Conductivity and the electric modulus in polymers

At relatively high temperatures and low frequencies the electrical properties of many polymers are dominated by ionic conductivity. In cases where the glass transition is obscured by conductivity, it can be revealed by treating the data in terms of the electric modulus. The magnitude of the activation energy for conductivity (24–67 kcal/mol) for Nylons 6, 66, and 6I, polybutylene terephthalate, and polycarbonate indicates that the transport of charged particles requires the motion of polymer segments.     

Orientational–deformational nature of flow birefringence in solutions of rigid-chain polymers

The orientational–deformational nature of flow birefringence (FB) in solutions of rigid-chain polymers is confirmed experimentally. The possibility of a direct determination of the internal viscosity parameter by the dependence of the FB relaxation time on the solvent viscosity is demonstrated. Indirect manifestation of internal viscosity in the FB relaxation time is confirmed by the dependence of the form factor on the degree of coiling. © 1993 John Wiley & Sons, Inc.     

Vacuum-ultraviolet induced oxidation of the polymers polyethylene and polypropylene

The emission from low-pressure microwave plasmas in the vacuum-ultraviolet (VUV) region (λ < 200 nm) was investigated in order to use these plasmas as light sources for the study of the VUV photochemistry of polyethylene (PE) and polypropylene (PP) as part of the study of plasma-polymer interaction. These polymers, immersed in low-presure oxygen, were exposed to radiation with wavelengths down to 112 nm, the cut off of magnesium fluoride used as a window to separate the polymer specimen from the plasma light source. Total oxygen incorporation in the surface [O], and the formation of hydroxyl, carbonyl, and carboxyl groups were measured using XPS in combination with chemical derivatizations, particularly their dependence upon the radiation spectrum and the oxygen pressure around the sample. In most experiments the surface oxygen concentration [O] attained a constant value that appears to be related to the initial oxidation rate; this suggests a competition between oxygen incorporation and chain scission reactions, followed by the removal of volatile oxidation products. PE is usually oxidized to a higher level than PP, the latter appearing to be more susceptible to reaction with atomic oxygen than PE. A general initiation mechanism for the VUV experiments is proposed that allows us to explain the observed differences in behavior between PE and PP, and the results obtained under different irradiation conditions. The nature of oxidation products is in both cases very similar to what is observed after direct plasma treatment of the polymers. We conclude that short wavelength radiation contributes very appreciably to the observed surface modification effects during plasma treatment of PE and PP. © 1995 John Wiley & Sons, Inc.     

NMR free induction decay in crosslinked polydimethylsiloxane networks. Theoretical analysis

A theory of nuclear magnetic resonance free induction decay (FID) in crosslinked poly-dimethysiloxane networks is proposed. The anomalously small amplitude of the FID asymptotes at high temperatures is explained as due to crosslink motions. The Anderson-Weiss theory is generalized to account for the non-Gaussian distribution of local dipolar fields. © 1993 John Wiley & Sons, Inc.     

Nature of mechanoradical formation and reactivity with oxygen in methacrylic vinyl polymers

The formation of mechanoradicals under anaerobic conditions and their reactivity with oxygen at room temperature is described for several methacrylic vinyl polymers. Observed electron spin resonance (ESR) spectra of the mechanoradicals formed were all essentially identical and are clearly assigned to a respective endchain radical. The ESR kinetics of the mechanoradical formation of polymethylmethacrylate (PMMA) and polymethacrylamide (PMAAm) exhibit an interesting contrast; the progressive changes in the radical concentration in PMMA as a function of duration of milling gradually decrease after reaching a maximum value, while those of PMAAm show a parabolic increase. This discrepancy has been ascribed to mechanoradicals of PMAAm that are strongly stabilized by intermolecular and intramolecular doubly hydrogen-bonded networks among the amide groups. Such interactions also are to lower the reactivity of the mechanoradicals with oxygen. Thus, the mechanoradicals of both PMAAm and PMAA do not give a single peroxy radical, but rather a mixture of the mechanoradical and peroxy radical even after exposure to air, while the mechanoradicals of other polymers are rapidly converted to the corresponding peroxy radicals. Such a difference was observed in experiments on the mechanical fracture of such polymers under aerobic conditions.     

A relationship between macroradical decay kinetics and α-segmental dynamics in glassy amorphous polymers

For a series of five amorphous polymers with a broad range of T_g values the kinetics of macroradical decay was measured by ESR technique and evaluated by the second-order kinetic model. It was found that the temperature T_tr of the transition between two regions of different reactivity in free radical decay reaction agrees quite well with the temperature parameter T₀ of the Vogel-Fulcher-Tamman-Hesse (VFTH) equation for α-segmental dynamics. This parameter represents the onset of α-segmental mobility in glassy state below T_g. A nontraditional way of the estimation of T₀ values for α-segmental dynamics through study of the macroradical decay in glassy state of amorphous polymers has been suggested. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of new selenophene‐based conjugated polymers for organic photovoltaic cells

Three new polymers poly(3,4′′′‐didodecyl) hexaselenophene) (P6S), poly(5,5′‐bis(4,4′‐didodecyl‐2,2′‐biselenophene‐5‐yl)‐2,2′‐biselenophene) (HHP6S), and poly(5,5′‐bis(3′,4‐didodecyl‐2,2′‐biselenophene‐5‐yl)‐2,2′‐biselenophene) (TTP6S) that have the same selenophene‐based polymer backbone but different side chain patterns were designed and synthesized. The weight‐averaged molecular weights (M_w) of P6S, HHP6S, and TTP6S were found to be 19,100, 24,100, and 19,700 with polydispersity indices of 2.77, 1.48, and 1.41, respectively. The UV–visible absorption maxima of P6S, HHP6S, and TTP6S are at 524, 489, and 513 nm, respectively, in solution and at 569, 517, and 606 nm, respectively, in the film state. The polymers P6S, HHP6S, and TTP6S exhibit low band gaps of 1.74, 1.95, and 1.58 eV, respectively. The field‐effect mobilities of P6S, HHP6S, and TTP6S were measured to be 1.3 × 10^?4, 3.9 × 10^?6, and 3.2 × 10^?4 cm² V^?1 s^?1, respectively. A photovoltaic device with a TTP6S/[6,6]‐phenyl C₇₁‐butyric acid methyl ester (1:3, w/w) blend film active layer was found to exhibit an open circuit voltage (V_OC) of 0.71 V, a short circuit current (J_SC) of 5.72 mA cm^?2, a fill factor of 0.41, and a power conversion efficiency (PCE) of 1.67% under AM 1.5 G (100 mW cm^?2) illumination. TTP6S has the most planar backbone of the tested polymers, which results in strong π–π interchain interactions and strong aggregation, leading to broad absorption, high mobility, a low band gap, and the highest PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

The effect of lattice compressibility on the thermodynamics of gas sorption in polymers

A compressible lattice model with holes, the glassy polymer lattice sorption model (GPLSM), was used to model the sorption of carbon dioxide, methane, and ethylene in glassy polycarbonate and carbon dioxide in glassy tetramethyl polycarbonate. For glassy polymers, an incompressible lattice model, such as the Flory–Huggins theory, requires concentration-dependent and physically unrealistic values for the lattice site volumes in order to satisfy lattice incompressibility. Rather than forcing lattice incompressibility, GPLSM was used and reasonable parameter values were obtained. The effect of conditioning on gas sorption in glassy polymers was analyzed quantitatively with GPLSM. The Henry's law constant decreases significantly upon gas conditioning, reflecting changes in the polymer matrix at infinite dilution. Treating the Henry's law constant as a hypothetical vapor pressure at infinite dilution, gas molecules in the conditioned polymer are less “volatile” than those in the unconditioned polymer. Flory–Huggins theory was used to model the sorption of carbon dioxide, methane, and ethylene in silicone rubber. Above the glass transition temperature, the criterion of lattice incompressibility for Flory-Huggins theory was satisfied with physically realistic and constant values for the lattice site volumes. © 1992 John Wiley & Sons, Inc.     

Cell culture on polymers prepared by radiation-induced grafting of various monomers

The adhesion and growth of tissue cells on polymers prepared by radiation grafting was investigated. The apparent rates of initial attachment and growth of Chang liver and C₆ cells were promoted on surfaces with increased wettability and with a heterogeneous structure for grafted polyvinyl fluoride film. The degree of cell attachment and growth on surfaces having a dense microblock structure, formed by grafting of methyl methacrylate in acetone solvent, was greater than that caused by other factors, such as wettability.     

Depolarized light scattering studies on single-phase mixtures of dissimilar polymers: Evidence for local ordering

Depolarized light scattering measurements on single-phase mixtures of dissimilar polymers, poly(methyl methacrylate) (PMMA)/poly (acrylonitrile-co-styrene) (SAN, AN content = 15 wt %) and PMMA/poly (vinylidene fluoride) (PVDF) were carried out. The effective mean-square optical anisotropy γ² of the mixtures was found to be much higher than that estimated by the simple additivity of γ² of component polymers. From the deviation, the order parameter (1 + J₁₂) was estimated to be in a range of 2–13, depending on the blend composition. This suggests local ordering in the single-phase mixtures, i.e., nematic alignment of the locally stretched dissimilar chains. In contrast, the deviation was slight in the polymer/solvent systems, SAN/MMA (monomer) and PVDF/butanone. The degree of ordering decreased with increasing temperature. T. The Specific interaction evidenced by FTIR spectroscopy exhibited a similar temperature dependence. Thus, local ordering seems to be induced by specific interactions and chain connectivity. The temperature dependence of J₁₂ was successfully described by the Landau-de Gennes theory; J ∞ (T + T₀)/ T, T₀ being the isotropic-nematic transition temperature, as in the case of liquid crystals.     

Energy-consuming micromechanisms in the fracture of glassy polymers. I. Chain scission in polystyrene

The number of chain scissions per unit area that occur during the fracture of partially annealed latex films from M_n ? 180,000 g/mol polystyrene particles of about 275 Å radius were measured and correlated to annealing times. A curve with four regimes was found. At short annealing times the curve is nearly flat, in what is called the chain pull-out regime. In the second regime, the number of chains broken per unit area increases with a 0.8 power of annealing time as entanglement of the diffusing polymer chains increases in neighboring host particles. This is in good agreement with Wool's theory which predicts a 0.75 power dependence. Then, after reaching a peak, the number of scissions decreases in the third regime, indicating a change in fracture mechanism. The number of chain scissions increases again in the fourth regime, as final healing of the film interface takes place. Fracture surface analysis reveals a rough surface for short annealing times and a smooth surface for longer annealing times. The number of polymer chain scissions per unit area of fracture surface showed no dependence on initial molecular weights for t ? τ_r where t and τ_r are annealing and relaxation times, respectively. The number of chain bridges crossing a unit area of interface was suggested as the basic molecular property. © 1992 John Wiley & Sons, Inc.     

Summary of ISO/TC 201 Standard: ISO 29081: 2010, surface chemical analysis—Auger electron spectroscopy—reporting of methods used for charge control and charge correction

This international standard specifies the minimum amount of information required for describing the methods of charge control and charge correction in measurements of Auger electron transitions from insulating specimens by electron‐stimulated AES to be reported with the analytical results. Information is provided in an Annex on methods that have been found useful for charge control prior to or during AES analysis. The Annex also includes a summary table of methods or approaches, ordered by simplicity of approach. A similar international standard has been published for XPS (ISO 19318: 2003(E), Surface chemical analysis—XPS—reporting of methods used for charge control and charge correction. Copyright © 2010 John Wiley & Sons, Ltd.     

Morphology of Nylon-6 blends with styrenic polymers

The morphology of blends of styrenic polymers in a matrix of 75% Nylon-6 prepared in a Brabender Plasti-Corder was examined by scanning electron microscopy. Styrene/acrylonitrile copolymers (SAN) form smaller particles as the AN level increases owing to the corresponding decrease in the SAN–polyamide interfacial tension. Various styrenic polymers containing functional groups, maleic anhydride or oxazoline type, that can react with Nylon-6 during melt processing were added to the SAN phase which also led to a decrease in the particle size owing to the graft copolymer formed in situ. The effects of functional group type, amount of functional groups per chain, amount of functional polymer added, and the miscibility of the styrene/maleic anhydride (SMA) and SAN copolymers on the morphology of the styrenic phase in the Nylon-6 matrix are described. © 1992 John Wiley & Sons, Inc.     

Antimicrobial anilinium polymers: The properties of poly(N,N‐dimethylaminophenylene methacrylamide) in solution and as coatings

Antimicrobial polymers have been widely reported to exert strong biocidal effects against bacteria. In contrast with antimicrobial polymers with aliphatic ammonium groups, polymers with anilinium groups have been rarely studied and applied as biocidal materials. In this study, a representative polymer with aniline side functional groups, poly(N,N‐dimethylaminophenylene methacrylamide) (PDMAPMA), was explored as a novel antimicrobial polymer. PDMAPMA was synthesized and its physicochemical properties evaluated. The methyl iodide‐quaternized polymer was tested against the Gram‐positive Staphylococcus aureus, with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 16–32 and 64–128 μg mL^?1, respectively. Against the Gram‐negative Escherichia coli, the MIC and MBC were both 64–128 μg mL^?1. To broaden the range of applications, PDMAPMA was coated on substrates via crosslinking to endow the surface with contact‐kill functionality. The effect of charge density of the coatings on the antimicrobial behavior was then investigated, and stronger biocidal performance was observed for films with higher charge density. This study of the biocidal behavior of PDMAPMA both in solution and as coatings is expected to broaden the application of polymers containing aniline side groups and provide more information on the antimicrobial behavior of such materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1908–1921     

A study of the behavior of charge carriers in an organic non‐volatile memory device with a thin metal layer between polymers

The behaviors of charge carriers were investigated to understand the reversible bistability in the polymer device with an embedded thin metal layer between the metal electrodes. The reversible bistability was sensitive to the condition of the embedded thin metal layer that was prepared by depositing 5 nm Al by 0.8 Å/sec. The device was controlled by the charge and the discharge in the effective trap sites of the embedded Al layer. Poly(N‐vinylcarbazole) as an organic active material merely conducted the charge transport function. The effective trap sites were contributed by the change of the reversible conductance and also preferred to be in a high conduction state. They took relatively low energy states easily as the device was affected by thermal stimulation at 150°C. The modification of the embedded Al layer improved its performances. Copyright © 2009 John Wiley & Sons, Ltd.     

Direct measurement of free-volume hole distributions in polymers by using a positronium probe

We have directly measured the free-volume hole distributions in semicrystalline polypropylene by positron lifetime annihilation spectroscopy. A Laplace inversion technique was engaged to analyze the positron lifetime spectra measured under quasi-isotropic external pressures of 0, 4.2, and 14.7 kbar into continuous lifetime distributions. The hole radii distributions as determined from the ortho-positronium lifetime distributions are found to be between 4.0 and 0.5 Å and to have maxima at 3.0, 1.9, and 1.1 Å under the external pressures of 0, 4.2, and 14.7 kbar, respectively. © 1992 John Wiley & Sons, Inc.     

聚合物内压测定及对应状态模型

实验测定了PEG(M~n=200),PEG(M~n=300),PEG(M~n=400),PDMS(M~w=15000)和PDMS(M~w=20000)在20-90℃温度范围的热压力系数和密度,它们的热压力系数和内压几乎与分子量无关。据此还建立了一个聚合物内压的对应状态模型,它只含一个可调参数,能满意地适用于各种聚合物。     

A novel staining technique for studying toughening mechanisms in saturated acrylic rubber-modified polymers

A novel technique which utilizes a two-stage staining approach, (i.e., styrene absorption followed by osmium tetraoxide staining) is introduced for staining saturated polyacrylate rubbers. This novel staining approach, which stains and hardens polyacrylate rubber, is found to be useful for room temperature microtomy of polyacrylate rubber-modified polymers. Therefore, both the morphology and the crack tip toughening mechanisms of polyacrylate rubber-modified systems can be studied. Details concerning staining time, staining media, and use of solvents are discussed.     

Novel pH‐responsive mixed‐charge copolymer brushes based on carboxylic acid and quaternary amine monomers

In this study, we report on the fabrication of tunable mixed‐charged copolymer brushes consisting of negatively charged carboxylic acid monomer (4‐vinylbenzoic acid, VBA) and positively charged quaternary amine monomer ((ar‐vinylbenzyl)trimethylammonium chloride) via reversible addition–fragmentation chain transfer‐mediated polymerization. The copolymer brushes have negative charge under neutral and basic conditions, and are positively charged under acidic conditions owing to the protonation of the carboxylate groups. The copolymer brushes revealed a unique reversible wetting behavior with pH. The reversible properties of the copolymer brushes can be employed to regulate the adsorption of charged biomacromolecules such as DNA and proteins. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Field-dependent electric conductivities of silicone rubbers deduced from measured currents and surface potential decay characteristics

Measurements of DC electric conductivities of four types of silicone rubber-based polymers for use in high voltage insulation systems of power components are reported. The field dependences of the conductivities obtained by two different techniques, namely by utilizing steady-state currents through materials’ samples placed between metallic electrodes and by employing surface potential decay characteristics in an open circuit configuration, are compared and discussed. It is shown that the surface potential decay technique allows for a wider range of electric field strength and reduces the time span of the measurements.