase structure that forms during nonsolvent‐induced phase inversion is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1461–1467, 1999     

Porosity‐dependent Young's modulus of membranes from polyetherether ketone

The porosity‐dependent Young's modulus for PEEK membranes was determined and the data compared to several empirical and semiempirical equations often applied to porous systems. The Spriggs equation, Wang's approximation, Sudduth's equation, and the foam modulus‐density relationship were all tested against the data. The relatively wide range of porosities tested in these experiments shows the Spriggs equation to be inadequate to fitting the data, especially above 50% porosity where the Young's modulus decreases rapidly. Wang's approximation to second order fitted the data well, and the porosity‐modulus relations had non‐negative coefficients as required and consistent with the ceramic data obtained by others. The data also fitted Sudduth's equations, usually applied to sintered ceramics, but equivalently good fits were obtained with nonunique fitting parameters. The foam modulus‐density relationship fitted the data for foamlike membranes but fitted less well to nonfoam morphology membranes. Finally, the data were used to determine the range of porosities and hollow fiber dimensions necessary for microfiltration and composite membrane application. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1168–1174, 2003     

Morphology of micron‐sized,monomer‐adsorbed,crosslinked polymer particles having snowmanlike shapes prepared by the dynamic swelling method

A series of monomer‐adsorbed, crosslinked polystyrene/polydivinylbenzene composite particles having snowmanlike shapes were prepared by the dynamic swelling method that the authors had proposed in 1991. The morphology of the snowman‐shaped particles was estimated with the contact angle of the monomer phase on the polymer particle. Influences of the kind of monomers and polyvinyl alcohol colloidal stabilizer on the morphology were obviously observed and discussed from the viewpoint of thermodynamic stability. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3106–3111, 2001     

Synthesis,characterization, and computational modeling of benzodithiophene donor–acceptor semiconducting polymers

Donor–acceptor semiconducting polymers containing benzodithiophene with decyl phenylethynyl substituents have been synthesized. Density functional calculations on the polymers' band gaps and frontier orbitals energies provide reasonable agreement with cyclic voltammetry, photoelectron spectroscopy, and UV–vis absorption measurements. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Modification of the universal calibration of gel permeation chromatography to include macromolecules presenting a draining effect

A new universal calibration for gel permeation chromatography is proposed in which the hydrodynamic volume of the macromolecular chains is expressed by the quantity [η]M/Φ instead of the commonly used quantity [η]M (where [η] is the intrinsic viscosity, M is the molecular mass, and Φ is Flory's parameter). Introducing Φ into the hydrodynamic volume is necessary because its value changes from one polymer to another when the polymers present a certain draining effect. The proposed procedure also allows the determination of Φ of any wormlike polymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 707–710, 2003     

Prediction and estimation of solvent diffusivities in polyacrylate and polymethacrylates

The relationship between polymer side‐chain length and the hole free volume that is effective for solvent diffusion was investigated for polyacrylates and polymethacrylates on the basis of free‐volume theory. Measurements of a polymer's viscoelasticity and solvent diffusivity provided experimental evidence for polymer segment mobility, and the results indicated that hole free volume in a linear polymer increases with hydrocarbon side‐chain length. Because the molecular mechanisms of polymer viscoelasticity and diffusivity are identical, the free‐volume parameters obtained for polyacrylates and polymethacrylates by measuring the polymer viscoelastic‐temperature dependence can reliably be used in predicting the solvent diffusion coefficient. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1393–1400, 2003     

Morphology and bridging properties of (AB)n multiblock copolymers

Motivated by recent experiments (Spontak, R. J.; Smith, S. D. J Polym Sci Part B: Polym Phys 2001, 39, 947) on morphological and mechanical properties of multiblock copolymers (AB)_n, we theoretically elucidate the links between microscopically determined properties, such as the bridging fraction of chains, and mechanical properties of these materials. We do this by applying self‐consistent mean‐field theory to determine morphological aspects such as period and interfacial width and calculate the bridging fractions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 104–111, 2003     

Thermodynamic interaction parameter of star–star polybutadiene blends

The value of the thermodynamic interaction parameter, χ_eff, for star–star polybutadiene blends was determined with small‐angle neutron scattering. Blends in which the stars have the same number of arms and blends in which the stars have different numbers of arms are investigated. For star–star isotopic blends with components having the same number of arms, the presence of the junction point of the star leads to a value of χ_eff that is larger than that for an analogous linear–linear isotopic blend. However, changes in the value of χ_eff resulting from small dissimilarities in the number of arms of the two components in the isotopic star–star blends were too small to resolve. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 247–257, 2003