Connectivity and spacing effects in hydrogen-bonding polymer solutions and blends

In recent experimental work, it was found that the number of hydrogen bonds in polymer mixtures is strongly influenced by chain-connectivity effects and the spacing of functional groups along the chain. In this article, the relationships between the equilibrium constants used to describe the number of hydrogen bonds in mixtures of various types (blends, solutions, random copolymers, etc.) is elucidated and described. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1273–1281, 1998     

Desorption of water vapor in hydrogen-bonded polymer blends

Successive desorption experiments of water vapor in poly(methyl methacrylate) (PMMA) were performed at temperatures from 31.0 to 45.0°C. The solubility of water in PMMA was found to be independent of temperature in agreement with literature findings. But the results for diffusion showed stronger dependence on water concentration than those in literature. The diffusion coefficients of water in PMMA became almost independent of temperature at high water concentrations. However, at lower water concentrations, the temperature effect on diffusion was more pronounced. The observed weak temperature dependence of diffusivity at high concentrations is likely due to a high degree of clustering of water molecules found in the PMMA we prepared. Two modified polystyrenes containing 5 and 15 mol %, respectively, 4-hydroxystyrene as comonomer units were blended with PMMA to form hydrogen-bonded polymer blends. Successive desorption experiments of water vapor in the hydrogen-bonded polymer blends were carried out at 31.0°C. The solubility of water in both blends was found to increase with increasing composition of PMMA. The diffusion coefficients for PMMA and its blends increased with increasing concentration of water first, reached a maximum, then decreased with water concentration. When the desorption results were plotted with the previous study of absorption, hysteresis phenomenon of sorption existed in all blend compositions for our experimental time span. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 39–45, 1998     

Laser light scattering studies of ternary polymer solutions

Ternary polymer solutions [polystyrene and poly(methylvinylether) dissolved in a single solvent] have been studied to investigate the thermodynamic compatibility of the polymers and the solvents, and also to facilitate the investigation of the self-diffusion of polystyrene to greater polymer concentration. Both good and poor quality solvents have been used in this study. The self-diffusion coefficient of the polystyrene has been measured by dynamic light scattering and by pulsed field gradient NMR where appropriate. The self-diffusion data are also used to critically examine the recent theoretical developments in this field. Important confirmation of theory has been demonstrated for good solvent solutions and intriguing discrepancies have been discovered for poor solvent solutions.     

A molecular thermodynamic model for binary lattice polymer solutions

A molecular thermodynamic model for binary lattice polymer solutions with concise and accurate expressions for the Helmholtz energy of mixing and other thermodynamic properties is established. Computer simulation results are combined with the statistical mechanics to obtain the expressions. Yan et al.'s model for Ising lattice and the sticky-point model of Cumming, Zhou and Stell are incorporated in the derivation. Besides the nearest neighbor cavity correlation function obtained from the Ising lattice, the long range correlations beyond the close contact pairs are represented by a parameter λ, the linear chain-length dependence of which is obtained by fitting the simulated critical parameters of two systems with chain lengths of 4 and 200. The predicted critical temperatures and critical compositions, spinodals and coexistence curves as well as internal energies of mixing for systems with various chain lengths are in satisfactory agreement in comparison with the computer simulation results and experimental data indicating the superiority of the model over other theories. The model can serve as a basis to develop more efficient models for practical applications.     

Data fitting in photon correlation spectroscopy studies of dilute polymer solutions

Two methods of processing data from photon correlation studies of polydisperse polymer samples in dilute theta solution have been compared using computer generated correlation functions. Force-fitting a single exponential to the data gives a value for the diffusion coefficient D only slightly less than D_z, the z-average value returned by the cumulants method. Both methods are shown to give the same concentration dependence for D.     

Ternary blends for polymer bulk heterojunction solar cells

The objective of this mini‐review is to outline current major ternary blends used in the active layer of polymer bulk heterojunction photovoltaic solar cells and to give an insight into the direction of the field. The use of a third‐component material in polymer ? fullerene blends is described in two sections. On the one hand, the first family of solid state additives enables us to enlarge photon collection by expanding the action spectra of the solar cells. The second section deals with materials used to engineer bulk heterojunction morphology at the nanoscale. The different approaches explored for many of the ternary blend systems suggest the great potential of such mixtures to significantly improve the optoelectronic properties of solar cells on a long‐term basis. © 2013 Society of Chemical Industry     

Phase behavior of ternary polymer blends with hydrogen bonding

Atactic poly (methyl methacrylate) (aPMMA) was found to be almost completely immiscible with poly(vinyl acetate) (PVAc). Both aPMMA and PVAc are known to be miscible with poly(vinyl phenol) (PVPh) according to literature. Adding of PVPh into immiscible aPMMA/PVAc mixtures is likely to improve their miscibility. Therefore, PVPh can be used as cosolvent to cosolubilize aPMMA and PVAc. A ternary blend consisting of aPMMA, PVAc, and PVPh was prepared and determined calorimetrically in this article. According to the calorimetry data, the ternary blend was determined to be miscible. The reason for the observed miscibility is because the interactions between PVAc and PVPh are similar to those between aPMMA and PVPh. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2797–2802, 2004     

Flow of viscoelastic polymer solutions in mixed beds of particles

New extensive pressure drop-flow rate data are reported for the creeping flow of well characterised viscoelastic polymer solutions through packed beds of mixed size spheres and of spheres and cylinders. It is established that the effective mean surface diameter is adequate in correlating the pressure loss data in flow through packed beds of mixed size and shape. A distinct correlation exists between the excess pressure loss observed with viscoelastic fluids and the Weissenberg number.     

A study on the micromixing performance in microreactors for polymer solutions

Microreactors are widely applied for various polymerization processes to produce polymers with controlled molecular weight and structures. In this work, the mixing of polymer solutions in capillary microreactors was investigated with the aid of the biazo‐coupling reaction system and high‐speed camera. A smaller inner diameter, a higher Dean number and a lower Torsion number could promote the micromixing performance in microreactors. Unlike the mixing of Newtonian fluids in microreactors or micromixers, the mixing of polymer solutions follows different mechanisms and it is more difficult to reach homogeneous condition. However, the good micromixing performance in capillary microreactor systems for polymer solutions still could be obtained with high shear rates and long enough capillary length at relatively high correlated Reynolds numbers (N_Re > 29). Furthermore, the micromixing time in the capillary microreactors was evaluated based on a modified stretching efficiency model and its value was in the range of 0.1–8.0 ms. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3479–3490, 2018     

Quasielastic scattering from dilute polymer solutions

The initial slope $\text{Ω(q)}$ of the time-dependent scattering function and the static structure factor S(q) of macromolecules in good solvents are calculated without using the Gaussian assumption. For S(q), the scaling relation S(q)～q^?1.7 is confirmed in the intermediate q range, whereas no q dependent cross-over behaviour can be observed. The calculation of $\text{Ω(q)}$ reveals a q³ dependence in this range and no evidence is seen for an exponent apart from 3. The time-dependent scattering function S(q,t) is treated within the framework of the Gaussian assumption. Hydrodynamic as well as excluded volume interactions are incorporated. It has been found that excluded volume effects decrease the decay of the scattering function in comparison with the Gaussian chain.     

Rheological behaviors of PVA/H2O solutions of high‐polymer concentration

The dynamic viscoelastic properties of poly(vinyl alcohol) (PVA)/H₂O solutions with concentrations of 10 to 25 wt % have been characterized by controlled‐stress rheometry at 30°C. Parameters relating to the linear and nonlinear viscoelasticities include complex viscosity (η*), storage modulus (G′), loss tangent (tan δ), relaxation time (λ), thixotropy, and creep. Change curves of η*, G′, tanδ, and λ with frequency (ω) have been obtained for the PVA/H₂O solutions. Creep and recovery testing yielded compliance (J′) curves with loading and unloading. Shear stress versus rate profiles of the PVA solutions have been obtained through thixotropic measurements. The PVA concentration has been found to have a profound influence on the rheological properties of the aqueous solutions. Four aqueous solutions of 10, 15, 20, and 25 wt % PVA at 30°C exhibited shear‐thinning and showed different transition behaviors of η* and G′ with frequency, and different degrees of creep under constant stress to recovery with time. The 10 wt % PVA solution was viscous and displayed the lowest η* and G′; the 25 wt % PVA solution was viscoelastic and displayed the highest η* and G′; the 15 and 20 wt % PVA solutions showed η* and G′ values and creep to recovery behaviors intermediate between those of the 10 wt % and 25 wt % PVA solutions. The different rheological properties of these PVA/H₂O solutions are considered to correlate with interchain hydrogen bonds and shear‐induced orientation in the solutions. Shearing is able to break the intrachain and interchain hydrogen bonds, and, at the same time, the orientation creates new interchain hydrogen bonding. The reorganization of hydrogen‐bonding mode contributes to the transitions of the macroscopic viscoelasticity with frequency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Wetting by polymer solutions

Very small droplets of polystyrene dissolved in toluene were placed on a glass slide and studied under a goniometer microscope. The drops were allowed to spread and dry and their extent of spreading is plotted as a variation of the concentration of the polymer in the solution. It was observed that drops of polystyrene in a volatile solvent such as toluene, spread to some extent and then gets dried up thus preventing the contact line from moving further. When liquid PDMS in non-volatile solvent, HMDS, and in volatile solvent, toluene, was used, the droplets continued to spread. One conclusion among others, is that even if the droplet dries but leaves behind a mobile contact line then the solution spreads out, on the other hand if the droplet dries and the contact line loses its mobility, the spreading automatically comes to a stop.     

Achieving miscible ternary polymer blends with hydrogen bonding

Poly(vinyl phenol) (PVPh) has previously been found to be successful in making immiscible poly(methyl methacrylate) (PMMA)/poly(vinyl acetate) (PVAc) miscible. Poly(ethyl methacrylate) (PEMA) with one more methyl group than PMMA is also immiscible with PVAc. PEMA and PVAc are miscible with PVPh according to the literature. To determine whether PVPh can also cosolubilize PEMA/PVAc, PVPh samples of two different molecular weights have been mixed in this study with PEMA and PVAc to produce a ternary blend. On the basis of the calorimetry data, the ternary PEMA/PVAc/PVPh blend, regardless of the molecular weight of PVPh, has been determined to be miscible. The reason for the observed miscibility is probably that the interactions between PVAc and PVPh are similar in magnitude to those between PEMA and PVPh. A modified Kwei equation based on the binary interaction parameters proposed previously is used to describe the experimental glass‐transition temperature of the miscible ternary blend almost quantitatively well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 643–652, 2006     

The concentration dependence of diffusion in semi-dilute polymer solutions

Dynamic light-scattering data for polystyrene fractions in a good solvent (benzene) and a theta solvent (cyclopentane, 20.4°C) are presented. They encompass a broad concentration interval in the semi-dilute range. These data are compared with those for the systems poly(ethylene oxide)/water and hydroxyethylcellulose/water. The entanglement network in these systems is reflected in part by the nature of the concentration dependence of the mutual diffusion coefficient and in part by the presence of a slow relaxation, information on which may be derived from the non-exponential autocorrelation function.     

Effect of solvent quality on Poiseuille flow of polymer solutions in microchannels: A dissipative particle dynamics study

The Poiseuille flows of polymer solutions for varying quality solvents in microchannels have been simulated using dissipative particle dynamics. In particular, the velocity distributions and the polymer migration across the channel have been investigated for good, athermal, and poor solvents. The velocity profiles for all three kinds of solvent deviate from the parabolic profile, and the velocity profile of the athermal solvent falls in between the good solvent and the poor solvent. For the athermal solvent, a migration away from the wall due to the hydrodynamic interactions between the chains and the wall is observed, and a migration away from the channel center due to the different chain Brownian diffusivities is also observed. For the good solvent, because of the more stretched polymer chains, the migration away from the wall is stronger than that for the athermal solvent. However, the migration away from the channel center is not observed for good solvents. For the poor solvent, the hydrodynamic interaction within the chains is screened, and the polymer chains migrate toward the wall and appear to be absorbed by the wall. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47345.     

The surface chemistry of water-reducible polymer solutions/dispersions 1. Surface tension behavior

Both static tension and dynamic surface tension of water-reducible (W/R) polymer solutions were carefully examined. It is shown that the cosolvent and its concentration are controlling factors in surface tension behavior for most concentration regions of W/R polymer solutions. This is true for both static and dynamic surface tensions. The polymer and its concentration have a much smaller effect on static surface tension than does the cosolvent. Much of the dynamic surface tension correlates with the bulk shear viscosity of W/R polymer solutions. The examination of cosolvent /water mixtures shows a critical solution concentration (CSC) for most cosolvents, analogous to the critical micelle concentration (CMC) in surfactant solutions. Both CSC and CMC originate from the same structural characteristics, i.e. molecules having a hydrophilic head and hydrophobic tail. Typically cosolvents have a less hydrophobic nature so values of CSC are higher than those typical of CMC for surfactants. This CSC plays a unique role in the surface tension of W/R polymer solutions. Above the CSC, constant surface tension is observed, while below the CSC a rapid increase in surface tension with decrease of cosolvent concentration occurs.     

智能高分子与高分子凝胶

简述智能高分子材料，并进行了详细分类。从合成及其加工设备、新产品开发、设计方案、应用前景等诸方面详细的阐述了智能高分子凝胶。     

Diffusion of rigid rodlike polymer in isotropic solutions studied by dissipative particle dynamics simulation

Dissipative particle dynamics (DPD) was employed to simulate the diffusion of rigid rodlike polymers in isotropic solutions. In a dilute solution range, the simulated diffusion behavior is in good agreement with that as described by the Kirkwood theory. In a semi-dilute range, the simulation shows that the DPD model adopting soft repulsive interactions can effectively reproduce the entanglement effect on both rotational and translational diffusions. The rotational diffusion coefficient D_r obeys the asymptotic scaling law D_r ∼ (νL³)⁻² (ν is the number of polymers per volume and L is the polymer length) for the large νL³, which corresponds to formation of a completely enclosed tube in the Doi-Edwards theory. The parallel translational diffusion coefficient D_‖ decreases with ν increase, which can be attributed to the friction effect of surrounding medium. The perpendicular translational diffusion coefficient D_⊥ decays more drastically with ν increase, which is caused by the topological constraint.     

Infrared spectroscopy method reveals hydrogen bonding and intermolecular interaction between components in polymer blends

An infrared spectroscopy method was devised to uncover evidence of hydrogen bonding and intermolecular interaction between components in solid poly(lactic acid) (PLA) and poly(hydroxyester ether) (PHEE) blends. The method compares Gaussian/Lorentzian deconvoluted infrared spectra of the polymer blends with deconvoluted spectra of weight ratio‐equivalent mixtures of the physically separated polymers. Infrared spectra of polymer blends, where hydrogen bonding exists, differ from spectra of physical mixtures of the polymers. Deconvoluting spectra of the blends into their underlying peaks revealed theoretically expected differences between hydrogen‐bonded and nonhydrogen bonded components. The findings are supported by differential scanning calorimetry, scanning electron microscopy, and mechanical rheometry studies. The new method, differential spectral deconvolution, afforded a quantitative estimate of the extent of hydrogen bonding between PLA and PHEE and could therefore be used to measure the degree of interaction between components in thermoplastic blends. This technique is superior to conventional spectral subtraction and it should be applicable to intimate mixtures or solid solutions in general. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 813–821, 2005     

Photoinduced cooperative reorientation in polymer blend films with hydrogen-bonded mesogenic side groups

Thermally enhanced photoinduced cooperative reorientation in hydrogen (H)-bonded polymer blend films was investigated. The films consisted of two kinds polymethacrylates with hexamethylene spacer groups terminated with 4-oxycinnamic acid (P6CA), 4-oxybenzoic acid (P6BA) or 4-(4′-oxyphenyl)benzoic acid (P6PBA) in the side chains. The films were subjected to linearly polarized ultraviolet (LPUV) light and subsequent annealing. Sufficient cooperative in-plane molecular reorientation in P6CA–P6BA blend films was achieved for the first time. In P6CA–P6PBA blend films, however, reorientation was not observed. The molecular weight, as well as the thermal properties of the homopolymers and the degree of photoreaction all played an important role in the cooperative reorientation behavior of the blend films. Finally, uniform alignment control of low-molecular-weight liquid crystals (LCs) on the molecularly reoriented polymer blend films perpendicular to the polarization E of LPUV light was obtained.